鲁西石马—胡家庄稀土矿成矿机制研究——来自地球化学、电子探针的新约束

Study on Metallogenic Mechanism of Shima—Hujiazhuang Rare Earth Deposit in Western Shandong Province——New Evidence from Geochemistry and Electron Probe

摘要:

在山东省西部莱芜—淄博一带的石马、胡家庄、八陡、雪野等地分布有大量含稀土矿的碳酸岩体，这些碳酸岩内发育的稀土矿床多为内生类的轻稀土矿床。鲁西石马—胡家庄碳酸岩的稀土总量变化于920×106～111742×106，尤其富集轻稀土，LREE/HREE=21.56～35.36，(La/Yb)N=55.81～207.82，其中重稀土的分异较为显著，(Gd/Yb)N=5.33～13.41，而轻稀土的分馏相对较弱，(La/Sm)N=4.36～6.27，具有弱铕负异常（δEu＝0.8～0.90），其方解石的δ13CVPDB变化范围为5.83‰~1.55‰，δ18OVSMOW介于9.47‰~16.81‰之间，电子探针分析研究显示鲁西碳酸岩中出现大量蚀变矿物蛭石、绿泥石等，其黑云母属于镁质黑云母，淄博石马—莱芜胡家庄稀土矿属岩浆热液型矿床，是活动大陆边缘的产物。

Abstract:

A large number of carbonate bodies containing rare earth ores are distributed in Shima, Hujiazhuang, Badou and Xueye in Laiwu-Zibo area in western Shandong province. Most of rare earth deposits developed in these carbonate rocks are endogenetic light rare earth deposits. The total REE content of Shima—Hujiazhuang carbonate rocks in western Shandong varies from 920×10-6 to 111742×10-6. Light rare earths are enriched especially. LREE/HREE=21.56~35.36, (La/Yb)N=55.81~207.82, and the heavy REE content is significantly different, (Gd/Yb)N=5.33~13.41. The fractionation of light rare earth is relatively weak, (La/Sm)N=4.36~6.27. It has a weak europium negative anomaly (δEu =0.8~0.90). The δ13CVPDB of calcite ranges from5.83‰ to 1.55‰, and δ18OVSMOW ranges from 9.47‰ to 16.81‰. Electron microprobe analysis shows that there are a large number of altered minerals, such as vermiculite and chlorite in carbonate rocks in western Shandong. Its biotite belongs to magnesian biotite. Rare earth deposits in Shima—Hujiazhuang area belong to magmatic hydrothermal deposits. It is the product of active continental margin.