FAN Yun-fei^1,2, YANG Jin-biao³, SHI Zeng-long⁴, GAN Tian^1,2, LUO Tai-yi¹

(1. The state Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry,Chinese Academy of Sciences, Guiyang 550081, China;
2. School of the Earth Sciences, University of Chinese Academy of Sciences,Beijing 100049, China;
3. Yunnan Lancang Lead Mine Co. Ltd., Lancang 665601, China;
4. Yunnan Chihong Zn & Ge Co. Ltd., Qujing 655011, China)

Abstract: Himalayan granitic porphyry concealed invaded into the basaltic volcanic strata of early Carboniferous Yiliu Formation in middle of Lancang rift, which has been resulted in forming the porphyry-skarn hydrothermal alteration system relative with the large Mo-Cu-Ag-Pb-Zn polymetallic ore deposit of Laocang Area, Yunnan Province, China. A distinguishing hydrothermal alteration system has been predicted for deep concealed granitic porphyry invaded into the calstic rocks of early Carboniferous Nanduan Formation in Daheishan exploration area. Preliminary research on a comprehensive vertical section in Daheishan area indicates that: (1) the deep part of hydrothermal system in Nanduan Formation forms quartz veinlet characterized by distinct positive Eu anomaly(δEu=1.58) and Pb-Bi-Ag-Zn-Cu enrichment model similar to Laocang altered porphyry, revealing that there is Laochang-type granitic porphyry and Mo mineralization in deep of Daheishan exploration area; (2) the deep hydrothermal system mixed with the shallow low-temperature meteoric fluid system in C1n/C2+3 lithological interface, and nearly 40 meters iron-manganese calcitization alteration zone typical with prominent positive Eu abnormal(the highest δEu=5.71) and Pb-Zn-Ag mineralization has been formed. During the processes of alteration, the move out of Mg and the addition of Ca-Fe-Mn have a good relationship, and the new hydrothermal system enriched with Mg-Mn also has been produced; and (3) hydrothermal breccia dolomitization, which is represented by linear positive topography of Heishan ridge in Daheishan area, caused by the Mg-Mn enrichment hydrothermal fluid alterated with the overlying bioclastic limestone of the Permain. The hydrothermal breccia dolomitization is a character with obvious Sr-U depletion and strong Mn-enrichment, and is an important resource for the surface Mn-Ag mineralization. The vary of hydrothermal breccia dolomitization in the surface limestone has been confirmed as a good indicator for deep magmatic hydrothermal activity and relative mineralization through the research of comprehensive Daheishan section.

Keywords: Himalayan porphyry hydrothermal system; quartz veinlet; iron-manganese calcitization; hydrothermal breccia dolomitization; Lancang rift

E-mail: luotaiyi@vip.gyig.ac.cn

ACTA MINERALOGICA SINICA Vol. 36, No. 3, 2016, Page 343-353