粤北乐昌市和尚田钨锡多金属矿成矿时代及其地质意义

Metallogenic Age of the Heshangtian Tungsten-Tin Polymetallic Deposit in Northern Guangdong Province,and Its Geological Significance

粤北乐昌市和尚田钨锡多金属矿是近年来新发现的一个具有＂五层楼＂成矿特征的大型（云英岩）-石英脉型矿床。因其主要矿体的围岩是碳酸盐岩而不是碎屑岩且矿区离出露的花岗岩体较远而受到关注。测年结果显示：一条含矿（云英岩）-石英脉中的白云母Ar-Ar坪年龄和等时线年龄分别为158.91±0.96 Ma（MSWD=0.68）和157.8±1.8Ma（MSWD=1.80）、石英矿物Rb-Sr等时线年龄为166±7Ma（MSWD=1.01）;另一条含矿（云英岩）-石英脉中的石英矿物Rb-Sr等时线年龄为158.8±2.6Ma（MSWD=0.74）。它们在误差范围内一致,为粤北乃至整个南岭地区成岩成矿高峰期150~160Ma的产物。通过石英包裹体氢及石英氧同位素组成的初步分析,本文认为成矿流体主要来自岩浆水,在矿床深部可能存在隐伏花岗岩体。上述成果为研究区域成矿规律,指导类似无岩体出露的碳酸盐岩分布区的找矿勘查工作具有重要的现实意义。

Heshangtian is a recently discovered large scale tungsten-Tin polymetallic deposit. As seen in other tungsten-tin lode, the vertical distribution of ＂five floors style＂ is a typical feature of this deposit. But more fascinating feature is host rocks of all W Sn lodes are carbonates （not clastic rock as usual） far away from granitic intrusions opened a new window in W Sn exploration in Nanling Range. In this paper, both 4~Ar-agAr isotopic technique of muscovite and Rb-Sr isotopic technique of fluid inclusions in quartz are used on two W lodes to constraint the precise metallogenic age of this deposit. The result shows Muscovite plateau age of one lode is 158.91±0.96 Ma（MSWD=0.68） （with isochron age of 157.8＋1.8 Ma（MSWD =1. 80）） ,related Rb-Sr isoehron age is 166＋7 Ma（MSWD=l.01）. Rb-Sr isochron age of another lode is 158.8--2.6 Ma（MSWD--0.74）. Those ages consistent with each other in error limit effectively illustrate this deposit is also one of numerous products of diagenetic and metallogenic activity in Nanling Range in early Yanshanian. Through preliminary analysis of fluid inclusion in quartz, a magmatic hydrothermal origin of ore forming fluid of this deposit can be deduced. Mineralization regulation drawn from this study can provide guidance for exploration in the areas of such kind without exposure of intrusion, and thus of great significance.