东天山康古尔-黄山剪切带的活动与成矿:对区域找矿勘查的指示

Movement and mineralization of the Kanggur-Huangshan shear zone in the East Tianshan:Implications for regional exploration

中亚造山带在显生宙期间经历了强烈的陆壳增生与改造作用,其地壳增生过程和成矿作用复杂多样。晚古生代的天山以大规模走滑剪切变形、同构造岩浆和多金属成矿作用为显著特征,是中亚造山带增生汇聚作用的典型地区。前人的研究主要关注于剪切带起源与演化时限、变形特征或独立矿床的典例剖析,缺乏针对剪切带演化与成矿时空联系的综合研究。本文选取天山康古尔-黄山剪切带出露的代表性矿床——康古尔金矿和红山南金矿,开展金矿石中绢云母^(40)Ar/^(39)Ar定年研究,并结合前人报道的年代学数据来探讨金成矿与大规模剪切活动的时空联系,从而揭示区域差异性隆升与成矿作用的耦合关系。定年结果显示,康古尔金矿的成矿时代为264.8±1.7Ma,而红山南金矿的成矿时代为261.5±1.5Ma,与康古尔-黄山剪切带右行走滑运动时间(约279~249Ma)一致。基于康古尔-黄山剪切带西段和东段在区域地质、动力学背景、岩浆作用时间、右行走滑运动的相似性和矿床空间分布的差异性,本文认为康古尔-黄山剪切带中西段的岩浆镍铜硫化物矿床和(中成至深成)造山型金矿床可能尚未出露,深部找矿潜力大,而东段出露深度大,岩浆铜岩浆镍铜硫化物矿床分布广,但中-浅成造山带金矿剥蚀殆尽,深部潜力不足。综合区域构造演化历史,本文认为康古尔-黄山剪切带的东-西差异是天山-北山三叠纪斜向汇聚所引起的区域差异性隆升导致,而差异性隆升则是区域内现今构造变形和矿床空间分布分布巨大差异的主要原因。

The Central Asian Orogenic Belt(CAOB) was subjected to continental crust accretion and transformation during the Phanerozoic,leading to complex deformation and mineralization events.Late Paleozoic large-scale strike-slip shear deformation features,syn-kinematic magmatic rocks and polymetallic mineral deposits are prominent characteristics of the Tianshan,a region of accretion and convergence in the CAOB.Although numerous studies have characterized the geology of this region,they mainly focused on understanding the origin and timing of shear zones,deformation characteristics and genesis of independent ore deposits.Few studies have comprehensively assessed the spatio-temporal relationship between shear zone evolution and mineralization,as well as the link between regional differential uplift and mineralization.This contribution focuses on two representative gold deposits(the Kanggur and the Hongshannan) in the Kanggur-Huangshan Shear Zone(KHSZ) in the Tianshan,and characterizes the timing of their mineralizing events using ^(40)Ar/^(39)Ar dating of sericite from auriferous ores.Combined with previous geochronological data,it characterizes the spatio-temporal relationship between gold mineralization and large-scale shear movements.The new dating results demonstrate that the age of mineralization in the Kanggur gold deposit is 264.8±1.7Ma,whereas the age of mineralization of the Hongshannan gold deposit is 261.5±1.5Ma;both of these ages are within the timing of dextral strike-slip movement of the KHSZ(279~249Ma).Based on the similarity in regional geology,geodynamics,timing of magmatism and dextral strike-slip movement,and the difference in spatial distribution of ore deposits between the western and eastern portions of the KHSZ,it is suggested that the western and central portions of the KHSZ were not significantly exhumed,allowing the epithermal and epizonal orogenic gold deposits to be preserved.A consequence of this interpretation is that mesozonal to hypozonal orogenic gold and magmatic Ni-Cu sulfide deposits may be preserved at depth in the central and western portion of the KHSZ.In contrast,the eastern portion of the KHSZ was subjected to significant uplift,allowing substantial amounts of crustal material to be exhumed and eroded,destroying the orogenic gold deposits and exposing the deep-seated magmatic Ni-Cu sulfide deposits.Based on the regional tectonic evolution of the Tianshan,it is suggested that the difference in metallogeny and deformation between the regions east and west of the KHSZ was likely caused by regional differential uplift induced by the oblique convergence of the Tianshan and Beishan regions during the Triassic.