青海沙柳河矿区侵入岩地质特征及成矿意义

沙柳河矿区大地构造位置属于柴北缘加里东地槽褶皱带东缘,区内印支期侵入岩分布广泛.通过对侵入岩物质成分、岩性特征、岩石化学特征的研究,从侵入岩形成时代、岩石特征及岩石地球化学特征等方面分析了侵入岩与钨锡矿成矿之间的关系.分析认为区内成矿岩体以黑云二长花岗岩为主,属于S型花岗岩,具有酸度大、含碱量不高的特点,属弱碱性—过碱性硅铝过饱和类型花岗岩,其含副矿物种类较多.岩石中Pb、Zn、W、Sn元素含量均高于世界花岗岩平均值的1.5~3.3倍,为钨锡成矿提供了物质来源.利用花岗岩K+Na与Si相关图、SiO_2-(CaO+MgO+FeO)-(Na_2O+K_2O+Al_2O_3)三相图、分异指数直方图等方法对区内的花岗岩进行分析,认为普查区似斑状黑云二长花岗岩(含云英岩化二长花岗岩)在岩性特征、岩石化学、物质成分及形成时间等方面,均表现出与国内外锡钨成矿岩体非常相似之处,属有利的成矿母岩.

GEOLOGICAL CHARACTERISTICS AND METALLOGENIC IMPLICATION OF THE INTRUSIVE ROCKS IN SHALIUHE OREFIELD,QINGHAI PROVINCE

The Shaliuhe tungsten-tin orefield in Qinghai Province,tectonically belonging to the eastern margin of the Caledonian synclinorium fold belt in northern Qaidam Basin,is broadly intruded by Indosinian rocks.With discussion on the composition,lithology and petrochemistry of intrusive rocks,this paper analyzes the relationship between the rocks and the W-Sn metallogenesis.The result shows that the ore-forming rock in the orefield is dominated by biotite monzogranite,belonging to S-type of weak alkaline-peralkaline silica-aluminum supersaturated granite,with various kinds of accessory minerals.The Pb,Zn,W and Sn contents in the rock are 1.5-3.3 times higher than the world average values of granite,suggesting that the intrusive rock in the area is the material source for W-Sn mineralization.The granite is analyzed with the approaches of (K +Na)-Si correlation diagram,SiO2-(CaO +MgO +FeO)-(Na2O +K2O +Al2O3) phase diagram and differentiation index histogram.It is concluded that the porphyraceous biotite monzogranite in the orefield shows great similarity to the W-Sn ore-forming rocks both in China and abroad in lithology,petrochemistry,composition and forming time,to be a favorable metallogenic parent rock.