广东云浮大降坪超大型黄铁矿矿床的热水沉积特征

CHARACTERISTICS OF THE HYDROTHERMAL SEDIMENTATION OF THE DAJIANGPING SUPERLARGE PYRITE DEPOSIT IN YUNFU, GUANGDONG

大降坪黄铁矿矿床由含矿地层的中部碳酸盐岩和碎屑岩系、上部细碎屑岩系、二者之间的热水沉积黄铁矿矿层、硅岩层和硅化岩及地层中的火山质岩构成的礁硅岩套的控制。矿体呈规模不等的透镜体与围岩整合顺层产出，透镜体边缘常分叉与围岩过渡。3号矿体矿石为条带状和条纹状构造，并伴有准同生的变形构造，4号矿体几乎全由黄铁矿构成的块状构造为主，发育有内碎屑角砾状、致密条带状和条纹状等原生沉积组构及菌藻微生物组构，反映了原生热水沉积的特征。矿石常量元素组成显示以石英和黄铁矿为主，有少量的细粒碎屑物，是热水沉积成分单一的表现。矿石中含有较高的有机质，条带状和块状矿石的有机质含量的差异主要与所含的碎屑组分的不同有关，与后期的改造作用无关。矿石的U、Th元素特征反映了热水沉积特点。条带状和块状矿石的Co／Ni比值反映出热水沉积温度的空间分布特征。块状矿石和条带状矿石的单矿物黄铁矿及4号矿体铁白云石脉的稀土元素为典型的热水沉积特征，硅质物和条带状矿石的稀土元素与细碎屑岩的特征相似，与它们含有较高的细碎屑陆源物有关。

The Dajiangping pyrite deposit is controlled by the bio-reef-chert suite which iscomposed of detrital rocks and massive crystallized limestones in the middle part, fineclastic rocks in the upper part, hydrothermal sedimentary pyrite-chert-silicified rockbeds between them, and volcanic detrital and tuffaceous rocks in ore-bearing strata.The ore body occurrdd conformably along the bed as lensses in different scale. Thelens is offen offset in its margin and transitional with host rocks. The structure in theNo.3 ore body is mainly banded and ribbon structure with synsedimentary deformationfabric, and in the No.4 ore body is mainly massive structure, which is almost totallyconsisted of pyrite, with intraclast, dense laminar, and thallogen fabric, which showsthe original feature of the hydrothermal sedimentation. The major element componentof ore indicates that the ore is mainly consisted of quartz and pyrite with minimalfine clast, showing a pure fearture of hydrothermal sedimentary product. The orecontains high organic content, and the differences of organic content between bandedand massive ores result from the different clastic content and do not relate toreformation in late stage. Contents of U and Th in the ore indicate hydrothermalsedimentary feartures. The Co/Ni ratios in the banded and massive ore shows thedistributive characteristics of hydrothermal sedimentary temperature. The REE fearturesof the ferrodolomite vein in the No.4 ore body and the pyrite of massive and bandedore are similar to hydrothermal sedimentary fearture. The REE feartures of the chertsand banded ore, which resulted from high clastic content, are similar to that of hostrock.