河南南阳独山玉矿物碎裂成玉过程研究

独山玉是迄今为止世界上唯一发现的达到宝石工艺要求的黝帘石化斜长岩质玉种, 目前, 有关独山玉的成玉过程研究还比较薄弱, 本文在独山玉矿的野外考察和实验室标本观察的基础上, 结合薄片的镜下鉴定研究发现: 独山玉以脉状和多期多阶段产出; 主要组成矿物有斜长石、黝帘石、角闪石，另有云母类矿物、榍石、葡萄石、方解石、电气石等次要矿物; 独山玉常具有粒状结构、碎裂结构、残斑结构、熔蚀交代结构, 似斑状结构, 偶见针状变晶结构和糜棱结构; 成玉的物理过程表现为辉长岩(独山玉的母岩)在韧性剪切应力下破裂和糜棱化, 特别是由于剪切作用, 斜长石脆塑性变形——细粒化, 并遭受黝帘石化等作用形成玉脉。

Tentative Discussion on the Mineral Cataclasis Jade-forming Process of Dushan Jade in Nanyang City, Henan Province

Dushan Jade is the only zoisitized plagioclase in the world which can meet jewelry technologic requirements, but the research on the formation process of Dushan Jade is very insufficient. Based on detailed field investigation and ore sample examination in laboratory, the authors identified optical slices of Dushan Jade. The results show that Dushan Jade is characterized by the vein-like form and the multi-phase and multi-stage mineralization, with the minerals being mainly plagioclase, zoisite, hornblende, and subordinately mica, sphene, prehnite, tourmaline etc. Granular texture, cataclastic texture, porphyroid texture, corrosion texture, porphyritoid texture and, rarely, acicular texture and mylonitic texture can be seen in Dushan Jade. The jade-forming process finds expression in the shattering and mylonitization of gabbro under the ductile shear stress. Brittle and plastic deformation and zoisitization of plagioclase resulted in the formation of Dushan Jade veins.