青海省九八沟透闪石玉矿床成矿机制研究

研究格尔木九八沟透闪石玉矿这一典型昆仑玉矿床的地质特征、矿物化学、矿体产状、含矿地层和侵入体岩石地球化学特征及成岩时代, 确定其成矿时代和成矿机理。结果表明, 控矿岩体似斑状二云母二长花岗岩的锆石U-Pb年龄为427.1±4.7 Ma。矿区内岩浆热液交代成因的矽卡岩中发育阳起石, 玉石中则为透闪石, 二者具有明显不同的矿物化学特征。结合岩浆、围岩、玉矿石和蚀变岩的全岩微量元素特征, 认为成矿过程是岩浆侵入含硅质团块白云岩, 引发接触热变质作用, 使得白云石和硅质团块直接发生变质反应而形成透闪石玉矿床。

Study on Metallogenic Mechanism of the Tremolite Jade Deposit in Jiubagou,Qinghai Province

Jiubagou tremolite jade deposit in Golmud district is one of the typical Kunlun jade deposits. The metallogenic mechanism and age of this deposit are determined based on the systematic study of field geological characteristics, mineral chemistry, ore body occurrence, geochemical characteristics of ore-bearing strata and intrusion, and diagenetic age. The metallogenic intrusive rock is dominated by porphyritic two-mica monzogranite with a zircon U-Pb age of 427.1±4.7 Ma. Actinolite is developed in skarn of magmatic hydrothermal metasomatism, while tremolite is developed in the tremolite jade. They have obviously different mineral chemical characteristics. Combined with the whole rock trace element characteristics of magma, wall rock, the tremolite jade and the skarn, it is proposed that the magma intrudes into the siliceous dolomite and causes the contact thermal metamorphism, which leads to the direct metamorphism between the dolomite and the siliceous mass and forms the tremolite deposit.