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

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.