西藏冲江铜矿含矿岩体与非含矿岩体区分探讨

The preliminary study of the discrimination of ore-bearing and ore-free rocks in the Chongjiang copper deposit, Xizang

关键词:  西藏  冲江铜矿  热释光标型  石英粒度标型

Key words:  Xizang  Chongjiang copper deposit  thermoluminescence typomorphism  quartz grain-size typomorphism

摘要:

冲江铜矿位于世界三大斑岩成矿域的特提斯-喜马拉雅成矿域,其大地构造位置属冈底斯-念青唐古拉构造带的冈底斯陆缘火山-岩浆弧中部。矿区含矿岩体与非含矿岩体的岩性相同,很难通过肉眼或常规分析方法把它们区分开来。热释光测试结果表明,矿区岩石的热释光曲线有单峰和双峰两种,矿化主要发生在具单峰的似斑状二长花岗岩中。岩石矿化程度越强,热释光总积分强度值越小。另外,高岭土化对岩石天然热释光有叠加作用,具高岭土化的岩石明显具有更高的热释光值,且高岭土化与矿化成负相关。因此,热释光值可作为判断矿化的一个岩石标型。石英粒度统计也表明,含矿岩体的石英粒度曲线呈韵律式变化,而不含矿的岩石粒度曲线呈渐进式变化。故岩石中的石英粒度也可作为矿化的一个矿物标型。

Abstract:

The Chongjiang copper deposit, Xizang is located in the Tethys-Himalayan metallogenic domain known as one of three metallogenic domains of porphyry in the world. Tectonically, it lies in the middle part of the Gangdise epicontinental volcanic-magmatic arc within the Gangdise-Nyainqentanglha tectonic zone. It is often difficult to distinguish the ore-bearing porphyries and ore-free wall rocks with the aid of macroscopic examination or conventional analysis because of the similarities between ore-bearing intrusive rocks and ore-free wall rocks. Two analytical methods of thermoluminescence and grain-size statistics are used in this study. The thermoluminescence curves for the rocks in the mining district display both the unimodal and bimodal distribution. The mineralization occurs dominantly in the unimodal porphyroid adamellite, and the higher the mineralization degrees, the smaller the total integration intensity values of thermoluminescence. In addition, the gaolinized rocks have much higher values of thermoluminescence, and the gaolinization often has negative correlation with mineralization. The grain-size curves for the ore-bearing porphyries display rhythemic variation, while those for the ore-free rocks exhibit gradual changes. It can be seen that both the values of thermoluminescence and quartz grain-size statistics may be employed as the criteria for the recognition of mineralization.