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Zheng C.,CAS Tianjin Institute of Industrial Biotechnology | He J.,Chengdu Institute of Geology and Mineral Resources | Wang Y.,CAS Lanzhou Institute of Geology and Geophysics | Wang M.,CAS Tianjin Institute of Industrial Biotechnology | Huang Z.,CAS Tianjin Institute of Industrial Biotechnology
Bioresource Technology | Year: 2011

Geobacillus pallidus XS2 and XS3 were isolated from oil contaminated soil samples in Yumen oilfield, China, and were able to produce bioemulsifiers on different hydrocarbons. Biodegradation assays exhibited that approximately 70% of PAH (250. mg/L) or 85% of crude oil (500. mg/L) was removed by the thermophilic bacteria after 20. days. The bioemulsifiers of the two strains were isolated and obtained a productive yield of 4.24 ± 0.08 and 3.82 ± 0.11. g/L, respectively. GPC analysis revealed that the number-average molecular weights (M n) of the two bioemulsifiers were 271,785. Da and 526,369. Da, with PDI values of 1.104 and 1.027, respectively. Chemical composition studies exhibited that the bioemulsifier XS2 consisted of carbohydrates (68.6%), lipids (22.7%) and proteins (8.7%) while the bioemulsifier XS3 was composed by carbohydrates (41.1%), lipids (47.6%) and proteins (11.3%). Emulsification assays approved the effectiveness of bioemulsifiers over a wide range of temperature, pH and salinity. © 2011 Elsevier Ltd.

Burchfiel B.C.,Massachusetts Institute of Technology | Zhiliang C.,Chengdu Institute of Geology and Mineral Resources
Memoir of the Geological Society of America | Year: 2013

The region of southeastern Tibet and its adjacent foreland presently lie north and east of the Eastern Himalayan syntaxis and consist of 14 tectonic units of which only five (Yangtze, Transitional, Baoshan, Lhasa, and Tengchong units) can be considered to be large continental fragments with a coherent Precambrian basement. The others are underlain by either thinned continental crust, or fragments of continental crust, arcs, and oceanic rocks swept together as a collage and forming a basement for late Paleozoic, Mesozoic, and Cenozoic arcs and sedimentary sequences that make up current tectonic elements. The history of fragmentation, accretion, and deformation has been complex and related to tectonic activity at several plate boundaries that have been active at different times from Paleozoic to Recent and have been reactivated at numerous times during the evolution of the region. Here we focus on the evolution from mid-Paleozoic to Recent with the major emphasis on Mesozoic and Cenozoic time, discussing the Yangtze, Transitional, Songpan Ganze, Yidun Arc, Qiangtang, Lanping-Simao, Lhasa, Bangong Suture Zone, Syntaxial, Tengchong, Baoshan, Changning-Menglian, Lin Cang, and Ailao Shan units, and synthesizing their relationships. The area contain examples of the complex heterogeneous evolution of regions where there was early accretion of fragments forming a collage, later modified by rifting with the deposition of thick sequences of sedimentary rocks to form some tectonic units later deformed by intracontinental shortening and disruption by large strike-slip faults. Most of the folded belts of several ages must be basement involved and probably decoupled from the deeper crust, but the nature of their relations to the middle and lower crust remains unproven. The major early Cenozoic shear zones have large-scale displacements related to southeastward extrusion and often contain mylonitic rocks that suggest they were not only zones of dominantly lateral shear, but also had components of vertical extrusion of heated ductile lower crust during their formation in a transpressional tectonic environment. Numerous late Cenozoic shear zones bound crustal fragments that rotate clockwise around the Eastern Himalayan syntaxis. Many of these shear zones reactivate older sutures or shear zones, however, some formed by breaking though previously unfaulted areas. Superposed deformations in different tectonic settings are common, indicating a temporal and spatial pattern of changing rheology and strain. The Cenozoic deformation is the result of the interaction between two dynamic systems: the India-Eurasia intracontinental convergence system and the Western Pacifi c-Indonesian subduction system. Unfortunately, southeastern Tibet and its foreland is a region of mostly poorly known geology for which unraveling its detailed evolution will require extensive future research, although many of the important areas for investigation are discussed herein. © 2012 The Geological Society of America. All rights reserved.

Xu Z.,Chinese Academy of Geological Sciences | Ji S.,Chinese Academy of Geological Sciences | Ji S.,Ecole Polytechnique de Montréal | Cai Z.,Chinese Academy of Geological Sciences | And 3 more authors.
Gondwana Research | Year: 2012

Field observations, deformation and fabric analyses, and precise age data acquired by zircon SHRIMP, LA-ICP-MS U-Pb and 40Ar-39Ar dating methods have yielded new constraints on the kinematics and dynamics of the Namche Barwa Syntaxis (NBS) which is the eastern corner of the Himalaya. A two-stage model has been established to explain the formation and evolution of the NBS. The northward indentation of the Indian plate beneath the Lhasa terrane began at 55-40Ma, and crustal materials at this corner were subducted to depths >70km where they experienced HP (UHP?) metamorphism. Since 40Ma, large-scale, right-lateral strike-slip along the Sagaing fault has accommodated the rapid northward movement of the eastern Indian plate corner with respect to the Indochina block. This caused significant and progressive bending of the Indus-Yarlung suture zone (IYSZ) such that it became the Dongjiu-Milin left-lateral, strike-slip, shear zone (DMSZ) in the west and the Aniqiao-Motuo right-lateral, strike-slip, shear zone (AMSZ) in the east. Both zones underwent strong mylonitization. Meanwhile, the HP (UHP?) metamorphic rocks were rapidly exhumed, first into the deep crust at 22-18Ma and then to the shallow crust to form an antiformal dome at 6-2Ma. Our model provides new insight into the processes of post-collisional crustal thickening related to the formation of the Himalayan orogenic belt. © 2011 International Association for Gondwana Research.

Chen J.-L.,CAS Guangzhou Institute of Geochemistry | Xu J.-F.,CAS Guangzhou Institute of Geochemistry | Ren J.-B.,Guangzhou Marine Geological Survey | Huang X.-X.,CAS Guangzhou Institute of Geochemistry | And 2 more authors.
Gondwana Research | Year: 2014

Ore-bearing porphyritic rocks are widely distributed in the Zhongdian arc in the southern part of the Yidun arc, eastern Tibet. New U-Pb zircon dates, and previous results, show that the porphyritic rocks formed mainly between 221 and 211Ma, with a peak at 217-215Ma. These Late Triassic porphyritic rocks and associated volcanic rocks are primarily calc-alkaline igneous rocks, some of which have geochemical affinities with adakite, such as high SiO2 (≥56wt.%), Al2O3 (≥14wt.%), and Sr, and low Y and heavy rare earth element contents. However, moderate Sr/Y and La/Yb ratios of these rocks compared with typical adakites characterize them as being transitional between adakites and normal arc rocks. Those rocks that do not have adakitic affinities are typical normal arc volcanic rocks. The porphyritic and associated volcanic rocks occur in the eastern and western parts of the Zhongdian arc, and both have the same geochemical characteristics and ages. The new dates, geochemical data, and Sr-Nd isotopic ratios, combined with previous data on the Zhongdian arc (particularly the Xiaxiaoliu basalt that has enriched mid-ocean ridge basalt characteristics), suggest that these rocks are probably related to slab break-off or slab-tearing of the westward subducting Garze-Litang oceanic crust in the Late Triassic. The enriched mantle wedge metasomatized by subducted fluids and sediments was heated by ascending asthenosphere and underwent partial melting. These magmas then probably interacted with underplated mafic material and experienced a melting-assimilation-storage-homogenization process (MASH) in the lower crust and/or with slab-derived melts, resulting in formation of the porphyritic rocks and associated porphyry deposits in the Late Triassic Zhongdian arc. © 2013 International Association for Gondwana Research.

Fu X.-g.,Chengdu Institute of Geology and Mineral Resources | Wang J.,Chengdu Institute of Geology and Mineral Resources | Tan F.-w.,Chengdu Institute of Geology and Mineral Resources | Chen M.,Chengdu Institute of Geology and Mineral Resources | Chen W.-b.,Chengdu Institute of Geology and Mineral Resources
Gondwana Research | Year: 2010

The Late Triassic Nadi Kangri volcanic rocks, with nearly EW trending outcrops within the Qiangtang basin, northern Xizang (Tibet), China, are composed mainly of acid tuff, dacite, rhyolite and minor basic volcanic rocks. There exists a significant depositional hiatus between the Nadi Kangri volcanic rocks and underlying strata. Therefore, the Nadi Kangri volcanic rocks represent a new evolution history of the Mesozoic Qiangtang basin. The magma emplacement age of the Nadi Kangri volcanic rocks in the Geladaindong area is 220.4 ± 2.3 Ma, representing the onset of the Mesozoic Qiangtang basin. The Nadi Kangri basalts have high Nb/Zr (0.049-0.058), Ta/Hf (0.12-0.15) and Zr/Y (4.95-6.01) ratios. In the tectonic discrimination diagrams, such as Zr vs. Zr/Y and Th/Hf vs. Ta/Hf, the Nadi Kangri basaltic rocks mostly plot in the "within-plate" setting field. The geological background and the geochemical characteristics suggest that the Nadi Kangri volcanic rocks were formed in a continental rift setting. Crown Copyright © 2009.

Chen J.-L.,CAS Guangzhou Institute of Geochemistry | Zhao W.-X.,Sun Yat Sen University | Xu J.-F.,CAS Guangzhou Institute of Geochemistry | Wang B.-D.,Chengdu Institute of Geology and Mineral Resources | Kang Z.-Q.,CAS Guangzhou Institute of Geochemistry
Gondwana Research | Year: 2012

It is generally believed that Cenozoic potassic and ultrapotassic volcanic rocks of the Tibetan Plateau were generated by partial melting of an enriched mantle region or lower crustal materials. The Miocene Bugasi volcanic rocks (BVR) in the western part of the Lhasa block are composed mainly of trachyandesites and trachytes, both of which belong to the shoshonite series. The trachytes show somewhat transitional compositions between the mantle-derived trachyandesites of the BVR and the crust-derived potassic rocks of Konglongxiang, most evident in their Sr, Ba, and Ni concentrations, Nb/Ta, Rb/Sr, Th/Nb, Zr/Nb, and Ba/Rb trace element ratios, and Sr and Nd isotopic compositions. These features, coupled with the relatively high Cr and Ni concentrations and Mg#, suggest that the trachytes are the product of mixing between mantle-derived and lower crust-derived melts. © 2011 International Association for Gondwana Research.

Ni H.-Y.,Chengdu Institute of Geology and Mineral Resources
Environmental Earth Sciences | Year: 2015

Debris flows usually occur abruptly and rapidly in mountainous areas and it is difficult to observe their occurrence progress. Therefore, an experiment has become an important method to study debris flow initiation mechanism in recent years. In this paper, taking Xiongjia Gully in SW China as an example and on the basis of artificial rainfall experiment, the author has studied the initiation of gully-type debris flow. Experiment results indicate some relation between rainfall intensity and gully erosion, failure mode of soil mass, initiation mechanism and characteristics of debris flow. Based on several groups of experiments, conclusions were drawn as follows: (1) Under strong precipitation, the infiltration rate and soil water content in different depths are inversely proportional to the rainfall intensity. Intense rainfall favors the overland flow, gully runoff and erosion, but is not conducive to water infiltration. (2) Slope failure modes and initiation mechanism of debris flow vary with different rainfall and runoff conditions. Under the condition with the rainfall intensity of 55 mm/h, the slope failure mode presents a soil liquefaction and landslide. Accordingly, the debris flow initiation mechanism belongs to landslide transformation. However, under the condition of intense rainfall and runoff, gully beds are easy to be eroded and slopes are prone to collapse. Then, debris flows occurred with initiation mechanism of entrainment. (3) In terms of debris flow characteristics, the debris flow occurrence process consists of several intermittent flows. In addition, the debris flow magnitude and flow viscosity are not consistent with rainfall intensity. On the contrary, under condition of intense rainfall of 65 and 75 mm/h, debris flows tend to be watery. However, under the rainfall condition of 55 mm/h, the flow viscosity is higher. The experiment results are consistent well with the natural debris flow occurrence from Xioangjia Gully. © 2014, Springer-Verlag Berlin Heidelberg.

Zhu D.-C.,China University of Geosciences | Zhao Z.-D.,China University of Geosciences | Niu Y.,China University of Geosciences | Niu Y.,Durham University | And 6 more authors.
Earth and Planetary Science Letters | Year: 2011

The Lhasa Terrane in southern Tibet has long been accepted as the last geological block accreted to Eurasia before its collision with the northward drifting Indian continent in the Cenozoic, but its lithospheric architecture, drift and growth histories and the nature of its northern suture with Eurasia via the Qiangtang Terrane remain enigmatic. Using zircon in situ U-Pb and Lu-Hf isotopic and bulk-rock geochemical data of Mesozoic-Early Tertiary magmatic rocks sampled along four north-south traverses across the Lhasa Terrane, we show that the Lhasa Terrane has ancient basement rocks of Proterozoic and Archean ages (up to 2870Ma) in its centre with younger and juvenile crust (Phanerozoic) accreted towards its both northern and southern edges. This finding proves that the central Lhasa subterrane was once a microcontinent. This continent has survived from its long journey across the Paleo-Tethyan Ocean basins and has grown at the edges through magmatism resulting from oceanic lithosphere subduction towards beneath it during its journey and subsequent collisions with the Qiangtang Terrane to the north and with the Indian continent to the south. Zircon Hf isotope data indicate significant mantle source contributions to the generation of these granitoid rocks (e.g., ~50-90%, 0-70%, and 30-100% to the Mesozoic magmatism in the southern, central, and northern Lhasa subterranes, respectively). We suggest that much of the Mesozoic magmatism in the Lhasa Terrane may be associated with the southward Bangong-Nujiang Tethyan seafloor subduction beneath the Lhasa Terrane, which likely began in the Middle Permian (or earlier) and ceased in the late Early Cretaceous, and that the significant changes of zircon εHf(t) at ~113 and ~52Ma record tectonomagmatic activities as a result of slab break-off and related mantle melting events following the Qiangtang-Lhasa amalgamation and India-Lhasa amalgamation, respectively. These results manifest the efficacy of zircons as a chronometer (U-Pb dating) and a geochemical tracer (Hf isotopes) in understanding the origin and histories of lithospheric plates and in revealing the tectonic evolution of old orogenies in the context of plate tectonics. © 2010 Elsevier B.V.

Forchielli A.,Free University of Berlin | Steiner M.,Free University of Berlin | Kasbohm J.,GeoENcon Ltd. | Hu S.,Chengdu Institute of Geology and Mineral Resources | Keupp H.,Free University of Berlin
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2014

The Chengjiang and Guanshan fossil Lagerstätten of Yunnan represent key fossil deposits to understand and reconstruct early metazoan evolution. Despite extensive studies on the systematics of taxa from these Lagerstätten, the major mechanisms of exceptional soft-tissue preservation at these fossil Lagerstätten have remained controversial. The Chengjiang and Guanshan fossil Lagerstätten represent typical Burgess Shale-type deposits, influenced by late alteration and weathering that led to some major transformations in clay and iron minerals, as well as dissolution of dolomite and skeletal biominerals. The detailed geochemical screening of various fossil groups, such as brachiopods, priapulids, arthropods, and sponges, indicates a more complex preservational history than hitherto supposed. Besides oxidation processes during sub-recent/recent weathering, clay mineral formation and/or alteration, carbonization, phosphatization, and pyritization played key roles in the preservation of various metazoans. The Chengjiang fossil Lagerstätte is characterized by the existence of clay-dominated background beds (BGBs) and event beds (EBs). Fossil preservation varies considerably in the two different depositional settings, with soft-tissue preservation occurring preferentially in EBs, whereas skeletal accumulations are typical of BGBs.The samples were analyzed and classified into three groups with different degrees of alteration and fundamentally different chemistries. The specific clay mineral composition shows increasing chlorite and goethite, decreasing kaolinite, 2M1-mica, and dolomite, and a rise in the chemical alteration of mudstones. It also indicates slight variations between the primary types of beds (EB, BGB), hinting at variations in the source of clastics or the hydrochemical environment during the deposition of strata. Furthermore, the geochemical paleoredox proxy data indicate that dysoxic or anoxic conditions were not permanently present during the deposition of EBs and BGBs in the Chengjiang and Guanshan fossil Lagerstätten.We consider that rapid deposition in finest claystones had a greater influence on the preservation of highly volatile tissues than the presence of bottom-water anoxia, even though bottom-water anoxia and microbial sealing may further increase the probability of soft-tissue preservation. Using different geochemical proxies such as various redox indicators and iron speciation, statistics on framboid sizes, classical geological observation, and clay mineralogy, we show that iron mineral precipitation onto organic carcasses of the Chengjiang-type fossils is mostly confined to later diagenetic processes and thus is not crucial for the early fixation of easily decayable tissues in Burgess Shale-type faunas. © 2013 Elsevier B.V.

Wang B.,Chengdu Institute of Geology and Mineral Resources | Chen J.,CAS Guangzhou Institute of Geochemistry | Xu J.,CAS Guangzhou Institute of Geochemistry | Wang L.,Chengdu Institute of Geology and Mineral Resources
Lithos | Year: 2015

Ultrapotassic lavas are widespread throughout southern Tibet and are generally thought to have formed from magmas generated by partial melting of an enriched mantle source that was metasomatized during earlier subduction events. Here, we report new geochemical and Sr-Nd-Pb-Os isotope data for Miocene ultrapotassic rocks within the Sailipu area of the western Lhasa terrane, southern Tibet. The Sailipu ultrapotassic rocks are enriched in the large ion lithophile elements relative to the high field strength elements, and have extremely radiogenic Sr (87Sr/86Sr(i)=0.714480-0.727323), Pb (206Pb/204Pb=18.414-18.787, 207Pb/204Pb=15.693-15.749, 208Pb/204Pb=39.439-39.765), and Os isotopic signatures (187Os/188Os(i)=0.1095-0.37454), and unradiogenic Nd (εNd(t)=-11.5 to -15.2) isotopic compositions. These geochemical and isotopic characteristics, coupled with high K2O (>5wt.%) and MgO (5.20-13.70wt.%) concentrations, Mg# values of 68-76, high Rb/Sr (0.13-0.95) and low Ba/Rb (3.33-12.3) ratios, and the relatively low Os contents and radiogenic Os isotopic compositions of the Sailipu ultrapotassic rocks, do not support any significant crustal contamination. Instead, we consider these rocks to be analogous to the Cenozoic ultrapotassic rocks from Italy and the Balkans, suggesting that they were produced by interaction between melts derived from phlogopite-rich clinopyroxene veins and surrounding peridotitic mantle material. The Sailipu ultrapotassic rocks can be divided into type-1 and type-2 suites based on differences in major and trace element concentrations, and isotopic compositions. Type-1 ultrapotassic rocks are relatively enriched in the heavy rare earth elements, most likely as a result of interaction between melts derived from phlogopite-rich clinopyroxene veins and the surrounding spinel-bearing peridotite material, whereas the type-2 rocks are enriched in rare earth elements and have high (Gd/Yb)N values (8.3-12.2), both of which are indicative of interaction between melts derived from phlogopite-rich clinopyroxene veins and surrounding garnet-bearing peridotite material that also contained carbonates. Although both the existing convective removal and oblique subduction models can explain some of the geological observations associated with the formation of the Tibetan Plateau, we suggest that the former more accurately explains the spatial and temporal distributions of ultrapotassic rocks and other Cenozoic lavas in this area and the associated topographic uplift recorded in southern Tibet. © 2014 Elsevier B.V.

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