粤东北地区石人背盆地锂地球化学特征及其找矿指示意义

    Lithium geochemistry and its implications for ore prospecting in the Shirenbei Basin, northeastern Guangdong

    • 摘要: 为查明粤东北石人背盆地沉积黏土型锂矿的地球化学特征及其找矿指示意义,探讨区域成矿条件与找矿标志,在1∶20万水系沉积物测量基础上,基于矿床学、沉积学、矿物学与地球化学分析方法,对Li地球化学特征及其与地层、岩性和沉积环境的关系进行了综合研究。研究区共圈定Li异常2处,其中北部异常规模较大,Li峰值高达234.3×10−6,异常中心出露叶塘组(K2yt);综合异常由Li、F、Na2O等16种元素(或氧化物)组成,各异常之间套合良好。调查发现:叶塘组(K2yt)整体为湖相蒸发沉积建造,沉积中心位于盆地北部,Li高值区主要对应含钙质细碎屑岩发育区,岩矿学分析表明全岩Li2O含量与黏土矿物含量呈显著正相关关系;叶塘组(K2yt)的全岩Li地球化学背景值显著高于其他地质单元,富集中心为叶塘组(K2yt)第4层;研究区圈定含矿层3层,主要分布于叶塘组中上部,总厚度达226.14 m,含矿岩系出露面积约5.2 km2,显示出良好的找矿潜力。研究认为,水系沉积物Li地球化学特征能够有效反映区域成矿背景,Li-F-Na2O组合异常可作为沉积黏土型锂矿的重要找矿标志;成矿受古气候、蒸发沉积环境、岩相古地理格局、特定地层及其岩性建造等因素共同控制;南岭成矿带东段及邻区武夷成矿带发育多处类似沉积盆地,具备进一步找矿突破前景。

       

      Abstract: This study aims to determine the geochemical characteristics of sedimentary clay-type lithium (Li) deposits and their implications for ore prospecting in the Shirenbei Basin, northeastern Guangdong, China, as well as exploring the regional metallogenic conditions and ore-prospecting indicators. Based on a 1∶200,000 stream sediment geochemical survey, this study conducted a comprehensive analysis of the geochemical characteristics of Li and their relationships with strata, lithologies, and sedimentary environments using methods of economic geology, sedimentology, mineralogy, and geochemistry. Two Li anomalies were delineated in the study area. Among them, the Li anomaly in the north exhibits a larger scale and a peak anomaly value of 234.3×10−6, with the Yetang Formation (K2yt) exposed in the anomaly center. The composite anomaly consists of 16 elements (or oxides), including Li, fluorine (F), and sodium oxide (Na2O), with distinct overlapping relationships observed among them. Investigations reveal that the Yetang Formation is a lacustrine evaporative sedimentary suite, with its sedimentary center located in the northern part of the basin. Zones with high Li content correspond primarily to zones containing calcareous, fine-grained clastics. Rock and mineral analyses indicate a significant positive correlation between whole-rock Li2O content and clay mineral content. The Yetang Formation exhibits significantly higher geochemical background values of whole-rock Li content than other geological units, with the Li enrichment center identified in the fourth layer of the formation. Three ore-bearing layers were delineated in the study area. They are primarily distributed in the middle and upper parts of the Yetang Formation, with a total thickness of 226.14 m. The ore-bearing rock series show an exposed area of approximately 5.2 km2, demonstrating great potential for ore prospecting. The results of this study suggest that the Li geochemistry in stream sediments can effectively reflect the regional metallogenic background and that the Li-F-Na2O anomaly combination serves as a significant ore-prospecting indicator for clay-type lithium deposits. Lithium mineralization is jointly controlled by factors including paleoclimate, evaporative sedimentary environment, lithofacies paleogeographic framework, specific stratigraphic units, and lithologic suites. Additionally, multiple similar sedimentary basins occur in the eastern segment of the Nanling metallogenic belt and its adjacent Wuyi metallogenic belt, holding prospects for further breakthroughs in ore prospecting.

       

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