冈底斯斑岩铜矿带东段早中新世剥蚀作用及对渐新世—中新世斑岩矿床时空分布的影响  

Early Miocene Exhumation History in the Eastern Gangdese Porphyry Copper Belt and Its Influence on the Spatiotemporal Distribution of Oligocene-Miocene Porphyry Deposits

作　　者：周敖日格勒 王英[2] 唐菊兴[1] 王晓南 张冠 田斌 林文海 ZHOU Aorigele;WANG Ying;TANG Juxing;WANG Xiaonan;ZHANG Guan;TIAN Bin;LIN Wenhai(MLR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Sichuan Province Energy Investment Group Co.Ltd.,Chengdu 610081,Sichuan,China;Tibet University,Lhasa,850000,Xizang,China;Zhongkai Mineral Industry Co ltd Tibet,Lhasa 850000,Xizang,China)

机构地区：[1]中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [3]四川省能源投资集团有限责任公司,四川成都610081 [4]西藏大学,西藏拉萨850000 [5]西藏中凯矿业股份有限公司,西藏拉萨850000

出　　处：《西北地质》2022年第3期286-296,共11页Northwestern Geology

基　　金：国家重点研发计划青年科学家项目“藏北高Sr/Y淡色花岗岩W-Nb-Ta成矿作用与找矿快速定位”(2021YFC2900100);国家自然科学基金青年基金项目“西藏甲玛斑岩-矽卡岩型矿床隆升剥露历史研究”(41902095);国家重点研发计划项目“甲玛-驱龙铜多金属资源基地深部勘查与增储示范”(2018YFC0604101);西藏中凯矿业有限公司横向项目“西藏龙玛拉铅锌(铁)矿区成矿条件与找矿方向综合研究”(HE2114)联合资助。

摘　　要：冈底斯渐新世—中新世斑岩铜矿带是特提斯成矿域重要组成部分,已经发现了多处超大型-大型斑岩-矽卡岩型铜-钼-金矿床。然而,渐新世以来铜矿带所处的青藏高原经历了强烈抬升与剥蚀作用,在此背景下带内矿床是如何保存下来的尚未清楚,带内剥蚀作用的发育特征及对渐新世—中新世斑岩矿床的分布影响如何,控制机制有待解决。笔者通过泽当以北40km处冈底斯弧内部垂直剖面锆石和磷灰石(U-Th)/He定年,发现成矿带内部发育了早中新世(17.3~15.1 Ma)快速剥蚀作用,期间平均剥蚀速率>1.82 km/Ma,剥蚀量为4.0 km,而后剥蚀速率降低至0.14~0.19 km/Ma,15.1 Ma至今剥蚀量~2.5 km。结合前人数据,笔者发现成矿带内早中新世强快速剥蚀区呈东—西向带状分布,且受谢通门-沃卡剪切带向南逆冲作用控制,其南、北两侧也发育同期剥蚀作用,强度明显低于剪切带活动区域,说明高原内部中新世以来的隆升与剥蚀作用具有差异性。冈底斯带渐、中新世斑岩矿床分别分布在早中新世强剥蚀区南、北两侧弱剥蚀区内,指示差异剥蚀作用是成矿带内已发现的渐新世—中新世矿床时空分布的重要影响因素。Gangdese Oligocene-Miocene porphyry copper belt is the important component of Tethys metallogenic domain,where numerous giant and large porphyry-skarn Cu-Mo-Au deposits have been discovered.However,the Tibetan Plateau that hosts this copper belt has suffered intense and rapid uplifting and erosion since Oligocene.How these Oligocene-Miocene deposits preserved in that environment suffering rapid uplifting and erosion remains as mystery and how the temporal and spatial distribution of erosion dominate the Oligocene-Miocene deposits in the belt remains unsettled.Basing on the zircon and apatite(U-Th)/He dating on the vertical section inner Gangdese arc 40km north of Zedong area,the author discovered an early Miocene(17.3~15.1 Ma)intense and rapid erosion event in the Gangdese porphyry Cu belt,during which the average erosion rate was>1.82 km/Ma,the erosion amount was 4 km.And then the erosion rate decreased to 0.14~0.19 km/Ma with the erosion amount from 15.1 Ma to present of~2.5 km.Integrating the previous thermo-chronological data,the author reveals that the early Miocene intense erosion zone in the Gangdese porphyry Cu belt was E-W trending and controlled by the southward thrusting of Xietongmen-Oiga shear zone.Even though the contemporaneous erosional event was also developed on the southern and northern sides,the intensities were significantly lower than the shear zone area,indicating that the uplifting and erosion in the plateau has varied temporally and spatially since Miocene.Besides,the Oligocene and Miocene porphyry deposits are distributed in the weak erosion zones on the southern and northern sides of the early Miocene E-W trending intense erosional belt respectively,indicating that the differential erosion is one of the restrictive factors for the temporal and spatial distribution of Oligocene-Miocene deposits in the belt.

关 键 词：冈底斯 斑岩 谢通门-沃卡剪切带 (U-Th)/He 剥蚀 

分 类 号：P578.25[天文地球—矿物学]