|
|
|
Similarities in the structural evolution of rift basins and rift-zone grabens
1999-07-01
Sedimentary rift basins are either half-grabens or grabens, both of which are generated by tension. Data from drill holes and 3D seismic studies of the sedimentary basins associated wth grabens, such as the Central Graben and the Viking Graben offshore Norway, can be used to provide detailed conceptual models on the graben structures and evolution. Some of these models show striking geometric similarities to analogue models generated in experiments using plaster. The faults associated with these grabens are unavailable for direct field studies for testing the details of the model implications. However, field studies of normal faults similar to these can be made in on-land rift zones. In the rift zone of Iceland, current rifting episodes with development of normal faults and grabens can be compared with the results of field studies of the infrastructure of grabens that have drifted out of the active rift zone. Field observations and theoretical studies suggest that graben-faults in Iceland nucleate on sets of echelon joints or large-scale tension fractures at shallow depths These results, with appropriate modifications, may be applicable to many normal-fault systems in sedimentary rift basins. The author writes out the appropriate equations and applies the theory to a numerical example.
The fissure swarm of the Askja volcanic system along the divergent plate boundary of N Iceland
2009-01-01
Divergent plate boundaries, such as the one crossing Iceland, are characterized by a high density of subparallel volcanic fissures and tectonic fractures, collectively termed rift zones, or fissure swarms when extending from a specific volcano. Volcanic fissures and tectonic fractures in the fissure swarms are formed during rifting events, when magma intrudes fractures to form dikes and even feeds fissure eruptions. We mapped volcanic fissures and tectonic fractures in a part of the divergent plate boundary in northern Iceland. The study area is ~1,800km2, located within and north of the Askja central volcano. The style of fractures changes with distance from Askja. Close to Askja the swarm is dominated by eruptive fissures. The proportion of tectonic fractures gets larger with distance ...
2010-01-01
Iceland brings exceptional opportunity for analysing extension related to rifting of the Mid-Atlantic ridge, especially revealing fresh structural patterns in active fissure swarms. Post-glacial fracture systems of the Thingvellir rift segment of the West Volcanic Zone (WVZ) and interaction with holocene lava flow overlapping are analysed in detail in this paper. We mapped 5390 fractures at metric to kilometric scales in order to realise a precise structural map, a representative fault length distribution analysis and some statistical calculations in terms of fault length/number growth rates from Holocene to recent time. Mapping and 3-D geometrical analysis of faults and fissures are based on use of photogrammetric techniques, GPS positioning at ground control points and validation from ge...
Influence of margin segmentation upon the break-up of the Hatton Bank rifted margin, NE Atlantic
2008-01-01
The Hatton Bank margin, flanking the Iceland Basin, is an example of a volcanic rifted margin and has been studied to examine the along margin tectono-magmatic variability. Integration of 5660km of new seismic reflection profiles with
Tracking Melt Injection in Iceland with Earthquakes.
DescriptionUnderstanding the way in which melt generated deep in the underlying mantle is injected into the lower crust and then moves by stages to a shallow magma chamber before eruption is a crucial part of understanding the creation of igneous crust. Iceland is a classic igneous island generated by rifting above the Iceland mantle plume. Over several years of fieldwork, we have mapped thousands of local earthquakes which delineate shallow (c. 5 km depth) magma chambers under the most active Icelandic v [continued...]
Geothermal Resources in Iceland
This website provides an overview of geothermal resources in Iceland, focusing specifically on heating and electricity plans in Reykajavik. Topics include the history of geothermal sources of energy in Iceland, how the plant works, geothermal resources in Iceland, output and distribution, economy and investments, and research and outlook for future developments. The content includes detailed information about the geologic setting of the geothermal areas and the mechanics of the geothermal energy plant in Reykjavik. This site also provides a link to statistical figures on geothermal district heating systems in Iceland under the "District Energy in Iceland" link.
Tracking melt injection under the Mid-Atlantic Rift near Askja, central Iceland
2009-10-22
Objectives(1) To map the locations, temporal movement, size and fault plane mechanisms of small (magnitude DescriptionThe crust of the large oceanic island of Iceland in the North Atlantic is formed almost entirely from successive volcanic eruptions which fill the gap caused by the separation (rifting) of the plates on which North America and Europe sit. The massive volcanism in Iceland is caused by the deep mantle there being hotter than normal, and so melting more than normal to produce large amounts of molten rock, or magma. Although the melt is formed in the deep mantle at depths of 40-100 kilometres, i [continued...]
2010-01-01
We studied fracture-controlled geothermal fields in the Hreppar Rift-Jump Block (HRJB), a micro-plate bounded by two NNE rifts and the E-W transform zone of the South Iceland Seismic Zone (SISZ). Distinguishing whether the extensional rift swarm or the transform zone shear fractures host the geothermal activity is challenging. GPS mapping of 208 springs and tectonic analysis indicate that six Riedel shear fracture sets of an older transform zone in the HRJB are permeable. Northerly dextral strike-slip faults are the principal permeable faults, although the highest discharge and temperature are found at their intersections with other fracture sets. Two northerly faults from the HRJB connect to the source faults of the major 1784 and 1896 earthquakes within the active SISZ. The 1784 earthqua...
Rhyolites at Kerlingarfjll, Iceland: the evolution and lifespan of silicic central volcanoes
2010-01-01
Kerlingarfjll central volcano is Icelands second largest outcrop of Quaternary rhyolite and is part of the Icelandic Western Rift Zone. Geochemical and Ar/Ar age data show that at least 21 different rhyolite eruptions have taken place at Kerlingarfjll over the last 350ka. Ar/Ar dating was carried out on samples of obsidian which showed variable reproducibility, illustrating the difficulty in dating young Icelandic volcanics. Nevertheless, reasonable estimates of eruption age have been derived for a number of eruptive units that are consistent with observed stratigraphy, enabling an understanding of the temporal evolution of Kerlingarfjll. Two rhyolite magma types are present. The first is an older, low-Nb rhyolite that was erupted episodically along a cryptic curved fracture sys...
Research Drilling on the Mid-Atlantic Ridge: IDDP Wells of Opportunity at Reykjanes, Iceland
There are some 10 new geothermal wells at Reykjanes, in SW-Iceland, being considered by the Iceland Deep Drilling Project (IDDP) as potential candidate wells of opportunity to explore for deep (4-5 km) supercritical fluids. The drill field is located where the Mid-Atlantic Ridge emerges from the Atlantic ocean at the tip of the Reykjanes Peninsula. The site is an ideal locality for a combined study on the evolution of a rifted oceanic crust and an active black smoker-type geothermal system. However, the oceanic pillow basaltic crust at Reykjanes is some 2-3 times thicker than normal ocean floor crust, which undoubtedly relates to it being part of the Icelandic Large Igneous Province. The deepest of the geothermal wells at Reykjanes is Drillhole RN-17, that was completed to 3082 m depth in February 2005. It is currently the prime candidate for deepening by the IDDP. The plan is to deepen it to 4 km in 2006, and to 5 km depth in 2007, with funding coming from Icelandic energy companies (Hitaveita Sudurnesja, Landsvirkjun and Orkuveita Reykjavikur), the Government of Iceland, the International Scientific Continental Drilling Program (ICDP) and the US National Science Foundation (NSF). The well RN-17 was drilled as a conventional production well with a 12 inch drillbit to 3082 m depth, and left barefoot, with a 13 3/8 inch production casing cemented down to 900 m. It will be flow tested this autumn. If the RN-17 well is selected by the IDDP for deepening, a 9 5/8 inch in casing will be cemented to 3081 m and drilling will be continued with an 8 inch tricone bit to 4 km in the autumn of 2006. The ICDP and NSF will fund spot coring for scientific studies in this depth interval and a second flow test would be performed in winter 2007. The following autumn, a 7 inch casing would be cemented to 4 km depth and then a 5 inch retrievable liner would be inserted to support a hybrid coring system to continuously core down to 5 km depth, retrieving HQ sized core. A third flow test would be carried out in 2008-2009. In RN-17 high-grade hydrothermal alteration occurs at shallower depth than in any other well at Reykjanes. This is revealed by the presence of widespread epidote, starting at only 312 m depth, that formed at temperature of ~ 250C. Near the bottom of the well, lower greenschist facies rock replacement of pillow basalts is locally complete, indicating alteration temperatures in the 300C to 350C range. On-going studies on hydrothermal minerals such as amphiboles, and on fluid inclusions, are adding details to these estimates. Direct temperature logging of the borehole has so far been hampered by an obstruction at 2100 m, a problem that is currently being dealt with. In the next few months, studies of the other wells on the Reykjanes Peninsula will be concluded and the candidate best suited for deepening will be selected. The operating company, Hitaveita Sudurnesja, is contracted to deliver some 100 MWe of new electric power to the market by mid-year 2006, a situation of primary concern at the moment. Three new production wells will be drilled at Reykjanes this autumn and early winter, adding 3 new potential wells of opportunity for IDDP to consider. As all the production wells at Reykjanes are of identical design, the technical planning for deepening a borehole to 4 km autumn 2006 is more or less independent of which of the available wells is selected for deepening. http://www.icdp-online.org/sites/iceland/news/
The Health Protection Agency and Health Protection Scotland used existing syndromic surveillance systems to monitor community health in the UK following the volcanic eruption in Iceland in April 2010.
DescriptionAskja (1,516 m) is a prominent central volcano in Iceland. It is the locus of activity on the ~20-km-wide and ~100-km-long Askja volcanic system in North Iceland and is traversed by a fissure swarm striking 520 degrees. The volcanic edifice, mostly constructed from
A system of northwest striking Neoproterozoic rift basins underlies Paleozoic strata in the southern Georgina Basin of central Australia. Normal faults bounding these rift basins were selectively reactivated during the mid-Paleozoic Alice Springs Orogeny and are now expressed as high-angle reverse faults that invert the preexisting rift basins. Exhumed and eroded rift basin remnants are present in the hanging wall of the Oomoolmilla, Lucy Creek, Tarlton, and Toomba reverse faults, and rift basins may be preserved in the subsurface beneath the Toko Syncline and Burke River Structural Belt. Rift basin fill indicates two periods of extension: a major rift-forming episode between approximately 700 and 650 Ma (coeval with Sturtian glacial deposits) and a second episode of extension at approximately 600 Ma (coeval with Marinoan glacial deposits). This northwest striking rift system in central Australia supports results from other regions, indicating that the Neoproterozoic continental margin of Australia consisted of northwest striking rift segments offset by northeast striking transform faults. Such a configuration is geometrically incompatible with a Laurentian continental margin consisting of northeast striking rift segments and conflicts with reconstructions such as SWEAT and AUSWUS that match Australia with western Laurentia in the Rodinia supercontinent.
Usage of an early warning and information system Web-site for real-time seismicity in Iceland
2008-01-01
Iceland has been subjected to destructive earthquakes and volcanic eruptions throughout history. Such events are often preceded by changes in earthquake activity over varying timescales. Although most seismicity is confined to micro-earthquakes, large earthquakes have occurred within populated regions. Following the most recent hazardous earthquakes in 2000, the Icelandic Meteorological Office (IMO) developed an early warning and information system (EWIS) Web-site for viewing near-real-time seismicity in Iceland. Here we assess Web-site usage data in relation to earthquake activity, as recorded by the South Iceland Lowland (SIL) seismic network. Between March 2005 and May 2006 the SIL seismic network recorded 12,583 earthquakes. During this period, the EWIS Web-site logged a daily median o...
Major geothermal areas occur in regions of normal faulting and accompanying volcanic activity caused by tectonic tension. Specifically they are associated with (1) Quaternary volcanic centers in structures caused by volcanic processes, (2) Quaternary volcanic centers in structures caused by tectonic processes, (3) Cenozoic tectonism producing hinterland fault block structures, (4) Cenozoic rift zones, (5) Cenozoic tectonism in hinterland basins, and (6) foreland and platform areas. Descriptions are given of the fault patterns for the Geysers, Larderello and Monte Amiata, Wairakei and Broadlands, Imperial Valley, Cerro Prieto and Pathe, Matsukawa and Otake, Pauzhetsk, Yellowstone Park, Iceland, and Long Valley. 19 figures (LBS)
1975-12-01
Major geothermal areas occur in regions of normal faulting and accompanying volcanic activity caused by tectonic tension. Specifically they are associated with (1) Quaternary volcanic centers in structures caused by volcanic processes, (2) Quaternary volcanic centers in structures caused by tectonic processes, (3) Cenozoic tectonism producing hinterland fault block structures, (4) Cenozoic rift zones, (5) Cenozoic tectonism in hinterland basins, and (6) foreland and platform areas. Descriptions are given of the fault patterns for the Geysers, Larderello and Monte Amiata, Wairakei and Broadlands, Imperial Valley, Cerro Prieto and Pathe, Matsukawa and Otake, Pauzhetsk, Yellowstone Park, Iceland, and Long Valley. 19 figures (LBS)
2010-01-01
Shear wave splitting analysis using SKS, SKKS and S waveforms recorded at eight broadband seismic stations within and in the vicinity of the Proterozoic Godavari rift system in the south Indian shield yielded 104 new measurements of azimuthal anisotropy. Our results reveal that the delay times lie between 0.70 and 1.20s, similar to the previous measurements from the Indian shield. The orientations of fast polarization directions at most of the stations within and beyond the rift are generally aligned orthogonal to the rift axis, consistent with asthenospheric flow in the extension direction. Absence of clear evidences for a preferentially thinner lithosphere beneath the Godavari rift or anomalously high heat flow values coupled with the fact that the NE oriented fast polarization direction...
The NASA Ames Ecosystem Science and Technology Branch and the U.S. Army Medical Research Institute of Infectious Diseases are conducting research to detect Rift Valley fever (RVF) vector habitats in ...
The Icelandic Bank collapse: challenges to governance and risk management
2010-01-01
Purpose - The purpose of this paper is to examine the extreme case of the Icelandic banking crisis in relation to critical governance issues at governmental, industry and civil society levels. Design/methodology/approach - This is a case study of the Icelandic banking collapse in 2008. Findings - The examination of governance failures within the Icelandic banking system reveals that government institutions need to find a balance between entrepreneurial growth, risk exposure and sustainable societal development. A euphoric attitude of laissez-faire, where risk issues and issues of balanced development are largely ignored, creates challenges for sustainable banking. The findings suggest that achieving the necessary balance requires stressing governance issues on three levels; at the governme...
Numerical modeling of geothermal systems with applications to Krafla, Iceland and Olkaria, Kenya
The use of numerical models for the evaluation of the generating potential of high temperature geothermal fields has increased rapidly in recent years. In the present paper a unified numerical approach to the modeling of geothermal systems is discussed and the results of recent modeling of the Krafla geothermal field in Iceland and the Olkaria, Kenya, are described. Emphasis is placed on describing the methodology using examples from the two geothermal fields.
Numerical modeling of geothermal systems with applications to Krafla, Iceland and Olkaria, Kenya
The use of numerical models for the evaluation of the generating potential of high temperature geothermal fields has increased rapidly in recent years. In the present paper a unified numerical approach to the modeling of geothermal systems is discussed and the results of recent modeling of the Krafla geothermal field in Iceland and the Olkaria, Kenya, are described. Emphasis is placed on describing the methodology using examples from the two geothermal fields.
Numerical modeling of geothermal systems with applications to Krafla, Iceland and Olkaria, Kenya
1987-08-01
The use of numerical models for the evaluation of the generating potential of high temperature geothermal fields has increased rapidly in recent years. In the present paper a unified numerical approach to the modeling of geothermal systems is discussed and the results of recent modeling of the Krafla geothermal field in Iceland and the Olkaria, Kenya, are described. Emphasis is placed on describing the methodology using examples from the two geothermal fields.
Ground radan survey of a geothermal area in Hawaii
1980-04-01
Rates of ground radon emanation, in the Puna geothermal area on the lower east rift of Kilauea volcano, were measured by alpha particle sensitive cellulose nitrate films. The survey successfully defined an area of thermal significance associated with the rift structure, and suggests that a thermally driven ground gas convection system exists within, and peripheral to, the rift. This type of survey was found suitable for the basaltic island environmnet characteristic of Hawaii and is now used in Hawaii as a routine geothermal exploration technique.
Exploring magmatic plumbing systems in rift environments: Kula, Turkey
2008-12-31
DescriptionContinental rifting results in melting of the mantle, with subsequent volcanism. The ways in which the mantle melts move upwards through the rifting crust are not known, and in particular we know little about the likelihood that these small amounts of melt will get trapped temporarily in crustal magma chambers. The way to answer these questions is to look at fragments of partially crystallised material broken from the magma chamber margins, or the walls of the magmatic conduits, and subsequentl [continued...]
Regional geophysical setting of the Rio Grande rift
1978-07-01
The Rio Grande rift encompasses uplifts of the southern Rocky Mountains and their southern extension as well as axial fault blocks. The rift widens irregularly southward from a narrow horst in Colorado into a broad collapsed vault, characterized by grabens, in southern New Mexico. Whether manifested by horsts or grabens, primarily extensional strain is involved which increases in magnitude southward. Extensional faulting along the rift occurred in Neogene to Quaternary time, but the rift follows an axis of Laramide, Pennsylvanian, and possibly earlier uplifts. Gravity gradients due to the low density of graben fill delineate major faults of the rift system, which show a gridded or en echelon pattern over distances of tens of kilometers. Aeromagnetic data show these faults to be aligned with basement structural grain. Zigzags hundreds of kilometers long in the trend of the rift may also be related to basement grain. Basement trends in the Colorado Plateau to the west seem to differ in direction from those in the High Plains to the east. Seismic data also show that the rift occurs in an area of transition between anomalous crustal and upper mantle structure typical of the Cordillera and crustal structure typical of the High Plains. Deep seismic data are sparse within the rift, but high heat flow, high elevation, high electrical conductivity, and both residual positive (shallow source) and negative (deep source) gravity anomalies suggest the presence of symmetrical anomalous crustal and upper-mantle structure along the axis of the rift. In the Socorro area, where the rift has been studied intensively, available data indicate relatively low compressional velocity, rapid Holocene uplift, and the presence of magma within the crust. In view of geomorphic evidence for widespread Holocene faulting, the seismicity of the rift is surprisingly low.
Mid-Continent rift system - a frontier hydrocarbon province
1983-08-01
Geophysical evidence in the Mid-Continent has led to delineation of a rift system active during the Proterozoic Y Era. The Mid-Continent rift system can be traced by the Mid-Continent gravity high and corresponding aeromagnetic anomaly signature from the surface exposure of the Keweenawan Supergroup in the Lake Superior basin southwest in the subsurface through Wisconsin, Minnesota, Iowa, Nebraska, and Kansas. The aeromagnetic anomaly signature of the rift trend discloses where these sediments have been preserved. Thick accumulations of upper Proterozoic sediments are indicated by both upward continuation of the aeromagnetic profiles across the rift trend and gravity models which incorporate: 1) a deep mafic body to create the narrow gravity high, 2) anomalously thick crust to account for the more regional gravity low, and 3) sedimentary accumulations on the Precambrian surface to explain the small-scale notches which occur within the narrow gravity high. Reflection seismic data are virtually unknown in the rift area; however, data recently acquired by COCORP across the southern end of the feature in Kansas provide evidence of thick stratified sequences in the rift valley. Studies of the East African rift have revealed that the tropical rift valley is an exceptionally fertile environment for deposition and preservation of kerogenous material. The Sirte, Suez, Viking, Dnieper-Donetz, and Tsaidam basins are just a few of the rift basins currently classed as giant producers. The existence of a rift basin trend with thick accumulations of preserved sediments, demonstrably organic rich, introduces the northern Mid-Continent US as a new frontier for hydrocarbon exploration.
A novel hyperthermophilic strictly chemolithoautotrophic member of the genus Methanococcus was isolated from a shallow (depth: 106 m) submarine vent system at the Kolbeinsey ridge, Iceland. The isolate grew ...
Hydrothermal alteration of basalts from Hawaii Geothermal Project Well-A, Kilauea, Hawaii
1978-07-01
Mineralogical examination of basaltic rocks obtained during drilling of a successful 1,962-m-deep geothermal well (HGP-A) in the east rift zone of Kilauea Volcano, Hawaii, reveals three zones of hydrothermal alteration beneath a zone of unaltered lavas. Each alteration zone is characterized by the dominance of a particular mineral: zone 1, montmorillonite; zone 2, chlorite; zone 3, actinolite. Three zones of relative permeability can be tentatively identified on the basis of filled versus partly filled vesicles and fractures. Because the well has not returned to thermal equilibrium as of this writing, stability relations between secondary minerals and temperatures cannot be calculated with accuracy. However, the latest downhole temperatures measured at the boundaries of alteration zones, compared with similar data from high-temperature geothermal areas in Iceland, indicate that HGP-A temperatures are considerably higher than those encountered for the same alteration-zone boundaries in Icelandic wells. This indicates that the present-day thermal regime in HGP-A is relatively young and that the hydrothermal minerals probably have not reached equilibrium with existing conditions.
2009-07-01
The NE Rift of Tenerife is an excellent example of a persistent, recurrent rift, providing important evidence of the origin and dynamics of these major volcanic features. The rift developed in three successive, intense and relatively short eruptive stages (a few hundred ka), separated by longer periods of quiescence or reduced activity: A Miocene stage (7266 {+-}156 ka), apparently extending the central Miocene shield of Tenerife towards the Anaga massif; an Upper Pliocene stage (2710{+-} 58 ka) and the latest stage, with the main eruptive phase in the Pleistocene. Detailed geological (GIS) mapping, geomagnetic reversal mapping and stratigraphic correlation, and radioisotopic (K/Ar) dating of volcanic formations allowed the reconstruction of the latest period of rift activity. In the early phases of this stage the majority of the eruptions grouped tightly along the axis of the rift and show reverse polarity (corresponding to the Matuyama chron). Dykes are of normal and reverse polarities. In the final phase of activity, eruptions are more disperse and lavas and dykes are consistently of normal polarity (Brunhes chron). Volcanic units of normal polarity crossed by dykes of normal and reverse polarities yield ages apparently compatible with normal subchrons (M-B Precursor and Jaramillo) in the Upper Matuyama chron. Three lateral collapses successively mass-wasted the rift: The Micheque collapse, completely concealed by subsequent nested volcanism, and the Guimar and La Orotava collapses, that are only partially filled. Time occurrence of collapses in the NE rift apparently coincides with glacial stages, suggesting that giant landslides may be finally triggered by sea level chan-ges during glaciations. Pre-collapse and nested volcanism is predominantly basaltic, except in the Micheque collapse, where magmas evolved towards intermediate and felsic (trachytic) compositions. Rifts in the Canary Islands are long-lasting, recurrent features, probably related to primordial, plume-related fractures acting throughout the entire growth of the islands. Basaltic volcanism forms the bulk of the islands and rift zones. However, collapses of the flanks of the rifts disrupt their established fissural feeding system, frequently favouring magma accumulation and residence at shallow emplacements, leading to differentiation of magmas, and intermediate to felsic nested eruptions. Rifts and their collapse may therefore act as an important factor in providing petrological variability to oceanic volcanoes. Conversely, the possibility exists that the presence of important felsic volcanism may indicate lateral collapses in oceanic shields and ridge-like volcanoes, even if they are concealed by post-collapse volcanism or partially mass-wasted by erosion. (Author) 76 refs.
Geophysical characteristics of the hydrothermal systems of Kilauea volcano, Hawaii
1993-08-01
Clues to the structure of Kilauea volcano can be obtained from spatial studies of gravity, magnetic, and seismic velocity variations. The rift zones and summit are underlain by dense, magnetic, and seismic velocity variations. The rift zones and summit are underlain by dense, magnetic, high P-wave-velocity rocks at depths of about 2 km less. The gravity and seismic velocity studies indicate that the rift structures are broad, extending farther to the north than to the south of the surface features. The magnetic data allow separation into a narrow, highly-magnetized, shallow zone and broad, flanking, magnetic lows. The patterns of gravity, magnetic variations, and seismicity document the southward migration of the upper east rift zone. Regional, hydrologic features of Kilauea can be determined from resistivity and self-potential studies. High-level groundwater exists beneath Kilauea summit to elevations of +800 m within a triangular area bounded by the west edge of the upper southwest rift zone, the east edge of the upper east rift zone, and the Koa'e fault system. High-level groundwater is present within the east rift zone beyond the triangular summit area. Self-potential mapping shows that areas of local heat produce local fluid circulation in the unconfined aquifer (water table). Shallow seismicity and surface deformation indicate that magma is intruding and that fractures are forming beneath the rift zones and summit area. Heat flows of 370--820 mW/m[sup 2] are calculated from deep wells within the lower east rift zone. The estimated heat input rate for Kilauea of 9 gigawatts (GW) is at least 25 times higher than the conductive heat loss as estimated from the heat flow in wells extrapolated over the area of the summit caldera and rift zones. 115 refs., 13 figs., 1 tab.
Shell and Norsk Hydro have opened the world's first hydrogen station in Iceland
2003-07-01
The world's first hydrogen refueling station for cars and buses was opened in Iceland in April 2003. It was opened at an existing commercial fuel retail site in Reykjavik. The Shell station was constructed using Norsk Hydro's hydrogen technology. The operation of the hydrogen station is part of ECTOS (Ecological City TranspOrt System ), a project supported by the EU designed to investigate the socio-economic and environmental implications of changing the energy base. The hydrogen is produced from water on site by electrolysis. The electricity used in the electrolysis process is obtained fro Iceland's natural geothermal and hydroelectric energy sources.
2008-01-01
Reconstructing climate change quantitatively over millennial timescales is crucial for understanding the processes that affect the climate system. One of the best methods for producing high resolution, low error, quantitative summer air temperature reconstructions is through chironomid analyses. We analysed over 50 lakes from NW and W Iceland covering a range of environmental gradients in order to test whether the distribution of the Icelandic chironomid fauna was driven by summer temperature, or whether other environmental factors were more dominant. A range of analyses showed the main environmental controls on chironomid communities to be substrate (identified through loss-on-ignition and carbon content) and mean July air temperature, although other factors such as lake depth and lake ar...
Field Studies of Geothermal Reservoirs Rio Grande Rift, New Mexico
The Rio Grande rift provides an excellent field laboratory to study the nature of geothermal systems in an extensional environment. Much of the geologic complexity that is found in the Basin and Range is absent because the rift is located on cratonic crust with a thin and well-characterized Phanerozoic stratigraphy and tectonic history. On the other hand, the Neogene thermo-tectonic history of the rift has many parallels with the Basin and Range to the west. The geology of the southern Rio Grande rift is among the best characterized of any rift system in the world. Also, most geologic maps for the region are rather unique in that detailed analyses of Quaternary stratigraphic and surficial unit are added in concert with the details of bedrock geology. Pleistocene to Holocene entrenchment of the Rio Grande and tributaries unroofs the alteration signatures and permeability attributes of paleo outflow plumes and upflow zones, associated with present-day, but hidden or ''blind,'' hydrothermal systems at Rincon and San Diego Mountain.
Structural evolution of the Orange Basin gravity-driven system, offshore Namibia
2010-01-01
The Orange Basin records the development of the Late Jurassic to present day volcanic-rifted passive margin of Namibia. Regional extension is recorded by a Late Jurassic to Lower Cretaceous Syn-rift Megasequence, which is separated from a Cretaceous to present day post-rift Megasequence by the Late Hauterivian (ca. 130Ma) break-up unconformity. The Late Cretaceous Post-rift evolution of the basin is characterized by episodic gravitational collapse of the margin. Gravitational collapse is recorded as a series of shale-detached gravity slide systems, consisting of an up-dip extensional domain that is linked to a down-dip zone of contraction domain along a thin basal detachment of Turonian age. The extensional domain is characterized by basinward-dipping listric faults that sole into the basa...
Petroleum system in deepwater basins of the northern South China Sea
2009-01-01
The northern South China Sea margin has experienced a rifting stage and a post-rifting stage during the Cenozoic. In the rifting stage, the margin received lacustrine and shallow marine facies sediments. In the post-rifting thermal subsidence, the margin accumulated shallow marine facies and hemipelagic deposits, and the deepwater basins formed. Petroleum systems of deepwater setting have been imaged from seismic data and drill wells. Two kinds of source rocks including Paleogene lacustrine black shale and Oligocene-Early Miocene mudstone were developed in the deepwater basin of the South China Sea. The deepwater reservoirs are characterized by the deep sea channel fill, mass flow complexes and drowned reef carbonate platform. Profitable capping rocks on the top are mudstones with huge thi...
Integrated seismic and subsidence analysis of conjugate margin systems in the Eastern Black Sea.
2007-11-17
DescriptionWe propose to test depth-dependent stretching models of highly extended lithosphere at rifted margins by determining stretching factors and strain rates using a combination of seismic imaging and state-of-the-art inverse modelling of subsidence data. Our analysis will focus on conjugate margins in the Eastern Black Sea basin, where a rapid sediment supply has ensured that post-rift subsidence is better constrained than on most rifted margins. Forward and inverse modelling of wide-angle seismic d [continued...]
Integrated seismic and subsidence analysis of conjugate margin systems in the Eastern Black Sea.
2007-11-29
DescriptionWe propose to test depth-dependent stretching models of highly extended lithosphere at rifted margins by determining stretching factors and strain rates using a combination of seismic imaging and state-of-the-art inverse modelling of subsidence data. Our analysis will focus on conjugate margins in the Eastern Black Sea basin, where a rapid sediment supply has ensured that post-rift subsidence is better constrained than on most rifted margins. Forward and inverse modelling of wide-angle seismic d [continued...]
2010-01-01
High resolution multibeam (EM300 and SEABEAM) data of the Southern Havre Trough (SHT), combined with observations and sample collections from the submersible Shinkai6500 and deep-tow camera, are used to develop a model for the evolution and magmatism of this backarc system. The Havre Trough and the associated Kermadec Arc are the product of westward subduction at the PacificAustralian plate boundary. Detailed studies focus on newly discovered features including a seamount (Saito Seamount) and a deep graben (Ngatoroirangi Rift,
2006-12-15
In this final report, we discuss both theoretical and applied research resulting from our DOE project, ICEKAP 2004: A Collaborative Joint Geophysical Imaging Project at Krafla and IDDP. The abstract below begins with a general discussion of the problem we addressed: the location and characterization of blind geothermal resources using microearthquake and magnetotelluric measurements. The abstract then describes the scientific results and their application to the Krafla geothermal area in Iceland. The text following this abstract presents the full discussion of this work, in the form of the PhD thesis of Stephen A. Onacha. The work presented here was awarded the Best Geophysics Paper at the 2005 Geothermal Resources Council meeting, Reno. This study presents the modeling of buried fault zones using microearthquake and electrical resistivity data based on the assumptions that fluid-filled fractures cause electrical and seismic anisotropy and polarization. In this study, joint imaging of electrical and seismic data is used to characterize the fracture porosity of the fracture zones. P-wave velocity models are generated from resistivity data and used in locating microearthquakes. Fracture porosity controls fluid circulation in the hydrothermal systems and the intersections of fracture zones close to the heat source form important upwelling zones for hydrothermal fluids. High fracture porosity sites occur along fault terminations, fault-intersection areas and fault traces. Hydrothermal fault zone imaging using resistivity and microearthquake data combines high-resolution multi-station seismic and electromagnetic data to locate rock fractures and the likely presence fluids in high temperature hydrothermal systems. The depths and locations of structural features and fracture porosity common in both the MT and MEQ data is incorporated into a joint imaging scheme to constrain resistivity, seismic velocities, and locations of fracture systems. The imaging of the fault zones is constrained by geological, drilling, and geothermal production data. The objective is to determine interpretation techniques for evaluating structural controls of fluid circulation in hydrothermal systems. The conclusions are: directions of MT polarization and anisotropy and MEQ S-splitting correlate. Polarization and anisotropy are caused by fluid filled fractures at the base of the clay cap. Microearthquakes occur mainly on the boundary of low resistivity within the fracture zone and high resistivity in the host rock. Resistivity is lowest within the core of the fracture zone and increases towards the margins of the fracture zone. The heat source and the clay cap for the hydrothermal have very low resistivity of less than 5m. Fracture porosity imaged by resistivity indicates that it varies between 45-5% with most between 10-20%, comparable to values from core samples in volcanic areas in Kenya and Iceland. For resistivity values above 60m, the porosity reduces drastically and therefore this might be used as the upper limit for modeling fracture porosity from resistivity. When resistivity is lower than 5m, the modeled fracture porosity increases drastically indicating that this is the low resistivity limit. This is because at very low resistivity in the heat source and the clay cap, the resistivity is dominated by ionic conduction rather than fracture porosity. Microearthquakes occur mainly above the heat source which is defined by low resistivity at a depth of 3-4.5 km at the Krafla hydrothermal system and 4-7 km in the Longonot hydrothermal system. Conversions of S to P waves occur for microearthquakes located above the heat source within the hydrothermal system. Shallow microearthquakes occur mainly in areas that show both MT and S-wave anisotropy. S-wave splitting and MT anisotropy occurs at the base of the clay cap and therefore reflects the variations in fracture porosity on top of the hydrothermal system. In the Krafla hydrothermal system in Iceland, both MT polarization and MEQ splitting directions align with zones that have high fracture porosity below the clay cap. These zones coincide with fault zones trending in the NNE-SSW and NW-SE directions in otherwise uniform volcanic rocks and laterally continuous geology. The NW-SE orientation is parallel to the regional shear fractures while the NNE-SSW trending polarizations align parallel to rift zone fracture swarms. This suggest that correlations between MT polarizations and MEQ splitting may be related to fluid filled fractures. In areas of high resistivity (60m), the P-wave velocity approaches that of the rock matrix. S-wave splitting polarization is determined from measurements of angles of rotation to get the optimum direction of polarization. The use of MEQ and resistivity for imaging fractures requires that the MEQ data acquisition system be located close to the fracture zone.
Episodic rifting and subsidence in the South China sea
1986-09-01
The South China Sea experienced at least three stages of rifting and two intervening stages of sea-floor spreading since the Early Cretaceous. Its evolution can be described by an episodic model of tectonism, one of thermal cooling and subsidence, pulsed by temporally and spatially confined heating events. Analysis of regional geologic and geophysical data suggests episodes of rifting and associated thermal activities initiated during the Late Cretaceous, the late Eocene, and the late early Miocene. The rift system corresponding to the first episode trends northeast-southwest, whereas those of the second and third trend east-west. These two trends coincide with the orientations of the major tectonic lineations within the basin. Age estimates from heat-flow and bathymetric data suggest the oceanic crust in the Southwest subbasin is considerably older (55 Ma) than that in the Northwest (35-36 Ma) or East (32 Ma) subbasins. In terms of hydrocarbon potential, the episodes of rifting and drifting would be conducive to the development of overprinted structures and the deposition of several discrete transgressive packages of source rocks and reservoirs, separated by widespread unconformities. The thermal maturity of sedimentary organic matter affected by episodic rifting and subsidence may be greater than expected on a purely passive margin of equivalent age that had not experienced repeated heating. 21 figures.
2008-08-31
ObjectivesThe primary objective of this proposal is to develop a state-of-the-art modelling framework to predict the transport behaviour of fluoride in representative volcanic soils of Iceland under a range of volcanogenic deposition conditions. Specifically, the strategy to reach this objective will involve three complementary tasks: (i) Experimental determination of the effect of temperature, pH, ionic strength and competitive anion (i.e., sulphate) concentration on fluoride adsorption on a series of [continued...]DescriptionAround 225 years ago, 10,000 Icelanders - roughly one in five - died and most of the livestock on the island perished. This catastrophe, the greatest to affect Iceland since human occupation began, was caused by the awakening of a volcanic fissure system, known as Lakakigar. During several months, Lakakigar erupted prodigious quantities of noxious acidic gases and particles into the air, and fluoride was a conspicuous part of these emissions. Fluoride is renowned for its harmful effects on plant [continued...]
The July 1978 deflation of the Krafla volcano in the volcanic rift zone of NE-Iceland was in most respects typical of the many deflation events that have occurred at Krafla since December 1975. Separated by periods of slow inflation, the deflation events are characterized by rapid subsidence in the caldera region, volcanic tremor and extensive rifting in the fault swarm that transects the volcano. Earthquakes increase in the caldera region shortly after deflation starts and propagate along the fault swarm away from the central part of the volcano, sometimes as far as 65 km. The deflation events are interpreted as the result of subsurface magmatic movements, when magma from the Krafla reservoir is injected laterally into the fault swarm to form a dyke. In the July 1978 event magma was injected a total distance of 30 km into the northern fault swarm. The dyke tip propagated with the velocity of 0.4-0.5 m/sec during the first 9 hours, but the velocity decreased as the length of the dyke increased. Combined with surface deformation data, these data can be used to estimate the cross sectional area of the dyke and the driving pressure of the magma. The cross sectional area is variable along the dyke and is largest in the regions of maximum earthquake activity. The average value is about 1200 m{sup 2}. The pressure difference between the magma reservoir and the dyke tip was of the order of 10-40 bars and did not change much during the injection.
1978-07-01
The July 1978 deflation of the Krafla volcano in the volcanic rift zone of NE-Iceland was in most respects typical of the many deflation events that have occurred at Krafla since December 1975. Separated by periods of slow inflation, the deflation events are characterized by rapid subsidence in the caldera region, volcanic tremor and extensive rifting in the fault swarm that transects the volcano. Earthquakes increase in the caldera region shortly after deflation starts and propagate along the fault swarm away from the central part of the volcano, sometimes as far as 65 km. The deflation events are interpreted as the result of subsurface magmatic movements, when magma from the Krafla reservoir is injected laterally into the fault swarm to form a dyke. In the July 1978 event magma was injected a total distance of 30 km into the northern fault swarm. The dyke tip propagated with the velocity of 0.4-0.5 m/sec during the first 9 hours, but the velocity decreased as the length of the dyke increased. Combined with surface deformation data, these data can be used to estimate the cross sectional area of the dyke and the driving pressure of the magma. The cross sectional area is variable along the dyke and is largest in the regions of maximum earthquake activity. The average value is about 1200 m{sup 2}. The pressure difference between the magma reservoir and the dyke tip was of the order of 10-40 bars and did not change much during the injection.
Petroleum geology of Cretaceous-Tertiary rift basins in Niger, Chad, and Central African Republic
1993-08-01
This overview of the petroleum geology of rift basins in Niger, Chad, and Central African Republic (CAR) is based on exploration work by Exxon and partners in the years 1969-1991. The work included 50,000 km of modern reflection seismic, 53 exploration wells, 1,000,000 km[sup 2] of aeromagnetic coverage, and about 10,500 km of gravity profiles. The results outline ten Cretaceous and Tertiary rift basins, which constitute a major part of the West and Central African rift system (WCARS). The rift basins derive from a multiphased geologic history dating from the Pan-African (approximately 750-550 Ma) to the Holocene. WCARS in the study area is divided into the West African rift subsystem (WAS) and the Central African rift subsystem (WAS) and the Central African rift subsystem (CAS). WAS basins in Niger and Chad are chiefly extensional, and are filled by up to 13,000 m of Lower Cretaceous to Holocene continental and marine clastics. The basins contain five oil (19-43[degrees]API) and two oil and gas accumulations in Upper Cretaceous and Eocene sandstone reservoirs. The hydrocarbons are sourced and sealed by Upper Cretaceous and Eocene marine and lacustrine shales. The most common structural styles and hydrocarbon traps usually are associated with normal fault blocks. CAS rift basins in Chad and CAR are extensional and transtensional, and are filled by up to 7500 m of chiefly Lower Cretaceous continental clastics. The basins contain eight oil (15-39[degrees]API) and one oil and gas discovery in Lower and Upper Cretaceous sandstone reservoirs. The hydrocarbons are sourced by Lower Cretaceous shales and sealed by interbedded lacustrine and flood-plain shales. Structural styles range from simple fault blocks through complex flower structures. The main hydrocarbon traps are in contractional anticlines. Geological conditions favor the discovery of potentially commercial volumes of oil in WCARS basins, of Niger, Chad and CAR. 108 refs., 24 figs., 4 tabs.
The hydrogeology of Kilauea volcano
1993-08-01
The hydrogeology of Kilauea volcano and adjacent areas has been studied since the turn of this century. However, most studies to date have focused on the relatively shallow, low-salinity parts of the ground-water system, and the deeper hydrothermal system remains poorly understood. The rift zones of adjacent Mauna Loa volcano bound the regional ground-water flow system that includes Kilauea, and the area bounded by the rift zones of Kilauea and the ocean may comprise a partly isolated subsystem. Rates of ground-water recharge vary greatly over the area, and discharge is difficult to measure, because streams are ephemeral and most ground-water discharges diffusely at or below sea level. Hydrothermal systems exist at depth in Kilauea's east and southwest rift zone, as evidenced by thermal springs at the coast and wells in the lower east-rift zone. Available data suggest that dike-impounded, heated ground water occurs at relatively high elevations in the upper east- and southwest-rift zones of Kilauea, and that permeability at depth in the rift zones. Available data suggest that dike-impounded, heated ground water occurs at relatively high elevations in the upper east- and southwest-rift zones of Kilauea, and that permeability at depth in the rift zones (probably [le]10[sup [minus]15] m[sup 2]) is much lower than that of unaltered basalt flows closer to the surface ([ge]10[sup [minus]10] m[sup 2]). Substantial variations in permeability and the presence of magmatic heat sources influence that structure of the fresh water-salt water interface, so the Ghyben-Herzberg model will often fail to predict its position. Numerical modeling studies have considered only subsets of the hydrothermal system, because no existing computer code solves the coupled fluid-flow, heat- and solute-transport problem over the temperature and salinity range encountered at Kilauea. 73 refs., 7 figs., 2 tabs.
Fractionation of Boron Isotopes in Icelandic Hydrothermal Systems
1995-01-01
Boron isotope ratios have been determined in a variety of different geothermal waters from hydrothermal systems across Iceland. Isotope ratios from the high temperature meteoric water recharged systems reflect the isotope ratio of the host rocks without any apparent fractionation. Seawater recharged geothermal systems exhibit more positive {delta}{sup 11}B values than the meteoric water recharged geothermal systems. Water/rock ratios can be assessed from boron isotope ratios in the saline hydrothermal systems. Low temperature hydrothermal systems also exhibit more positive {delta}{sup 11}B than the high temperature systems, indicating fractionation of boron due to adsorption of the lighter isotope onto secondary minerals. Fractionation of boron in carbonate deposits may indicate the level of equilibrium attained within the systems.
2004-07-01
The facies analysis of the stratigraphic interval represented by Sergi, Itaparica, and Agua Grande formations (Brotas and Santo Amaro groups) of Reconcavo basin was guided by cores description of the well 1-CAL-1-BA (Caldeirao 1), located in the Northwestern part of the Reconcavo Basin. Sedimentary facies (lithofacies) were described and grouped into four facies association interpreted as fluvial (upper Sergi Fm.), fluvial-lacustrine (Itaparica Fm.), and fluvial-eolian (Agua Grande Fm.) depositional systems; also, forced-regression erosive surfaces (unconformities) and transgressive ones were identified. The analysis of these results points that the upper Sergi Fm. would have subsided as consequence of the early rifting of the basin, creating space for the formation of shallow lake (Itaparica Fm.). This ancient lake undergone several forced regressions due to a continuous early tectonism (rifting), responsible by the sand input into the lake, in a coarsening up cycle topped by the expressive fluvio-eolian system of the Agua Grande Fm. Each forced regression smaller cycle is capped by lake flooding shales. Above this major CU cycle, the intensification of tectonic event subsided the basin and created a deep lake (Candeias Fm.) - the Rift Phase. So, the initial rifting would not have started during a 'Candeias time', but by earlier, in a less intense way. It must be stressed that this interpretation was based solely in only one well, but it's important to keep this new idea in mind for revision or new studies on this interval. (author)
Rift basins of ocean-continent convergent margins
Modern and ancient circum-Pacific convergent margins contain many examples of forearc basins where subsidence, occurring simultaneously with subduction of oceanic lithosphere, is controlled by rifting transverse to the margin. The elongate axes of these deep and narrow basins jut obliquely from the plate margin into the interior of the forearc. Similar to aulacogens, faulting and related subsidence appear greatest at their seaward limits and decreases inland. Examples from eastern Pacific forearcs suggest that localized rifting accommodates margin-parallel extension of forearc blocks that are kinetically linked to motions along major margin-parallel strike-slip fault systems. The most prominent examples of modern forearc rift basins are the Sanak and East Sanak basins of the western Alaska Peninsula subduction zone. In this region, the continental shelf is being rifted apart by a series of northwest- and northeast-trending faults. Basement-activated normal faults bounding the basins have listric geometries. Seismostratigraphic relationships within the basins indicate the protracted, synsedimentary, and active nature of faulting and basin subsidence. Along the Peru-Chile trench, two prominent rifted basins also occur: the Gulf of Guayaquil and the Gulf of Penas-Taitao basin of southern Chile. There, margin-parallel rifting controls subsidence in localized basins at the southern terminus to margin-parallel dextral fault systems. These and other examples suggest that strike-slip motion and transverse rifting of forearcs is a common phenomenon inadequately described by existing two-dimensional models of forearcs. Margin-parallel motions of forearc blocks can be related not only to oblique plate convergence, but also to the geometric and compositional nature of the overriding and subducted plates.
Rift basins of ocean-continent convergent margins
1986-05-01
Modern and ancient circum-Pacific convergent margins contain many examples of forearc basins where subsidence, occurring simultaneously with subduction of oceanic lithosphere, is controlled by rifting transverse to the margin. The elongate axes of these deep and narrow basins jut obliquely from the plate margin into the interior of the forearc. Similar to aulacogens, faulting and related subsidence appear greatest at their seaward limits and decreases inland. Examples from eastern Pacific forearcs suggest that localized rifting accommodates margin-parallel extension of forearc blocks that are kinetically linked to motions along major margin-parallel strike-slip fault systems. The most prominent examples of modern forearc rift basins are the Sanak and East Sanak basins of the western Alaska Peninsula subduction zone. In this region, the continental shelf is being rifted apart by a series of northwest- and northeast-trending faults. Basement-activated normal faults bounding the basins have listric geometries. Seismostratigraphic relationships within the basins indicate the protracted, synsedimentary, and active nature of faulting and basin subsidence. Along the Peru-Chile trench, two prominent rifted basins also occur: the Gulf of Guayaquil and the Gulf of Penas-Taitao basin of southern Chile. There, margin-parallel rifting controls subsidence in localized basins at the southern terminus to margin-parallel dextral fault systems. These and other examples suggest that strike-slip motion and transverse rifting of forearcs is a common phenomenon inadequately described by existing two-dimensional models of forearcs. Margin-parallel motions of forearc blocks can be related not only to oblique plate convergence, but also to the geometric and compositional nature of the overriding and subducted plates.
1989-01-01
New K-Ar datings of a large rock sampling from the South Kivu volcanic province (Zaire, Rwanda, Burundi) are reported. No ages older than 10 Ma have been obtained. This result contrasts with older assumptions and puts severe constraints on the relations between volcanism and rift evolution. From 10 to 7.5 Ma tholeiitic volcanism predominates corresponding to an episode of fissural eruptions. From 7.5 to 5 Ma alkali basalts and their differentiates are mainly erupted in localized rifts. A culmination of activity occurs between 6.0 and 5.5 Ma ago. Pleistocene alkalic volcanism is restricted to localized areas. The transition from tholeiites to alkali-basaltic volcanism dated around 7.5 Ma would correspond to a major rifting phase which corresponds with the initiation of Lake Kivu Basin formation. The distribution of tholeiitic rocks in the central part of the rift, and ...
1998-01-01
The drainage system in Kenya is determined and influenced by the Great Rift Valley, running approximately from north to south. From the flanks of Rift Valley, surface water flows westwards towards Lake Victoria, and eastwards to the Indian Ocean, with the Rift Valley itself having an internal drainage system. The drainage system in Kenya is divided into five basins primarily on account of the topography and drainage of the country's major perennial rivers. The national annual water volume potential is estimated at 20,000 million m3, consisting of surface and groundwater with a projected annual water demand of 3,874 and 5, 817 million m3, respectively for the years 2000 and 2010. this implies that the demand by the year 2010 will be less than 30% of the total water resources potential. The quality and quantity of the groundwater in Kenya is extremely ...
Geothermal energy resource assessment of parts of Alaska. Final report
The central Seward Peninsula was the subject of a geological, geophysical and geochemical reconnaissance survey during a 30-day period in the summer of 1980. The survey was designed to investigate the geothermal energy resource potential of this region of Alaska. A continental rift system model was proposed to explain many of the Late Tertiary-to-Quaternary topographic, structural, volcanic and geothermal features of the region. Geologic evidence for the model includes normal faults, extensive fields of young alkalic basalts, alignment of volcanic vents, graben valleys and other features consistent with a rift system active from late Miocene time to the present. Five traverses crossing segments of the proposed rift system were run to look for evidence of structure and geothermal resources not evident from surface manifestation. Gravity, helium and mercury soil concentrations were measured along the traverses. Seismic, resistivity, and VLF studies are presented.
Geothermal energy resource assessment of parts of Alaska. Final report
1982-08-01
The central Seward Peninsula was the subject of a geological, geophysical and geochemical reconnaissance survey during a 30-day period in the summer of 1980. The survey was designed to investigate the geothermal energy resource potential of this region of Alaska. A continental rift system model was proposed to explain many of the Late Tertiary-to-Quaternary topographic, structural, volcanic and geothermal features of the region. Geologic evidence for the model includes normal faults, extensive fields of young alkalic basalts, alignment of volcanic vents, graben valleys and other features consistent with a rift system active from late Miocene time to the present. Five traverses crossing segments of the proposed rift system were run to look for evidence of structure and geothermal resources not evident from surface manifestation. Gravity, helium and mercury soil concentrations were measured along the traverses. Seismic, resistivity, and VLF studies are presented.
Isotopic constraints on ice age fluids in active geothermal systems: Reykjanes, Iceland
2009-01-01
The Reykjanes geothermal system is located on the landward extension of the Mid-Atlantic Ridge in southwest Iceland, and provides an on-land proxy to high-temperature hydrothermal systems of oceanic spreading centers. Previous studies of elemental composition and salinity have shown that Reykjanes geothermal fluids are likely hydrothermally modified seawater. However, dD values of these fluids are as low as -23permil, which is indicative of a meteoric water component. Here we constrain the origin of Reykjanes hydrothermal solutions by analysis of hydrogen and oxygen isotope compositions of hydrothermal epidote from geothermal drillholes at depths between 1 and 3km. dDEPIDOTE values from wells RN-8, -9, -10 and -17 collectively range from -60 to -78permil, and d18OEPIDOTE in these wells are...
Chemical transport in geothermal systems in Iceland:Evidence from hydrothermal alteration
2008-01-01
This study focuses on the chemical changes in basaltic rocks in fossil low- and high-temperature hydrothermal systems in Iceland. The method used takes into account the amount of dilution caused by vesicle and vein fillings in the rocks. The amount of dilution allows a calculation of the primary concentration of the immobile element Zr, and by multiplying the composition of the altered rock by the ratio of Zr (protolith)/Zr (altered rock) one can compute the mass addition caused by the dilution of the void fillings, and also make a direct comparison with the likely protoliths from the same areas. The samples were divided into three groups; two from Tertiary fossil high-temperature systems (Hafnarfjall, Geitafell), and the third group from a low temperature, zeolite-altered plateau basalt s...
Regional paleogeographic evolution of west Africa: Implications for hydrocarbon exploration
1991-03-01
New paleogeographic reconstructions of west African continental margins provide a regional framework to contrast differences in hydrocarbon habitat and tectonostratigraphic style. Five regional provinces are delineated: (1) Northwest Africa margin from mauritania to Sierra Leone, (2) Transform margin from Liberia to Benin, (3) Niger delta of Nigeria, Cameroon, and Equatorial Guinea, (4) South Atlantic Salt basin margin from Cameroon to Angola, and (5) Southwest Africa margin of Namibia and South Africa. Computer-constrained paleogeographic reconstructions based on exploration data depict the separation of west Africa from South and North America during the Late Triassic to the present along three rift systems. In northwest Africa rifting began in the Late Triassic associated with the opening of the Central Atlantic. In southwest Africa rifting began between the southern tips of Africa and South America in the Early Cretaceous (Valanginian) and propagated northward to the Benue Trough, a broad zone of left-lateral shear and extensional basins that began to open in the Aptian. Between these two rift systems, the Transform margin rift system initiated in the Early Cretaceous (Barremain) as a wrench-fault dominated eastward extension of the Proto-Caribbean ocean that propagated to the Benue Trough by the middle Albian. The most important variables affecting the tectonostratigraphic and hydrocarbon evolution of the west African margins include (1) the geometry, kinematics, and duration of rifting; (2) distribution of rift basins relative to paleoclimate zones (which affects the deposition of lacustrine source rocks and evaporites while influencing the type and quantity of sediment derived from land); (3) sea-level fluctuations; and (4) distribution of deltaic and turbiditic depocenters.
Regional paleogeographic evolution of West Africa: Implications for hydrocarbon exploration
1993-11-01
New paleogeographic reconstructions of west African continental margins provide a regional framework to contrast differences in hydrocarbon habitat and tectonostratigraphic style. The framework consists of five regional provinces: (1) northwest Africa margin from Mauritania to Sierra Leone, (2) transform margin from Libera to Benin, (3) Niger Delta of Nigeria, Cameroon, and equatorial Guinea, (4) South Atlantic Salt Basin margin from Cameroon to Angola, and (5) southwest Africa margin of Namibia and South Africa. Computer-constrained paleogeographic reconstructions based on exploration data depict the separation of west Africa from South and North America along three rift systems during the Late Triassic to the Holocene. In northwest Africa, rifting began in the Late Triassic associated with the opening of the central Atlantic. In southwest Africa, rifting began between the southern tips of Africa and South America in the Early Cretaceous and propagated northward to the Benue trough, a broad zone of left-lateral shear and extensional basins that began to open in the Aptian. Between these two rift systems, the transform margin rift system initiated in the Early Cretaceous (Barremian) as a wrench-fault-dominated eastward extension of the Proto-Caribbean ocean that propagated to the Benue trough by the middle Albian. The most important variables affecting the tectonostratigraphic and hydrocarbon evolution of the west African margins include (1) the geometry, kinematics, and duration of rifting, (2) distribution of rift basins relative to paleoclimate zones (which affects the deposition of lacustrine source rocks and evaporites while influencing the type and quantity of sediment derived from land), (3) sea level fluctuations, and (4) distribution of deltaic and turbiditic depocenters.
Petroleum system of the Shelf Rift Basin, East China Sea
1996-12-31
The Tertiary section of the Oujioang and Quiontang Depressions of the East China Sea Basin consists of at least eight rift-related depositional sequences identified seismically by regionally significant onlap and truncation surfaces. These sequences are calibrated by several wells including the Wenzhou 6-1-1 permitting extrapolation of petroleum system elements using seismic facies analysis. Gas and condensate correlated to non-marine source rocks and reservoired in sandstone at the Pinghu field to the north of the study area provides an known petroleum system analogue. In the Shelf Rift Basin, synrift high-amplitude parallel reflections within the graben axes correlate with coaly siltstone strata and are interpreted as coastal plain and possibly lacustrine facies with source rock potential. Synrift clinoform seismic facies prograding from the northwest footwall correlate with non-marine to marginal marine conglomerate, sandstone and siltstone, and are interpreted as possible delta or fan-delta facies with reservoir potential although porosity and permeability is low within the Wenzhou 6-1-1 well. Post-rift thermal sag sequences are characterized by parallel and relatively continuous seismic reflections and locally developed clinoform packages. These facies correlate with porous and permeable marine sandstone and siltstone. Shales of potential sealing capacity occur within marine flooding intervals of both the synrift and post-rift sequences. Traps consist of differentially rotated synrift fill, and post-rift inversion anticlines. Major exploration risk factors include migration from the synrift coaly source rocks to the post-rift porous and permeable sandstones, and seismic imaging and drilling problems associated with extensive Tertiary igneous intrusions.
Active faulting of the northern shore of the Corinth rift, Greece
2007-09-30
DescriptionThe Gulf of Corinth continental rift is the location of frequent earthquakes and very rapid rates of extension. The development of this rift is relevant to rifting processes in general, the evolution of continental rifts into ocean basins and to processes forming reservoirs in rift settings (e.g., North Sea). Significant research has been undertaken on the southern shore of the rift, but until recently the offshore part of the rift and the northern shore have been relatively neglected. A recent [continued...]
Helium isotopes in geothermal systems: Iceland, The Geysers, Raft River and Steamboat Springs
1982-01-01
Helium isotope ratios have been measured in geothermal fluids from Iceland, The Geysers, Raft River, Steamboat Springs and Hawaii. These ratios have been interpreted in terms of the processes which supply He in distinct isotopic ratios and in terms of the processes which can alter the isotopic ratio. Using this interpretational scheme, Iceland is found to be an area of hot-spot magmatic He implying an active volcanic source although the data are suggestive of high-temperature weathering release of crustal He incorporated in the geothermal fluids. By comparison to fumarolic gases from Hawaii and Juan De Fuca and Cayman Trench basaltic glass samples, The Geysers contains MOR type magmatic He again implying an active volcanic source possibly a 'leaky' transform related to the San Andreas Fault System. Raft River contains only crustal He indicating no active volcanic sources. ...
The Midcontinent rift system and the Precambrian basement in southern Michigan
1994-04-01
The Precambrian basement within Michigan consists of at least three provinces, each characterized by distinctive potential field anomalies: (1) the Eastern Granite-Rhyolite Province (EGRP) in the south, (2) the Grenville Province in the southeast and (3) the Penokean Province to the north. Also located within the basement is the Mid-Michigan rift (MMR), which is the eastern arm of the Midcontinent rift system (MRS). Southwest and parallel to the MMR is a series of linear positive gravity anomalies which has been referred to as the Ft. Wayne rift (FWR) and the Southwest Michigan Anomaly (SWMA). The EGRP, which is characterized by undeformed and unmetamorphosed rhyolite to dacite and epizonal granites, was emplaced ca. 1510--1450 Ma. However, the EGRP may be comprised of several terranes of varying extent and origin based on analysis of potential field data and rock and mineral ages. The MMR and the FWR/SWMA are characterized by linear arrays of positive magnetic and gravity anomalies, which are probably due to thick accumulations of mafic igneous rocks within the rifts. The extent and trends of the FWR/SWMA have been largely inferred from geophysical data with a presumption of the age of about 1,100 Ma. The continuation of the MMR southward into Ohio and Kentucky as a sequence of gravity highs is questionable and needs further resolution. The FWR/SWMA may be part of the East Continent Rift Basin (ECRB). The ECRB, which is a large complex of related rift basins of Keweenawan age (1300 --1100 Ma), may be an extension of the MRS but it is not physically continuous with it. The ECRB lies to the west of the Grenville Front and extends at least from northwest Ohio to central Kentucky. Extensions of the ECRB north and south are speculative.
Implementing the hydrogen economy
2006-01-01
In the Icelandic community the use of renewable energy and the tests with a clean domestic fuel that most people refer to as the fuel of the future have become the points of focus. In Reykjavik this future has arrived. Hydrogen is used currently as the energy carrier within the public transportation system and is electrolyzed from water with hydroelectric power and leaves the system as water again.A small collaboration platform, Icelandic New Energy Ltd (INE), has been working on projects related to hydrogen as an energy carrier since 1999. A number of projects and feasibility studies are currently being carried out in Reykjavik, revolving around the issue of making hydrogen domestically from water and renewable energy (hydro and geothermal power), abundant local resources.In April 2003 th...
2009-01-01
SummaryBackground Chronic obstructive pulmonary disease (COPD) is characterized by an irreversible chronic airflow obstruction and by an accelerated decline in lung function. Elevated circulating levels of C-reactive protein (CRP) and interleukin-6 (IL-6), both markers of systemic inflammation, have been found in COPD. Their possible associations with chronic airflow obstruction have mostly been evaluated in highly selected patient samples. Our objective was to evaluate the association between postbronchodilator lung function CRP and IL-6 in a randomly selected sample of the Icelandic population, 40 years and older, while adjusting for gender, age, smoking, and body weight. Methods Serum CRP and IL-6 values were measured among participants in the Burden of Obstructive Lung Disease (BOLD) s...
Numerical models for the evaluation of geothermal systems
We have carried out detailed simulations of various fields in the USA (Bada, New Mexico; Heber, California); Mexico (Cerro Prieto); Iceland (Krafla); and Kenya (Olkaria). These simulation studies have illustrated the usefulness of numerical models for the overall evaluation of geothermal systems. The methodology for modeling the behavior of geothermal systems, different approaches to geothermal reservoir modeling and how they can be applied in comprehensive evaluation work are discussed.
Numerical models for the evaluation of geothermal systems
1986-08-01
We have carried out detailed simulations of various fields in the USA (Bada, New Mexico; Heber, California); Mexico (Cerro Prieto); Iceland (Krafla); and Kenya (Olkaria). These simulation studies have illustrated the usefulness of numerical models for the overall evaluation of geothermal systems. The methodology for modeling the behavior of geothermal systems, different approaches to geothermal reservoir modeling and how they can be applied in comprehensive evaluation work are discussed.
Long-lived eruptions from basaltic volcanoes involving episodic or steady activity indicate that a delicate balance has been struck between the rate of magma cooling in the dike system feeding the vent and the rate of ...
Deployment of Autonomous GPS Stations in Marie Byrd Land, Antartica
During the 1998-1999 Antarctic field season, we installed three autonomous GPS stations in Marie Byrd Land, West Antarctica to measure glacio-isostatic rebound and rates of spreading across the West Antartic Rift System.
Special session of the International Geothermal Symposium
1971-01-01
The special session of the international geothermal symposium, sponsored by the Transport and Resources Division of the United Nations, had three themes: United Nations activities in the field of geothermal development, prospects for the development of geothermal resources in developing countries, and the multi-purpose utilization of geothermal energy. Ian W. Innes (New Zealand) reported on the difficulty of performing a geothermal exploitation survey at 14,000 ft (about 4600 m) in Chile. Sveinn Einarsson (Iceland) reported on the reinjection of hot water discharged from the Ahuahapan geothermal field. Edoardo Dominco (Italy) reported on the results of a feasibility survey that found steam and hot water capable of generating about 20,000 kW electricity in Turkey. Nakamura (Japan) reported on the status of geothermal development in Ethiopia where a geothermal project was started in January 1970, and investigations for making maps of hot springs and exhalations were being conducted in the Rift valley. In general, the major topics of the session concentrated on the technological and economic problems of geothermal power generation, on the multi-purpose utilization of geothermal energy, an on the disposal of waste hot water.
1986-06-01
The primary objective of this paper is to review inversion algorithms employed to interpret magnetotelluric data by the geophysical/electromagnetics group at Brown University. Examples are presented from a variety of tectonic regimes - the Rio Grande rift, the Colorado Plateau, and Iceland. Following a brief tutorial in which the basic relations for the inverse problem are developed, the authors discuss the detectability and resolvability of various elements of the models. The correlation between certain model parameters is stressed, a phenomena well-known to interpreters. In this paper the authors emphasize the importance of identifying the precise range of values for which two or more parameters are coupled - these ranges are defined by what they term saturation limits. Generalized inverse theory is employed to arrive at optimal models which are evaluated in terms of resolution and information matrices. The degree to which models fit a given data base can be assessed using several quantitative approaches. The authors have found that it is important not only to determine the best fitting model, but also to identify those marginal solutions which also fall within the range of uncertainty of the data. The results from the direct inverse method agree favorably with those from Monte Carlo methods.
2009-01-01
A thermobarometric and petrologic study of basanites erupted from young volcanic cones along the submarine portions of the three El Hierro rift zones (NE-Rift, NW-Rift and S-Ridge) has been performed to reconstruct magma plumbing and storage beneath the island. Mineral-melt thermobarometry applied to naturally quenched glass and clinopyroxene rims yields pressures ranging from 350 to 1070MPa with about 80% of the calculated pressures being in the range of 600800MPa. This corresponds to a depth range of 1926km, implying that the main level of final crystal fractionation is within the uppermost mantle. No systematic dependence between sample locality and fractionation pressures could be observed. Olivine and clinopyroxene crystals in the rocks are complexly zoned and have, on an ...
The Neogene was a period of long-term global cooling and increasing climatic variability. Variations in African-Asian monsoon intensity over the last 7 Ma have been deduced from patterns of eolian dust export into the Indian Ocean and Mediterranean Sea as well as from lake level records in the East African Rift System (EARS). However, lake systems not only depend on rainfall patterns, but also on the size and physiography of river catchment areas. This study is based on stable isotope proxy data (18O/16O, 13C/12C) from tooth enamel of hippopotamids (Mammalia) and aims in unravelling long-term climate and watershed dynamics that control the evolution of palaeolake systems in the western branch of the EARS (Lake Albert, Uganda) during the Late Neogene (7.5 Ma to recent). Having no dietary preferences with respect to wooded (C3) versus grassland (C4) vegetation, these territorial, water-dependant mammals are particularly useful for palaeoclimate analyses. As inhabitants of lakes and rivers, hippopotamid tooth enamel isotope data document mesoclimates of topographic depressions, such as the rift valleys and, therefore, changes in relative valley depth instead of exclusively global climate changes. Consequently, we ascribe a synchronous maximum in 18O/16O and 13C/12C composition of hippopotamid enamel centred around 1.5-2.5 Ma to maximum aridity and/or maximum hydrological isolation of the rift floor from rift-external river catchment areas in response to the combined effects of rift shoulder uplift and subsidence of the rift valley floor. Structural rearrangements by ~2.5 Ma within the northern segment of the Albertine Rift are well constrained by reversals in river flow, cannibalisation of catchments, biogeographic turnover and uplift of the Rwenzori horst. However, a growing rain shadow is not obvious in 18O/16O signatures of the hippopotamid teeth of the Albertine Rift. According to our interpretation, this is the result of the overriding effect of evaporation on 18O/16O responding to aridification of the basin floor by a valley air circulation system through relative deepening of the valley. On the other hand, a synchronous arid pulse is not so clearly recorded in palaeosol data and mammalian fauna of the eastern branch of the EARS. This discrepancy indicates that rift mesoclimates may represent an underestimated aspect in previous palaeoclimate reconstructions from rift valley data and represent a clear limitation to attempts at global climate reconstructions. The results of this study also suggest that using 18O/16O data as a proxy to rain shadow evolution must take into account relative basin subsidence to properly document mountain range uplift.
2008-01-01
Models of fault growth propose that rift initiation starts with short fault segments. Knowledge of the growth of these segments and their interactions is important to understanding rift geometry and evolution. In the northern part of the Borborema Province, northeastern Brazil, a continental-scale, Cretaceous extensional system of faults has been observed to have reactivated ductile Precambrian shear zones. The faults form small grabens that represent the rift stage of the sedimentary basins. We integrated airborne radiometric and magnetic data with terrestrial gravity survey to investigate the influence of crustal heterogeneity on fault growth and the development of the extensional faults in one of these grabens, the Iguatu basin. Previous studies presented geophysical data, which provide...
2010-01-01
The Cheb Basin, located in the western Eger (Ohe) Rift, is part of the European Cenozoic Rift system. Although presently non-volcanic, it is the most active area within the European Rift with signs of recent geodynamic activity like emanations of mantle derived CO2, and the repeated occurrence of swarm earthquakes, which are common features in active volcanic regions. It is assumed that the fluids, uprising in permeable channels, play a key role for the genesis of these earthquake swarms. An image of the distribution of the electrical conductivity (resp. resistivity) in the upper crust can give information about the fluid distribution since the electrical patterns reflect pathways of fluids and fluid properties like ionic content. This was the motivation to start both a regional-scale di...
2010-01-01
The erosional pattern of passive margins often follows the fabric of ancient, compressional geological structures exposed by the topographic energy of rifting. As erosion cuts into these belted outcrop systems they impose initial and boundary conditions that steer drainage recession into the plateau edge and control escarpment-forming conditions. Pattern therefore controls process. Although generic surface process models predict scarp patterns and retreat in settings devoid of geological heterogeneity, they tend to do so only at isolated locations and for periods shorter than the lifespan of the escarpments. Thus, to focus on relatively narrow strike-perpendicular swaths of passive margin topography misses important aspects of drainage integration, which involves mobile drainage basin boun...
Active seeps, investment climate draw interest to Uganda
1995-05-01
Production has not been established in Uganda, but the hydrocarbon generating capacity of its rift basin is clearly evident. Reports of oil seeps date to 1925 to observations by Wayland; who relates 52 hydrocarbon occurrences in and around Lake Albert. Although not all remain active, nine oil seeps in the rift basin are confirmed active at present. The Albertine graben, a part of the East African rift system, dominates the geology of Uganda. Other, larger basins of similar evolution in Africa include the Sirte basin and the Gulf of Suez basin. These prolific basins account for one third of Africa`s total reserves. The paper describes the geologic setting, reservoirs, source rocks, geologic seals, structures, exploration history, licenses available, and fiscal terms.
2010-01-01
Southern Kenya Rift has been known as a region of high geodynamic activity expressed by recent volcanism, geothermal activity and high rate of seismicity. The active faults that host these activities have not been investigated to determine their subsurface geometry, faulting intensity and constituents (fluids, sediments) for proper characterization of tectonic rift extension. Two different models of extension direction (E-W to ESE-WNW and NW-SE) have been proposed. However, they were based on limited field data and lacked subsurface investigations. In this research, we delineated active fault zones from ASTER image draped on ASTER DEM, together with relocated earthquakes. Subsequently, we combined field geologic mapping, electrical resistivity, ground magnetic traverses and aeromagnetic da...
2010-01-01
Virus-like particles (VLPs) present viral antigens in a native conformation and are effectively recognized by the immune system and therefore are considered as suitable and safe vaccine candidates against many viral diseases. Here we demonstrate that chimeric VLPs containing Rift Valley fever virus (RVFV) glycoproteins GN and GC, nucleoprotein N and the gag protein of Moloney murine leukemia virus represent an effective vaccine candidate against Rift Valley fever, a deadly disease in humans and livestock. Long-lasting humoral and cellular immune responses are demonstrated in a mouse model by the analysis of neutralizing antibody titers and cytokine secretion profiles. Vaccine efficacy studies were performed in mouse and rat lethal challenge models resulting in high protection rates. Taken ...
1989-09-01
New K-Ar datings of a large rock sampling from the South Kivu volcanic province (Zaire, Rwanda, Burundi) are reported. No ages older than 10 Ma have been obtained. This result contrasts with older assumptions and puts severe constraints on the relations between volcanism and rift evolution. From 10 to 7.5 Ma tholeiitic volcanism predominates corresponding to an episode of fissural eruptions; from 7.5 to 5 Ma alkali basalts and their differentiates are mainly erupted in localized rifts. A culmination of activity occurs between 6.0 and 5.5 Ma ago. Pleistocene alkalic volcanism is restricted to localized areas. The transition from tholeiites to alkali-basaltic volcanism dated around 7.5 Ma would correspond to a major rifting phase which corresponds with the initiation of Lake Kivu Basin formation. The distribution of tholeiitic rocks in the central part of the rift, and predominantly alkalic rocks along the western active border fault, strengthens the idea that the former are associated with tension, the latter with vertical, possibly also strike-slip movements. Volcanism in the Western Rift is restricted to areas where tension occurs in a zone which is located between two zones of strike-slip. In the South Kivu area normal faults intersect strike-slip faults and this seems to have determined the location of volcanic activity. Magma formation is considered to be related with shear heating combined with adiabatic decompression in ascending diapirs. This implies heating at the lithosphere-asthenosphere boundary as a result of extension. Generation of tholeiitic or alkalic magmas is connected with the variable ascent velocity of mantle diapirs or with variable shear heating along the shear zone. Changes in both magma composition and intensity of volcanic activity with time are considered to be related to major phases of rift evolution. (orig.).
2006-01-01
The suture zone between the Bhandara cratonand the granulite-facies rocks of the Eastern Ghats Province in SE India contains a number of deformed alkaline and tholeiitic intrusives. The Khariar alkaline complex is one of the several occurrences which intruded in the Mesoproterozoic (1,48017 Ma, 2r) and was deformed during the Pan-African tectonothermal event. The geochemical signatures indicate a rift-related setting for the magmatic activity. The nepheline syenite parentmagma may have been produced by in-mantle fractionation of clinopyroxene and Ti-rich amphibole from a basanitic primary magma derived from an enriched spinel lherzolite mantle source in the sub-continental lithosphere. Geochemical variations in the Khariar alkaline suite can be modeled by the fractionation of clinopyroxene, amphibole, titanite, zircon, apatite and allanite. The Mesoproterozoic alkaline magmatism at Khariar marks the initiation of a NE-SW rift which formed several craton margin basins and opened an ocean towards the south. The sediments of the cratogenic basins and the Eastern Ghats Province were deposited in these rift-related basins. A K-Ar age of 1,33053 Ma from glauconites in sandstone suggests that the NW-SE trending Godavari-Pranhita graben formed at approximately the same time as the rift at the craton margin. If the two are related, the Godavari-Pranhita graben may represent the failed arm of a rift system in which the NE-SW arm was the active segment. The granulite-facies deformation and metamorphism of the Eastern Ghats Province sediments may be related to an episode of Grenvillian basin inversion. The Mesoproterozoic rifting and Grenvillian basin closure may thus represent two well-defined parts of a Wilson cyclei.e. the opening and closure of an ocean. The Khariar and other alkaline bodies were, however, deformed during a Pan-African collisional event associated with the westward thrusting of the Eastern Ghats Province granulites over the cratonic foreland. Publisher: Department of Applied Geology
Iceland harnesses heat from lava while geothermal projects gather steam
1977-05-26
A pilot installation in the Vestman Islands (Iceland) has successfully delivered 85-90/sup 0/C water to a hospital and 40 residences. Plans call for expansion of the facility to heat most of the 1000 residences in the town of Vestmannsaeyjar. The system utilizes steam produced by 1000/sup 0/C lava beneath 10-20 m of volcanic ash produced by a volcanic eruption in 1973. Pipes in 1.6 m diameter holes carry steam to heat exchangers. The lava fields are expected to produce steam for about 15-20 years and research is underway on methods of prolonging their usefulness. Also in Iceland, the city of Reykjavik has been using geothermal heat since 1930. Approximately 46% of the homes were heated geothermally in 1973 and the present goal is to provide heat to 77% by 1985. A 1% sales tax has produced 4 million dollars for geothermal R D. Eleven wells at Laugavegur produce 18,000 liters/min of water at 128/sup 0/C and five wells at Ellioaar produce about 10,000 liters/min at 103/sup 0/C.
2010-01-01
This paper examines the relationship between volcanic risk and the tourism sector in southern Iceland and the complex challenge emergency management officials face in developing effective volcanic risk mitigation strategies. An early warning system and emergency response procedures were developed for communities surrounding Katla, the volcano underlying the Myrdalsjokull ice cap. However, prior to and during the 2007 tourist season these mitigation efforts were not effectively communicated to stakeholders located in the tourist destination of orsmork despite its location within the hazard zone of Katla. The hazard zone represents the potential extent of a catastrophic jokulhlaup (glacial outburst flood). Furthermore, volcanic risk mitigation efforts in orsmork were based solely on informat...
2010-01-01
This paper presents the findings of risk identification and risk perception research conducted in relation to the fisheries systems of four distinct and diverse European countries: Faroes, Iceland, Greece and the UK. Risk research traditionally attempts to quantify the potential threat or consequences from a range of risk events or hazards. This research, however, adopted a social sciences perspective and so assumed that a risk event or hazard can mean different things to different people and that these perceptions are also context and culturally dependent. Risk perceptions were examined and risk registers developed in each country for a range of stakeholder groups. A ‘mental modelling’ approach was adopted in a series of qualitative interviews. Findings were examined in te...
1988-01-01
The aim was to find effective ways of protecting vulnerable concrete facades of buildings in Iceland by using various kinds of outside insulation materials. It was concluded that plastering insulation systems on outside walls reduce moisture in the conrete in relation to the thickness of the insulation and the quality of the materials used. Moisture reduction takes place over a period of some years and is also dependant on the inside insulation, yet cracks in plastering seem to have little significance. Ventilation in the plastering insulation further promotes moisture reduction. It is claimed that this form of renovation results in considerable conservation of energy, and prevents frost damage because of the raised temperature of the walls themselves. Alkali-silicone reactions can be stopped if the amount of moisture reduction is sufficient. (AB) 11 refs.
New light on caldera evolution - Askja, Iceland
1991-04-01
The large multiple-caldera volcanic system of Askja, central Iceland, is composed principally of subglacial basaltic hyaloclastite-pillow-lava formations and postglacial basaltic scoria and flows. Traditionally, such calderas are believed to be formed by downfaulting and ring-fracture collapse. Whereas this certainly applies to the smaller A.D. 1875 caldera, the older main caldera may have developed positive relief during subglacial construction of laterally confined hyaloclastite ridges above erupting fractures. This is supported by the evidence of a large negative gravity anomaly that reaches minima over the marginal low-density ridges but which is less negative within the caldera, where relatively dense postglacial lavas are believed to cover a more limited hyaloclastite succession beneath the caldera floor.
2009-01-01
New field work and petrological investigations of the largest gabbro outcrop in Iceland, the Hvalnesfjall gabbro of the 67Ma Austurhorn intrusive complex, have established a stratigraphic sequence exceeding 800m composed of at least 8 macrorhythmic units. The bases of the macrorhythmic units are composed of 210m thick melanocratic layers rich in clinopyroxene and sometimes olivine, relative to the thicker overlying leucocratic oxide gabbros. While the overall compositional variation is limited (Mg# clinopyroxene 7284; An% plagioclase 5685), the melanocratic bases display spikes in Mg# and Cr2O3 of clinopyroxene and magnetite indicative of magma replenishment. Some macrorhythmic units show mineral trends indicative of up-section fractional crystallisation over up to 100m...
2008-11-14
DescriptionThe upper mantle is generally held to be the source of chemically depleted mid-ocean ridge basalts (MORB). Enriched material recycled through plumes from the lower mantle is thought to be the principal source of ocean island basalt. High 3He/4He in some plume-derived basalt suggests that the lower mantle has remained largely undegassed since Earth accretion. Paradoxically, data obtained recently from proto-Iceland plume basalts erupted in Baffin Island, Greenland, Scotland and Iceland suggest th [continued...]
Potential effects of the Hawaii geothermal project on ground-water resources on the Island of Hawaii
1994-07-01
This report provides data and information on the quantity and quality of ground-water resources in and adjacent to proposed geothermal development areas on the Island of Hawaii Geothermal project for the development of as much as 500 MW of electric power from the geothermal system in the East Rift Zone of Kilauea Volcano. Data presented for about 31 wells and 8 springs describe the chemical, thermal, and hydraulic properties of the ground-water system in and adjacent to the East Rift Zone. On the basis of this information, potential effects of this geothermal development on drawdown of ground-water levels and contamination of ground-water resources are discussed. Significant differences in ground-water levels and in the salinity and temperature of ground water within the study area appear to be related to mixing of waters from different sources and varying degrees of ground-water impoundment by volcanic dikes. Near Pahoa and to the east, the ground-water system within the rift is highly transmissive and receives abundant recharge from precipitation; therefore, the relatively modest requirements for fresh water to support geothermal development in that part of the east rift zone would result in minimal effects on ground-water levels in and adjacent to the rift. To the southwest of Pahoa, dike impoundment reduces the transmissivity of the ground-water system to such an extent that wells might not be capable of supplying fresh water at rates sufficient to support geothermal operations. Water would have to be transported to such developments from supply systems located outside the rift or farther downrift. Contaminant migration resulting from well accidents could be rapid because of relatively high ground-water velocities in parts of the region. Hydrologic monitoring of observation wells needs to be continued throughout development of geothermal resources for the Hawaii Geothermal Project to enable the early detection of leakage and migration of geothermal fluids.
1999-07-01
The northern North Sea basin system resulted from multiple-stage crustal extension, commencing with Devonian collapse of the Caledonides, and followed by Permian and Jurassic crustal thinning. Each of these events were followed by thermal crustal contraction. This presentation deals with post-rift development that succeded the mid Jurassic to earliest Cretaceous extension. The overall analysis and modelling of the basin demanded a continuous multi-disciplinary approach utilizing results from palaeontology, seismic interpretation sedimentology, stratigraphy and structural geology.
Structure formation in areas of nontransform offsets of axial spreading zones (analog modeling)
2010-01-01
The results of experimental modeling and features of structure formation in the zones of nontrans-form offsets (NTOs) of spreading axes are presented. The experiments were performed on materials that are colloidal systems based on liquid and solid hydrocarbons, taking into account the similarity of conditions. The following parameters were changed during the experiments: (1) the thickness of the model lithosphere of the rift zone, (2) the thickness of the lithosphere in the zone of nontransform offsets between the rift segments; (3) the spreading velocity. The critical values of offsets for the spreading axes at which a character of structure formation in the zones of NTOs is changed were established.
Latest erosional incision in river valleys of southern East Siberia
2010-01-01
Examples of the geological and geomorphic framework of river valleys in the Tunka rift basin (Baikal rift system) and in the Irkutsk amphitheater (Siberian craton) have been used to show that horizontal and vertical motions of tectonic units in southern East Siberia are superposed with periodic movements. In the latter, the waves of slow uplift are attendant with erosional incision events, whereas during the subsidence cycles the incised valleys become filled with mainly alluvial sediments. The latest incision events in the area occurred in the past 70 kyr.
2006-11-30
DescriptionMid-oceanic ridges are the most important magmatic systems on the planet. Generation and emplacement of magma is controlled by the large-scale rifting (stretching) of the ocean crust and underlying mantle at mid-ocean ridges. Oceanic core-complexes are areas where a large scale fault allows the deeper parts of the mid-ocean ridge complex to be exposed and accessible. The large faults are themselves an important component of the rifting process. In this project we will study rocks from an oceanic [continued...]
Geophysical Evidence for the Availability of Geothermal Energy in New Britian
This paper combines some of the results and interpretations of geological mapping, seismic refraction, marine seismic, and gravity surveys to show that large tracts of New Britain could be favorable targets for geothermal power development. It is shown that the fractured and faulted lithosphere is associated with grabens and rifts in which mantle material has risen to within 10 to 15 km from the surface. The grabens and rifts are marked by volcanism in which the dominant volcanic rocks are olivine--and tholeiitic--basalts, with a sprinkling of more acid volcanics ranging from dacite to andesite. Following A. Rittman the basalts are believed to have originated in the asthenosphere when the lithosphere was broken up under a tensional stress regime; the acid volcanics were formed by magmatic differentiation within the crust. it was argued that ideal geothermal reservoirs are capped with altered ash deposits or other nonpermeable volcanics. To feed such reservoirs conduits are required which are naturally located on fault or shear zones. The two areas selected as favorable for future geothermal power development are located between Talasea and Lolobau Is., say around Hoskins; and near Rabaul, between Matupi Harbor and Matupi. As a type area, the rift between the Gazelle Peninsula and New Ireland resembles the Afar triangle, at the northern end of the Great Valley Rift system of Africa.
The author has identified the following significant results. Combined aerial IR surveys and DCP heat flux estimates at Mt. Baker, Washington, revealed that recurrent snow, ice, and debris avalanches were in ...
Some considerations for geothermal district heating
The distribution of geothermal resources in relation to the location of population centers in the U.S. is considered. Capital aspects of district heating systems are discussed. Estimates are given of distribution network capital investment as a function of population in service area. Swedish and Icelandic cost experience is taken into consideration. The need for more specific assessment of the potential for direct use of geothermal energy is cited. (JGB)
Some considerations for geothermal district heating
1977-06-22
The distribution of geothermal resources in relation to the location of population centers in the U.S. is considered. Capital aspects of district heating systems are discussed. Estimates are given of distribution network capital investment as a function of population in service area. Swedish and Icelandic cost experience is taken into consideration. The need for more specific assessment of the potential for direct use of geothermal energy is cited. (JGB)
Deep Sea Fauna and Environment of the North Atlantic and Mediterranean Sea
2006-09-30
DescriptionAlthough the deep sea is uniformly, cold and dark with high pressure at depth, life on the sea floor varies according to food supply from the surface and other factors. Using robot camera systems mobile animals living on the Mid-Altantic Ridge from the Azores to Iceland will be studied North and South of the Sub Polar Front at ca. 52N. These observations will be compared with other regions of the North Atlantic Ocean and the Mediterranean Sea
...June 1968) Gabon (effective June 1964) Grenada (effective April 1983) Guatemala (effective October 1978) Guyana (effective September 1969) Iceland (effective December 1980) Ivory Coast Jamaica (effective July 1968)...
Volcanic hazards of the Idaho National Engineering Laboratory and adjacent areas
1994-12-01
Potential volcanic hazards are assessed, and hazard zone maps are developed for the Idaho National Engineering Laboratory (INEL) and adjacent areas. The basis of the hazards assessment and mapping is the past volcanic history of the INEL region, and the apparent similarity of INEL volcanism with equivalent, well-studied phenomena in other regions of active volcanism, particularly Hawaii and Iceland. The most significant hazards to INEL facilities are associated with basaltic volcanism, chiefly lava flows, which move slowly and mainly threaten property by inundation or burning. Related hazards are volcanic gases and tephra, and ground disturbance associated with the ascent of magma under the volcanic zones. Several volcanic zones are identified in the INEL area. These zones contain most of the volcanic vents and fissures of the region and are inferred to be the most probable sites of future INEL volcanism. Volcanic-recurrence estimates are given for each of the volcanic zones based on geochronology of the lavas, together with the results of field and petrographic investigations concerning the cogenetic relationships of INEL volcanic deposits and associated magma intrusion. Annual probabilities of basaltic volcanism within the INEL volcanic zones range from 6.2 {times} 10{sup {minus}5} per year (average 16,000-year interval between eruptions) for the axial volcanic zone near the southern INEL boundary and the Arco volcanic-rift zone near the western INEL boundary, to 1 {times} 10{sup {minus}5} per year (average 100,000-year interval between eruptions) for the Howe-East Butte volcanic rift zone, a geologically old and poorly defined feature of the central portion of INEL. Three volcanic hazard zone maps are developed for the INEL area: lava flow hazard zones, a tephra (volcanic ash) and gas hazard zone, and a ground-deformation hazard zone. The maps are useful in land-use planning, site selection, and safety analysis.
Magmatic-tectonic evolution of a volcanic rifted margin
1990-05-01
Many North Atlantic margins are underlain by huge volcanic edifices near the continent-ocean boundary. A crustal hole drilled at the outer Voering Plateau during ODP (Ocean Drilling Project) Leg 104 has provided important constraints on the breakup history and the subsequent margin evolution by penetrating more than 900 m of igneous rocks and interbedded sediment below a post-early Eocene cover. The recovered basement rocks constitute two different volcanic series. The Upper Series, comprising a seaward-dipping reflector wedge, consists of transitional mid-oceanic tholeiitic lava flows and thin volcaniclastic sediments. Dacitic flows, some dikes and thicker sediments constitute the Lower Series. The margin evolved by Paleocene crustal extension, uplift and pervasive intrusion in the rift zone. Just prior to breakup, magma from shallow crustal melts produced the Lower Series. The Upper Series was constructed during an intense, rapidly waning subaerial surge following breakup in the earliest Eocene. The Upper Series covers both new oceanic crust and large areas of continental crust. The dipping wedge was formed by subsidence due to loading and thermal contraction probably amplified by a tectonic force. When the surge had abated, the injection center subsided and a normal oceanic crust was formed. A direct temporal and compositional relationship exists between the onshore North Atlantic Volcanic Province and the volcanic margins. Whereas the central transverse part of the province, near the Iceland hotspot has been active for 60 m.y., the volcanic margins reflect a 2,000-km-long transient phenomenon lasting only 3 m.y. The breakup volcanism and lack of initial subsidence are related to a regional, about 50C{degree}, increased temperature at the base of the lithosphere (hot carpet) combined with opening in previously extended crust.
2007-02-15
The high geothermal potential of East Africa, especially of the Eastern Rift, is known for a long time. Since these pioneer studies, geothermal plants have been constructed at three sites in East Africa. Nevertheless, up to now geothermal has been a success story only in Kenya. The steam power plant Olkaria I in Kenya is running reliability since 25 years. Today, the country produces more than 12% of its electricity from geothermal. Now, Eritrea, Djibouti, Uganda, Tanzania and Ethiopia which are also situated along the East African Rift, are planning similar projects. The countries need to develop new energy sources because oil prices have reached a critical level. In the past, hydro power was regarded to be a reliable source of energy, but increased droughts changed the situation. Thus, the african states are searching for alternatives to be able to stabilise their energy supply and to cover the growing energy demand. There is much hope that the success of the Kenyan geothermal power plants will be repeated in the neighbouring countries. The East African countries have joined their forces to give impetus to the use of the regional geothermal resources. On behalf of the Federal Ministry for Economic Cooperation and Development, the Federal Institute for Geosciences and Natural Resources supports the countries in realising their plans as part of the GEOTHERM Programme. Together with further donors (Iceland, France, USA, Global Environment Facility) the path will be paved for geothermal power plants in the above mentioned six East African countries. The following main steps are necessary: - Awareness raising of political decision makers about the advantages of including geothermal into the national power plans - Improvement of knowledge about potentials geothermal sites - Development of a regional equipment pool including the necessary geophysical equipment, laboratories, etc. - Training in geothermal exploration and plant maintenance, to minimise risks of site development and plant operation. - Establish a risk mitigation fund for exploratory drilling - Search for investors for development of sites, construction and operation of power plants. (orig.)
The Origin of Noble Gas Isotopic Heterogeneity in Icelandic Basalts
Two models for generation of heterogeneous He, Ne and Ar isotopic ratios in Icelandic basalts are evaluated using a mixing model and the observed noble gas elemental ratios in Icelandic basalts,Ocean island Basalt (OIBs) and ...
1992-01-01
Detailed studies of the subsurface structure of the Cambrian Reelfoot rift (RFR) in the Midwestern US provide important insights into continental rifting processes and into the structural fabric of a zone of modern intracratonic seismicity (New Madrid zone). High-quality oil industry seismic reflection data show that in the area of transition between the RFR and the Rough Creek Graben (RCG) the geometry of the Cambrian rift system is that of a half-graben that thickens to the southeast. This contrasts with the northward-thickening half-graben observed to the east in the RCG and with the more symmetric graben to the south in the RFR. An 82.8-km segment of a northwest-southeast seismic reflection profile in southeastern Illinois and western Kentucky shows that near Hicks Dome, Illinois, Middle and Lower Cambrian syn-rift sedimentary rocks occupy about 0.35 s (two-way travel time) on the seismic reflection section (corresponding to a thickness of about 970 m). This stratigraphic interval occupies about 0.45 s (1,250 m) near the Ohio river and is thickest against the Tabb Fault System (TFS) in Kentucky, where it occupies 0.7 s (1,940 m). The seismic data show that in this part of the Cambrian rift the master fault was part of the TFS and that normal displacement on the TFS continued through middle Paleozoic time. The seismic data also provide new information on the late Paleozoic development of Hicks-Dome and the surrounding Fluorspar Area Fault Complex (FAFC) in southeastern Illinois and western Kentucky. A series of grabens and horsts in the FAFC document a late Paleozoic reactivation of the RFR. Comparison of the reflection data with surface mineralization patterns shows that in most cases mineralized graben-bounding faults clearly cut basement or are splays from faults that cut basement.
1996-07-05
The initial stage of continental rifting in the Central and South Atlantic has been accompanied by tholeiitic magmatism, which is mainly represented by sills, dykes, layered intrusions and lava flows. During the rifting progression, the syn-rift stage in the South Atlantic has been accompanied by abundant alkaline magmatism. A geochronological and geochemical study has been performed on these formations with the aim to contribute to the understanding of the early continental rifting processes and their evolution. {sup 40}Ar/{sup 39}Ar analyses have been done on tholeiitic intrusives of Guinea and French Guyana/Surinam, tholeiitic dykes, associated with the Parana volcanism (Brazil), and alkaline dykes in the region of Rio de Janeiro (Brazil). The geochemical and isotopic study has been focused on the tholeiitic intrusions from Guinea and French Guyana/Surinam. These three arms may represent the three branches of a triple junction which was active between 134 to 129 Ma, and which was at the origin of at least the northern Parana traps. Even if the principal magmatic activity can be related to the thermal anomaly due to the Tristan da Cunha hotspot, which favours an active rifting, the tectonic system of the triple junction is not compatible in time and space with this hotspot and therefore with this geodynamic model. It is possible that the Parana traps (133-130 Ma) are only partly contemporaneous and therefore, they might be not related to the same mode of geodynamic initiation. Biotites from the alkaline magmatics of the dyke swarm (NE-SW) near Rio de Janeiro display plateau ages between 82 and 70 Ma; this intense alkaline magmatism was related to vertical movements characterising the syn-rift stage not only in SE-Brazil but also in equatorial Africa. (author) 183 refs.
Transfer of {sup 137}Cs to cows` milk in the Nordic countries
1994-12-31
A comparison has been made of the transfer of Chernobyl derived {sup 137}Cs cows` milk in the different Nordic countries. A compilation is given of data on {sup 137}Cs levels in both dairy milk and milk from individual farms. In 1986 and 1987 the levels of {sup 137}Cs were higest in Finland and Norway, intermediate in Sweden, the Faroe Islands and Iceland ({sup 137}Cs from global fallout only) and lowest in Denmark. The aggregated transfer coefficient (T{sub a}g) to cows` milk was 2-10 times higher in the Faroe Islands, Iceland and Norway compared to that in Denmark, Finland and Sweden for all years after 1986. The effective ecological half-life (T{sub 1/2ecol}) for dairy cows` milk ranged from 1-2.3 y for all countries, except Iceland where the T{sub 1/2ecol} was 18.4 y (global fallout). It was therefore concluded that cows` milk production in the Faroe Islands and Norway was most sensitive to the Chernobyl {sup 137}Cs fallout. Though milk production systems and management systems change over time and could alter the sensitivity to {sup 137}Cs fallout, it is concluded that the Faroe Islands, Iceland and Norway would be most susceptible to future {sup 137}Cs fallout. (orig.).
Magma supply and storage at Kilauea Volcano, Hawaii, 1956-1983
1984-08-01
Shallow crustal magma reservoirs beneath the summit of Kilauea Volcano and within its rift zones are linked in such a way that the magma supply to each can be estimated from the rate of ground deformation at the volcano's summit. The model builds on the well-documented pattern of summit inflation as magma accumulates in a shallow summit reservoir, followed by deflation as magma is discharged to the surface or into the rift zones. Magma supply to the summit reservoir is thus proportional to summit uplift, and supply to the rift zones is proportional to summit subsidence; the average proportionality constant is 0.33 x 10/sup 6/ m/sup 3//..mu..rad. This model yields minimum supply estimates because it does not account for magma which escapes detection by moving passively through the summit reservoir or directly into the rift zones. Calculations suggest that magma was supplied to Kilauea during July 1956-April 1983 at a minimum average rate of 7.2 x 10/sup 6/ m/sup 3//month. Roughly 35% of the net supply was extruded; the rest remains stored within the volcano's east rift zone (55%) and southwest rift zone (10%). It remains unclear whether pulses in magma supply from depth give rise to corresponding increases in shallow supply, or if instead unloading of a delicately balanced magma transport system during large eruptions or intrusions triggers more rapid ascent from a relatively constant mantle source.
1985-02-01
Current tectonic models for the formation of the Gulf of Mexico generally include continental rifting starting in the Triassic and continuing through the Jurassic. A comparison between the sedimentology and structural geology of known continental rifts (such as the Gulf of Suez, Egypt) and the Triassic and Jurassic of the Gulf of Mexico suggests the following. (1) The interior salt basins of Texas, Louisiana, Mississippi, and Alabama probably were deposited within a failed continental rift. (2) Positive features such as the Angelina-Caldwell flexure, Wiggins arch, and Middle ground arch probably represent the southern edge of the failed rift. (3) Positive features such as the Sabine uplift and Monroe arch are probably isolated horst blocks within the failed rift. Pre-evaporite sediments account for much of the production in the Gulf of Suez, and these rock sequences are well exposed there on shore. Depositional and structural histories for these rocks are similar in both the Gulf of Mexico and Gulf of Suez, and a careful comparison suggests new play concepts for the Gulf of Mexico. The post-evaporite sequences of the Gulf of Suez are also similar to the Norphlet and Smackover Formations of the Gulf of Mexico, although Smackover equivalents are currently being deposited in the Gulf of Suez. Comparisons between the two rift systems indicate that a clearer understanding of the structural setting of the Gulf of Mexico at the time of deposition of the Norphlet and Smackover should lead to better exploration plays for these syntectonic formations.
Continuous sea-floor spreading in Red Sea: an alternative interpretation of magnetic anomaly pattern
1985-04-01
The magnetic anomaly pattern over the Red Sea can be modeled as a continuous system of sea-floor spreading from the early Miocene to the present by using a timevarying process filter. The half spreading rate is approximately 1 cm/yr (0.4 in./yr) since initial rifting. The parameters that determine the process filter and development of the transition zone are the intrusion parameter (a measure of the dispersion of feeder dikes or horizontal strain about the rift axis), a flow parameter (a measure of the average flow width), and the effusion parameter (a measure of the volcanic effusion and thickness of layer 2). The authors estimate the flow parameter to be 2.7km(1.7 mi) and the intrusion parameter to be 7.5km(4.7 mi) at early rifting. These values suggest that a wide distribution of axial dikes or horizontal strain is the dominant factor in forming the magnetic anomaly pattern. Reduction in the width of the intrusion parameter and the effusion rate as rifting proceeded resulted in focusing of the strain, thinning of layer 2, and formation of the Red Sea deeps. Their modeling suggests that phase 2, or the stratoid phase, began about the time of anomaly 5C or chron C5C approximately 16 Ma. This age is compatible with geologic estimates of the initial rifting at the late Oligocene to early Miocene (Coleman, 1974; Gass, 1977). The opening rate for Africa-Arabia plate motion has remained relatively constant since early rifting although the African margin appears to be accreting faster than the Arabian plate.
Magma reservoir systems inferred from tilt patterns
1981-01-01
Inflation patterns based on water-tube tilt-meter and levelling observation show different features for Krafla Volcano in Iceland and Kilauea Volcano in Hawaii. Monotonous sawtooth shape inflation is observed at Krafla, while inflation curves at Kileauea are more or less complicated. The difference was attributed to differences in the system of magma reservoir and volcanic conduit as a capacitor and a resistor, an electrical oscillator was considered to be a possible model for a magma reservoir system. In the case of Krafla, the magma resrvoir system is replaced with one electric oscillator called Single system or Icelandic type system. The complicated inflation pattern of Kilauea was interpreted as the assembly of a main magma reservoir and the group of surrounding small resrvoirs. The equivalent electric analogue is the composite parallel and serial connection of a single oscillator which generates irregular output voltage during a charging process. The proposed magma reservoir system of Kilauea is called Multi-coupled system or Hawaiian type system which also help in interpreting the wondering of the uplift center and tidal phenomena of the Halemaumau lava lake.
Costs for frequency reserve and regulation power options in Iceland
2005-07-01
The price for ancillary services that ensures an efficient use of resources is equal to the marginal costs of providing these services. In an expanding hydro power system there are two optimal designs for expansion; one design is optimal when ancillary services are not to be provided and another design is optimal when these services are to be provided. The right price for ancillary services cover the net difference in costs between the two designs. The difference in design in an expanding system is specific for that particular system and hence no general number can be specified. In an expanding hydro power system, the efficient price typically covers parts of the marginal investment costs for excess capacity in turbine and generator, but no investment costs for waterways and reservoirs.
2004-01-01
The stratigraphy, facies relationship and paleoenvironment of selected West African and the Brazillian rift basins permit the recognition of at least two major petroleum systems apart from the prolific Niger Delta petroleum system. The Lower Cretaceous fluivio-lacustrine petroleum system and Upper Cretaceous to Lower Tertiary, marine dominated petroleum system. Our combined studies of the stratigraphic, structural framework, paleoenvironment and time-space relationships of the petroleum systems in the Benue/Dahomey and the Potiguar/Ceara basins indicated that rifting and subsequent drifting during the opening of the South Atlantic controlled subsidence, sediment deposition and facies associations in individual basins. Whereas in the Potiguar/Ceara basins, the best developed source rocks are within the Neomacin-Aptian fluvio- lacustrine sequence of the ...
The boron isotope systematics of Icelandic geothermal waters: 1. Meteoric water charged systems
2000-02-01
The authors have measured the boron isotope composition and boron and chloride concentrations of 27 Icelandic geothermal fluids from both high- and low-temperature systems. The {delta}{sup 11}B values range from {minus}6.7{per{underscore}thousand} in the Krafla system, to +25.0% in a warm spring from the Southern Lowlands. In addition, the authors have also determined the {delta}{sup 11}B values of basaltic glass from Nesjavellir ({minus}5.3 {+-} 1.4{per{underscore}thousand}) and travertine from Snaefellsnes ({minus}22 {+-} 0.5{per{underscore}thousand}). The B isotope and Cl/B systematics of the high-temperature systems are dominated by the composition of the local basalts. The lower temperature systems show evidence for mixing with B and Cl or a marine origin, together with some uptake of B into secondary mineral phases. The data from the Snaefellsnes geothermal system indicate that the fluids have undergone interaction with basalts that have undergone significant low-temperature alteration by seawater.
Structural evolution and hydrocarbon accumulation of Luxi Depression
Located in the eastern Inner Mongolia Autonomous Region, China, Luxi Depression covers an area of 760 km[sup 2] and is one of the more than 250 small rifts of Northeast Rift System, the basement of which is Hercynian told belt. The Depression has undergone two Late Jurassic events: rifting and depression. The rifting sedimentation (the main period) may be divided into four stages: in the initial tensional faulting stage (Yixian Age) are accumulated a set of mantle-sourced volcanic rocks; in the fast subsiding stage (Jiufotang Age) the sedimentary system is distributed in belts under the control of boundary faults; in the steep area alluvial fans and near-shore sublacustrine fans are developed; in the gentle area braided deltas are developed; in the central deep area dark mudstones and sublacustrine gravity flows are developed. Meanwhile the rollover structures began to form on the down-thrown walls of the faults and the drape structures are formed on the convex side of the volcanic rocks. The stable subsiding stage (Shahai Age) is mainly a shallow-semi-deep lacustrine system; the rollover structures are generally finished (Fuxin Age). Most of the fill of the re-rising shrinking stage are near-shallow-lake and marsh facies sedimentation. There are five kinds of oil reservoirs distributed around the oil-generating depressions: rollover anticline, structure-lithology reservoir, updip pinch out, lenticular sandstone, and impermeable sandstone seals. Such reservoir formation models are relatively representative in rift system and can be a model for oil and gas exploration in similar depressions.
Structural evolution and hydrocarbon accumulation of Luxi Depression
1996-01-01
Located in the eastern Inner Mongolia Autonomous Region, China, Luxi Depression covers an area of 760 km[sup 2] and is one of the more than 250 small rifts of Northeast Rift System, the basement of which is Hercynian told belt. The Depression has undergone two Late Jurassic events: rifting and depression. The rifting sedimentation (the main period) may be divided into four stages: in the initial tensional faulting stage (Yixian Age) are accumulated a set of mantle-sourced volcanic rocks; in the fast subsiding stage (Jiufotang Age) the sedimentary system is distributed in belts under the control of boundary faults; in the steep area alluvial fans and near-shore sublacustrine fans are developed; in the gentle area braided deltas are developed; in the central deep area dark mudstones and sublacustrine gravity flows are developed. Meanwhile the rollover structures began to form on the down-thrown walls of the faults and the drape structures are formed on the convex side of the volcanic rocks. The stable subsiding stage (Shahai Age) is mainly a shallow-semi-deep lacustrine system; the rollover structures are generally finished (Fuxin Age). Most of the fill of the re-rising shrinking stage are near-shallow-lake and marsh facies sedimentation. There are five kinds of oil reservoirs distributed around the oil-generating depressions: rollover anticline, structure-lithology reservoir, updip pinch out, lenticular sandstone, and impermeable sandstone seals. Such reservoir formation models are relatively representative in rift system and can be a model for oil and gas exploration in similar depressions.
Structural evolution and hydrocarbon accumulation of Luxi Depression
1996-12-31
Located in the eastern Inner Mongolia Autonomous Region, China, Luxi Depression covers an area of 760 km{sup 2} and is one of the more than 250 small rifts of Northeast Rift System, the basement of which is Hercynian told belt. The Depression has undergone two Late Jurassic events: rifting and depression. The rifting sedimentation (the main period) may be divided into four stages: in the initial tensional faulting stage (Yixian Age) are accumulated a set of mantle-sourced volcanic rocks; in the fast subsiding stage (Jiufotang Age) the sedimentary system is distributed in belts under the control of boundary faults; in the steep area alluvial fans and near-shore sublacustrine fans are developed; in the gentle area braided deltas are developed; in the central deep area dark mudstones and sublacustrine gravity flows are developed. Meanwhile the rollover structures began to form on the down-thrown walls of the faults and the drape structures are formed on the convex side of the volcanic rocks. The stable subsiding stage (Shahai Age) is mainly a shallow-semi-deep lacustrine system; the rollover structures are generally finished (Fuxin Age). Most of the fill of the re-rising shrinking stage are near-shallow-lake and marsh facies sedimentation. There are five kinds of oil reservoirs distributed around the oil-generating depressions: rollover anticline, structure-lithology reservoir, updip pinch out, lenticular sandstone, and impermeable sandstone seals. Such reservoir formation models are relatively representative in rift system and can be a model for oil and gas exploration in similar depressions.
Petroleum systems of Chinese nonmarine basins
2010-01-01
Abstract The petroleum systems of Chinese nonmarine rifted and depression basins, dominated by lacustrine strata, have distinctive source rocks, reservoir types and trap characteristics. The rifted basins are characterized by numerous faults and multiple structural salients and sags (half grabens). Sags include many subdivisions and smaller isolated sags. Most sags constitute relatively independent petroleum systems that have efficiently generated and expelled hydrocarbons, have excellent reservoir properties in a variety of sand-body types, and have multiple traps. These attributes impart a petroliferous character to the entire sag. Depression basins (intracratonic flexural basins) developed on large cratons and hosted large lacustrine systems. They feature very gentle structure, large de...
2010-01-01
During the late Permian (Kungurian to Kazanian) a Neotethyan rift basin evolved at the western boundary of the Arabian Plate, in what is called today the Dead Sea Valley of western Jordan. The break-up of Pangaea was accompanied by low-sinuosity sandy braided- to meandering-fluvial drainage systems which were fed by the uplift of the Arabian Shield and by poorly aerated swamps and ponds that concentrated plant debris of the Cathaysian floral province in the Um Irna Formation. These proximal wet fan sediments are overlain by a dry fan characterized by extensive reddish floodplain deposits, anastomosing channel systems and paleosols. The wet fan is underlain by Cambrian sandstones. These units serve as the top and bottom seals of the OM-bearing system of the Um Irna Formation. The sedimentar...
Geothermal District Heating System City of Klamath Falls
1991-12-01
The city of Klamath Falls became interested in the possibility of a establishing geothermal district heating system for downtown government buildings in January 1977. Since that time, the project has undergone some controversial and interesting developments that may be of educational value to other communities contemplating such a project. The purpose and content of this article is to identify the historical development of the project; including the design of the system, well owner objections to the project, aquifer testing, piping failure, and future expansion and marketing incentives. The shallow geothermal reservoir in Klamath falls extends for at least 6.8 miles in a northwest-southeast direction, as shown on Figure 1, with a width of about 2 miles. More than 550 thermal wells ranging in depth from about 10 to 2,000 ft, and obtaining or contacting water from 70 to 230oF, have been drilled into the reservoir. The system is not geologically homogeneous. Great variations in horizontal permeability and many vertical discontinuities exist because of stratigraphy and structure of the area. Basalt flows, eruptive centers, fluvial and lacustrine deposits, diatomite and pyroclastic materials alternate in the rock column. Normal faults with large throw (estimated up to 1,700 ft) are spaced less than 3,300 ft apart and appear to be the main avenue of vertical movement of hot fluids. In order to more effectively utilize this resource, the city of Klamath Falls decided in 1978 to apply for a federal grant (Program Opportunity Notice to cost share field experiment projects) to construct a geothermal district heating system that would deliver geothermal fluids to areas not located on the resource. In 1977, several Geo-Heat Center staff members visited Reykjavik, Iceland, to study the design of their geothermal district heating systems. This was in part the basis for the conceptual design and feasibility study (Lund, 1979) of a downtown commercial district. The main difference between the Icelandic systems and the Klamath Falls design was that the Icelanders used an open-type system delivering geothermal fluids directly to the customers; whereas, the Klamath Falls type was a closed-system design employing a central heat exchanger.
Novel suspension cell-based vaccine production systems for Rift Valley fever virus-like particles
2010-01-01
Rift Valley fever virus (RVFV) is an arthropod-borne pathogen that often results in severe morbidity and mortality in both humans and livestock. As its geographic range continues to expand, it presents a real threat to naive populations around the world by accidental introduction (e.g., the result of increased travel) or intentional release (e.g., a bioterror event). While there is a clear need for a safe and efficacious vaccine against this emerging and re-emerging pathogen, no FDA-approved vaccine is currently available. This need was addressed by the establishment of novel mammalian and insect suspension cell line systems for the efficient production of RVF virus-like particle (VLP)-based vaccine candidates. A direct comparison of the production of RVF VLPs in these systems was performe...
2008-01-01
The assemblage structure and vertical distribution of deep-pelagic fishes relative to a mid-ocean ridge system are described from an acoustic and discrete-depth trawling survey conducted as part of the international Census of Marine Life field project MAR-ECO http://www.mar-eco.no. The 36-station, zig-zag survey along the northern Mid-Atlantic Ridge (MAR; Iceland to the Azores) covered the full depth range (0 to
2010-01-01
Iceland's neo-liberal laboratory ended in economic crash and political chaos. The business-oriented sectoral corporatist structure in Iceland created an ideal framework for the neo-liberal agenda. A comprehensive democratic corporatist framework, including the conditions for economic flexibility and political stability, was missing. The culture of consensus did not prevail. The paper shows how Iceland does not fit Katzenstein's theory. At the same time, the case of Iceland shows the value of the corporatist model in analyzing the process of change in a small society and its successes and failures.
2010-01-01
We review intraplate magmatism in Siberia and its folded surroundings from 480Ma to the present. We describe several large igneous provinces (LIPs) and the intervals in which they were continuously formed within the limits of the Siberian continent: the Altay-Sayan Early Paleozoic magmatic area (598-446Ma), the Altay-Sayan LIP (408-393Ma), the Viluy LIP (380-350Ma), the Barguzin-Vitim LIP (310-275Ma), the Late Paleozoic rift system of Central Asia (318-242Ma), the Siberian traps and West Siberian rift system (250-249Ma), the East-Mongolian and West-Trans-Baikalian LIP (228-195Ma), and a number of various aged Late Mesozoic and Cenozoic rift zones and magmatic areas (from 160Ma to the present day). Following Lawver and Muller (1994), Kharin (2000), Lawver et al. (2002) and Chernysheva et al...
2010-01-01
The three-dimensional shear velocity lithospheric structure at depths from 0 to 70 km beneath the southern Baikal rift system and its surroundings has been imaged by inversion of P-to-SV receiver functions from 46 digital stations operated in two teleseismic international projects in southern Siberia and Mongolia. The receiver functions were determined from teleseismic P waveforms and inverted to obtain depth dependences of S velocities at each station which were related to tectonic structures. The computed vertical and horizontal sections of the 3D shear velocity model imaged a transition from relatively thin crust of the southern Siberian craton to thicker crust in the folded area south and southeast of Lake Baikal, with a local zone of thin crust right underneath the South Baikal basin....
2010-01-01
We elucidated fine-scale heterogeneities of the seismogenic structure associated with the 2004 mid-Niigata Prefecture Earthquake (thrust fault), Japan, by deploying a dense portable seismic array in the southwestern edge of the source region to observe the aftershocks. A velocity model inverted from double-difference tomographic analysis with first arrival times shows that most aftershocks were aligned between sedimentary strata in the hanging wall and the basement in the footwall. The basement is characterized by clear step-like and tilted block structures that gradually deepen toward the west. The domino-tilted block structures of the basement reveal evidence of a Miocene rift system buried beneath the thick sedimentary sequence. The aftershocks appear to be aligned roughly along pre-exi...
2010-01-01
The use in regional interpretations of the Earth Gravity Model (EGM08) and Earth magnetic model (EMAG2) is evaluated by comparison to ground gravity and aeromagnetic data in the central sector of the West and Central African Rift System (WCARS). The comparison includes upward continuation, spectral analysis and pseudogravity calculation and statistical evaluation. A correlation between EMAG2 (which contains roughly 25km resolution aeromagnetic data in the region) and near-surface aeromagnetic data over WCARS is only true for the very low wavelength part but a strong similarity between EGM08 and ground gravity data can be confirmed. Interpretation of the EGM08 data allows identifying and confirming the position of major structural trends, and provides new information on the crustal architec...
Back arc extension in the Okinawa Trough
The Okinawa Trough, lying to the east of China, is a back arc basin formed by extension within continental lithosphere behind the Ryukyu trench-arc system. Middle to late Miocene uplift, associated with normal faulting of the initially adjacent Ryukyu nonvolcanic arc and the Taiwan-Sinzi folded belt, corresponds to the first rifting phase. The timing of rifting is supported by the presence of marine sediments of corresponding age drilled in the northern Okinawa Trough. The rifting occurred after a major early Miocene change in the motion of the Philippine plate with respect to Eurasia and ceased during the Pliocene. A second rifting phase started about 2 m.y. ago, at the Plio-Pleistocene boundary and has continue until the present time. It has proceeded to a more advanced stage in the middle and southern Okinawa Trough than it has farther north. Detailed bathymetric (Sea Beam), seismic reflection and magnetics data collected during the POP 1 cruise of the R/V Jean Charcot reveal the principal features of the extensional processes. The back are spreading phase started very recently in the southern and middle Okinawa Trough, as exemplified by several and echelon and, in some cases, overlapping active, central graben oriented N70/sup 0/ E--N80/sup 0/ E. Some of these depressions are intruded by volcanic ridges of fresh back arc basalt with associated large magnetic anomalies. Transform faults between these en echelon active rifts are not obvious.
Back arc extension in the Okinawa Trough
1987-12-10
The Okinawa Trough, lying to the east of China, is a back arc basin formed by extension within continental lithosphere behind the Ryukyu trench-arc system. Middle to late Miocene uplift, associated with normal faulting of the initially adjacent Ryukyu nonvolcanic arc and the Taiwan-Sinzi folded belt, corresponds to the first rifting phase. The timing of rifting is supported by the presence of marine sediments of corresponding age drilled in the northern Okinawa Trough. The rifting occurred after a major early Miocene change in the motion of the Philippine plate with respect to Eurasia and ceased during the Pliocene. A second rifting phase started about 2 m.y. ago, at the Plio-Pleistocene boundary and has continue until the present time. It has proceeded to a more advanced stage in the middle and southern Okinawa Trough than it has farther north. Detailed bathymetric (Sea Beam), seismic reflection and magnetics data collected during the POP 1 cruise of the R/V Jean Charcot reveal the principal features of the extensional processes. The back are spreading phase started very recently in the southern and middle Okinawa Trough, as exemplified by several and echelon and, in some cases, overlapping active, central graben oriented N70/sup 0/ E--N80/sup 0/ E. Some of these depressions are intruded by volcanic ridges of fresh back arc basalt with associated large magnetic anomalies. Transform faults between these en echelon active rifts are not obvious.
Preliminary studies of two-phase effects on pressure transient data
1986-03-01
In this paper we perform scoping calculations on the effects of two-phase zones on well pressure transients. Three different cases are considered. The first is that of a fully two-phase system (e.g. Krafla, Iceland). Some of the complexities of this type of system are discussed. The second problem is that of a single-phase liquid reservoir with a localized two-phase zone. Possible field examples include Cerro Prieto, Mexico and Baca, New Mexico, USA. We investigate the pressure transients in a well located near an isolated two-phase zone in a single-phase liquid reservoir, and compare them to type curves based upon the constant pressure approximation. The third problem considered is that of a two-phase layer overlying a single-phase liquid layer. One example of such a reservoir is the Svartsengi geothermal field in Iceland. The numerical code MULKOM is used to simulate the three cases.
Hydrothermal processes at seafloor spreading centers,
1983-01-01
This book examines research on the description and interpretation of hydrothermal and associated phenomena at seafloor spreading centers. An interdisciplinary overview of the subject is presented, including geological, geophysical, geochemical, and biological discoveries. The implications of the discoveries for understanding the earth's heat transfer, geochemical mass balances and cycles, mineralization, and biological adaptation are discussed. Topics considered include geologic setting (e.g., the four dimensions of the spreading axis, geological processes of the mid-ocean ridge), hydrothermal convection (e.g., oxygen and hydrogen isotope studies, the basic physics of water penetration into hot rock), Iceland and oceanic ridges (e.g., chemical evidence from Icelandic geothermal systems, the physical environment of hydrothermal systems), mass balances and cycles (e.g., reduced gases and bacteria in hydrothermal fluids, the effects of hydrothermal activity on sedimentary organic matter), ferromanganese deposits, hydrothermal mineralization, and the biology of hydrothermal vents.
Magneto-variational and magneto-telluric soundings in the central European rift system. Final report
The aims of the project are: (1) to investigate the relation between electrical conductivity and temperature of the crust and mantle of the Rhinegraben and associated areas; (2) to develop a digital recording system and the computer software for geoelectric and geomagnetic field data; (3) to analyze and interpret the data to obtain models of the conductivity structure.
Magneto-variational and magneto-telluric soundings in the central European rift system. Final report
The aims of the project are: (1) to investigate the relation between electrical conductivity and temperature of the crust and mantle of the Rhinegraben and associated areas; (2) to develop a digital recording system and the computer software for geoelectric and geomagnetic field data; (3) to analyze and interpret the data to obtain models of the conductivity structure.
Cretaceous oil and gas accumulation
1983-01-01
A review is cited of Cretaceous oil and gas bearing basins of the world which are confined to the epirift troughs, to taphrogeneous semigrabens in continental margins and to leaward seas of systems of island arcs. The circumstance of broad epicontinental seas, the saline stratification of the sea waters, the glacierless climate and the highly productive vegetation which is favorable for accumulation of hydrocarbons (UV) came together as a result of the tectonomagmatic evolution of the rift systems which formed in the early Mesozoic and the vertical movements and inertial advancement of the plates along the boundary fractures.
Structure of the Espanola Basin, Rio Grande Rift, New Mexico, from SAGE seismic and gravity data
Seismic and gravity data, acquired by the SAGE program over the past twelve years, are used to define the geometry of the Espanola basin and the extent of pre-Tertiary sedimentary rocks. The Paleozoic and Mesozoic units have been thinned and removed during Laramide uplift in an area now obscured by the younger rift basin. The Espanola basin is generally a shallow, asymmetric transitional structure between deeper, better developed basins to the northeast and southwest. The gravity data indicate the presence of three narrow, but deep, structural lows arrayed along the Embudo/Pajarito fault system. These sub-basins seem to be younger than the faults on the basin margins. This apparent focussing of deformation in the later history of the basin may be a response to changes in regional stress or more local accommodation of the rift extension. Future work is planned to develop seismic data over one of these sub-basins, the Velarde graben, and to better define the gravity map in order to facilitate three-dimensional modeling.
Structure of the Espanola Basin, Rio Grande Rift, New Mexico, from SAGE seismic and gravity data
Seismic and gravity data, acquired by the SAGE program over the past twelve years, are used to define the geometry of the Espanola basin and the extent of pre-Tertiary sedimentary rocks. The Paleozoic and Mesozoic units have been thinned and removed during Laramide uplift in an area now obscured by the younger rift basin. The Espanola basin is generally a shallow, asymmetric transitional structure between deeper, better developed basins to the northeast and southwest. The gravity data indicate the presence of three narrow, but deep, structural lows arrayed along the Embudo/Pajarito fault system. These sub-basins seem to be younger than the faults on the basin margins. This apparent focussing of deformation in the later history of the basin may be a response to changes in regional stress or more local accommodation of the rift extension. Future work is planned to develop seismic data over one of these sub-basins, the Velarde graben, and to better define the gravity map in order to facilitate three-dimensional modeling.
Structure of the Espanola Basin, Rio Grande Rift, New Mexico, from SAGE seismic and gravity data
1995-04-01
Seismic and gravity data, acquired by the SAGE program over the past twelve years, are used to define the geometry of the Espanola basin and the extent of pre-Tertiary sedimentary rocks. The Paleozoic and Mesozoic units have been thinned and removed during Laramide uplift in an area now obscured by the younger rift basin. The Espanola basin is generally a shallow, asymmetric transitional structure between deeper, better developed basins to the northeast and southwest. The gravity data indicate the presence of three narrow, but deep, structural lows arrayed along the Embudo/Pajarito fault system. These sub-basins seem to be younger than the faults on the basin margins. This apparent focussing of deformation in the later history of the basin may be a response to changes in regional stress or more local accommodation of the rift extension. Future work is planned to develop seismic data over one of these sub-basins, the Velarde graben, and to better define the gravity map in order to facilitate three-dimensional modeling.
1995-12-31
The Jatoba basin is located at the southern portion of the State of Pernambuco, northeastern Brazil. It represents an inflection of the Tucano-Jatoba rift system which is oriented N-S in the south and turns to N 70{sup 0} C E within the Jatoba basin, where the presence of the Pernambuco lineament exerts structural control. The orientation of the pre-existing weakness zones submitted to the rift generator stress field resulted in strike-slip tectonics, active since the beginning of basin formation. This tectonism is evident in many seismic sections showing flower structures, difference in layer thickness on each side of faults, intense fragmentation zones and en echelon faults on seismic maps. The tress direction responsible for the rift-opening is supposed to be E-W. Inversion tectonic structures observed in seismic sections are interpreted as restricted transpressive events. (author). 9 refs., 5 figs
2010-01-01
At the northwest end of the Lake Turkana Basin (northern Kenya Rift), intensive fieldwork conducted on the Plio-Pleistocene fluvio-lacustrine Nachukui Formation by the National Museums of Kenya and the West Turkana Archaeological Project (WTAP), led to the discovery of more than 50 archaeological sites aged between 2.4 and 0.7Ma. Among them is the Lokalalei archaeological site complex, which includes the two oldest archaeological sites (2.34Ma) found in the Kenyan segment of the East African Rift System. The environmental background of the two sites was described as a succession of ephemeral streams with floodplain palaeosols in which the archaeological sites are situated, bordering the western bank of a large axial meandering river flowing southward. The Lokalalei 1 (LA1) and Lokalalei 2C...
Geologic evolution of the Jemez Mountains and their potential for future volcanic activity
Geophysical and geochemical data and the geologic history of the Rio Grande rift and the vicinity of the Jemez Mountains are summarized to determine the probability of future volcanic activity in the Los Alamos, New Mexico area. The apparent cyclic nature of volcanism in the Jemez Mountains may be related to intermittent thermal inputs into the volcanic system beneath the region. The Jemez lineament, an alignment of late Cenozoic volcanic centers that crosses the rift near Los Alamos, has played an important role in the volcanic evolution of the Jemez Mountains. Geophysical data suggest that there is no active shallow magma body beneath the Valles caldera, though magma probably exists at about 15 km beneath this portion of the rift. The rate of volcanism in the Jemez Mountains during the last 10 million years has been 5 x 10/sup -9//km/sup 2//y. Lava or ash flows overriding Laboratory radioactive waste disposal sites would have little potential to release radionuclides to the environment. The probability of a new volcano intruding close enough to a radioactive waste disposal site to effect radionuclide release is 2 x 10/sup -7//y.
Geologic evolution of the Jemez Mountains and their potential for future volcanic activity
1982-01-01
Geophysical and geochemical data and the geologic history of the Rio Grande rift and the vicinity of the Jemez Mountains are summarized to determine the probability of future volcanic activity in the Los Alamos, New Mexico area. The apparent cyclic nature of volcanism in the Jemez Mountains may be related to intermittent thermal inputs into the volcanic system beneath the region. The Jemez lineament, an alignment of late Cenozoic volcanic centers that crosses the rift near Los Alamos, has played an important role in the volcanic evolution of the Jemez Mountains. Geophysical data suggest that there is no active shallow magma body beneath the Valles caldera, though magma probably exists at about 15 km beneath this portion of the rift. The rate of volcanism in the Jemez Mountains during the last 10 million years has been 5 x 10/sup -9//km/sup 2//y. Lava or ash flows overriding Laboratory radioactive waste disposal sites would have little potential to release radionuclides to the environment. The probability of a new volcano intruding close enough to a radioactive waste disposal site to effect radionuclide release is 2 x 10/sup -7//y.
2006-08-15
This report describes the Norwegian Radiation Protection Authority's equipment for use in quality control of non-dosimetric parameters in CT-based radiotherapy. Results from six radiotherapy centers in Norway and one in Iceland are presented. The feasibility of the phantoms is evaluated and a system for distribution of the phantoms to the radiotherapy departments in Norway is organized. (author)
Phreatomagmatic volcanic hazards where rift-systems meet the sea, a study from Ambae Island, Vanuatu
2009-01-01
Ambae Island is a mafic stratovolcano located in the northern Vanuatu volcanic arc and has a NESW rift-controlled elongated shape. Several hundred scoria cones and fissure-fed lava fields occur along its long axis. After many decades of quiescence, Ambae Island erupted on the 28th of November 2005, disrupting the lives of its 10,000 inhabitants. Its activity remained focused at the central (crater-lake filled) vent and this is where hazard-assessments were focused. These assessments initially neglected that maars, tephra cones and rings occur at each tip of the island where the eruptive activity occurred
Noble gas compositions of the lithospheric mantle below the Chyulu Hills volcanic field, Kenya
2007-01-01
We performed a noble gas isotope study on mantle xenoliths from the Quaternary volcanic field of Chyulu Hills, S Kenya, c. 100km east of the Kenya rift graben. 4He/3He ratios were in the range of 100000120000 and indistinguishable from other subcontinental lithospheric mantle compositions worldwide and similar to most results of the East African rift system. 21Ne/22Ne ratios corrected for atmospheric contributions displayed less nucleogenic values compared to mid ocean ridge basalts. This requires addition of Ne from a more primitive mantle source, that could be assigned to the postulated Kenyan mantle plume or alternatively might be attributed to the high 3He/4He Afar hotspot c. 2000km distant. Whereas He and Ne isotopes reflect a rather homogeneous source composition, we ...
2010-01-01
The Parentis and Arzacq-Mauleon basins located in front of the V-shaped oceanic propagator in the Bay of Biscay present evidence for extreme crustal thinning. In this paper we investigate the 3D structure of these rift basins, based on field observations and the interpretation of seismic data. We compare these results with those obtained from two different and independent inversion methods: first a 3D gravity inversion and second the standard Euler deconvolution. For the Mauleon Basin our results show that the positive gravimetric anomaly identified above its southern margin is the consequence of two shallower high density bodies that are separated by the Pamplona fault and a deeper high density body. The high density bodies can be explained by the presence of mid-crustal and mantle rocks ...
Strategic aspects of exploiting geothermal energy for industrial purposes
Geothermal energy is widely used in Iceland for space heating swimming pools and snow melting systems as well as for greenhouses and soil heating and aquaculture. Its contribution to the standard of living in Iceland is very substantial. The industrial applications are, however, fewer today than anticipated twenty years ago. This paper considers some of the socio-economic reasons for that. Although geothermal energy is generally a cost competitive source of energy, it is site limited and does not by itself provide sufficient economic incentive to attract manufacturing or process industries. This generally requires another, locally available production factor offering further competitive advantage to justify greenfield investments. World economic slow-downs, and structural problems in many process industries after the energy crisis of the seventies have reduced interest for investments in energy intensify industries world wide. While public sector initiative motivated by technological possibilities was instrumental for developing geothermal resources in the past, time has now come for private sector initiative, led by market interest, to identify and exploit opportunities for using geothermal energy for industrial purposes. National and local governments must, however, provide the appropriate incentives to stimulate such developments.
Rapid evolution of phenotypic divergence in fish populations
2010-12-31
ObjectivesThe main objective is to exploit Arctic charr populations in Iceland to investigate the parallel evolution of phenotypic traits in different populations subject to similar environments as well as the role of intraspecific competition in producing phenotypic divergence. In particular, we will use a combination of laboratory experiments and field studies to address the fundamental issue of how selection and plasticity manifest themselves at the level of physiological systems and how this produces [continued...]DescriptionIceland represents a natural laboratory for studying the colonization of freshwater habitats by fish since rivers and lakes all date from the end of the last Ice-Age less than 10,000 years ago. The North Atlantic provided a refuge for species such as arctic charr (Salvelinus alpinus) which invaded freshwater once the ice retreated. New habitats and the lack of competing species led to the appearance of different forms of Artic charr, called morphs. In particular, 27 discrete populations of dwarf [continued...]
2010-01-01
We present Interferometric Synthetic Aperture Radar (InSAR) data from 1992-1999 and 2003-2008 as well as GPS data from 2000-2009 for the active plate boundary on the Reykjanes Peninsula, southwest Iceland. The geodetic data reveal deformation mainly due to plate spreading, anthropogenic subsidence caused by geothermal fluid extraction and, possibly, increasing pressure in a geothermal system. Subsidence of around 10cm is observed during the first 2years of production at the Reykjanes geothermal power plant, which started operating in May 2006. We model the surface subsidence around the new power plant using point and ellipsoidal pressure sources in an elastic halfspace. Short-lived swarms of micro-earthquakes as well as aseismic fault movement are observed near the geothermal field followi...
The Reykjanes geothermal system is an active, high-temperature, seawater-dominated system located on the southwestern coast of Iceland and is a target site for deep drilling by the Iceland Deep Drilling Project (IDDP). Geothermal fluids produced from drillholes in the Reykjanes geothermal system contain As concentrations up to 240 ppb; however, the distribution of arsenic within the geothermal system is poorly known. The Reykjanes geothermal system is located along the landward continuation of the Mid-Atlantic Ridge (MAR) and has been studied extensively through the efforts of the IDDP and others, and so provides an opportunity to evaluate the hydrothermal geochemistry of arsenic in a basalt-hosted geothermal system. We measured the bulk rock concentration of As, Fe, S, Ti and thirteen other trace metals and metalloids by ICP-MS and ICP-OES in fifty drillhole cutting samples from 350 to 3050 m depth in Reykjanes geothermal well RN-17. The host rock consists of layers of hyaloclastite and fractured crystalline basalts that are frequently intruded by shallow mafic intrusives. Previous studies indicate that the As content of Icelandic basalts is related to their degree of differentiation, with olivine-tholeiites containing 0.02-0.18 ppm As, tholeiites 0.36-0.38 ppm As, and Icelandites 0.76-1.59 ppm As. In RN-17, As content varied between 0.4 and 0.8 ppm for ~70% of the 2700 m profile, suggesting a background concentration of ~0.6 ppm As for the system. The As minima was 0.3 ppm at 2000 m. There were two distinct As maxima in the drillhole cuttings: As was elevated to 0.8-2.3 ppm and 1.7-2.9 ppm at 400-650 m and 1750-1900 m, respectively. From 2300 to ~2700 m, arsenic was slightly elevated (>0.6 - 1.1 ppm). Of the elements analyzed, As correlated most closely with S, and it did so more closely than any of the other elements, including the common chalcophiles Ni, Cu, Zn and Pb. This suggests that hydrothermal sulfides efficiently sequester arsenic and that arsenic is behaving similarly to sulfur within high-temperature geothermal systems. The depths at which arsenic and sulfur were enriched partially overlap with hyaloclastite basaltic tuffs and/or breccias, suggesting that host-rock permeability and the related variables of fluid pressure and water/rock ratio may control sulfide formation and therefore also arsenic distribution. Within the global As cycle, As is concentrated in sedimentary rocks (5-10 ppm) and in felsic extrusive rocks (3.2-5.4 ppm). The results presented here indicate that hydrothermal alteration of basaltic rocks also locally concentrates As up to ~ 3 ppm, producing initial As and S heterogeneities that will influence the geochemical signature of later metamorphism.
Cenozoic Evolution of the Nile Basin
2009-01-01
The Cenozoic evolution of the Nile basin reflects a complex interaction between tectonic, volcanic and climatic events. The Ethiopian and Ugandan headwaters of the Nile attain elevations in excess of 2 km, while the watersheds rise to over 5 km. The Ethiopian tributaries of the Nile (notably the Blue Nile/Abbai and the Atbara/Tekezze) provide the bulk of the flood discharge and sediment load, but the Ugandan tributaries, via the White Nile, provide the reliable dry season discharge responsible for maintaining perennial flow in the main Nile. The hydrologi-cal differences between the Blue and White Nile rivers reflect their very different geomorphic histories, reflecting the Cenozoic tectonic and volcanic evolution of their respective headwaters. The volume of rock eroded from the Ethiopian headwaters of the Blue Nile/Abbai and the Atbara/Tekezze river basins since the extrusion of the Oligocene Trap Series basalts 30 Ma ago amounts to 102,000 ± 50 km3 from a catchment area of 275,000 km2. The volume of rock eroded from the Ethiopian headwaters region of the Blue Nile and Atbara rivers is comparable to that estimated for the total volume of the Nile delta and submerged Nile cone in the eastern Mediterranean, which amounts to 150,000 ± 50,000 km3. The concordance between these two independent estimates is consistent with an Ethiopian source for the bulk of the Nile cone sediment since the Pliocene, when there seems to have been an increase in erosion in the Blue Nile headwaters linked to an increase in the rate of tectonic uplift. The origin of the White Nile as a large, permanent river is intimately connected with the development of the western branch of the East African rift system. Prior to the onset of rifting much of the drainage from central Africa was directed westward, into the Congo basin. Rifting led to the capture of a number of major tributaries of the Congo River and the redirection of river systems, producing south-to-north directed axial drainage within the rift and radial drainage into the Victoria basin. Rifting and associated rift-flank uplift was also responsible for the development of the large lake basins (Victoria, Albert, Edward, George and Kyoga), which characterise the upper White Nile catchment. Exactly when drainage from the present headwaters became linked to the White Nile is still unclear, but it seems likely that Lake Victoria, which today provides around 90% of the runoff to the White Nile, may be no more than about 0.5 million years old. While rift development and ongoing rift-related tectonic activity have controlled the long-term evolution of the White Nile headwaters, it is clear that much of the shorter term variations in discharge are probably related to climate change. There is evidence of a progressive tendency to drier conditions over the past 1.5 Ma, which may have been related to the development of topographic barriers that limited the penetration of humid air masses into the continental interior. Superimposed on this long-term trend are astronomically driven changes and brief, abrupt climatic excursions that were probably driven by events outside tropical Africa.Michael R. Talbot and Martin A.J. Williams Publisher: Springer Contributor: School of Social Sciences : Geographical and Environmental Studies Relation: Monographiae Biologicae ; v. 89 Other identifier: The Nile: Origin, Environments, Limnology and Human Use / H. J. Dumont (ed.), pp.37-60; 9781402097256; 0020097112; 10.1007/978-1-4020-9726-3_3 Language: en Rights: 2009 Springer Science + Business Media B.V.
2010-01-01
The Reykjanes geothermal system is a seawater-recharged hydrothermal system that appears to be analogous to seafloor hydrothermal systems in terms of host rock type and low water/rock alteration. The similarities make the Reykjanes system a useful proxy for seafloor vents. At some time during the Pleistocene, the system was dominated by meteoric water recharge, and fluid composition at Reykjanes has evolved through time as a result of changing proportions of meteoric water influx as well as differing pressure and temperature conditions. The purpose of this study is to characterize secondary mineralization, degree of metasomatic alteration, and bulk composition of cuttings from well RN-17 from the Reykjanes geothermal system. The basaltic host rock includes hyaloclastite, breccia, tuff, ext...
Preliminary isotopic study of Lake Asal system (Republic of Djibouti)
1979-01-01
The saline Lake Asal at 155 m below sea level in the Afar Rift (Republic of Djibouti) is fed mainly by sea water. In spite of the intense evaporation (about 3 m annually), the 18O and deuterium enrichments of the lake water are relatively low, because of the reduced activity of water as a consequence of the high salt content. Isotopic balance of the lake, as well as lithium and sulphate balances, support the hypothesis of leakages from the lake of about 15 to 20% of the inflow. (author)
Plate tectonics and the Gulf of California region
1990-11-01
The geology and tectonism of California have been influenced greatly by the collision and interaction between the Pacific plate and the North American plate. The forces generated by this interaction caused substantial horizontal movement along the San Andreas fault system and created the Gulf of California rift zone. This article summarizes the unique features of the gulf, describes the theory of plate tectonics, explains how tectonism may have affected the geologic evolution and physiography of the gulf, and illustrates the process by which the Colorado River became linked to the gulf.
1999-07-01
Early Cretaceous ostracods living within the rift lakes of Central Gondwana reflect, through their morphology, abundance and species diversity, depositional environments and changes in water chemistry that occurred within the lakes at that time. By studying the indigenous ostracod assemblages it is possible to interpret past environmental changes with respect to both water depth and water chemistry, and to utilize this information to estimate the probability of source and reservoir sediment deposition. The alternation of siliclastic and carbonate sequences throughout rift lacustrine sediments can be explained by changes in the depositional environments and related water-level movements. Such changes being brought about as a direct result of tectonism leading to increases or decreases in precipitation as a consequence of river capture or regional changes in climate. Two cycles of sedimentary infill are recognized, each initiated by an onlapping, fining-upwards transgressive systems tract within which a maximum flooding surface is developed. This is followed by a coarsening-upwards highstand systems tract in which a prograding sequence retains the diverse ostracod fauna of the transgressive systems tract below. A coarsening-upwards lowstand systems tract, having a low diversity of ostracod fauna, brings each cycle to a close. An understanding of the cyclic sequence stratigraphy of these basins suggests that the break-up of Gondwana commenced as early as the late Barremian. Commercially, these rift basin lakes contain excellent hydrocarbon source rocks, but it is the interpretation of the lacustrine faunas that provides the essential information as to lake size and hydrocarbon potential.
Fault Growth and reactivation during 3-D strain accommodation in transtensional hydrocarbon basins
2006-09-30
DescriptionTectonic stretching or rifting of the Earths' crust leads to the development of actively subsiding regions known as basins into which sedimentary material derived from the erosion of surrounding mountainous regions accumulates. Brittle faults are one of the main ways in which such stretching and subsidence are accommodated in the upper crust. The shapes, sizes and interaction of fault systems changes as they grow and this plays a central role in controlling ihe shape and history of subsidenc [continued...]
Cretaceous:Tectonics and Paleoclimate
As part of the Berkeley Museum of Paleontology site, this page provides general information about earth systems of the Cretaceous Period. The site contains text, supporting diagrams and links to more detailed resources concerned with plate tectonics and past climates. Specific topics covered in this site include the rifting of Pangea, global climate, appearance and diversification of angiosperms, end of Cretaceous extinction and Chicxulub impact.
Reconstructing the tectonic history of Fennoscandia from its margins: The past 100 million years
1995-12-01
In the absence of onland late Mesozoic and Cenozoic geological formations the tectonic history of the Baltic Shield over the past 100 million years can be reconstructed from the thick sedimentary basins that surround Fennoscandia on three sides. Tectonic activity around Fennoscandia through this period has been diverse but can be divided into four main periods: a. pre North Atlantic spreading ridge (100-60 Ma) when transpressional deformation on the southern margins of Fennoscandia and transtensional activity to the west was associated with a NNE-SSW maximum compressive stress direction; b. the creation of the spreading ridge (60-45 Ma) when there was rifting along the western margin; c. the re-arrangement of spreading axes (45-25 Ma) when there was a radial compression around Fennoscandia, and d. the re-emergence of the Iceland hot-spot (25-0 Ma) when the stress-field has come to accord with ridge or plume `push`. Since 60 Ma the Alpine plate boundary has had little influence on Fennoscandia. The highest levels of deformation on the margins of Fennoscandia were achieved around 85 Ma, 60-55 Ma, with strain-rates around 10{sup -9}/year. Within the Baltic Shield long term strain rates have been around 10{sup -1}1/year, with little evidence for significant deformations passing into the shield from the margins. Fennoscandian Border Zone activity, which was prominent from 90-60 Ma, was largely abandoned following the creation of the Norwegian Sea spreading ridge, and with the exception of the Lofoten margin, there is subsequently little evidence for deformation passing into Fennoscandia. Renewal of modest compressional deformation in the Voering Basin suggest that the `Current Tectonic Regime` is of Quaternary age although the orientation of the major stress axis has remained consistent since around 10 Ma. The past pattern of changes suggest that in the geological near-future variations are to be anticipated in the magnitude rather than the orientation of stresses.
The light lithophile (Li, Be and B) and halogen (F, Cl) elements are powerful tracers of fluid transfer due to their mobility during high temperature hydrothermal processes and metamorphic devolatilisation. Moreover, although a great deal of studies have been carried out on these elements in whole rock and minerals of altered rocks from divergent and convergent plate margins, an inventory for mineral phases from the altered Icelandic oceanic crust is still incomplete. In the present paper we report the results of in situ EPMA and SIMS investigations on variously altered magmatic (plagioclase and clinopyroxene) and hydrothermal phases (amphibole and epidote) from selected cuttings drilled at different depths (400 - 3000 m) of the well RN-17, Reykjanes geothermal system (SW Iceland). Our study has benefited from the use of high-magnification SEM investigations; from ICP-MS on Li, P-TIMS determinations of boron isotope composition (?11B) and ID analyses of B contents on the whole rock. Particularly, SIMS data on epidote have shown that alteration beneath Reykjanes has been more efficient in the shallow and intermediate cuttings, while whole rock data on boron isotope composition have revealed that the alteration has been caused firstly by ?11B-poor fluids and successively by ?11B-rich seawater-hydrothermal fluids.
The Rome trough and evolution of the Iapetean margin
1991-08-01
Recent structural mapping of the Rome trough suggests a complex structure very different from the symmetrical and laterally continuous graben commonly depicted. Early and Middle Cambrian extension in the Rome trough of eastern Kentucky and adjacent areas resulted in a series of alternately facing half-grabens with variable displacement. These half-grabens are bounded by southwest-northeast-trending normal faults (e.g., Kentucky River and Warfield faults), which are laterally continuous only on the order to tens of kilometers. The Rome trough is laterally segmented by north-south-trending faults (e.g., Lexington fault) commonly expressed as flexures in younger rocks (e.g., Burning Springs anticline and Floyd County channel). Many of these north-south-trending faults have significant left-lateral displacement, and probably represent reactivated thrust faults of the Grenville tectonic front. The Rome trough and the associated Mississippi Valley, Rough Creek, and Birmingham fault systems were initiated during an Early Cambrian shift in sea-floor spreading from the Blue Ridge-Pine Mountain rift to the Ouachita rift along the Alabama-Oklahoma transform fault. These fault systems have been proposed as having originated from extensional stress propagated northward from the Ouachita rift across the transform fault. In the alternate model proposed here, faulting was brittle, extensional failure resulting form subsidence and flexure of the continental margin to the east. Following initiation of sea-floor spreading at the Blue Ridge-Pine Mountain rift in the latest Proterozoic, margin subsidence in the presence of the Alabama-Oklahoma transform boundary and the inherited Grenville tectonic front resulted in this interior cratonic fault system.
Coarse-grained deep-water gravity flow deposits from the Cretaceous of East Greenland
1999-07-01
Coarse-grained deep-water gravity flow deposits of Cretaceous age are important exploration targets on the outer West Norway shelf. Correlative deposits are exposed onshore East Greenland and were formed during a succession of rift events. A spectrum of gravity flow deposits are identified, ranging from chaotic olisthostrome- type, base-of-slope breccias, over resedimented conglomerates and slide and slump sandstones, to well-organized sandy turbidite sheet systems. Transport directions were always due east, away from the fault scarps. It has been argued that the wide Jurassic fault blocks were fragmented into narrower blocks during the Cretaceous rift events. If this were the case, gravity flows would have been deflected into north-south directions following the axes of the narrow tilted blocks. This configuration undoubtedly results from Cenozoic syn- and post-break up rift-tectonism. The gravity flow systems are too small to have been part of the feeder system for the correlative deposits of the outer Norwegian shelf. The wide spectrum of Cretaceous gravity flow deposits of East Greenland provide good outcrop analogues for the deeply buried correlative deposits on the Norwegian shelf and aid in dating Cretaceous rift events in the seaway between Greenland and Norway.
Continental rifting - Progress and outlook
1981-07-21
It is noted that in spite of the flood of new data on continental rifts in the last 15 years, there is little consensus about the basic mechanisms and causes of rifting. The remarkable similarities in rift cross sections (shown in a figure), are considered to suggest that the anomalous lithospheric structure of rifts is more dependent on lithosphere properties than the mode of rifting. It is thought that there is a spectrum of rifting processes for which two fundamental mechanisms can be postulated: an active mechanism, whereby thermal energy is transmitted into the lithosphere from the underlying asthenosphere, and a passive mechanism by which mechanical energy is transmitted laterally through the lithosphere as a consequence of plate interactions at a distance. In order to permit the concept of the two fundamentally different mechanisms to be tested, a tentative classification is proposed that divides rifts into two basic categories: active rifting and passive rifting. Here, the magnitude of active rifting will depend on the rate at which lithosphere moves over the thermal source, with rifts being restricted to stationary or slow-moving plates.
Hydrocarbon prospectivity of the Argentine Continental Slope
A rift basin containing stratigraphic and structural closures is developed along the Argentine slope over a distance of some 1000 km and area of 50,000 km[sup 2] in potentially exploitable water depths of 200 to 1500 m. No wells exist on this part of the continental margin. Rifting began during the Late Triassic/Jurassic and ended in Early Cretaceous. The first marine seaways flooded the Rift alluvial plains and lake. In Hauterian-Barrenian time, low circulation marine conditions with oxygen deficiency prevailed up to Rio Grande/Walvis Ridge flooding in part the coastal pull-apart basins. A major marine transgression in the Maastrichtian formed a widespread seal over the entire shelf and slope area. Four play types were identified: (1) a major north-east trending elongate delta system sourced inland from the San Julien (N. Malvinas) Basin and deposited on the southern Patagonian shelf and rise, (2) reworked deltaic barrier sands accumulated along the crest of the Outer Basement Ridge, (3) The Outer Basement Ridge, a major structural closure 400 km long, and (4) a series of margin-parallel rift systems in the offshore region between the 200 m and 1500 m isobaths. Regional seismic data and geological correlations suggest that oil prone source rocks are likely in the Middle and Upper Jurassic and Cretaceous formations. Source rocks are probably mature east and west of the Outer Basement Ridge and in the easterndepocenter of the Colorado Basin. Eastward migration from Jurassic age lacustrine source rocks in the Colorado Basin may have charged traps along the crest of the Outer Basement Ridge. Westward directed migration from deeply buried Aptian age marine source rocks in the Atlantic basins has probably charged prospective stratigraphic and structural traps in a suite of coast-parallel grabens developed on the Argentine continental shelf and slope. The Argentine offshore region, therefore, offers significant encouragement as a productive hydrocarbon province.
Hydrocarbon prospectivity of the Argentine Continental Slope
1993-02-01
A rift basin containing stratigraphic and structural closures is developed along the Argentine slope over a distance of some 1000 km and area of 50,000 km[sup 2] in potentially exploitable water depths of 200 to 1500 m. No wells exist on this part of the continental margin. Rifting began during the Late Triassic/Jurassic and ended in Early Cretaceous. The first marine seaways flooded the Rift alluvial plains and lake. In Hauterian-Barrenian time, low circulation marine conditions with oxygen deficiency prevailed up to Rio Grande/Walvis Ridge flooding in part the coastal pull-apart basins. A major marine transgression in the Maastrichtian formed a widespread seal over the entire shelf and slope area. Four play types were identified: (1) a major north-east trending elongate delta system sourced inland from the San Julien (N. Malvinas) Basin and deposited on the southern Patagonian shelf and rise, (2) reworked deltaic barrier sands accumulated along the crest of the Outer Basement Ridge, (3) The Outer Basement Ridge, a major structural closure 400 km long, and (4) a series of margin-parallel rift systems in the offshore region between the 200 m and 1500 m isobaths. Regional seismic data and geological correlations suggest that oil prone source rocks are likely in the Middle and Upper Jurassic and Cretaceous formations. Source rocks are probably mature east and west of the Outer Basement Ridge and in the easterndepocenter of the Colorado Basin. Eastward migration from Jurassic age lacustrine source rocks in the Colorado Basin may have charged traps along the crest of the Outer Basement Ridge. Westward directed migration from deeply buried Aptian age marine source rocks in the Atlantic basins has probably charged prospective stratigraphic and structural traps in a suite of coast-parallel grabens developed on the Argentine continental shelf and slope. The Argentine offshore region, therefore, offers significant encouragement as a productive hydrocarbon province.
A mechanism to thin the continental lithosphere at magma-poor margins.
Where continental plates break apart, slip along multiple normal faults provides the required space for the Earth's crust to thin and subside. After initial rifting, however, the displacement on normal faults observed at the sea floor seems not to match the inferred extension. Here we show that crustal thinning can be accomplished in such extensional environments by a system of conjugate concave downward faults instead of multiple normal faults. Our model predicts that these concave faults accumulate large amounts of extension and form a very thin crust (< 10 km) by exhumation of mid-crustal and mantle material. This transitional crust is capped by sub-horizontal detachment surfaces over distances exceeding 100 km with little visible deformation. Our rift model is based on numerical experiments constrained by geological and geophysical observations from the Alpine Tethys and Iberia/Newfoundland margins. Furthermore, we suggest that the observed transition from broadly distributed and symmetric extension to localized and asymmetric rifting is directly controlled by the existence of a strong gabbroic lower crust. The presence of such lower crustal gabbros is well constrained for the Alpine Tethys system. Initial decoupling of upper crustal deformation from lower crustal and mantle deformation by progressive weakening of the middle crust is an essential requirement to reproduce the observed rift evolution. This is achieved in our models by the formation of weak ductile shear zones.
HYDROCARBON CONSTITUENTS OF ICELAND LEAF FOSSIL
1970-10-01
The hydrocarbon content of leaf fossils from Iceland has been investigated by gas chromatography-mass spectrometry. The distribution patterns of normal hydrocarbons, branched hydrocarbons, and cyclic hydrocarbons are compared to those of present-day living organisms. The diagenetic pathways of these hydrocarbons are discussed.
Earth Observatory: Ash Plume across the North Atlantic
This Earth Observatory image of the day shows the ash plume of Iceland's Eyjafjallajokull volcano spreading from Iceland to continental Europe. The page includes a short article on the volcano and its effect on European airspace.
Vatnajokull, Iceland, is the Earth's most studied ice cap and represents a classical glaciological field site on the basis of S. Palsson's seminal glaciological field research in the late 18th century. Since ...
Broiler Campylobacter Contamination and Human Campylobacteriosis in Iceland ▿ †
2008-11-01
To examine whether there is a relationship between the degree of Campylobacter contamination observed in product lots of retail Icelandic broiler chicken carcasses and the incidence...Full Text Available
Asphalt facing for Icelandic dam
1978-08-01
Sigalda dam, with an associated 150 MW powerplant, is the first structure of its size and type with an impervious frontal facing, to be built in Iceland. Its design and construction are described, including details of the application of the asphalt facing.
Website Policies and Important Links Comments
 |
 |
 |
WorldWideScience.org is maintained by the
U.S. Department of Energy's
Office of Scientific and Technical Information as the Operating Agent
for the WorldWideScience Alliance.