QIAN Zhi-kuan1,2, LUO Tai-yi1, HUANG Zhi-long1, TONG Xiang3, YANG Bao-fu3, Yang Wen-bao3, Lu Rong-yu3
(1. State Key Laboratory of Ore Deposit Geochemistry, Chinese Academy of Sciences,Guiyang 550002,China；
2. Graduate University ofChinese Academy of Sciences,Beijing 100039,China;
3. Group Company of StannaryGejiu in Yunnan, Gejiu 610000,China)
Abstract: Most of Xinshan bedded and Quasi-bedded diopside rocks, with light green color, present in the interlayer of carbonate formation at the top of Xinshan granites. The most abundant mineral of the diopside rocks is sahlite, whose content is over 50%. The second abundant minerals are anorthite and so on, whose granularity is small and with cryptocrystalline texture. However, the main mineral of typical diopside skarn in this mine area in the contact zone between Xinshan granites and carbonate formation is hedenbergite, with content over 65%. The relatively lesser abundant minerals are tremolite, garnet and wollastonite, which have coaser grain size and crystalline structure. Xinshan bedded and Quasi-bedded diopside rocks have high Mg, Ti, and P, are enriched in Sr and LILE (Rb, Th, U), with different depletion in Ba and K, showing a LREE-enriched pattern, and Eu is minor anomaly with δEu of 0.40～0.61. The characteristics of trace elements and REE in Xinshan bedded and Quasi-bedded diopside rocks are similar to those of alkali-basalts in the mine area, which is obviously different from granites and typical diopside skarn in Xinshan. Geological, petrological and geochemical studies show that the protolith of Xinshan bedded and Quasi-bedded diopside rocks may well be the Indo-Chinese Epoch alkali-basalts, and the origin mechanism is that in the hot brine system, mafic volcanic eruption and intrusion rocks are metasomated and alternated by hot brine in the tension-rifted environment.
Key words: stratiform diopside rocks; hydrothermal metasomatic;Xinshan Cu-Sn ore deposit; Gejiu, Yunnan
E-mail: luotaiyi@vip.gyig.ac.cn
ACTA MINERALOGICA SINICA Vol. 31, No. 3, 2011, Page 338-352
