|
|
|
题名
|
作者
|
年代
|
出处
|
被引量
|
| 1 | An Early Cretaceous gold mineralization event in the Triassic West Qinling orogen revealed from U-Pb titanite dating of the Ma'anqiao gold deposit显示文摘The West Qinling orogen in central China,formed from continental collision between the North China and Yangtze cratons in the Late Triassic,hosts numerous gold deposits with a total Au endowment of about 2000 t.Most deposits were emplaced at ca.250-195 Ma and are genetically associated with the Triassic orogenesis.Here in situ U-Pb titanite dating with laser ablation inductively coupled plasma mass spectrometry indicates the Ma’anqiao gold deposit in the northern portion of this orogen has a distinctive age and under a contrasting tectonic regime.This structurally controlled gold deposit is hosted in Late Ordovician to Early Silurian sub-greenschist facies metasedimentary rocks.The gold mineralization is hosted in quartz-pyritepyrrhotite veins and pyrite-pyrrhotite disseminations in hydrothermally altered rocks,which are crosscut by K-feldspar-calcitechlorite±pyrite veins.Titanite,present both in the disseminated sulfide ores and later veins,was used for in situ U-Pb dating.Titanite from three disseminated sulfide ore samples with Th and U averaging 27.46 and 39.31 ppm(1 ppm=1μg g^(-1)),respectively,yielded lower-intercept ages of 121.1±3.1 to 120.7±3.5 Ma(2σ)in the Tera-Wasserburg diagram.Titanite from three later vein samples with much lower Th and U concentrations averaging 2.74 and 16.21 ppm,respectively,yielded overlapping ages of 120.8±3.2 to 120.3±5.8 Ma(2σ).These new titanite U-Pb ages tightly constrain the formation of the Ma’anqiao gold deposit at ca.121-120 Ma and,when combined with independent geological data,indicate it is not related to the Triassic Qinling orogeny.Rather,its formation is attributed to lithospheric thinning and destruction of the North China craton during the Late Jurassic to Early Cretaceous which has generated numerous gold deposits along the southern margin of this craton.This catastrophic event caused extensive magmatism in large areas of the North Qinling terrane and northern edge of the West Qinling orogen immediately to the south of the North China craton.The heat flux and elevated geothermal gradients associated with this magmatism could have induced prograde metamorphism of the Paleozoic sedimentary infrastructure in and beneath these areas with the derived fluids ascending along pre-existing crustal-scale regional structures to form the Ma’anqiao gold deposit.We suggest that areas in the North Qinling terrane that have been affected by the Late Mesozoic magmatism are potential targets for future exploration of the decratonization-related gold deposits.Additionally,this study highlights the use of titanite U-Pb dating as a robust geochronometer for metasedimentary rock-hosted gold deposits in Phanerozoic orogens,which has previously not been utilized. | Chongguo HE Jianwei LI Daniel J.KONTAK Xiaoye JIN Yafei WU Hao HU Bo ZU Xueling YU Shaorui ZHAO Shiguang DU Yunlong ZHU Huan TAO | 2023 | Science China Earth Sciences2023，66，2： | 0 |
| 2 | Integrity and Failure Analysis of Cement Sheath Subjected to Coalbed Methane Fracturing显示文摘Perforation and fracturing are typically associated with the development of coalbed methane wells.As the cement sheath is prone to failure during this process,in this work,the effects of the casing pressure,elastic modulus of the cement,elastic modulus of the formation,and casing eccentricity on the resulting stresses are analyzed in the frame of a finite element method.Subsequently,sensitivity response curves of the cement sheath stress are plotted by normalizing all factors.The results show that the maximum circumferential stress and Mises stress of the cement sheath increase with the casing internal pressure,elastic modulus of the cement and casing eccentricity.As the elastic modulus of the formation increases,the maximum circumferential stress of the cement sheath decreases,and its maximum Mises stress increases slightly.The cement sheath undergoes tensile failure during coalbed methane fracturing.The stress sensitivity of the cement sheath to the influential parameters is in the following order:casing internal pressure>elastic modulus of cement sheath>casing eccentricity>elastic modulus of formation. | Lingyun Zhao Heng Yang Yuanlong Wei Yuhuan Bu Shaorui Jing Peiming Zhou | 2023 | Fluid Dynamics & Materials Processing2023，19，2： | 0 |
| 3 | Stable Isotopes and Halogen Geochemistry of the Huayuan Carbonate-hosted Pb-Zn Ore District, South China: Implications for the Salt Source of Ore-forming Fluids显示文摘The Huayuan Pb-Zn ore district in China,located in western Hunan Province,is a giant carbonate-hosted Pb-Zn ore district.The source of ore-forming brines in this ore district remains poorly constrained.Whether the highly saline brines are derived from evaporated seawater or dissolved evaporates continues to be intensely debated.Carbonate minerals associated with Pb-Zn mineralization haveδ^(13)CV-PDB andδ^(18)OV-SMOW values ranging from−5.55‰to+1.35‰(mean value of−0.69‰;n=14)and+16.28‰to+25.05‰(mean value of+20.22‰;n=14),respectively.This indicates that carbonate minerals are dominantly formed from dissolved ore-hosted carbonate rocks.Theδ^(34)S values of sulfides range from+20.2‰to+36.8‰,with an average value of+30.0‰(n=27).These results suggest that sulfur is predominantly derived from the thermochemical sulfate reduction of marine sulfate.The crush-leach analyzed solute data of fluid inclusions in sphalerite show the ore-forming fluids have Cl/Br molar ratios range from 118 to 384,and Na/Br molar ratios from 39 to 160(n=8).These Cl/Br ratios of hydrothermal fluid are much lower than those of seawater(657 to 564),but are consistent with bittern brines through early halite precipitation.We propose that ore-forming fluids are mainly derived from evaporitic basin brines,which leached base metals from the basement and/or country rocks.The brine then migrated to the basin margins through clastic rocks of basement and then precipitated sulfides by thermochemical sulfate reduction. | YANG Zhen JIANG Mengjie ZHAO Shaorui DING Zhenju HE Mouchun | 2022 | Acta Geologica Sinica(English Edition)2022，96，2： | 0 |
| 4 | Trace Element and Sulfur Isotope Compositions of Gold-bearing Pyrite from the Zhangjiawa Iron Skarn Deposit,Laiwu District:Implications for Sources of Early Cretaceous Gold Mineralization in the North China Craton显示文摘Objective The Zhangjiawa iron deposit is the largest-tonnage and representative iron skarn deposit,with proven reserves of 290 Mt at an average of 46%Fe(up to>65%),in the Laiwu district,eastern North China Craton(NCC)(Figs.1 a,b;Duan and Li,2017).Iron mineralization at Zhangjiawa is mainly hosted along a northern contact zone between the Kuangshan dioritic intrusion and Middle Ordovician carbonate rocks that host numerous evaporite intercalations(Figs.1b,c). | DUAN Zhuang FU Yangang LI Chunjia ZHAO Shaorui GAO Mingbo GAO Jilei JIN Lijie LI Siyuan NGO Dac Xuan | 2021 | Acta Geologica Sinica(English Edition)2021，95，5： | 0 |
您所在的机构暂未开通此部分的功能，请联系管理员