北天山冰草沟铀磷矿床元素地球化学特征及其指示意义

Geochemical Characteristics of Elements and Their Indicative Significance in the Bingcaogou Uranium-Phosphate Deposit in North Tianshan

北天山冰草沟铀磷矿床严格受玄武安山岩与砂岩的接触界面控制,属于典型的热液铀磷矿床。本文利用显微镜、X荧光光谱仪、电感耦合等离子质谱仪等手段,对该矿床典型剖面展开了元素地球化学研究。成矿过程中,铀与磷同步富集。在剖面上,与新鲜砂岩相比,原岩为砂岩的矿石除富集U和P外,还高度富集Ca、Sr、Zr、HREE和Y,同时亏损Rb等元素。表明成矿过程中,成矿流体带来了大量的Ca、P、U、Sr、Zr、HREE和Y,同时,Rb等元素活化迁出。与新鲜玄武安山岩相比,蚀变玄武安山岩明显亏损Rb、Ba和Sr。矿石OX值(Fe 2O 3/FeO)介于16.92~26.46之间,远高于赋矿围岩OX值。新鲜玄武安山岩具有相对较高的FeO含量(4.74%)和较低的OX值(0.9),蚀变后玄武安山岩则具有相对较低的FeO含量(0.86%)和较高的OX值(7.18),显示成矿流体具有强氧化性,新鲜玄武安山岩表现出较强的还原能力,可能为铀矿体的空间定位提供了还原障。

The Bingcaogou deposit in North Tianshan is strictly controlled by the contact interface between basaltic andesite and sandstone,a typical hydrothermal uranium-phosphorus deposit.This work studied the elemental geochemistry of typical sections of this deposit by means of microscopy,X-ray fluorescence spectrometer and inductively coupled plasma mass spectrometry.Research suggests that during the mineralization process,uranium and phosphorus were enriched simultaneously.In the section,compared with fresh sandstone,the original rock is sandstone ore,which is not only enriched in U and P,but also highly enriched in Ca,Sr,Zr,HREE and Y,while depleted in Rb and other elements.Compared with the fresh basaltic andesite,the altered basaltic andesite is obviously depleted in Rb,Ba and Sr.The OX value(Fe 2O 3/FeO)of ore is between 16.92 and 26.46,much higher than that of the ore-bearing host rock.The fresh basaltic andesite has relatively high FeO content(4.74%)and low OX value(0.9).After the alteration,the basaltic andesite has a relatively low FeO content(0.86%)and a high OX value(7.18),indicating that the ore-forming fluid has strong oxidizing capacity.The fresh basaltic andesite shows strong reduction capacity,which may provide a reduction barrier for the spatial location of uranium ore bodies.