Chinese Academy of Geological Sciences

Research Article| April 01, 1992 Remnants of ≥3800 Ma crust in the Chinese part of the Sino-Korean craton D. Y. Liu; D. Y. Liu 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Search for other works by this author on: GSW Google Scholar A. P. Nutman; A. P. Nutman 2Research School of Earth Sciences, Australian National University, Canberra A.C.T., Australia Search for other works by this author on: GSW Google Scholar W. Compston; W. Compston 2Research School of Earth Sciences, Australian National University, Canberra A.C.T., Australia Search for other works by this author on: GSW Google Scholar J. S. Wu; J. S. Wu 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Search for other works by this author on: GSW Google Scholar Q. H. Shen Q. H. Shen 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Search for other works by this author on: GSW Google Scholar Author and Article Information D. Y. Liu 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China A. P. Nutman 2Research School of Earth Sciences, Australian National University, Canberra A.C.T., Australia W. Compston 2Research School of Earth Sciences, Australian National University, Canberra A.C.T., Australia J. S. Wu 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Q. H. Shen 1Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1992) 20 (4): 339–342. https://doi.org/10.1130/0091-7613(1992)020<0339:ROMCIT>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation D. Y. Liu, A. P. Nutman, W. Compston, J. S. Wu, Q. H. Shen; Remnants of ≥3800 Ma crust in the Chinese part of the Sino-Korean craton. Geology 1992;; 20 (4): 339–342. doi: https://doi.org/10.1130/0091-7613(1992)020<0339:ROMCIT>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Ion microprobe U-Pb analyses of zircons from the Sino-Korean craton have identified remnants of ≥3800 Ma crust at two localities—near Caozhuang east of Beijing, and near Anshan, northeast China. Near Caozhuang, the detrital zircons in an Archean metaquartzite are 3550 Ma or older; about one-fourth have ages between 3800 and 3850 Ma. The ages for detrital zircons with concordant U-Pb ages form a polymodal distribution, interpreted to show that the detritus that formed the quartzite was derived from a terrane containing early Archean rocks of several ages. Near Anshan, sheared gneiss is present in a complex containing ca. 3300 and 3000 Ma granites. Some of the zircons in this gneiss are concordant with a weighted mean 207Pb/206Pb age of 3804 ±5 Ma (2 σ), interpreted to be the age of the protolith of the gneiss. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

INDEPTH geophysical and geological observations imply that a partially molten midcrustal layer exists beneath southern Tibet. This partially molten layer has been produced by crustal thickening and behaves as a fluid on the time scale of Himalayan deformation. It is confined on the south by the structurally imbricated Indian crust underlying the Tethyan and High Himalaya and is underlain, apparently, by a stiff Indian mantle lid. The results suggest that during Neogene time the underthrusting Indian crust has acted as a plunger, displacing the molten middle crust to the north while at the same time contributing to this layer by melting and ductile flow. Viewed broadly, the Neogene evolution of the Himalaya is essentially a record of the southward extrusion of the partially molten middle crust underlying southern Tibet.

The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purpose\nunderground liquid scintillator detector, was proposed with the determination\nof the neutrino mass hierarchy as a primary physics goal. It is also capable of\nobserving neutrinos from terrestrial and extra-terrestrial sources, including\nsupernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos,\natmospheric neutrinos, solar neutrinos, as well as exotic searches such as\nnucleon decays, dark matter, sterile neutrinos, etc. We present the physics\nmotivations and the anticipated performance of the JUNO detector for various\nproposed measurements. By detecting reactor antineutrinos from two power plants\nat 53-km distance, JUNO will determine the neutrino mass hierarchy at a 3-4\nsigma significance with six years of running. The measurement of antineutrino\nspectrum will also lead to the precise determination of three out of the six\noscillation parameters to an accuracy of better than 1\\%. Neutrino burst from a\ntypical core-collapse supernova at 10 kpc would lead to ~5000\ninverse-beta-decay events and ~2000 all-flavor neutrino-proton elastic\nscattering events in JUNO. Detection of DSNB would provide valuable information\non the cosmic star-formation rate and the average core-collapsed neutrino\nenergy spectrum. Geo-neutrinos can be detected in JUNO with a rate of ~400\nevents per year, significantly improving the statistics of existing geoneutrino\nsamples. The JUNO detector is sensitive to several exotic searches, e.g. proton\ndecay via the $p\\to K^++\\bar\\nu$ decay channel. The JUNO detector will provide\na unique facility to address many outstanding crucial questions in particle and\nastrophysics. It holds the great potential for further advancing our quest to\nunderstanding the fundamental properties of neutrinos, one of the building\nblocks of our Universe.

Research Article| November 01, 2003 Adakites from continental collision zones: Melting of thickened lower crust beneath southern Tibet Sun-Lin Chung; Sun-Lin Chung 1Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Dunyi Liu; Dunyi Liu 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Search for other works by this author on: GSW Google Scholar Jianqing Ji; Jianqing Ji 3School of Earth and Space Sciences, Peking University, Beijing, China Search for other works by this author on: GSW Google Scholar Mei-Fei Chu; Mei-Fei Chu 4Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Hao-Yang Lee; Hao-Yang Lee 4Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Da-Jen Wen; Da-Jen Wen 4Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Ching-Hua Lo; Ching-Hua Lo 4Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Tung-Yi Lee; Tung-Yi Lee 5Department of Earth Sciences, National Taiwan Normal University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Qing Qian; Qing Qian 6Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China Search for other works by this author on: GSW Google Scholar Qi Zhang Qi Zhang 6Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China Search for other works by this author on: GSW Google Scholar Geology (2003) 31 (11): 1021–1024. https://doi.org/10.1130/G19796.1 Article history received: 09 May 2003 rev-recd: 31 Jul 2003 accepted: 01 Aug 2003 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Sun-Lin Chung, Dunyi Liu, Jianqing Ji, Mei-Fei Chu, Hao-Yang Lee, Da-Jen Wen, Ching-Hua Lo, Tung-Yi Lee, Qing Qian, Qi Zhang; Adakites from continental collision zones: Melting of thickened lower crust beneath southern Tibet. Geology 2003;; 31 (11): 1021–1024. doi: https://doi.org/10.1130/G19796.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Adakites are geochemically distinct intermediate to felsic lavas found exclusively in subduction zones. Here we report the first example of such magmas from southern Tibet in an active continental collision environment. The Tibetan adakites were emplaced from ca. 26 to 10 Ma, and their overall geochemical characteristics suggest an origin by melting of eclogites and/or garnet amphibolites in the lower part (≥50 km) of thickened Tibetan crust. This lower-crustal melting required a significantly elevated geotherm, which we attribute to removal of the tectonically thickened lithospheric mantle in late Oligocene time. The identification of collision-type adakites from southern Tibet lends new constraints to not only the Himalayan-Tibetan orogenesis—how and when the Indian lithosphere started underthrusting Asia can be depicted—but also the growth of the early continental crust on Earth that consists dominantly of the tonalite-trondhjemite-granodiorite suites marked by adakitic geochemical affinities. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

We introduce a potential new working reference material – natural zircon megacrysts from an Early Pliocene alkaline basalt (from Penglai, northern Hainan Island, southern China) – for the microbeam determination of O and Hf isotopes, and U–Pb age dating. The Penglai zircon megacrysts were found to be fairly homogeneous in Hf and O isotopes based on large numbers of measurements by LA‐multiple collector (MC)‐ICP‐MS and SIMS, respectively. Precise determinations of O isotopes by isotope ratio mass spectrometry (IRMS) and Hf isotopes by solution MC‐ICP‐MS were in good agreement with the statistical mean of microbeam measurements. The mean δ 18 O value of 5.31 ± 0.10‰ (2 s ) by IRMS and the mean 176 Hf/ 177 Hf value of 0.282906 ± 0.0000010 (2 s ) by solution MC‐ICP‐MS are the best reference values for the Penglai zircons. SIMS and isotope dilution‐TIMS measurements yielded consistent 206 Pb/ 238 U ages within analytical uncertainties, and the preferred 206 Pb/ 238 U age was found to be 4.4 ± 0.1 Ma (95% confidence interval). The young age and variably high common Pb content make the Penglai zircons unsuitable as a primary U–Pb age reference material for calibration of unknown samples by microbeam analysis; however, they can be used as a secondary working reference material for quality control of U–Pb age determination for young (particularly &lt; 10 Ma) zircon samples.

Himalayan-Tibetan Underplate The Himalayas formed from the collision of India with Eurasia beginning about 50 million years ago, but the fate and position of the subducted Indian crust was not well defined until the Hi-CLIMB seismic experiment was initiated. The centerpiece of the project is an 800-kilometer-long, closely spaced, linear array of broadband seismographs, extending from the Ganges lowland, across the Himalayas, and onto the central Tibetan plateau. Nábělek et al. (p. 1371 ) present images of the crust and upper mantle of the Southern Tibetan plateau underthrust northward by the Indian plate, in which they trace the base of the Indian plate to 31°N. The character of the crust-mantle interface in this region suggests that the Indian crust is at least partly decoupled from the mantle beneath.

Crystalline porous materials are important in the development of catalytic systems with high scientific and industrial impact. Zeolites, ordered mesoporous silica, and metal-organic frameworks (MOFs) are three types of porous materials that can be used as heterogeneous catalysts. This review focuses on a comparison of the catalytic activities of zeolites, mesoporous silica, and MOFs. In the first part of the review, the distinctive properties of these porous materials relevant to catalysis are discussed, and the corresponding catalytic reactions are highlighted. In the second part, the catalytic behaviors of zeolites, mesoporous silica, and MOFs in four types of general organic reactions (acid, base, oxidation, and hydrogenation) are compared. The advantages and disadvantages of each porous material for catalytic reactions are summarized. Conclusions and prospects for future development of these porous materials in this field are provided in the last section. This review aims to highlight recent research advancements in zeolites, ordered mesoporous silica, and MOFs for heterogeneous catalysis, and inspire further studies in this rapidly developing field.

Research Article| October 01, 2002 Tectonic history of the Altyn Tagh fault system in northern Tibet inferred from Cenozoic sedimentation A. Yin; A. Yin 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA Search for other works by this author on: GSW Google Scholar P.E. Rumelhart; P.E. Rumelhart 2Department of Earth and Space Sciences, University of California, Los Angeles, California 90095, USA Search for other works by this author on: GSW Google Scholar R. Butler; R. Butler 3Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA Search for other works by this author on: GSW Google Scholar E. Cowgill; E. Cowgill 4Department of Earth and Space Sciences, University of California, Los Angeles, California 90095, USA Search for other works by this author on: GSW Google Scholar T.M. Harrison; T.M. Harrison 5Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA Search for other works by this author on: GSW Google Scholar D.A. Foster; D.A. Foster 6Department of Geological Sciences, University of Florida, Gainesville, Florida 32611, USA Search for other works by this author on: GSW Google Scholar R.V. Ingersoll; R.V. Ingersoll 7Department of Earth and Space Sciences, University of California, Los Angeles, California 90095, USA Search for other works by this author on: GSW Google Scholar Zhang Qing; Zhang Qing 8Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, People's Republic of China Search for other works by this author on: GSW Google Scholar Zhou Xian-Qiang; Zhou Xian-Qiang 8Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, People's Republic of China Search for other works by this author on: GSW Google Scholar Wang Xiao-Feng; Wang Xiao-Feng 8Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, People's Republic of China Search for other works by this author on: GSW Google Scholar A. Hanson; A. Hanson 9Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA Search for other works by this author on: GSW Google Scholar A. Raza A. Raza 10School of Earth Sciences, University of Melbourne, Melbourne, Victoria, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information A. Yin 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA P.E. Rumelhart 2Department of Earth and Space Sciences, University of California, Los Angeles, California 90095, USA R. Butler 3Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA E. Cowgill 4Department of Earth and Space Sciences, University of California, Los Angeles, California 90095, USA T.M. Harrison 5Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095, USA D.A. Foster 6Department of Geological Sciences, University of Florida, Gainesville, Florida 32611, USA R.V. Ingersoll 7Department of Earth and Space Sciences, University of California, Los Angeles, California 90095, USA Zhang Qing 8Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, People's Republic of China Zhou Xian-Qiang 8Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, People's Republic of China Wang Xiao-Feng 8Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, People's Republic of China A. Hanson 9Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA A. Raza 10School of Earth Sciences, University of Melbourne, Melbourne, Victoria, Australia Publisher: Geological Society of America Received: 11 Jun 2001 Revision Received: 10 Apr 2002 Accepted: 30 Apr 2002 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2002) 114 (10): 1257–1295. https://doi.org/10.1130/0016-7606(2002)114<1257:THOTAT>2.0.CO;2 Article history Received: 11 Jun 2001 Revision Received: 10 Apr 2002 Accepted: 30 Apr 2002 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation A. Yin, P.E. Rumelhart, R. Butler, E. Cowgill, T.M. Harrison, D.A. Foster, R.V. Ingersoll, Zhang Qing, Zhou Xian-Qiang, Wang Xiao-Feng, A. Hanson, A. Raza; Tectonic history of the Altyn Tagh fault system in northern Tibet inferred from Cenozoic sedimentation. GSA Bulletin 2002;; 114 (10): 1257–1295. doi: https://doi.org/10.1130/0016-7606(2002)114<1257:THOTAT>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The active left-slip Altyn Tagh fault defines the northern edge of the Tibetan plateau. To determine its deformation history we conducted integrated research on Cenozoic stratigraphic sections in the southern part of the Tarim Basin. Fission-track ages of detrital apatites, existing biostratigraphic data, and magnetostratigraphic analysis were used to establish chronostratigraphy, whereas composition of sandstone and coarse clastic sedimentary rocks was used to determine the unroofing history of the source region. Much of the detrital grains in our measured sections can be correlated with uplifted sides of major thrusts or transpressional faults, implying a temporal link between sedimentation and deformation. The results of our studies, together with existing stratigraphic data from the Qaidam Basin and the Hexi Corridor, suggest that crustal thickening in northern Tibet began prior to 46 Ma for the western Kunlun Shan thrust belt, at ca. 49 Ma for the Qimen Tagh and North Qaidam thrust systems bounding the north and south margins of the Qaidam Basin, and prior to ca. 33 Ma for the Nan Shan thrust belt. These ages suggest that deformation front reached northern Tibet only ∼10 ± 5 m.y. after the initial collision of India with Asia at 65–55 Ma. Because the aforementioned thrust systems are either termination structures or branching faults of the Altyn Tagh left-slip system, the Altyn Tagh fault must have been active since ca. 49 Ma. The Altyn Tagh Range between the Tarim Basin and the Altyn Tagh fault has been a long-lived topographic high since at least the early Oligocene or possibly late Eocene. This range has shed sediments into both the Tarim and Qaidam Basins while being offset by the Altyn Tagh fault. Its continuous motion has made the range act as a sliding door, which eventually closed the outlets of westward-flowing drainages in the Qaidam Basin. This process has caused large amounts of Oligocene–Miocene sediments to be trapped in the Qaidam Basin. The estimated total slip of 470 ± 70 km and the initiation age of 49 Ma yield an average slip rate along the Altyn Tagh fault of 9 ± 2 mm/yr, remarkably similar to the rates determined by GPS (Global Positioning System) surveys. This result implies that geologic deformation rates are steady state over millions of years during continental collision. 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Research Article| June 01, 1987 The closing of Tethys and the tectonics of the Himalaya M. P. SEARLE; M. P. SEARLE 1Department of Geology, The University, Leicester LE1 7RH, United Kingdom Search for other works by this author on: GSW Google Scholar B. F. WINDLEY; B. F. WINDLEY 1Department of Geology, The University, Leicester LE1 7RH, United Kingdom Search for other works by this author on: GSW Google Scholar M. P. COWARD; M. P. COWARD 2Department of Geology, Imperial College, Prince Consort Road, London SW7 2BP, United Kingdom Search for other works by this author on: GSW Google Scholar D.J.W. COOPER; D.J.W. COOPER 3Department of Geology, The University, Leicester LE1 7RH, United Kingdom Search for other works by this author on: GSW Google Scholar A. J. REX; A. J. REX 3Department of Geology, The University, Leicester LE1 7RH, United Kingdom Search for other works by this author on: GSW Google Scholar D. REX; D. REX 4Department of Earth Sciences, Leeds University, Leeds LS2 9JT, United Kingdom Search for other works by this author on: GSW Google Scholar LI TINGDONG; LI TINGDONG 5Chinese Academy of Geological Sciences, Baiwanzhong, Beijing, China Search for other works by this author on: GSW Google Scholar XIAO XUCHANG; XIAO XUCHANG 5Chinese Academy of Geological Sciences, Baiwanzhong, Beijing, China Search for other works by this author on: GSW Google Scholar M. Q. JAN; M. Q. JAN 6Department of Geology and National Centre of Excellence, Peshawar University, Peshawar, Pakistan Search for other works by this author on: GSW Google Scholar V. C. THAKUR; V. C. THAKUR 7Wadia Institute of Himalayan Geology, Dehra Dun, 248001, India Search for other works by this author on: GSW Google Scholar S. KUMAR S. KUMAR 7Wadia Institute of Himalayan Geology, Dehra Dun, 248001, India Search for other works by this author on: GSW Google Scholar Author and Article Information M. P. SEARLE 1Department of Geology, The University, Leicester LE1 7RH, United Kingdom B. F. WINDLEY 1Department of Geology, The University, Leicester LE1 7RH, United Kingdom M. P. COWARD 2Department of Geology, Imperial College, Prince Consort Road, London SW7 2BP, United Kingdom D.J.W. COOPER 3Department of Geology, The University, Leicester LE1 7RH, United Kingdom A. J. REX 3Department of Geology, The University, Leicester LE1 7RH, United Kingdom D. REX 4Department of Earth Sciences, Leeds University, Leeds LS2 9JT, United Kingdom LI TINGDONG 5Chinese Academy of Geological Sciences, Baiwanzhong, Beijing, China XIAO XUCHANG 5Chinese Academy of Geological Sciences, Baiwanzhong, Beijing, China M. Q. JAN 6Department of Geology and National Centre of Excellence, Peshawar University, Peshawar, Pakistan V. C. THAKUR 7Wadia Institute of Himalayan Geology, Dehra Dun, 248001, India S. KUMAR 7Wadia Institute of Himalayan Geology, Dehra Dun, 248001, India Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1987) 98 (6): 678–701. https://doi.org/10.1130/0016-7606(1987)98<678:TCOTAT>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation M. P. SEARLE, B. F. WINDLEY, M. P. COWARD, D.J.W. COOPER, A. J. REX, D. REX, LI TINGDONG, XIAO XUCHANG, M. Q. JAN, V. C. THAKUR, S. KUMAR; The closing of Tethys and the tectonics of the Himalaya. GSA Bulletin 1987;; 98 (6): 678–701. doi: https://doi.org/10.1130/0016-7606(1987)98<678:TCOTAT>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Recent geological and geophysical data from southern Tibet allow refinement of models for the closing of southern (Neo-) Tethys and formation of the Himalaya. Shelf sediments of the Indian passive continental margin which pass northward into deep-sea Tethyan sediments of the Indus-Tsangpo suture zone were deposited in the Late Cretaceous. An Andean-type margin with a 2,500-km-long Trans-Himalayan (Kohistan-Ladakh-Gangdese) granitoid batholith formed parallel to the southern margin of the Lhasa block, together with extensive andesites, rhyolites, and ignimbrites (Lingzizong Formation). The southern part of the Lhasa block was uplifted, deformed, and eroded between the Cenomanian and the Eocene. In the western Himalaya, the Kohistan island arc became accreted to the northern plate at this time. The northern part of the Lhasa block was affected by Jurassic metamorphism and plutonism associated with the mid-Jurassic closure of the Bangong-Nujiang suture zone to the north.The timing of collision between the two continental plates (ca. 50-40 Ma) marking the closing of Tethys is shown by (1) the change from marine (flysch-like) to continental (molasse-like) sedimentation in the Indus-Tsangpo suture zone, (2) the end of Gangdese I-type granitoid injection, (3) Eocene S-type anatectic granites and migmatites in the Lhasa block, and (4) the start of compressional tectonics in the Tibetan-Tethys and Indus-Tsangpo suture zone (south-facing folds, south-directed thrusts).After the Eocene closure of Tethys, deformation spread southward across the Tibetan-Tethys zone to the High Himalaya. Deep crustal thrusting, Barrovian metamorphism, migmatization, and generation of Oligocene-Miocene leucogranites were accompanied by south-verging recumbent nappes inverting metamorphic isograds and by south-directed intracontinental shear zones associated with the Main Central thrust. Continued convergence in the late Tertiary resulted in large-scale north-directed backthrusting along the Indus-Tsangpo suture zone. More than 500 km shortening is recorded in the foreland thrust zones of the Indian plate, south of the suture, and > 150 km shortening is recorded across the Indian shelf (Zanskar Range) and the Indus suture in Ladakh. There was also large-scale shortening of the Karakoram and Tibetan microplates north of the suture; as much as 1,000 km shortening occurred in Tibet. The more recent deformation, however, involved the spreading of this thickened crust and the lateral motion of the Tibetan block along major approximately east-west–trending strike-slip fault zones. 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A novel "wave" signal-smoothing and mercury-removing device has been developed for laser ablation quadrupole and multiple collector ICPMS analysis. With the wave stabilizer that has been developed, the signal stability was improved by a factor of 6.6-10 and no oscillation of the signal intensity was observed at a repetition rate of 1 Hz. Another advantage of the wave stabilizer is that the signal decay time is similar to that without the signal-smoothing device (increased by only 1-2 s for a signal decay of approximately 4 orders of magnitude). Most of the normalized elemental signals (relative to those without the stabilizer) lie within the range of 0.95-1.0 with the wave stabilizer. Thus, the wave stabilizer device does not significantly affect the aerosol transport efficiency. These findings indicate that this device is well-suited for routine optimization of ICPMS, as well as low repetition rate laser ablation analysis, which provides smaller elemental fractionation and better spatial resolution. With the wave signal-smoothing and mercury-removing device, the mercury gas background is reduced by 1 order of magnitude. More importantly, the (202)Hg signal intensity produced in the sulfide standard MASS-1 by laser ablation is reduced from 256 to 0.7 mV by the use of the wave signal-smoothing and mercury-removing device. This result suggests that the mercury is almost completely removed from the sample aerosol particles produced by laser ablation with the operation of the wave mercury-removing device. The wave mercury-removing device that we have designed is very important for Pb isotope ratio and accessory mineral U-Pb dating analysis, where removal of the mercury from the background gas and sample aerosol particles is highly desired. The wave signal-smoothing and mercury-removing device was applied successfully to the determination of the (206)Pb/(204)Pb isotope ratio in samples with low Pb content and/or high Hg content.

Seismic data from central Tibet have been combined to image the subsurface structure and understand the evolution of the collision of India and Eurasia. The 410- and 660-kilometer mantle discontinuities are sharply defined, implying a lack of a subducting slab beneath the plateau. The discontinuities appear slightly deeper beneath northern Tibet, implying that the average temperature of the mantle above the transition zone is about 300 degrees C hotter in the north than in the south. There is a prominent south-dipping converter in the uppermost mantle beneath northern Tibet that might represent the top of the Eurasian mantle lithosphere underthrusting the northern margin of the plateau.

We introduce and propose zircon M257 as a future reference material for the determination of zircon U‐Pb ages by means of secondary ion mass spectrometry. This light brownish, flawless, cut gemstone specimen from Sri Lanka weighed 5.14 g (25.7 carats). Zircon M257 has TIMS‐determined, mean isotopic ratios (2s uncertainties) of 0.09100 ± 0.00003 for 206 pb/ 238 U and 0.7392 ± 0.0003 for 207 pb/ 235 U. Its 206 pb/ 238 U age is 561.3 ± 0.3 Ma (unweighted mean, uncertainty quoted at the 95% confidence level); the U‐Pb system is concordant within uncertainty of decay constants. Zircon M257 contains ∼ 840 μg g −1 U (Th/U ∼ 0.27). The material exhibits remarkably low heterogeneity, with a virtual absence of any internal textures even in cathodoluminescence images. The uniform, moderate degree of radiation damage (estimated from the expansion of unit‐cell parameters, broadening of Raman spectral parameters and density) corresponds well, within the “Sri Lankan trends”, with actinide concentrations, U‐Pb age, and the calculated alpha fluence of 1.66 × 10 18 g −1 . This, and a (U+Th)/He age of 419 ± 9 Ma (2s), enables us to exclude any unusual thermal history or heat treatment, which could potentially have affected the retention of radiogenic Pb. The oxygen isotope ratio of this zircon is 13.9%o VSMOW suggesting a metamorphic genesis in a marble or calc‐silicate skarn.

The May 12, 2008 Wenchuan earthquake of China (Mw 7.9 or Ms 8.0) triggered hundreds of thousands of landslides. Mapping such a large number of landslides is a major task, considering the large size of the affected area and the availability of pre- and post-earthquake remote sensing images. This paper compares three (nearly) complete landslide inventories that were compiled from visual image interpretation. The three inventories differ in the manner in which the landslides are represented, either as polygons, centroid points, or top points. Landslides in the three inventories use one-to-one correspondence. Each of the three inventories includes a large proportion of the 197,481 landslides triggered by the earthquake. These landslides were delineated as individual solid polygons and points using visual interpretation of high-resolution aerial photographs and satellite images acquired following the earthquake and verified by selected field checking throughout a broad area of approximately 110,000 km2. These landslides cover a total area of approximately 1,160 km2. Based on the inventories of landslide polygons and landslide centroid points, two types of density maps were constructed. Correlations of landslide occurrence with seismic, geologic, and topographic parameters were analyzed using the three landslide inventories. Statistical analysis of their spatial distribution was performed using both the landslide area percentage (LAP), defined as the percentage of the area affected by the landslides and the landslide number density (LND), defined as the number of landslides per square kilometer. There are two types of LNDs: the LND-centroid (based on the centroid point of the landslide) and the LND-top (based on the top point of the landslide). We used the three indexes to determine how the occurrence of the landslides correlates with elevation, slope angle, slope aspect, slope position, slope curvature, lithology, distance from the epicenter, seismic intensity, distance from the Yingxiu-Beichuan surface fault rupture, peak ground acceleration (PGA), and coseismic surface displacements (including horizontal, vertical, and total displacements). Both the LAP and the two types of LND values were observed to have continuous positive or negative correlations with the slope angle, slope curvature, distance from the epicenter and from the Yingxiu-Beichuan surface fault rupture, seismic intensity, and coseismic surface displacement. In addition, the highest values of the LAP and LND values appear at ranges from 1,200 to 3,000 m in elevation. Moreover, the landslides have preferred orientations, dominated by the eastern, southeastern, and southern directions. In addition, the sandstone, siltstone (Z), and granitic rocks experienced more concentrated landslides. No obvious correlations were observed between the LAP and LND values and slope position. Finally, we studied the orders of eight earthquake-triggered landslide impact factor effect on landslide occurrence. The 197,481 landslides triggered by the 2008 Wenchuan earthquake were delineated. Three landslide inventories were constructed: polygon, centroid, and top point inventories. The landslides were spatially analyzed with topographic, lithology, and seismic parameters.

Research Article| August 01, 1997 Did the Indo-Asian collision alone create the Tibetan plateau? M. A. Murphy; M. A. Murphy 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095 Search for other works by this author on: GSW Google Scholar An Yin; An Yin 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095 Search for other works by this author on: GSW Google Scholar T. M. Harrison; T. M. Harrison 1Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095 Search for other works by this author on: GSW Google Scholar S. B. Dürr; S. B. Dürr 2Institut für Mineralogie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany Search for other works by this author on: GSW Google Scholar Chen Z; Chen Z 3Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing, People's Republic of China Search for other works by this author on: GSW Google Scholar F. J. Ryerson; F. J. Ryerson 4Lawrence Livermore National Laboratory, Livermore, California 94550 Search for other works by this author on: GSW Google Scholar W. S. F. Kidd; W. S. F. Kidd 5Department of Geological Sciences, State University of New York at Albany, Albany, New York 12222 Search for other works by this author on: GSW Google Scholar Wang X; Wang X 3Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing, People's Republic of China Search for other works by this author on: GSW Google Scholar Zhou X Zhou X 3Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing, People's Republic of China Search for other works by this author on: GSW Google Scholar Geology (1997) 25 (8): 719–722. https://doi.org/10.1130/0091-7613(1997)025<0719:DTIACA>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation M. A. Murphy, An Yin, T. M. Harrison, S. B. Dürr, Chen Z, F. J. Ryerson, W. S. F. Kidd, Wang X, Zhou X; Did the Indo-Asian collision alone create the Tibetan plateau?. Geology 1997;; 25 (8): 719–722. doi: https://doi.org/10.1130/0091-7613(1997)025<0719:DTIACA>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract It is widely believed that the Tibetan plateau is a late Cenozoic feature produced by the Indo-Asian collision. However, because Tibet was the locus of continental accretion and subduction throughout the Mesozoic, crustal thickening during that time may also have contributed to growth of the plateau. This portion of the geologic history was investigated in a traverse through the central Lhasa block, southern Tibet. Together with earlier studies, our mapping and geochronological results show that the Lhasa block underwent little north-south shortening during the Cenozoic. Rather, our mapping shows that ∼60% crustal shortening, perhaps due to the collision between the Lhasa and Qiangtang blocks, occurred during the Early Cretaceous. This observation implies that a significant portion of southern Tibet was raised to perhaps 3–4 km elevation prior to the Indo-Asian collision. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Research Article| September 01, 2006 Zircon U-Pb and Hf isotope constraints on the Mesozoic tectonics and crustal evolution of southern Tibet Mei-Fei Chu; Mei-Fei Chu 1Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Sun-Lin Chung; Sun-Lin Chung 1Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Biao Song; Biao Song 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Search for other works by this author on: GSW Google Scholar Dunyi Liu; Dunyi Liu 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Search for other works by this author on: GSW Google Scholar Suzanne Y. O'Reilly; Suzanne Y. O'Reilly 3Australian Research Council National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC), Department of Earth and Planetary Sciences, Macquarie University, Sydney, Australia Search for other works by this author on: GSW Google Scholar Norman J. Pearson; Norman J. Pearson 3Australian Research Council National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC), Department of Earth and Planetary Sciences, Macquarie University, Sydney, Australia Search for other works by this author on: GSW Google Scholar Jianqing Ji; Jianqing Ji 4School of Earth and Space Sciences, Peking University, Beijing, China Search for other works by this author on: GSW Google Scholar Da-Jen Wen Da-Jen Wen 5Department of Geosciences, National Taiwan University, Taipei, Taiwan Search for other works by this author on: GSW Google Scholar Author and Article Information Mei-Fei Chu 1Department of Geosciences, National Taiwan University, Taipei, Taiwan Sun-Lin Chung 1Department of Geosciences, National Taiwan University, Taipei, Taiwan Biao Song 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Dunyi Liu 2Institute of Geology, Chinese Academy of Geological Sciences, Beijing, China Suzanne Y. O'Reilly 3Australian Research Council National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC), Department of Earth and Planetary Sciences, Macquarie University, Sydney, Australia Norman J. Pearson 3Australian Research Council National Key Centre for Geochemical Evolution and Metallogeny of Continents (GEMOC), Department of Earth and Planetary Sciences, Macquarie University, Sydney, Australia Jianqing Ji 4School of Earth and Space Sciences, Peking University, Beijing, China Da-Jen Wen 5Department of Geosciences, National Taiwan University, Taipei, Taiwan Publisher: Geological Society of America Received: 20 Feb 2006 Revision Received: 11 Apr 2006 Accepted: 14 Apr 2006 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2006) 34 (9): 745–748. https://doi.org/10.1130/G22725.1 Article history Received: 20 Feb 2006 Revision Received: 11 Apr 2006 Accepted: 14 Apr 2006 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Mei-Fei Chu, Sun-Lin Chung, Biao Song, Dunyi Liu, Suzanne Y. O'Reilly, Norman J. Pearson, Jianqing Ji, Da-Jen Wen; Zircon U-Pb and Hf isotope constraints on the Mesozoic tectonics and crustal evolution of southern Tibet. Geology 2006;; 34 (9): 745–748. doi: https://doi.org/10.1130/G22725.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract The first in situ Hf and U-Pb isotope analyses of zircon separates from Mesozoic granites in southern Tibet identify a significant, previously unknown stage of magmatism. Igneous zircons (n = 34) from a granite within the Gangdese batholith show a weighted mean 206Pb/238U age of 188.1 ± 1.4 Ma and εHf(T) (the parts in 104 deviation of initial Hf isotope ratios between the zircon sample and the chondritic reservoir) values between +10.4 and +16.8, suggesting predominantly Early Jurassic intrusive activity with a juvenile mantle contribution. Of 40 inherited zircons from two Cretaceous S-type granites in the northern magmatic belt, 23 delineate a slightly older 206Pb/238U age cluster between 188 and 210 Ma. These zircons have εHf(T) values from −3.9 to −13.7, yielding crustal Hf model ages from ca. 1.4 to 2.1 Ga, suggesting a major episode of crustal growth in Proterozoic time and remelting of this crust in Early Jurassic time. Combining these with literature data, we interpret the Jurassic Gangdese magmatism as an early product of the Neo-Tethyan subduction that played a long-lasting role in the tectonic evolution of southern Tibet prior to the India-Asia collision. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Research Article| January 01, 1992 Sedimentary record and climatic implications of recurrent deformation in the Tian Shan: Evidence from Mesozoic strata of the north Tarim, south Junggar, and Turpan basins, northwest China MARC S. HENDRIX; MARC S. HENDRIX 1School of Earth Sciences, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar STEPHAN A. GRAHAM; STEPHAN A. GRAHAM 1School of Earth Sciences, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar ALAN R. CARROLL; ALAN R. CARROLL 1School of Earth Sciences, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar EDWARD R. SOBEL; EDWARD R. SOBEL 1School of Earth Sciences, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar CLEAVY L. McKNIGHT; CLEAVY L. McKNIGHT 1School of Earth Sciences, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar BENJAMIN J. SCHULEIN; BENJAMIN J. SCHULEIN 1School of Earth Sciences, Stanford University, Stanford, California 94305 Search for other works by this author on: GSW Google Scholar ZUOXUN WANG ZUOXUN WANG 2Institute of Geology and Mineral Resources, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, Beijing, China Search for other works by this author on: GSW Google Scholar GSA Bulletin (1992) 104 (1): 53–79. https://doi.org/10.1130/0016-7606(1992)104<0053:SRACIO>2.3.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation MARC S. HENDRIX, STEPHAN A. GRAHAM, ALAN R. CARROLL, EDWARD R. SOBEL, CLEAVY L. McKNIGHT, BENJAMIN J. SCHULEIN, ZUOXUN WANG; Sedimentary record and climatic implications of recurrent deformation in the Tian Shan: Evidence from Mesozoic strata of the north Tarim, south Junggar, and Turpan basins, northwest China. GSA Bulletin 1992;; 104 (1): 53–79. doi: https://doi.org/10.1130/0016-7606(1992)104<0053:SRACIO>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Detailed stratigraphic, sedimentologic, paleocurrent, and subsidence analyses were conducted on Mesozoic nonmarine sedimentary sections of the south Junggar, north Tarim, and Turpan basins, Xinjiang Uygur Autonomous Region, northwest China. These three basins have been foreland basins throughout the Mesozoic and Cenozoic eras, as demonstrated by asymmetrically distributed basinwide sediment accumulations, foreland-style subsidence profiles, and a variety of outcrop and subsurface facies data. Mesozoic paleocurrent indicators measured in the south Junggar and north Tarim basins, as well as Mesozoic sandstone compositions from both basins, indicate that the intervening Tian Shan has existed as a positive physiographic feature partitioning the two basins throughout Mesozoic and Cenozoic time. Paleocurrent, facies, and subsurface isopach data suggest that the Turpan basin was established as a discrete feature by the Early Jurassic period.The timing and style of depositional systems within the north Tarim Mesozoic depocenter, the south Junggar Mesozoic depocenter, and the central Turpan basin are remarkably similar. Upper Triassic strata of each basin consist of alluvial conglomerate and associated braided-fluvial sandstone and siltstone which fine upward into Lower through Middle Jurassic, locally organic-rich, meandering-fluvial, and lacustrine strata. Upper Jurassic braided-fluvial red beds in each basin are overlain by a distinct pulse of uppermost Jurassic alluvial conglomerate. Lower Cretaceous exposures consist of fine-grained red beds in north Tarim and Turpan and interbedded red and gray shale with local silty carbonates in south Junggar. Upper Cretaceous strata of the north Tarim and south Junggar basins are composed of alluvial conglomerate with associated braided-fluvial sandstone and siltstone.Subsidence curves constructed for all three basins are remarkably consistent. Each contains distinctly concave-down segments associated with the alluvial, coarse, clastic pulses in the latest Triassic, latest Jurassic, and, in the north Tarim basin, the Late Cretaceous periods. Flexurally driven Mesozoic subsidence and deposition of alluvial conglomerate in these basins occurred in response to periodic deformation of the Tian Shan and associated reactivation of basin-bounding thrust and reverse faults. These three main Mesozoic deformational episodes in the Tian Shan are interpreted to have been driven by tectonic accretion onto the south Asian margin of the Qiantang Block in the Late Triassic, the Lhasa Block in the latest Jurassic, and the Kohistan-Dras arc complex in the Late Cretaceous periods.The Mesozoic nonmarine stratigraphic record of central Xinjiang supports the hypothesis that a strong monsoonal circulation was present during Early and Middle Jurassic time, but it waned by Late Jurassic in response to the breakup of Pangea. During the Early Cretaceous period, rejuvenation of the Tian Shan markedly influenced the climate of central Xinjiang. As southward-directed paleo-winds crossed the Tian Shan, it cast a paleo-rain shadow in the north Tarim basin, whereas regionally extensive, well-oxygenated lakes developed in the south Junggar basin. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The formation and development of the southern Altaids is controversial with regard to its accretionary orogenesis and continental growth. The Altay-East Junggar orogenic collage of North Xinjiang, China, offers a special natural laboratory to resolve this puzzle. Three tectonic units were juxtaposed, roughly from North to South, in the study area. The northern part (Chinese Altay), composed of variably deformed and metamorphosed Paleozoic sedimentary, volcanic, and granitic rocks, is interpreted as a Japan-type island arc of Paleozoic to Carboniferous-Permian age. The central part (Erqis), which consists of ophiolitic mélanges and coherent assemblages, is a Paleozoic accretionary complex. The southern part (East Junggar), characterized by imbricated ophiolitic mélanges, Nb-enriched basalts, adakitic rocks and volcanic rocks, is regarded as a Devonian-Carboniferous intra-oceanic island arc with some Paleozoic ophiolites, superimposed by Permian arc volcanism. A plagiogranite from an imbricated ophiolitic mélange (Armantai) in the East Junggar yields a new SHRIMP zircon age of 503 ± 7 Ma. Using published age constraints, we propose the presence of multiple subduction systems in this part of the Paloasian Ocean in the Paleozoic. The intraoceanic arcs became accreted to the southern active margin of the Siberian craton in the middle Carboniferous-Permian. During the long accretionary processes, in addition to large-scale southward-directed thrusting, large-scale, orogen-parallel, strike-slip movements (for example, Erqis fault) in the Permian translated fragments of these intraoceanic arcs and associated accretionary wedges. This new tectonic model has broad implications for the architecture and crustal growth of Central Asia and for other ancient orogens.

Research Article| July 01, 2008 Cenozoic tectonic evolution of the Qaidam basin and its surrounding regions (Part 3): Structural geology, sedimentation, and regional tectonic reconstruction An Yin; An Yin * 1Structural Geology Group, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China, Permanent Address: Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567, USA *Email: yin@ess.ucla.edu Search for other works by this author on: GSW Google Scholar Yu-Qi Dang; Yu-Qi Dang 2Qinghai Oilfield Company, Dunhuang, Gansu Province, People's Republic of China Search for other works by this author on: GSW Google Scholar Min Zhang; Min Zhang 2Qinghai Oilfield Company, Dunhuang, Gansu Province, People's Republic of China Search for other works by this author on: GSW Google Scholar Xuan-Hua Chen; Xuan-Hua Chen 3Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing, People's Republic of China Search for other works by this author on: GSW Google Scholar Michael W. McRivette Michael W. McRivette 4Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567, USA Search for other works by this author on: GSW Google Scholar Author and Article Information An Yin * 1Structural Geology Group, School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China, Permanent Address: Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567, USA Yu-Qi Dang 2Qinghai Oilfield Company, Dunhuang, Gansu Province, People's Republic of China Min Zhang 2Qinghai Oilfield Company, Dunhuang, Gansu Province, People's Republic of China Xuan-Hua Chen 3Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing, People's Republic of China Michael W. McRivette 4Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095-1567, USA *Email: yin@ess.ucla.edu Publisher: Geological Society of America Received: 24 Mar 2007 Revision Received: 11 Aug 2007 Accepted: 14 Aug 2007 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2008 Geological Society of America GSA Bulletin (2008) 120 (7-8): 847–876. https://doi.org/10.1130/B26232.1 Article history Received: 24 Mar 2007 Revision Received: 11 Aug 2007 Accepted: 14 Aug 2007 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation An Yin, Yu-Qi Dang, Min Zhang, Xuan-Hua Chen, Michael W. McRivette; Cenozoic tectonic evolution of the Qaidam basin and its surrounding regions (Part 3): Structural geology, sedimentation, and regional tectonic reconstruction. GSA Bulletin 2008;; 120 (7-8): 847–876. doi: https://doi.org/10.1130/B26232.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Qaidam basin is the largest topographic depression inside the Tibetan plateau. Because of its central position, understanding the tectonic origin of the Qaidam basin has important implications for unraveling the formation mechanism and growth history of the Tibetan plateau. In order to achieve this goal, we analyzed regional seismic-reflection profiles across the basin and a series of thickness-distribution patterns of Cenozoic strata at different time slices. The first-order structure of the basin is a broad Cenozoic synclinorium, which has an amplitude ranging from >16 km in the west to <4 km in the east. The synclinorium has expanded progressively eastward across the Qaidam region: from the western basin against the Altyn Tagh fault at 65–50 Ma to the eastern basin at 24 Ma. The half-wavelength of the regional fold complex changes from ~170 km in the west to ~50 km in the east. The formation of the synclinorium was induced by an older thrust system initiated ca. 65–50 Ma in the northern margin and a younger thrust system initiated ca. 29–24 Ma in the southern basin margin. Cenozoic upper-crustal shortening decreases eastward across basin from >48% in the west to <1% in the east; the associated strain rates vary from 3.2 × 10−15 s−1 to 1.3 × 10−17 s−1. The eastward decrease in upper-crustal shortening requires a progressive shift in crustal-thickening mechanisms across Qaidam basin, from dominantly upper-crustal shortening in the west to dominantly lower-crustal shortening in the east. Although sedimentation began synchronously at 65–50 Ma across the entire basin, the initiation ages of the southern and northern basin-bounding structures are significantly different; deformation started at 65–50 Ma in the north and at 29–24 Ma in the south. This information and the existing inference that the uplift of the Eastern Kunlun Range south of Qaidam basin began after 30–20 Ma imply that the Paleogene (65–24 Ma) Qaidam and Hoh Xil basins on both sides of the Eastern Kunlun Range may have been parts of a single topographic depression, >500 km wide in the north-south direction between the Qilian Shan and Fenghuo Shan thrust belts in the north and south. The development of this large Paleogene basin in central Tibet and its subsequent destruction and partitioning by the Neogene uplift of the Eastern Kunlun Range requires a highly irregular sequence of deformation, possibly controlled by preexist-ing weakness in the Tibetan lithosphere. 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© 2015 Society of Economic Geologists, Inc. Magmatic-hydrothermal ore deposits in collisional orogens are new targets for modern mineral exploration, yet it is unclear why they preferentially occur in some specific tectonic environments within these orogenic belts. We integrate geologic and geochemical data (especially zircon U-Pb dating and Lu-Hf isotope data) for Mesozoic-Cenozoic magmatic rocks and associated ore deposits in the Lhasa terrane, a highly endowed tectonic unit within the Himalayan-Tibetan orogen, and provide the first example in a continental collision terrane of the application of zircon Hf isotope data to image the lithospheric architecture and its relationship with ore deposits. Three crustal blocks are identified within the Lhasa terrane by the Hf isotope mapping method. They include a central long-lived Precambrian microcontinent with local reworking and two surrounding juvenile Phanerozoic crustal blocks with significant mantle contributions to constituent magmatic rocks. The three crustal blocks are bounded by two E-W-trending terrane-boundary faults, and each block is cut by two N-S-striking concealed faults. Isotopic signatures of zircons from the juvenile crustal blocks indicate that the Phanerozoic continental crust grew from several Mesozoic volcanic-plutonic arcs and by underplating of mantle-derived magmas generated during Mesozoic accretion and Cenozoic collision. Mesozoic subduction-related porphyry Cu-Au deposits and Cenozoic collision-related Cu-Mo deposits are exclusively located in regions with high εHf (&gt;5) juvenile crust. Cu enrichment during differentiation of high fO2 arc magmas is the key for the formation of Mesozoic subduction-related porphyry Cu-Au. By contrast, remelting of the lower crustal Cu sulfide-rich magmatic cumulates within the juvenile crust is interpreted to have played a key role in the formation of Cenozoic collision-related Cu-Mo deposits. Granite-related Pb-Zn deposits cluster in the oldest crustal regions or developed along the margin of the old crustal block bounded by lithospheric faults. The porphyry Mo deposits are localized along the reworked margins of the old crustal block. It is suggested that crustal reworking released Mo from the old crust to form porphyry Mo deposits, whereas leaching of Pb and Zn from the Paleozoic carbonate cover strata by felsic intrusion-driven fluids is critical to the formation of Pb-Zn ore deposits. Skarn Fe-Cu ore deposits are typically localized along a terrane boundary fault, i.e., lithospheric discontinuity, through which crust-derived felsic melt mixed with Cu-rich mantle-derived mafic magmas ascending upward. Associated granitoid rocks usually bear microgranular mafic enclaves and show a zircon Hf isotope array from negative to positive εHf values (-7.3 to +6.7), supporting mixing of juvenile mantle and evolved crustal sources. The Hf isotope maps show temporal-spatial relationships between crustal structure and the location of ore deposits, demonstrating that the structure, nature, and composition of the crust controlled the localization of ore deposits and the migration of ore-forming metals in the terrane. This study shows that the lithospheric architecture of an orogenic terrane can be imaged by Hf isotope mapping to provide mappable units which can be used to explore for ore deposits at the terrane scale.

The genesis of continental collision-related porphyry Cu deposits (PCDs) remains controversial. The most common hypothesis links their genesis with magmas derived from subduction-modified arc lithosphere. However, it is unclear whether a genetic linkage exists between collision- and subduction-related PCDs. Here, we studied Jurassic subduction-related Cu-Au and Miocene collision-related Cu-Mo porphyry deposits in south Tibet. The Jurassic PCDs occur only in the western segment of the Jurassic arc, which has depleted mantle-like isotopic compositions [e.g., (87Sr/86Sr)i = 0.7041–0.7048; εNd(t) as high as 7.5, and εHf(t) as high as 18]. By contrast, no Jurassic PCDs have been found in the eastern arc segment, which is isotopically less juvenile [e.g., (87Sr/86Sr)i = 0.7041–0.7063, εNd(t) < 4.5, and εHf(t) ≤ 12]. These results imply that incorporation of crustal components during underplating of Jurassic magma induced copper accumulation as sulfides at the base of the eastern Jurassic arc, inhibiting PCD formation at this time. Miocene PCDs are spatially confined to the Jurassic arc, and the giant Miocene PCDs cluster in its eastern segment where no Jurassic PCDs occur. This suggests that the arc segment barren for subduction-related PCDs could be fertile for collision-related PCDs. Miocene ore-forming porphyries have young Hf model ages and Sr-Nd-Hf isotopic compositions overlapping with those of the Jurassic rocks in the eastern segment, whereas contemporaneous barren porphyries outside the Jurassic arc have abundant zircon inheritance and crust-like Sr-Nd-Hf isotopic compositions. These data suggest that remelting of the lower crustal sulfide-bearing Cu-rich Jurassic cumulates, triggered by Cenozoic crustal thickening and/or subsequent slab break-off, led to the formation of giant Miocene PCDs. The spatial overlap and complementary metal endowment between subduction- and collision-related magmas may be used to evaluate the mineral potential for such deposits in other orogenic belts.