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2011 Vol. 22, No. 1

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Balanced Cross-Section and Crustal Shortening Analysis in the Tanggula-Tuotuohe Area,Northern Tibet
李亚林, 王成善, 马超
2011, 13(1) doi: 10.1007/s12583-011-0152-2
Abstract:
The Tanggula (唐古拉) thrust system and the Tuotuohe (沱沱河) foreland basin, which represent major Cenozoic tectonic units of the central Tibetan plateau, have been recently studied. Field investigation, analyses of deformation and construction of two restored balanced structural sections suggest 75–100 km (51%–64%) of N-S shortening in the Tanggula thrust system and 55–114 km (42%–47%) of N-S shortening in the Tuotuohe basin. The shortening ratios indicate that the Tanggula- Tuotuohe area has undergone intensive deformation and crustal shortening during the Early Tertiary, resulting not only in crustal thickening, but also in large scale volcanism and in rapid uplift of the Tanggula Mountains.
Distribution of Tuvaella Brachiopod Fauna andIts Tectonic Significance
王成文, 李宁, 孙跃武, 宗普
2011, 13(1) doi: 10.1007/s12583-011-0153-1
Abstract:
Tuvaella brachiopod fauna are distributed in an arc in three areas, including the Zeya-Hailar (海拉尔)-Shinejinst area, the Najramdal Uul-Kyzyl area, and the Barkol-Fuyun (富蕴) area. The Tuvaella fauna in the Zeya-Hailar-Shinejinst area are distributed in the northern margin of Jiamusi (佳木斯)-Mongolia block along the Mongolia-Okhotsk suture between the Siberia plate and the Jiamusi-Mongolia block but not appear in the corresponding Siberia plate. The Tuvaella fauna in the Najramdal Uul-Kyzyl area are distributed in the southwestern part of the Siberia plate as the acceler-ated fold belts during the Salairian–Caledonian periods, and those in the Barkol-Fuyun area are dis-tributed in the northeastern margin of Kazakhstan plate. They are distributed along the Irtysh suture between the Siberia plate and the Kazakhstan plate. The Tuvaella fauna became domestic fauna during the Wenlock and Pridoli (Middle–Late Silurian) and form a unique biogeographic province, i.e., the Mongolia-Okhotsk Province...
Silica-Metal Spherules in Ignimbrites ofSouthern Primorye, Russia
Andrei V Grebennikov*
2011, 13(1) doi: 10.1007/s12583-011-0154-0
Abstract:
A comprehensive mineralogical-geochemical and petrological study of ignimbrites from the Yakut-Gora volcanic depression (Primorye, Far Eastern Russia) revealed a wide distribution of silica-metal spherules (“globules”) that are typical liquid immiscibility resultant. The metallic portion of a spherule (composition varies from low-carbon iron to cohenite) borders gas pores and is rimmed by symplectite that consists of quartz, magnetite, and silica-potassic glass. This allows us to consider that the whole formation formed through reduction of the enclosing silicate melt. Abundant evidence of high reduction states of ignimbrite melts and the presence of iron carbides suggest an H2-CH4 composi-tion of the fluidal phase in ignimbrite magmas.
Experimental Studies on Seismic Anisotropy Enhanced by Alignment of Melt: Implication for the Origin of Abnormal Anisotropy in Tibetan Crust
杨晓松, 陈建业, 杨彧, 张国苓
2011, 13(1) doi: 10.1007/s12583-011-0155-z
Abstract:
It is commonly agreed that seismic anisotropy, most likely caused by lattice preferred orientation (LPO) of major minerals, is a very important indicator of intracrustal deformation. Ultrasonic velocity measurements on the rocks from higher Himalayan crystallines (HHC) and Honghe (红河) strike-slip fault zone in Southwest China showed an average anisotropic magnitude of about 5%. However, a series of seismic measurements conducted in Tibet indicated marked anisotropy with a magnitude ranging from 8% to 18% within middle to lower crust. What causes the anomalously strong anisotropy within Tibetan crust? Parts of HHC rocks, to some extent, had undergone granulitic-grade metamorphism, the temperature and pressure of which were in excess of their solidus. Additionally, oriented leucocratic portions, which are accepted to be products crystallized from localized melt bands and aligned melt pocket (AMP), are present in HHC pervasively...
Isotope Geochemistry of Volcanic Rocks from the Barton Peninsula, King George Island, Antarctica
郑祥身
2011, 13(1) doi: 10.1007/s12583-011-0156-y
Abstract:
C, O, H, S and Sr isotopes were investigated to characterize the isotopic composition of the Paleocene–Eocene volcanic rocks in Barton Peninsula, King George Island, Antarctica. The analyzed samples of volcanic rocks cover a range from basalt to andesite. The δ13C and δ18O values of calcite in volcanic rocks range from -7.5‰ to -3.2‰ and 0.4‰ to 5.1‰, respectively. The homogenous δ13Ccal and depleted δ18Ocal values relative to primary magmatic values reflect the effect of high temperature alteration of volcanic rocks. The δ18O of volcanic rocks ranges from -1.1‰ to 7.2‰, and the majority of values are significantly lower than those of primary magmatic values. The low δ18OWR values are compatible with high temperature alteration...
On the Enigma of Nb-Ta and Zr-HfFractionation—A Critical Review
黄慧, 牛耀龄, 赵志丹, 黑慧欣, 朱弟成
2011, 13(1) doi: 10.1007/s12583-011-0157-x
Abstract:
Elemental ratios Zr/Hf and Nb/Ta are expected to be constant and of chondritic value (~36.30 and ~17.57, respectively) in mantle and mantle-derived rocks. Studies in recent years have shown, however, that these two ratios do vary in some of these rocks. For example, MORB-like seamount lavas from flanks of the East Pacific Rise (EPR) show a correlated Zr/Hf (~25–50) and Nb/Ta ( ~9–18) variation. These two ratios are also correlated with ratios of more incompatible over less incompatible elements (e.g., La/Sm, Rb/Cs, Th/U, Nb/U, Sm/Yb) and with radiogenic isotope ratios (e.g., 87Sr/86Sr, 143Nd/144Nd). Furthermore, abyssal peridotites, which are melting residues for MORB, also show a huge correlated variation between Zr/Hf (~2.5–335) and Nb/Ta (~1–170)...
Analysis of Onset and Development of OreFormation in Dajishan Tungsten Ore Area,Jiangxi Province, China
刘宁强, 於崇文
2011, 13(1) doi: 10.1007/s12583-011-0158-9
Abstract:
The “theory of self-similar oscillatory finite-time singularities” of Sornette reflects accurately the spatio-temporal evolution and trends of development of events and processes in complex systems approaching to the singularities, and the effect of prediction for catastrophic events has been tested to be satisfactory...
Structural and Tectonic Evolution of El-Faiyum Depression, North Western Desert, Egypt Based on Analysis of Landsat ETM+, and SRTM Data
Timothy M, Talaat M, Mahmoud M, Safwat Gabr
2011, 13(1) doi: 10.1007/s12583-011-0159-8
Abstract:
False color Landsat ETM+ (bands 7, 4, 2 in RGB) and SRTM images of the El-Faiyum depression, Egypt, highlights major NE-SW faults and other lineaments trending NW-SE and N-S. Airborne magnetic data reveal some E-W subsurface faults which are not recognized on Landsat ETM+ and SRTM images. Ratio images (5/7, 3/1, 4/3) and (5/7, 5/1, 4) were used for lithological discrimination of different rock types. The El-Faiyum area is occupied by sedimentary rocks of Middle Eocene, Upper Eocene, Oligocene, Lower Miocene, Pliocene, Pleistocene and Holocene. Understanding the structural regime of El-Faiyum depression in the Western Desert of Egypt is significant in relation to the neotectonics of the Nile Delta and to the development of new communities west of the delta...
Primary Intergranular Pores in Oolitic ShoalReservoir of Lower Triassic FeixianguanFormation, Sichuan Basin, Southwest China: Fundamental for Reservoir Formation andRetention Diagenesis
谭秀成, 刘宏, 李凌, 罗冰, 刘晓光, 牟晓慧, 聂勇, 席文艳
2011, 13(1) doi: 10.1007/s12583-011-0160-2
Abstract:
The Lower Triassic Feixianguan (飞仙关) Formation oolitic shoal reservoir in the Sichuan (四川) basin (Southwest China) is currently an exploration and research highlight in China. The reservoir is widely believed to be formed mainly by burial dissolution and/or dolomitization on the basis of primary intergranular pores. In this study, through a comprehensive geological study on the whole basin, the dissolution and dolomitization are suggested not to be the fundamental factor of reservoir formation and there thus may be a possible new fundamental mechanism—the preservation of primary intergranular pores, i.e., the retention diagenesis. Based on this, a complex and multi-stage reservoir evolution and formation model is proposed. In the model, the depositional environment is the basis of reservoir initial formation...
Why are Q-Ratios High in the Sulu UHPMetamorphic Rocks?
Liu Qingsheng* (刘庆生)
2011, 13(1) doi: 10.1007/s12583-011-0161-1
Abstract:
Rayleigh Wave Group VelocityDistribution in Ningxia
李红谊, 刘昕, 李信富, 盛菊琴, 蔡新华, 王同利
2011, 13(1) doi: 10.1007/s12583-011-0162-0
Abstract:
In this article, seven months ambient noise data and 10 events recorded at seven digital stations from the Ningxia (宁夏) regional seismic network and 5 500-t controlled source explosion data recorded by 15 temporary and 7 permanent seismic stations are used to measure dispersion curves of fundamental mode Rayleigh waves. The study region was divided into grids with 0.1°×0.1°; group velocity distributions of Rayleigh waves from 6–22 s were determined with the Occam’s inversion technique. These velocity distribution maps show the lateral velocity variations in the study area, and the velocity structures are correlated with surface geology and tectonic units. The Yinchuan (银川) basin is clearly featured with low velocities, and the Helan (贺兰) Mountain and southern mountain areas are revealed with high velocities.
2.5-D DC Resistivity Modeling ConsideringFlexibility and Accuracy
Tang Jingtian (汤井田), Wang Feiyan* (王飞燕), Xiao Xiao (肖晓), Zhang Lincheng (张林成)
2011, 13(1) doi: 10.1007/s12583-011-0163-z
Abstract:
We highlighted the flexibility of using unstructured mesh together with the local refinement by a resistivity model with complicated topography. The effect of topography is emphasized. Based on this, we calculated a specific class of layered models and found that the accuracy is not always satisfactory by utilizing the standard approach. As an improvement, we employed the layered earth as the reference model to calculate the wavenumbers. The comparison demonstrates that the accuracy is considerably improved by using this enhanced approach.