重庆城口地区早前寒武系黑色岩系研究:(1)铂族元素成矿潜力评估

PRE-EARLY CAMBRIAN BLACK ROCK SERIES IN CHENGKOU DISTRICT,CHONGQING:(1)PGE MINERALIZATION POTENTIAL REASSESSMENT

重庆城口地区从震旦统到下寒武统发育有丰富的黑色岩系,20世纪末期在该地区黑色岩系中开展了大量的铂族元素(PGE)的找矿工作,但是由于种种原因,关于该地区是否存在PGE矿化异常,还没有得到最终的结论。本次研究在PGE分析方法论证的基础上,进行了大量样品的PGE分析和微量元素分析。主要结论如下:①区域上上震旦统槽区和断块区两套黑色岩系在原始的沉积环境和物源供给上有较大的差异,虽然槽区上震旦统的黑色岩系具有和下寒武统黑色岩系相似但强度较低的V-Cu-Y-Mo-U异常,但基本上不具有明显的PGE-Au-Ag异常。②断块区水井沱组黑色岩系:和平剖面西段新发现的U-V-Mo-PGE异常可能是今后工作的重点,Pt+Pd最高达248.9×10-9,局部U-V都达到了工业品位。③槽区巴山组硅质岩:四个剖面都揭示了在硅质岩中广泛存在连续的PGE异常,87个碳质硅质岩平均含Pt+Pd 57.2×10-9,有10个样品Pt+Pd>100×10-9,最高达196.5×10-9;大部分碳质硅质岩都具有不同程度的V-Cu-Y-Mo-Tl-U组合异常,V都达到了独立矿床的品位要求,其中猪草河、燕子河等剖面还存在厚度较大的富矿地段,特别是燕子河剖面,局部还存在REE+Y的高异常,值得深入研究。④城巴地区下寒武统黑色岩系存在广泛的PGE异常,但没有达到PGE的矿化要求,建议加强该地区的钒矿和铀矿勘探研究,PGE可以综合评价。

Abundant Pre-Early Cambrian black rock series is of extensive occurrence in the Chengkou district, Chongqing City. Although a great deal of PGE exploration work had been done in the years of 1999 - 2000, the final conclusion about PGE mineralization is still uncertain for many reasons. This paper presents a lot of PGE and trace dement data based on the discussion on the PGE analyses methods. The main conclusions from these data are presented below： （1） There are some differences in preliminary sedimentary environment and material source between the Chengba block and the Chengha geosyncline in the Late Sinian period. Although the Lower Cambrian black rock series have similar but relatively low intense V-Cu-Y-Mo-U anomalies relative to Upper Sinian black rock series in the Chengba geosyncline, on the whole, there are no remarkable PGE-Au-Ag anomalies. （2）The Shuijingtuo Group black rock series in the Chengba block： U-V-Mo-PGE anomaly discovered in the western part of the Heping profile should be emphasized in future exploration, the highest Pt ＋ Pd in this study reaches 248.9 x 10-9,and U-V reaches the industrial grade locally. （3）The Bashan Group siliceous rocks in the Chengha geosyncline： extensive and continuous PGE anomalies have been revealed, with anaverage of about 57.2 × 10^-9 Pt＋ Pd for 87 samples, and there are 10 samples in which Pt＋ Pd〉 100× 10^-9, the highest Pt＋ Pd in these siliceous rocks is about 196.5 ×10^-9. The contents of V come up to the industrial grade in all the four profiles, and some thicker sections enriched in V have been found in the Zhucaohe and Yanzihe profiles. Furthermore, strong REE ＋ Y anomalies have also been found co-existing with V mineralization in the Yanzihe profile. （4）Extensive weak PGE anomalies have been found in the Lower Cambrian black rock series, but the PGE anomaly is not strong enough to reach the industrial grade. The authors suggest to strengthen V and U ore exploration in the Chengha district, and PGE mineralization could be assessed synthetically.