江西岩背含锡斑岩主要造岩矿物标型特征

TYPOMORPHIC CHARACTERISTICS OF MAIN ROCK-FORMING MINERALS IN TIN - BEARING PORPHYRIES, YANBEI, JIANGXI

江西会昌岩背J3－K1时期形成的火山穹窿由火山岩、次火山岩和侵入岩组成。大型斑岩型铝矿床里存于含黄玉花岗斑岩与（次）流纹班岩内外接触带上。成矿岩体花岗班岩和花岗岩富Si富F，其钾长石均为Al／Si有序的低微斜长石。黑云母为含Li富F的铁叶云母或黑鳞云母，具低Mg／∑Fe（MF）值。所含岩浆晚期阶段结晶的黄玉，其成分接近于氟黄玉端元，并具有较短的b轴。不同于玻利维亚Sn－B型，本区为Sn－F型，这是华南加里东褶皱带斑岩锡矿的重要特征之一。

The volcanic tectonic dome in the Yanbei area, Huichang County, Jiangxi Province, formedduring J3 to K1, is composed of a series of volcanic, subvolcanic and intrusive rocks. Thelarge-sized porphyry-type tin deposits occur in inner and outer contact zones between thetopaz-bearing granoporphyry and the subvolcanic rhyoritic porphyry. The ore-forminggranoporphyry and granite are rich in Si and F. The K-feldspar they contain usually is lowmicrocline or microline perthite very high in Al / Si ordering degree. The biotite is mostly Li-andF-bearing siderophylite or protolithionite with quite low MF values. The topaz directlycrystallized from granitic magma in later stages is essentially close to fluorine topaz end-memberin composition, and has a relatively short b dimension .Different from Bolivia Sn-B type, theYanbei porphyry tin depossits are of Sn-F type. This is an important feature of tin deposits in theCaledonian fold belt of South China.