准噶尔盆地乌尔禾地区二叠纪咸化湖盆热液喷流活动的比较沉积学研究

As the first case of abundant complex salt minerals, lacustrine dolomitic rock in hydrothermal exhalative deposition in Junggar Basin is selected as this study object. Based on field outcrops and drilling cores researches, this study found out unique hydrothermal sedimentary- salify characteristics and its geochemical characteristics of dolomitic rock, by petrology, mineralogy, major and trace element analysis, isotope test analysis, fluid inclusion analysis and zircon U-Pb dating analysis. At the same time, combine with the researches on Tengchong modern thermal spring and other sinter, and indoor thermal sedimentation- salt formation simulation experiment, this study focus on the comparative sedimentary characteristics between the ancient and modern salty hydrothermal eruption in lake, and analysis the internal relationships between salty lacustrine sedimentary construction and vulcanian eruptions, and between thermal brine sedimentation- salt formation and hydrothermal eruption on lakebed, in early Permian of North-western Junggar Basin, so that, we can recover the ancient sedimentary dynamics process of salty lacustrine hydrothermal eruption in continental rifting valley, and establish a model to describe the process of Hydrothermal eruption sedimentation- Diagenesis- Salt formation. Furthermore, this study will not only provide a new example for the lacustrine primary dolostone which is formed by hydrothermal sedimentary depositon in continental rifting basin in China, give proofs, and provide interpretation for its origin, but also enrich Lacustrine Hydrothermal Sedimentology and the theory of "salt deposited in deep hydrothermal lacustrine water".

以准噶尔盆地首例富含复杂盐类矿物的湖相热水沉积云质岩为研究对象，在露头和钻井岩心观察描述基础上，通过岩石学、矿物学、主、微量元素和同位素地球化学、流体包裹体和锆石U-Pb法定年的综合研究，查明纹层状云质岩独特的热水沉积-成盐特征和地球化学性质；结合腾冲现代热泉和泉华的调查，以及室内热水沉积-成盐模拟实验，开展古代与现代咸化湖盆热液喷流的比较沉积学研究，剖析准噶尔盆地西北缘早二叠世湖相含盐沉积建造与火山喷发、湖底热液喷流活动及热卤水沉积-成盐作用的内在关系，提出系统的湖相原生白云岩和复杂盐类矿物的热水喷流沉积识别标志，恢复地质时期陆内裂谷咸化湖盆热液喷流的沉积动力学过程，并建立热液喷流沉积-成岩-成盐模式。本项目研究不仅为我国陆内裂谷盆地湖相热水沉积成因的原生白云岩的存在提供新的实例、证据和成因解释，同时也将进一步完善和丰富湖相热水沉积学和深水湖盆热液成盐理论。

准噶尔盆地二叠系风城组发育一套国内外罕见的湖相沉积，不仅发育富有机质纹层状云质岩，而且富集碱盐、硅硼钠石等罕见盐类矿物。通过岩石学、矿物学、主、微量元素和同位素地球化学、流体包裹体和锆石U-Pb法定年的综合研究，结合腾冲现代热泉沉积，提出火山-碱湖-热水沉积-成岩的成因链模式。风城组沉积于早二叠世晚期，与哈萨克斯坦西部著名的Kungurian海相蒸发岩同期，受270-290 Ma塔里木地幔柱活动影响，发育于裂谷火山环境。碱性火山活动及伴生的热液活动是玛湖凹陷湖泊呈碱性的主要原因，干旱环境导致湖泊盐度升高，碱性环境一方面有利于有机质勃发，另一方面造成火山物质溶解产生大量溶解硅质。风城组岩性分布受气候波动和热液输入双重控制。高水位期，物源区石炭纪火山物质大量输入湖泊，湖泊以沉积层状凝灰质为主；低水位期，在湖泊中心沉积厚层碱盐，在斜坡-边缘区沉积硅质岩。热液输入属事件沉积，导致水位上升，湖内营养物质富集，藻类异常勃发，吸附大量B元素，消耗水中CO2，局部碱性升高，原生白云石形成。硅硼钠石受热力学条件控制，属晚期成岩产物，其B元素主要来源于原始湖泊水体。因此，乌尔禾地区风城组罕见的矿物组合均与火山-热液背景有关，与之类比的现代实例腾冲火山地热区泉华的形成也是深部热源、浅部地下水循环、区域构造活动的共同结果，但泉华体和湖底喷流岩之间存在较大差异，主要表现为：1）地表热泉环境的温度压力较低，而湖底喷口附近通常是高温高压环境；2）地表热泉环境下热泉水受区域地形差异的影响而处于流动状态，进而引发相变，而湖底喷流环境下热液移动是流体扩散作用的结果；3）地表热泉沉积物的类型受原始流体组成控制较大，其次为后期沉积环境中生物与非生物作用影响。本项目研究为火山热液活动对陆相含油气盆地沉积控制作用及其致密油勘探提供了重要指示。项目累计发表SCI论文5篇、中文核心论文4篇，获得行业科技进步奖1项，培养博士后1名，培养研究生7名、其中2名已毕业。