摘要:
错那洞片麻岩穹隆位于特提斯喜马拉雅南侧,靠近藏南拆离系,是北喜马拉雅片麻岩穹隆带(NHGD)中最新发现的新成员.本文在详实的野外地质调查基础上,首次全面介绍了错那洞片麻岩穹隆的结构组成,同时进行了片麻岩的年代学研究.结果表明,错那洞片麻岩穹隆由核-幔-边三部分组成,核部由花岗片麻岩及淡色花岗岩组成,并可见大量伟晶岩脉穿插;幔部为一套强变质变形的二云母片岩,从内至外具有夕线石+石榴石→蓝晶石+石榴石→十字石+石榴石→石榴石+十字石+堇青石→堇青石+石榴石的变质分带特征;边部主要为浅变质沉积岩系,可见较多因穹隆隆升而形成的A型褶皱.花岗片麻岩LA-ICP-MS锆石U-Pb年龄为(499.7±3.4)Ma(MSWD=0.025),与NHGD其它穹隆核部片麻岩时代基本一致,均为泛非—早古生代造山活动的产物.在本次野外地质调查过程中,在错那洞片麻岩穹隆中发现了矽卡岩型钨锡铍工业矿体以及铜金矿化体,同时在伟晶岩中还存在着大量的绿柱石等宝石矿产,这样的成矿作用与矿化组合在NHGD中尚属首次发现,基于此本文提出了北喜马拉雅片麻岩穹隆控矿新命题.
Abstract:
The Cuonadong gneiss dome is a newly discovered dome in the North Himalaya Gneiss Domes (NHGD) belt, which is near the southern Tibetan detachment system, southern Tethys Himalaya. Based on the detailed field work, the authors made a comprehensive description of the structure of the Cuonadong gneiss dome for the first time, and studied the chronology of gneiss. The results show that the Cuonadong gneiss dome is composed of three parts. The core is composed of gneiss and leucogranites and a large number of pegmatite veins. The mantle part is composed of mica schist, with the metamorphic zoning characteristics of sillimanite+garnet→ kyanite + garnet→staurolite + garnet→garnet + staurolite + cordierite→cordierite + garnet from inside to outside. The outer part is mainly composed of metamorphic sedimentary rocks, which have many A-folds due to the rise of the dome. Zircon U-Pb age of the gneiss is (499.7±3.4) Ma (MSWD=0.025), which is consistent with data of other gneiss in the NHGD, suggesting that both are products of the Pan-African and Early Paleozoic orogenic events. During the field geological survey, the authors discovered the skarn type W-Sn-Be-Cu-Au orebody and a large number of gemstones such as beryl in the pegmatite. This mineralization and mineralization combination was discovered in NHGD for the first time, and a new proposition for the ore-controlling role of NHGD was thus established.
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