| 我国西南部T1/T2粘土岩地质年代学、地球化学特征及其对粘土型锂矿的找矿意义 |
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| 引用本文： | 马圣钞,王登红,孙艳,李超,钟海仁.我国西南部T1/T2粘土岩地质年代学、地球化学特征及其对粘土型锂矿的找矿意义[J].地球科学,2019,44(2):427-440. |
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| 作者姓名： | 马圣钞 王登红 孙艳 李超 钟海仁 |
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| 作者单位： | 1.中国地质科学院矿产资源研究所, 自然资源部成矿作用与资源评价重点实验室, 北京 100037 |
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| 基金项目： | 中国地质调查局地质调查项目"大宗急缺矿产和战略性新兴产业矿产调查"工程；"华南重点矿集区稀有稀散和稀土矿产调查"DD20160056国家自然科学基金资助项目"柴达木盆地大风山特大型天青石矿床锶的富集成矿机制研究"41402084国家重点研发计划项目"锂能源金属矿产基地深部探测技术示范"课题"我国锂能源金属成矿规律、靶区优选与重点查证"2017YFC0602701 |
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| 摘 要： | 中国重庆、四川、贵州等地区的早、中三叠统地层界线（T1/T2）附近发育一套与火山喷发沉积有关的粘土岩层，其锂含量区域性富集.评价该套粘土层锂成矿潜力并确定粘土型锂矿的找矿方向具有重要现实意义.基于地质年代学及岩石地球化学方法，锆石U-Pb测年结果显示，重庆温泉、四川谢家湾、贵州辅处、贵州马落菁界限粘土岩年龄为248.6±0.8 Ma、242.5±0.7 Ma、246.1±0.6 Ma、248.1±0.8 Ma，与早-中三叠世界限年龄相近（247.2 Ma）.全岩富Li、K2O，高MgO，亏损Na2O；相对富集不相容元素（Rb、W、Sn、Bi、Th、U），相对亏损相容元素（V、Cr、Co、Ni）等；Li与不相容元素（Sn、Ta、Ga等）呈正相关关系，总体上显示与流纹-英安岩具有亲缘性.图解分析显示界限粘土岩为中酸性火山喷发-沉积岩经粘土化蚀变作用后的产物，构造背景为印支早期扬子板块西南缘俯冲碰撞引起的火山喷发活动或峨眉大火成岩省岩浆作用后续热液-沉积活动.综合分析认为中酸性火山喷发-沉积岩成分继承造成了界限粘土岩高K、富Li的地球化学特征，粘土矿物吸附作用也对界限粘土岩锂富集有所贡献，蒸发沉积作用对大面积沉积粘土层锂富集有限.今后在寻找沉积粘土型锂矿时建议以中国西南部T1/T2界线附近火山喷发-沉积成因粘土层为重要找矿层位，以同时代古火山口盆地或类似的古地貌分布区为重要找矿区域.
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| 关 键 词： | 早-中三叠世界线 火山沉积粘土岩 沉积型锂矿 峨眉大火成岩省 地球化学 中国西南部 |
| 收稿时间： | 2018-12-03 |
Geochronology and Geochemical Characteristics of Lower-Middle Triassic Clay Rock and Their Significances for Prospecting Clay-Type Lithium Deposit |
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| Abstract: | The Lower-Middle Triassic boundary clay rocks (LMTBC, for short), related to volcanic material eruption and deposition, are rich in lithium and widespread in Chongqing, Guangxi, Guizhou of southwest China. It is of great economic significance to evaluate the ore-forming potential of sedimentary clay-type lithium deposit and confirm the prospecting direction in LMTBC. Based on the method of chronology and geochemistry, MC-ICP-MS zircon U-Pb data indicates that the formation ages of LMTBC from Wenquan, Xiejiawan, Fuchu, Maluojing are 248.6±0.8 Ma, 242.5±0.7 Ma, 246.1±0.6 Ma, 248.1±0.8 Ma, and they all are close to the Lower-Middle Triassic boundary age (247.2 Ma). The geochemical data indicate that LMTBC is enriched in Li, K2O, high of MgO and depleted in Na2O, and displays high incompatible elements (Rb, W, Sn, Bi, Th, and U) abundances and low compatible element (V, Cr, Co and Ni) abundances. The Li shows positive correlation with the incompatible elements (Sn, Ta, and Ga), which is similar to rhyolitic-dacitic rocks. All above data suggest that LMTBC is the products of the clay-alteration from the Triassic multiple-stages volcanic eruption-deposit materials. Considering the spatio-temporal relationship geochemical characteristics of LMTBC and rhyolitic-dacitic igneous rocks in southwest China, it is suggested that the tectonic setting of volcanic activities is possibly the subduction and collision of Yangtze plate and Cathaysia plate, or the hydrothermal-sedimentary activities of subsequent Emei great igneous province. The inheritance component of the volcanic sedimentary materials is the key factor for Li anomalies of LMTBC, the ions adsorption effect of clay minerals may be also important; the superposition action of lithium rich brine caused by the evaporation hardly caused the large-scale lithium-rich LMTBC. Accordinlgly, it is suggested that the clay layers of LMTBC volcanic eruption-sedimentary origin are the ideal bedding for discovering the clay-type lithium deposits in southwest China. The contemporary ancient crater basins and similar paleogeomorphology are the favorable preservation of eruption sediments, and the important prospecting area for clay-type lithium deposits. |
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