LI Kai-xuan^1,2, JIANG Ting-li³, XING Le-cai^1,2, ZHOU Ming-zhong⁴, LUO Tai-yi¹

(1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Scinces, Guiyang 550002, China;

2. School of Chinese Academy of Scinces, Beijing 100080, China;
3. Guizhou Bureau of Quality and Technical Supervision, Guiyang 550004, China;
4. Guizhou Normal University, Guiyang 550001, China)

Abstract：Luodian nephrite consist of main tremolite with minor diopside and talc, with prevail interweave structure. The typical structure and mineral composion dominate the quality of nephrite. Value of trace elements content of Cr-Ni-Co in Luodian nephrite is much lower than that of serpentinite metasomatism type nephrite and has the same range of metasomatized dolomite type nephrite. The strong Ce negative anomaly (δCe=0.21－0.34) and not obvious Eu negative anomaly of the nephrite’s right-slop REE patterns make it obviously different from famous nephrite in Hetian and Xiuyan. Through  geochemical characteristics comparison of Luodian nephrite, diabase dyke, siliceous rock, it’s reasonable to consider that, during the mineralization of Luodian nephrite, the intrusion of diabase plays the role of heat-source and massive Mg possibly come from thermal circle of seawater. Features of REE inherited from siliceous rock with alteration replenish the information of cyclic thermal seawater. By summarizing the research result of areal geology, mineralogy, geochemistry, we conclude that, at about 255 Ma, the up-intrusion of the diabase dyke caused the overlying seawater forming large-scale heat exchange circulation through the fracture system and then the upper thick massively contacted metamorphic zone produced; simultaneously, the Mg was continually transmitted to bottom to generate dolomitization, diopsidization, tremolitization , steatitization and in the final, the nephrite ore deposite occurrence.

Key words: Luodian nephrite jade; mineralogy; geochemistry; genetical model