栾川矿集区黄背岭-中鱼库花岗岩中黑云母成分特征及成岩成矿意义

COMPOSITIONAL CHARACTERISTICS,PETROGENESIS AND METALLOGENIC SIGNIFICANCE OF BIOTITE FROM GRANITE IN THE HUANGBEILING-ZHONGYUKU REGION OF LUANCHUAN ORE CONCENTRATION AREA

黄背岭-中鱼库钼多金属矿矿区是栾川矿集区目前的重点找矿区域。通过对黄背岭含矿斑状花岗岩与中鱼库隐伏的黑云母二长花岗岩进行岩相学观察与黑云母的化学成分特征分析,探讨了本区的岩石成因及成矿潜力。结果表明黄背岭和中鱼库花岗岩中的黑云母都属于镁质黑云母。黄背岭花岗岩中的黑云母Ti=0.15apfu^0.20apfu,具有退变质与固相线下交代成因的特征,中鱼库花岗岩中的黑云母Ti=0.27apfu^0.35apfu,具有岩浆成因的特征。从岩体浅部到深部,黄背岭岩体结晶压力为93 MPa^14 MPa,结晶深度为3.4km^0.5km。中鱼库岩体结晶压力为145 MPa^58 MPa,结晶深度为5.3km^2.1km。两岩体浅部结晶压力大,深部结晶压力小,表明两者均为快速侵入。两岩体均属壳幔混源的I型花岗岩,是深源中浅成花岗岩。两岩体形成时的温度分别为939.4℃~1 006℃,833℃~966℃,氧逸度分别为10-11.8 MPa^10-10 MPa,10-13.08 MPa^10-10.4 MPa。两者形成时的温度与氧逸度均较高,与其共存的流体都富氟,有利于钼钨多金属矿成矿。综上并结合透岩浆成矿作用的观点,认为本区成矿潜力大。

Huangbeiling-Zhongyuku Molybdenum polymetallic mine area is currently the focus of the prospecting area in Luanchuan ore concentration area. Based on the research of the petrography observation and analysis of characteristics of the chemical composition of biotite in Huangbeiling porphyritic granite and Zhongyuku concealed biotite adamellite granite,this article discusses the genesis of rocks and the metallogenic potential in this area. It shows that the biotite in Huangbeiling granite and Zhongyuku granite both belong to magnesia biotite. The Ti of biotite in H uangbeiling granite is 0. 15 apfu-0.20 apfu,has the characteristics of retrograde metamorphism and metasomatic origin under the solidus,and the Ti of biotite in Zhongyuku granite is 0.27 apfu -0.35 apfu, has the characteristic of magmatic origin. From shallow to deep, the crystallization pressure of Huangbeiling and Zhongyuku granite is 93 MPa-14 MPa and 145 MPa-58 MPa respectively,crystallization depth of 3.4 km- 0.5 km and 5.3 km- 2.1 km respectively. In the shallow the crystallization pressure of the two rock masses is high, and in the deep the crystallization pressure is low, indicating that the two rock masses are characteristic of rapid invasion. They belong to I type granite of deep source and hypabyssal granite with crust--mantle mixed source. The formation temperature and the oxygen fugacity of the two rock masses is 939.4 ℃ - 1 006 ℃ ,10^-11.8 MPa-10^-10 MPa and 833℃-966 ℃, 10^-13.08 MP-10^-10.4 MPa respectively,and rich fluorine, favorable for the mineralization of molybdenum and tungsten.