柴达木盆地西部油田水富矿机制及硼同位素异常带的成因

The oilfield water in paleogene neogene period layer of western Qaidam basin is rich in K, B, Li, Rb, Cs. However，the research level of it is low. Based on previous study we found that the resource highly enriched characteristic of oilfield water is related to deep origin. At the same time, the boron isotope values of oil field water are much higher than that of salt lake brines in the western qaidam basin, and even higher than that of seawater. So the oilfield water is an unusual delta of boron isotope values in Qaidam basin.. Therefore, the theory that the supernormal metallogenic of oilfield water is controlled by deep origin needs further study. Meanwhile the causes of unusual delta of boron isotope values need to explore. Through the trace element and lead isotope trace the sources of ore-forming fluid is expected to find out the mechanism of supernormal metallogenic of oilfield water. .There are so many chance can promote the formation of unusual delta of boron isotope values ,such as high boron isotope values sources, fractionation caused by sedimentary process. Also boron isotope fractionation of oilfield water can caused by long-term interaction with organic matter or reservoirs, water rock reaction as well as the precipitation of salt during the process of evolution. By design the corresponding experiment for these possibilities so as to find out the causes of the high boron isotope values of oilfield water, which can enrich geochemical theory of oil field water...

柴达木盆地西部古近纪-新近纪油田水富含K、B、Li、Rb、Cs等国家战略性资源，是继第四纪盐湖之后又一盐类资源富集区，但目前研究程度较低。申请者前期对该区油田水的水化学和氢氧同位素研究发现其资源高度富集的特点可能与深源流体有关。同时，油田水的δ11B值远高于柴达木盆地盐湖湖表卤水，甚至高于海水，成为柴达木盆地δ11B异常带。因此，深源流体控制油田水超常富矿的理论需要进一步验证，油田水成为δ11B高值带的原因需要探究。通过微量元素和铅同位素进一步示踪成矿流体来源，有望查明油田水富矿机制。造成δ11B高值的可能性很多，如物源中含有高δ11B值物质、油田水的独有沉积过程中发生的分馏、与有机质或者油气藏长期相互作用导致的分馏、油田水演化过程中水岩反应以及盐类物质析出等作用导致的分馏，针对这些可能性开展相应实验，以期探讨油田水δ11B高值带的成因，丰富油田水地球化学理论。

柴达木盆地西部古近纪-新近纪油田水富含K、B、Li、Rb、Cs等资源，是继第四纪盐湖之后又一盐类资源富集区。对该区油田水的水化学和氢氧同位素研究发现其资源高度富集的特点可能与深源流体有关。同时，油田水成为柴达木盆地δ11B异常带。因此，本项目开展了微量元素和铅同位素研究，示踪成矿流体来源，进一步认识油田水富矿机制。造成δ11B高值的可能性很多，针对物源中含有高δ11B值物质、油田水的独有沉积过程中发生的分馏、与有机质或者油气藏长期相互作用导致的分馏、油田水演化过程中水岩反应以及盐类物质析出等作用导致的分馏等一切水文地质过程，开展相应实验，探讨油田水δ11B高值带的成因，丰富油田水地球化学理论。. 本项目查明了柴达木盆地西部钾硼锂资源的富集区域，进一步圈定富矿点。通过综合对比油田水与周围岩体以及基底岩体的微量、稀土以及铅同位素特征，油田水具有较高的稀土含量，微量元素更是高度富集，这与深部物源有关，然而铅同位素具有与下地壳以及周围山系花岗岩类相似的特征，充分体现周围岩石风化物质淋滤对油田水的贡献，而其中的深部物质目前来看没有体现幔源特征，推测存在下地壳重熔的岩浆地热水的掺杂作用。基于对柴达木盆地深部热泉水的长期观测研究，认为深部热水与地壳重熔有关，这类水体补给卤水成矿。. 研究显示油田水样品蒸发过程中硼同位素分馏值为5‰，这与卤水中硼富集程度有关，硼含量越高，析出硼酸盐越多，导致分馏越大。沉积物对水体硼的吸附导致的分馏大于2‰。对于油田水的硼同位素异常，确定如下地质过程导致其成因：一是可能在蒸发浓缩过程中发生硼酸盐析出，二是粘土与水体的长期作用，最主要的还是与其最初物源有关。