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Late Cretaceous-Cenozoic Multi-Stage Denudation at the Western Ordos Block： Constraints by the Apatite Fission Track Dating on the Langshan

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Acta Geologica Sinica(English Edition) 2018年第2期92卷 536-555页

作者： CUI Xianyue ZHAO Qihua ZHANG Jin WANG Yannan ZHANG Beihang NIE Fengjun QU Junfeng ZHAO Heng State Key Laboratory of Geohazard Prevention and Geoenvironment Protection (Chengdu University of Technology) Chengdu 610059 China The Institute of Geology Chinese Academy of Geological Seiences Beijing 100037 China Xinjiang Institute of Ecology and Geography Chinese Academy of Sciences Orumqi 830011 China Donghua Polytechnic University Nanchang 330013 China

The apatite fission track dating of samples from the Dabashan （i.e., the Langshan in the northeastern Alxa Block） by the laser ablation method and their thermal history modeling of AFT ages are conducted in this study. The obtained results and lines of geological evidence in the study region indicate that the Langshan has experienced complicated tectonic-thermal events during the the Late Cretaceous-Cenozoic. Firstly, it experienced a tectonic-thermal event in the Late Cretaceous （-90-70 Ma）. The event had little relation with the oblique subduction of the Izanagi Plate along the eastern Eurasian Plate, but was related to the Neo-Tethys subduction and compression between the Lhasa Block and Qiangtang Block. Secondly, it underwent the dextral slip faulting in the Eocene （-50-45 Ma）. The strike slip fault may develop in the same tectonic setting as sinistral slip faults in southern Mongolia and thrusts in West Qinling to the southwest Ordos Block in the same period, which is the remote far-field response to the India-Eurasia collision. Thirdly, the tectonic thermal event existed in the late Cenozoic （since -10 Ma）, thermal modeling shows that several samples began their denudation from upper region of partial annealing zone （PAZ）, and the denudation may have a great relationship with the growth of Qinghai-Tibetan Plateau to the northeast. In addition, the AFT ages of Langshan indicate that the main body of the Langshan may be an upper part of fossil PAZ of the Late Cretaceous （-70 Ma）. The fossil PAZ were destroyed and deformed by tectonic events repeatedly in the Cenozoic along with the denudation.

关键词： apatite fission track cooling history thermal modeling Late Cretaceous-Cenozoic,Langshan

Meso-Cenozoic Tectonothermal history of Permian Strata, Southwestern Weibei Uplift: Insights from Thermochronology and Geothermometry

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Acta Geologica Sinica(English Edition) 2019年第6期93卷 1647-1661页

作者： YU Qiang REN Zhanli LI Rongxi TAO Ni QI Kai JIANG Cheng WANG Baojiang The School of Earth Science and Resources Chang’an UniversityXi’an 710054China Key Laboratory of Western China's Mineral Resources and Geological Engineering Ministry of EducationChang'an UniversityXi'an 710054China State Key Laboratory of Continental Dynamics Northwest UniversityXi'an 710069China Department of Geology Northwest UniversityXi’an710069China State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400030China State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam Chongqing UniversityChongqing 400030China Research Institute of Yanchang Petroleum(Group)Company Limited Xi’anSichuan710075China

This study provides an integrated interpretation for the Mesozoic-Cenozoic tectonothermal evolutionary history of the Permian strata in the Qishan area of the southwestern Weibei Uplift,Ordos *** fission-track and apatite/zircon(U-Th)/He thermochronometry,bitumen reflectance,thermal conductivity of rocks,paleotemperature recovery,and basin modeling were used to restore the Meso-Cenozoic tectonothermal history of the Permian *** Triassic AFT data have a pooled age of^180±7 Ma with one age peak and P(χ2)=86%.The average value of corrected apatite(U-Th)/He age of two Permian sandstones is^168±4 Ma and a zircon(U-Th)/He age from the Cambrian strata is^231±14 *** reflectance and maximum paleotemperature of two Ordovician mudstones are 1.81%,1.57%and^210℃,~196℃*** undergoing a rapid subsidence and increasing temperature in Triassic influenced by intrusive rocks in some areas,the Permian strata experienced four cooling-uplift stages after the time when the maximum paleotemperature reached in late Jurassic:(1)A cooling stage(~163 Ma to^140 Ma)with temperatures ranging from^132℃to^53℃and a cooling rate of^3℃/Ma,an erosion thickness of^1900 m and an uplift rate of^82 m/Ma;(2)A cooling stage(~140 Ma to^52 Ma)with temperatures ranging from^53℃to^47℃and a cooling rate less than^0.1℃/Ma,an erosion thickness of^300 m and an uplift rate of^3 m/Ma;(3)(~52 Ma to^8 Ma)with^47℃to^43℃and^0.1℃/Ma,an erosion thickness of^500 m and an uplift rate of^11 m/Ma;(3)(~8 Ma to present)with^43℃to^20℃and^3℃/Ma,an erosion thickness of^650 m and an uplift rate of^81 m/*** tectonothermal evolutionary history of the Qishan area in Triassic was influenced by the interaction of the Qinling Orogeny and the Weibei Uplift,and the south Qishan area had the earliest uplift-cooling time compared to other parts within the Weibei *** early Eocene at^52 Ma and the late Miocene at^8 Ma,as two significant turning points after which both the rate of uplift and the rat

关键词： low temperature thermochronology fission track (U-Th)/He basin modeling cooling history uplift Ordos Basin

The Thermal history of the Huangmeijian Granite Intrusion in Anhui and Its Relation to Mineralization: Isotopic Evidence

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Acta Geologica Sinica(English Edition) 1996年第2期70卷 168-180页

作者： Zheng Yongfei Fu Bin and Gong Bing Department of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026 Liu Xinzhu Department of Earth and Space Sciences University of Science and Technology of China Hefei 230026

Whole-rock Rb-Sr, zircon U-Pb and hornblende, biotite and K-feldspar K-Ar ages areused to reconstruct the cooling history of the Huangmeijian intrusion in the Anqing-Lujiangquartz-syenite belt in Anhui. Oxygen isotope geothermometry of mineral pairs demonstrates thatdiffusion is a dominant factor controlling the closure of isotopic systems. Assuming the coolingof the intrusion is synchronous with a dicrease in local geothermal gradients, an emplacementdepth of about 8 km and the magma crystallization temperature of 800±50℃ are estimated. TheHuangmeijian intrusion experienced a rapid cooling process and uplifted after its emplacementand crystallization at 133 Ma B.P. with a cooling rate of 34.5℃/Ma and an uplifting rate of 0.35mm/a. The intrusion was rising until it rested at a depth of 3km at a temperature of 300±50℃about 14 Ma later. Then the intrusion was in slow cooling and uplifting with a cooling rate of4.4℃/Ma and an uplifting rate of 0.04 mm/a. U-Pb dating of pitchblende is done for the hydrothermal uranium deposit formed in thecontact zone of the Huangmeijian intrusion. The result shows that the mineralization age is closeto the closing time of the K-Ar system in biotite. The fluid inclusion thermometry indicates thatthe mineralization temperature is in agreement with the closure temperature of the biotite K-Arsystem. This suggests a close relationship between the slow cooling of the intrusion and thehydrothermal uranium mineralization process.

关键词： quartz syenite isotopic age oxygen isotope cooling history mineralization rate control