西藏玉龙铜矿床次生氧化富集作用机制

Mechanism of Secondary Oxidation and Enrichment in the Yulong Copper Deposit, Xizang(Tibet)

本文阐述了西藏玉龙铜矿床成矿过程中的“沉积初步富集期”和“西藏玉龙铜矿床次生氧化成矿作用模式”,这不仅对指导当前生产具有重要的现实意义,而且为在玉龙铜矿带进一步找矿工作开劈了新的方向。

In this paper, the authors put forward a new mineralization mechanism to explain the origin of oxidized stratiform ore bodies in the Yulong copper deposit. The proposed mechanism includes two stages, i. e. , the vertical oxidation and enrichment stage and the subsequent lateral migration and telescoped enrichment stage.After the Yulong porphyry body was emplaced into copper-bearing strata of the Upper Tri-assic Jiapela Formation, wrigglites and associated primary stratiform ore bodies were formed a-long the contact zone bet-ween hornhels of the Jiapela Formation and marbles of the Bolila Formation. With the rise of the earth's crust and denudation of cap rocks of the ore bodies, the stratiform porphyry ore bodies were uplifted to the surface in the first stage. They were significantly oxidized by underground water and, as a result, vertical telescoped mineralization developed. Oxidation of pyrite near the surface resulted in the downward penetration of acid oxidizing solutions through ore bodies and the formation of secondary sulfides near the water table. Since the CO2 content was low in the vertically leaching copper-bearing solution, secondary oxidation and enrichment zones were not well developed in the deposit.When stratiform porphyry ore bodies were uplifted to the surface in the second stage, Cu and some other useful elements were dissolved into water and laterally transported into oxidized ore bodies with a high porosity and permeability. During the long-term flow of acid solution a- long bedding, oxidization further developed and the preexisting secondary oxides and sulfid were dissolved once again. Ore-forming elements of oxidized stratiform ore bodies were deriv from both wrigglites and porphyry ore bodies. Therefore, the lateral migration and accumulati are believed to be responsible for the abnormal enrichment of copper in layered ore bodies in t Yulong deposit.