西昆仑赞坎铁矿地质和地球化学特征及矿床类型探讨

赞坎铁矿位于西昆仑造山带塔什库尔干地块西段,是近年新发现的一个大型沉积变质型磁铁矿床。铁矿体的顶一底板围岩分别为古元古代布伦阔勒群斜长角闪片岩和黑云母石英片岩;矿区南部出露早古生代花岗岩岩体;矿石类型以条带状及浸染状磁铁矿石为主,兼具少量块状磁铁矿石。在详细矿区地质观察的基础上,本文报道了矿石的地球化学特征与锆石U-Pb年代学分析结果。元素地球化学分析表明,条带状铁矿石具有较高的稀土总量,明显富集轻稀土,未呈现明显Ce和Y元素的异常(Ce/Ce~*=0.93~1.12、Y/Y~*=0.74~1.30);部分矿石显示Eu正异常(Eu/Eu~*=1.66~4.46),稀土配分形式与沉积变质型铁矿相似。矿体围岩变粒岩锆石U-Pb年龄为2 416±54 Ma,大致反映沉积铁矿的形成时代,而807±51 Ma的年龄反映变质作用时代。矿区一有铁矿捕虏体的花岗岩锆石U-Pb年龄为504±26 Ma。该期花岗岩的侵入对铁矿有明显的改造和叠加作用。

Geological and geochemical characteristics of Zankan iron deposit in the West Kunlun Mountains

Zankan iron deposit is in western Taxkorgan block, West Kunlun Mountains. It has been found a large sedimentary metamorphic iron deposit recently. The amphibolites and biotite quartz schist in Paleoproterozoic Bulunkuole Group were developed as main wall rocks of the ore bodies. The granites in Early Paleozoic are exposed in the southern area; Zankan iron deposit are predominantly banded and disseminated, with a scrap of massive. Based on geological observation. This article reported the geochemical characteristics of ores and zircons U-Pb age. Geochemical analyses show the banded iron ores are enriched in REE and enriched in LREE. Ce and Y elements of ores in Zankan had no clear anomaly(Ce/Ce^* =0.93～1.12、Y/Y^* =0.74～1.30)but positive Eu anomaly(Eu/Eu^* =1.66～4.46). The REE form is as same as the sedimentary metamorphic iron. Some zircon from granulite gave a U-Pb age of 2 416±54 Ma, which represented the sedimentary iron's formed age, and the metamorphic age was 807±51 Ma. The zircon from granite with iron ore xenoliths gave a U-Pb age of 504±26 Ma. It was obviously the granite was reformed.