摘要
新疆哈密南部发现的土屋、延东大型斑岩铜(钼)矿床,构成了东天山斑岩铜矿带。其中成矿的斜长花岗斑岩同位素年龄为369～356 Ma(Rb-Sr等时线法和单颗粒锆石U-Pb法),辉钼矿的同位素年龄为320 Ma(Re-Os等时线法),蚀变岩的同位素年龄为341～310Ma,含矿围岩由粗面质玄武岩到粗安岩,可能属于泥盆纪(416Ma,Sm-Nd法;>356 Ma、390 Ma、440 Ma,单颗粒锆石U-Pb法)。矿床成因归属为岛弧火山—深成作用产物。斑岩铜矿带的南部为著名的康古尔塔格金矿带,再往南为星星峡银矿带。这些造山带矿床组合由北而南构成斑岩型铜(钽)矿带→韧性剪切带型和浅成热液型金矿带→浅成热液型(构造蚀变带型)钼矿带,显示了构造岩浆是由北而南下插的,岩浆侵位时间北老南新,花岗质岩浆源区的部分熔融深度由北而南加深。反映壳幔演化的东天山构造岩浆作用从370 Ma到240 Ma、从北部的哈尔里克和康古尔塔格到南部的中天山,似乎存在一个连续的花岗质岩浆演化带,丝毫看不到深部作用过程由于古生代东天山数度拉张沦为海槽而被中断的迹象。基于以上主要证据,本文综合讨论了东天山斑岩型铜矿、韧性剪切带型金矿和构造蚀变带型银矿的形成机制及其大地构造格局,建立了东天山造山带的成矿模型,为今后找矿开辟了新方向。
The Tuwu and Yandong large porphyry copper (molybdenum) deposits were discovered recently in south-eastern Xinjiang, form the Eastern Tianshan porphyry copper belt. As shown by the chronological constraints, the age of plagiogranite porphyry related to mineralizaiton is about 369 ~ 356 Ma (Rb-Sr isochron dating and single-grain zircon U-Pb dating) , the age of molybdenite is 320 Ma (Re-Os isochron dating) , and the age of al-tered rocks is about 341-310 Ma. The ore-bearing wall-rocks, trachybasalt and trachyandesite probably oc-curred in the Devonian (Sm-Nb age, 416 Ma; single-grain zircon U-Pb ages, 356 Ma, 390 Ma and 440 Ma). The porphyry copper deposits are the product of island-arc volcanism-plutonism. To the south of the porphyry copper belt is the well-known Kanggurtag gold belt, and further south is the Xingxingxia silver belt. Therefor-e, from north to south, the assemblage of the erogenic deposits is manifested as the porphyry copper (molybde-num) belt-ductile shear and epithermal gold belt-epithermal (tectonic alteration) silver belt. The instrusion ages are older in the north than those in the south. All the evidence indicates that the partial melting depths of granitic magma became deeper southwards, and implies that the tectonomagmatic plane was subducted from north to south. As the reflection of the crust-mantle evolution, tectonomagmatism in the Eastern Tianshan persisted from 370 to 240 Ma, which implies that there seemed to be a belt of continuous evolution of granitic magma from Haerlike and Kanggurtag in the north to the Central Tianshan in the south. No sign is found that plutonism has been interrupted by several extension events that occurred in the Eastern Tianshan during the Pa-leozoic.The authors discusses the mineralization mechanisms and tectonic framework of porphyry copper deposits, gold deposits of ductile shear belt type and silver deposits of tectonic alteration type in the Eastern Tianshan and construct a mineralization model, which suggests the new direction in mineral prospecting in the Eastern Tian-shan orogen.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2002年第1期83-94,共12页
Acta Geologica Sinica
基金
中国地质调查局地质调查项目(编号0499165192)
