中国陆块海相盆地成钾条件与预测研究进展综述

摘要

Potash exploration in ancient marine basins has not achieved breakthrough, and potential for potash formation in ancient marine basins and marine-land transitional basins in China has long been a topic of controversy. It is critical to answer the question that whether small blocks of China have potential for formation of potash deposits or even large-scale potash deposits. In this study, with the plate tectonic activities as the main line, we conducted systematic summaries for drift history of main small blocks of China, structures of basin-formation, paleoclimate, paleogeography and sedimentary characteristics of evaporites within marine/ marine-land transitional basins, analyzed related potash-forming conditions and mineralization mechanism on the basis of potash-forming theory of coupled factors of tectonics, materials source and climate, summarized potash-forming features of global marine basins, established a corresponding evaluating index system, evaluated potash-forming potentials and predicted strategic targets by means of reconstruction of regional structures, paleogeography, material source and paleoclimate. The mineralization model suggests that the Cretaceous Lanping–Simao basin, Lower–Middle Triassic Sichuan basin in upper Yangzt block, Middle Ordovician northern Shaanxi basin in North China block and Paleogene Kuqa basin in Tarim block have relative good potential for potash formation. Combining with index system we defines the key targets in strategic target areas of the southern Lanping–Simao basin, mid-eastern Sichuan basin and Kuqa basin where drilling verifications can be conducted. All the above research results provide scientific basis for the future theoretical study and exploration of potash deposits in China’s marine basins.%中国古代海相钾盐找矿是一个“久攻不破”的难题，古代海相及海陆交互相盆地能否成钾也是长期争议的问题，也就是中国小陆块能否成钾、成大钾矿的关键问题。为此，本文以板块构造运动为主线，对中国主要小陆块漂移历史、成盆构造、古气候、古地理及海相/海陆交互相蒸发岩沉积特征进行了系统梳理和总结；在此基础上，基于盆地“构造-物源-气候”三要素耦合成钾理论，分析中国小陆块海相盆地成钾条件、成矿机理；同时，总结和借鉴全球海相钾盐成矿标志，建立钾盐成矿评价指标体系。基于这些研究基础，借助对主要陆块的区域构造和古地理特征、物质来源、古气候面貌等恢复及分析，对主要陆块的海相成钾潜力进行评价，同时预测找钾战略靶区。钾盐成矿模式研究表明：兰坪—思茅盆地白垩系、上扬子陆块四川盆地中—下三叠统、华北陆块陕北盆地中奥陶统及塔里木陆块库车盆地古近系等盆地及其层位具有较大的成钾潜力。结合成钾指标对比分析，优选圈定了思茅盆地南部、四川盆地中东部及塔里木的库车盆地等战略靶区内较为明确的重点靶区，可以进一步开展钻探验证。这些研究成果为在中国继续开展海相钾盐成矿研究和找钾提供科学依据。