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    东天山大地构造演化的成矿示踪

    Ore deposits as a guide to the tectonic evolution in the East Tianshan Mountains, NW China

    • 摘要: 提要:矿床是大地构造演化的重要指示标志,矿床特征和时空分布格局为重建东天山地区大地构造演化提供了新的制约。研究表明,夹于吐哈地块和中天山地块之间的东天山古生代造山带,在空间上可分为吐哈盆地南缘铜矿带(北带)、康古尔金矿带(中带)和阿齐山—雅满苏铁(铜)-银多金属矿带(南带)3个不同的构造-地层(岩浆)-成矿带。在时间上东天山造山带具有明显的三阶段演化性:(1)吐哈盆地南缘奥陶—泥盆纪为活动大陆边缘,形成了包括VMS型铜锌矿床和斑岩型铜矿床在内的古陆缘成矿系统;晚泥盆世末—早石炭世初古洋壳向北俯冲关闭,中天山地块增生拼贴到吐哈地块(属哈萨克斯坦—准噶尔板块组成部分)南缘。(2)早石炭世(维宪期)沿康古尔缝合带再次拉张,形成石炭纪裂陷槽火山-沉积岩系及相应的层控成矿系统(VMS型铜锌矿床、火山岩型铁(铜)矿床、自然铜矿床),裂陷槽封闭过程中发育了夕卡岩型银多金属矿床。(3)早二叠世形成与幔源岩浆底侵作用有关、跨构造单元发育的铜镍硫化物成矿系统和与剪切活动有关的金矿床。依据上述认识,对东天山地区的矿产勘查提出了新建议。

       

      Abstract: Abstract: Ore deposits are an important indicator for the tectonic evolution. The characteristics and space-time distribution pattern of ore deposits provide new constraints for reconstructing the tectonic evolution in the East Tianshan Mountains. Study indicates that the Paleozoic East Tianshan orogenic belt, sandwiched in between the Tuha block and Central Tianshan block, may be divided into three tectonic-strata (magmatic)-metallogenic belts in terms of spatial distribution, i.e.: the southern Tuha basin marginal copper metallogenic belt (north belt), Kanggur gold metallogenic belt (central belt) and Aqishan-Yamansu Fe (-Cu)-Ag- polymetallic metallogenic belt (south belt). The temporal evolution of the East Tianshan orogenic belt is distinctly characterized by three stages. (1) The southern margin of the Tuha Basin was an Ordovician-Devonian active continental margin, where there occurred a paleocontinental-margin metallogenic system including VMS Cu-Zn deposits and porphyry copper deposits. In the terminal Late Devonian-initial Early Carboniferous, the paleo-oceanic crust was subducted northward, closing the ocean, and the Central Tianshan block accreted and was amalgamated to the southern margin of the Tuha block (which belongs to the Kazakhstan-Junggar plate). (2) In the Early Carboniferous (Visean), the East Tianshan again underwent extension along the Kanggur suture, forming Carboniferous aulacogen volcanic-sedimentary rocks and a corresponding stratabound metallogenic system (including VMS type Cu-Zn deposits and volcanic-hosted Fe (-Cu) deposits and native copper deposits), and skarn type Ag polymetallic deposits formed during the closing stage of the aulacogen. (3) In the Early Permian, a Cu-Ni sulfide metallogenic system related to mantle-derived magma underplating and spanning tectonic units and gold deposits related to shearing formed in this area. Based on the above discussion, new suggestions about mineral prospecting in the East Tianshan area are put forward in this paper.

       

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