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Trending Faults (trending + fault)

Distribution by Scientific Domains

Earth and Environmental Science	75%

Selected Abstracts

K-Ar age determination, whole-rock and oxygen isotope geochemistry of the post-collisional Bizmi,en and Çalt, plutons, SW Erzincan, eastern Central Anatolia, Turkey

GEOLOGICAL JOURNAL, Issue 4 2005
Ayten Önal
Abstract Post-collisional granitoid plutons intrude obducted Neo-Tethyan ophiolitic rocks in central and eastern Central Anatolia. The Bizmi,en and Çalt, plutons and the ophiolitic rocks that they intrude are overlain by fossiliferous and flyschoidal sedimentary rocks of the early Miocene Kemah Formation. These sedimentary rocks were deposited in basins that developed at the same time as tectonic unroofing of the plutons along E,W and NW,SE trending faults in Oligo-Miocene time. Mineral separates from the Bizmi,en and Çalt, plutons yield K-Ar ages ranging from 42 to 46,Ma, and from 40 to 49,Ma, respectively. Major, trace, and rare-earth element geochemistry as well as mineralogical and textural evidence reveals that the Bizmi,en pluton crystallized first, followed at shallower depth by the Çalt, pluton from a medium-K calcalkaline, I-type hybrid magma which was generated by magma mixing of coeval mafic and felsic magmas. Delta 18O values of both plutons fall in the field of I-type granitoids, although those of the Çalt, pluton are consistently higher than those of the Bizmi,en pluton. This is in agreement with field observations, petrographic and whole-rock geochemical data, which indicate that the Bizmi,en pluton represents relatively uncontaminated mantle material, whereas the Çalt, pluton has a significant crustal component. Structural data indicating the middle Eocene emplacement age and intrusion into already obducted ophiolitic rocks, suggest a post-collisional extensional origin. However, the pure geochemical discrimination diagrams indicate an arc origin which can be inherited either from the source material or from an upper mantle material modified by an early subduction process during the evolution of the Neo-Tethyan ocean. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Using Temperature to Test Models of Flow Near Yucca Mountain, Nevada

GROUND WATER, Issue 5 2003
Scott Painter
Ground water temperatures in the fractured volcanic aquifer near Yucca Mountain, Nevada, have previously been shown to have significant spatial variability with regions of elevated temperatures coinciding roughly with near-vertical north-south trending faults. Using insights gained from one-dimensional models, previous investigators have suggested upwelling along faults from an underlying aquifer as a likely explanation for this ground water temperature pattern. Using a three-dimensional coupled flow and heat-transport model, we show that the thermal high coinciding with the Paintbrush fault zone can be explained without significant upwelling from the underlying aquifer. Instead, the thermal anomaly is consistent with thermal conduction enhanced slightly by vertical ground water movement within the volcanic aquifer sequence. If more than -400 m3/day of water enters the volcanic aquifer from below along a 10 km fault zone, the calculated temperatures at the water table are significantly greater than the measured temperatures. These results illustrate the potential limitations in using one-dimensional models to interpret ground water temperature data, and underscore the value in combining temperature data with fully coupled three-dimensional simulations. [source]

In situ hydraulic tests in the active fault survey tunnel, Kamioka Mine, excavated through the active Mozumi-Sukenobu Fault zone and their hydrogeological significance

ISLAND ARC, Issue 4 2006
Tsuyoshi Nohara
Abstract The spatial hydrogeological and structural character of the active Mozumi-Sukenobu Fault (MSF) was investigated along a survey tunnel excavated through the MSF in the Kamioka Mine, central Japan. Major groundwater conduits on both sides of the MSF are recognized. One is considered to be a subvertical conduit between the tunnel and the surface, and the other is estimated to be a major reservoir of old meteoric water alongside the MSF. Our studies indicate that part of the MSF is a sub-vertical continuous barrier that obstructs younger meteoric water observed in the south-eastern part of the Active Fault Survey Tunnel (AFST) and water recharge to the rock mass intersected by the north-western part of the AFST. The MSF might be a continuous barrier resulting in the storage of a large quantity of older groundwater to the northwest. The observations and results of in situ hydraulic tests indicate that the major reservoir is not the fault breccia associated with the northeast,southwest trending faults of the MSF, but the zone in which blocks of fractured rocks occur beside high angle faults corresponding to X shears whose tectonic stress field coincides with the present regional stress field and antithetic Riedel shears of the MSF. The results from borehole investigations in the AFST indicate that secondary porosity is developed in the major reservoir due to the destruction of filling minerals and fracture development beside these shears. The increase in hydraulic conductivity is not directly related to increased density of fractures around the MSF. Development of secondary porosity could cause the increase in hydraulic conductivity around the MSF. Our results suggest that minor conduits of the fracture network are sporadically distributed in the sedimentary rocks around the MSF in the AFST. [source]

Mesozoic-Cenozoic Tectonics of the Yellow Sea and Oil-Gas Exploration

ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2010
Tianfeng WAN
Abstract: The purpose of the present study was to study the tectonics of the Yellow Sea. Although oil-gas exploration has been undertaken for more than 30 years in the southern Yellow Sea, the exploration progress has achieved little. There are three tectonic periods with near N,S trending shortening and compression (260,200 Ma, 135,52 Ma and 23,0.78 Ma) and three tectonic periods with near E,W trending shortening and compression (200,135 Ma, 52,23 Ma and 0.78 Ma) at the Yellow Sea and adjacent areas during the Mesozoic and Cenozoic. The Indosinian tectonic period is the collision period between the Sino-Korean and Yangtze Plates, which formed the basic tectonic framework for the Yellow Sea area. There were strong intraplate deformations during the Yanshanian (200,135 Ma) and Sichuanian (135,52 Ma) periods with different tectonic models, which are also the main formation periods for endogenic metallic mineral deposits around the Yellow Sea. The three tectonic periods during the Cenozoic affect important influences for forming oil-gas reservoirs. The Eocene,Oligocene (52,23 Ma) is the main forming period for oil-gas sources. The Miocene,Early Pleistocene (23,0.78 Ma) was a period of favorable passage for oil-gas migration along NNE trending faults. Since the Middle Pleistocene (0.78 Ma) the NNE trending faults are closed and make good conditions for the reservation of oil-gas. The authors suggest that we pay more attention to the oil-gas exploration at the intersections between the NNE trending existing faults and Paleogene-Neogene systems in the southern Yellow Sea area. [source]