诸广岩体南部辉绿岩脉特征及其与铀成矿关系

Diabase Dikes in Southern Zhuguang Granitic Batholith:Its Charactristics and Relationship with Uranium Mineralization

诸广岩基南部侵入于印支-燕山早期花岗岩中的辉绿岩脉广泛分布,早期(±140 Ma)辉绿岩脉多以近EW向分布,第二期(110~103 Ma)、第三期(±90 Ma)主要为NNW向或NEE向展布,属板内拉斑玄武岩系列。蚀变辉绿岩较相对新鲜辉绿岩明显富集K2O和MgO,轻微富集Al2O3,而明显贫Na2O与CaO;对比分析辉绿岩、花岗岩和富矿石三者地球化学特征,认为成矿组分Cr,Co,Ni和U等主要来源于花岗岩而不是辉绿岩。无矿化的新鲜辉绿岩、含矿破碎辉绿岩、花岗质碎裂岩富矿石三种不同岩性的样品的δ34SV-CDT值具有明显的分段特征,分别为-0.2‰^-0.5‰、-6.5‰^-10.9‰、-17.4‰~17.9‰,认为成矿热液的硫主要来自地层中的生物成因硫或沉积硫,可能部分来自花岗岩。辉绿岩脉中的矿化与辉绿岩脉经过了后期构造的切割和破碎有很大的关系,辉绿岩脉在铀成矿过程中的主要起物理化学界面的作用,它的侵入为成矿作用提供导矿和储矿构造。

Three episodes of diabase dikes are well developed in southern Zhuguang granitic batholith, studies show that they belongs to continental tholeiite series. The early-stage （ ± 140 Ma） diabase dikes are nearly EW trending, the second-stage （110 - 103 Ma） and late-stage （ ±90 Ma） diabase dikes are mainly NNW or NEE tren-ding. Compared with the fresh diabase, the altered diabases is obviouly enriched in K2O and MgO, slight enrichment in A1203 , as well as obviously depletion in Na2O and CaO. It implicated that Cr, Co, Ni and U in the oreforming fluids may have been from the granites rather than the diabase, based on the analysised of the geochemistry characters of diabase, granite and uranium ore. The δ34Sv_cDy value of fresh diabase, mineralized diabase and uranium ore are in range of -0. 2‰ - -0. 5‰, -6.5‰ - - 10. 9‰ and - 17.4‰- - 17.9‰, these differences of sulfur isotopic compositions in fresh diabase, mineralized diabase and uranium ore, indicated that the sulfur in the mineralizing fluid mainly originated from the sedimentary or biogenic sulfur, and probably part derived from the granite. The diabase dikes have been cut and crushed was very important in the process of mineralization of diabase. Besides, the diabase dikes mainly played physicochemical interface roles in the uranium mineralization and provied with ore-fluid leading and ore-forming structure.