Geological Survey of Yunnan Province

Kunming, China

Geological Survey of Yunnan Province

Kunming, China
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Nie X.,Wuhan University | Nie X.,University of New England of Australia | Feng Q.,Wuhan University | Metcalfe I.,University of New England of Australia | And 2 more authors.
Journal of Asian Earth Sciences | Year: 2016

The Tibetan Plateau and western Yunnan are known to have formed by the amalgamation of Gondwana-derived continental blocks and arc terranes as a result of Tethyan subduction followed by continental collisions during the Paleozoic, Mesozoic and Cenozoic. The Devonian and the southern Lancangjiang zone, western Yunnan is a critical period and key region for studying the transformation between the "Proto-Tethyan" and Paleo-Tethyan oceanic systems. New geochemical data and LA-ICPMS U-Pb zircon ages of the Late Devonian volcanogenic sediments from the southern Lancangjiang zone in western Yunnan, SW China, are presented. The studied sedimentary rocks of the Nanguang Formation are volcaniclastic rocks with high volcanic lithic content (55-65%, mostly andesite, dacite, with some rhyolite and tuffs). Whole rock geochemistry, zircon trace elements and detrital modal analyses indicate derivation from a subduction-related magmatic arc. Three tuff samples yield Late Devonian weighted mean 206Pb/238U ages of 378 ± 4 Ma, 366 ± 5 Ma and 382 ± 8 Ma, suggesting a Late Devonian depositional age. 104 zircon U-Pb analyses on 104 zircon grains from two sandstone samples present extremely tight age clusters, mostly ranging from 380 Ma to 360 Ma. This indicates a single Late Devonian igneous source. A short transport distance and a high rate of denudation and deposition within an arc-related basin are considered likely for the tuffs and volcaniclastic rocks in this study. This implies the presence of an as yet unidentified Late Devonian magmatic arc in the southern Lancangjiang zone. The cryptic Late Devonian arc is likely to represent either a continuation of Late Ordovician-Late Silurian "Proto-Tethyan" subduction or the initial stage of the Paleo-Tethyan Lincang Arc and indicates that subduction of the Changning-Menglian ocean beneath the Simao/Indochina Block occurred in the Late Devonian. © 2016 Elsevier Ltd.

Xu Z.,Chinese Academy of Geological Sciences | Xu Z.,Nanjing University | Wang Q.,Chinese Academy of Geological Sciences | Wang Q.,Nanjing University | And 8 more authors.
Tectonophysics | Year: 2015

It is generally believed that the extrusion of SE Tibet was bounded by the dextral Gaoligong and the sinistral Ailaoshan-Red River strike-slip shear zones from the Oligocene to early Miocene. This study integrates field mapping, structural analysis and geochronology in western Yunnan (China), where foliated Precambrian basement rocks and late Cretaceous to early Eocene plutons are exposed to the west of the Gaoligong shear zone. We found that late Eocene to early Miocene flat-lying ductile shear zones were kinematically related to steeply dipping strike-slip shear zones. Four elongated gneiss domes (Donghe, Guyong, Yingjiang and Sudian) are cored by high-grade metamorphic rocks and pre-kinematic granite plutons, and bounded by top-to-NE detachments and NE-trending dextral strike-slip shear zones. Zircon U-Pb ages from LA-ICP-MS analysis and 40Ar/39Ar ages of micas and hornblende demonstrate that the flat-lying Donghe Detachment (>35-15Ma) and the Nabang dextral strike-slip shear zone (41-19Ma) were sites of prolonged, mostly coeval ductile deformation from amphibolite to greenschist facies metamorphism. The Gaoligong shear zone experienced dextral shearing under similar metamorphic conditions between 32 and 10Ma. Consistent 40Ar/39Ar ages of hornblende from the three shear zones indicate their contemporaneity at mid-crustal depth, causing the rapid exhumation and SW-ward extrusion of the Tengchong Terrane. The strain geometry and shear zone kinematics in the Tengchong Terrane are interpreted with folding of the anisotropic lithosphere around a vertical axis, i.e., the northeast corner of the Indian Plate since 41Ma. The newly discovered NE-trending Sudian, Yingjiang, and Lianghe strike-slip shear zones are subordinate ductile faults accommodating the initially rapid clockwise rotation of the Tengchong Terrane. The detachments caused mid-crustal decoupling and faster SW-ward extrusion below the sedimentary cover, whereas the strike-slip shear zones accommodated extrusion and clockwise rotation of the Tengchong Terrane around the proto-Eastern Himalayan syntaxis since the late Eocene. © 2015 The Authors.

Xu Z.,Chinese Academy of Geological Sciences | Yang J.,Chinese Academy of Geological Sciences | Li W.,Geological Survey of Yunnan Province | Li H.,Chinese Academy of Geological Sciences | And 3 more authors.
Acta Petrologica Sinica | Year: 2013

The Paleo-Tethys system in the Tibet Plateau formed under environment of multi-ocean basins, micro-terrains (ribben continents), island arcs, subductions and collisions. Its architectures include four ophiolite or ophiolitic melange belts representing Paleo-Tethys oceanic crustal relics (South Kunlun-Animaqen ophiolite zone, Jinshajiang-Ailaoshan-Songma ophiolite zone, Central Qiangtang-Lancangjiang-Changning Menglian ophiolite zone and Songduo ophiolite zone), five volcanic magmatic island arcs (Bulhanbuda arc, Yidun arc, Jiangda-Luchun arc, Dongdashan-Yunxian arc, Zuogong-Lincang arc-collision), four terrains (Songpan-Ganze terrain, North Qiangtang-Changdu-Simao terrain and South Qiangtang-Baoshan-Sibumasu terrain), three HP-UHP metamorphic belts (Derong HP belt, Longmu Tso-Shuanghu HP belt, Songduo UHP-HP belt), as well as five forearc accretionary wedges (AW) or accretionary complex belts (West Qinling AW, Bayan Har-Songpan Gangze AW, Jinshajiang AW, Shuanghu-Nierong- Jitang-Lincang AW and Songduo AW). The subduction-accretionary orogens constructed by multi Paleo-Tethys subductions-accretional complexes, were widespreadly recorded in the Paleo-Tethys composive orogeinic belts of the Tibet Plateau. The Paleo-Tethys subduction-accretional complexes including arc front sediment accretional wedges of strong deformation and exotic blocks composed of ophiolites, HP metamorphic rocks and island arc magmatic rocks, which indicate crustal accretion of active continental margin during Paleo-tethys oceanic subduction processes.

Qian X.,Wuhan University | Feng Q.,Wuhan University | Wang Y.,Sun Yat Sen University | Zhang Z.,Geological Survey of Yunnan Province
Acta Geologica Sinica | Year: 2016

The meta-basic volcanic rocks in the Tengtiaohe Zone yield zircon U-Pb ages of 258.8±2.5 Ma and 259.2±1.8 Ma, respectively which agree with the ages of flood basalts of ELIP and are similar to the basaltic rocks and komatiites from the Song Da Zone in northern Vietnam. The results suggest that the age of meta-basic volcanic rocks is Late Permian, rather than the Early Permian or Early Carboniferous ages as previously inferred. Most meta-basic volcanic rocks are strongly enriched in LREEs relative to HREEs and display trace element patterns similar to the ELIP high-Ti basalts, and are enriched in LILEs with negative Sr anomalies. Their initial 87Sr/86Sr ratios range from 0.705974 to 0.706188 and ϵNd(t) from -0.82 to -2.11. Their magmas were derived from an enriched and deep mantle source without significant crustal contamination. These meta-basic volcanic rocks formed in ELIP. Therefore, the Tengtiaohe Zone is not an ophiolite zone and can link to the Song Da Zone in northern Vietnam. © 2016 Geological Society of China.

Zhong W.-F.,Wuhan University | Feng Q.-L.,Wuhan University | Chonglakmani C.,Suranaree University of Technology | Monjai D.,Suranaree University of Technology | Zhang Z.-B.,Geological Survey of Yunnan Province
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2012

Stratigraphy is the basis for regional geology., Since the stratigraphic framework in northern Laos has not been worked out by investigation so far, it is very difficult to reconstruct its geological history and to make comparisons among tectonic belts in Laos and its adjacent areas. During last three years, stratigraphic investigation was carried out along the highway in northwestern Laos. The Upper Permian clastic strata with coal in studied area can be correlated to that in the Yangbazhai Formation in the Simao basin; the Middle Permian clastic rocks, to those in the Lazhuhe Formation; the black thinned limestones, to those in the Middle Triassic Choushui Formation; and the light grey massive dolomitic limestones, to those in the Middle Triassic Dashuijingshan Formation, which indicates that the strata distributed between the Luangprabang and Chiang Rai belts can be well compared with that in the Simao basin between the Ailaoshan and Lancangjiang belts. Therefore, the Nan River belt in northern Thailand can not be linked with the Lancangjing belt by crossing the northwestern Laos area.

Duan X.-D.,Wuhan University | Liu G.-C.,Geological Survey of Yunnan Province | Feng Q.-L.,Wuhan University
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2012

As a part of the Paleo-Tethyan orogenic belt in west Yunnan, the Changning-Menglian belt holds the sedimentary records formed by the main branch of the Archipelagic Paleo-Tethyan Ocean. It can be linked with the Chiang Mai belt southwardly and with the Gertse-Bitu belt northwardly. The Early Devonian-Late Triassic pelagic sedimentary strata with radiolarians have been discovered in the Chiang Mai belt and the Ladinian and Carnian radiolarian fauna have also been found in the Gertse-Bitu belt. But youngest radiolarian zone from the Changning-Menglian belt is the Anisian Triassocampe deweveri Zone. Recently, the Ladinian Oertlispongus inaequispinosus Subzone was gotten from chert in Gengma area, the middle Changning-Menglian belt. The fauna shows that the Changning-Menglian Paleo-Tethyan basin was closed after the Ladinian. Younger radiolarian fauna should be further investigated in the Changning-Menglian belt.

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