川东北普光地区下三叠统蒸发岩沉积特征与演化及其对钾盐矿形成的控制作用  

Sedimentary Characteristics and Evolution of the Lower Triassic Evaporite and Its Control on the Formation of Potassium Ore in the Puguang Area,Northeastern Sichuan Basin

作　　者：左璠璠 张永生[1,2,3] 苏奎[1] 桂宝玲[1] 邢恩袁[1] 牛新生[1] 彭渊[1] 商雯君 ZUO Fanfan;ZHANG Yongsheng;SU Kui;GUI Baoling;XING Enyuan;NIU Xinsheng;PENG Yuan;SHANG Wenjun(MNR Key Laboratory of Saline Lake Resources and Environments,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037;MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037;MNR SinoProbe Laboratory,Chinese Academy of Geological Sciences,Beijing 100037)

机构地区：[1]中国地质科学院矿产资源研究所自然资源部盐湖资源与环境重点实验室,北京100037 [2]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 [3]中国地质科学院自然资源部深地科学与探测技术实验室,北京100037

出　　处：《地球学报》2024年第5期651-664,共14页Acta Geoscientica Sinica

基　　金：国家重点研发计划项目“重点含盐盆地钾盐成矿规律、勘查技术与增储示范”所属课题“川东北海相新型杂卤石钾盐矿成矿规律、勘查技术与增储示范”(编号:2023YFC2906503);中国地质调查局地质调查二级项目“四川盆地东北部锂钾资源综合调查评价”(编号:DD20190172);中国地质调查局地质调查三级项目“我国重要含盐盆地钾盐重点调查区区块优选与综合研究”(编号:DD20230296)联合资助。

摘　　要：四川盆地中—下三叠统地层中发育大量膏-盐沉积,其中与石盐共伴生杂卤石(被命名为“新型杂卤石钾盐矿”)的大量发现和重新评估引起了近年来的广泛关注。但当前对此类杂卤石的研究主要集中在其矿物发育特征与成因类型等方面,对于其发育地层的沉积特征与演化规律的精细剖析及其对杂卤石形成的控制作用研究较少。本文利用川宣地1井连续取心的目的层段岩心资料进行了沉积微相和高精度层序地层学分析。共识别出14种沉积微相类型,并将其划分为6个微相组合,依次代表从局限台地到蒸发台地不同的沉积相带及能量、环境特征。在此基础上根据沉积微相的纵向发育演化、地层厚度以及典型诊断界面等信息,划分出4个四级沉积层序以及其内部的多个五级旋回。研究认为川东北地区与石盐共伴生的原生杂卤石是明显受不同级别海平面波动影响和控制的,主要发育在四级层序海退末期与五级旋回海侵的叠加时期,前者的强蒸发条件为杂卤石的形成提供了重要基础,但后者带来的海水补给则是其形成的必要条件。Thick layers of anhydrite and salt are deposited in the Middle and Lower Triassic strata in the Sichuan Basin.The rediscovery and transvaluation of polyhalite associated with salt,which has been called“a new type of polyhalite potassium ore”,has brought widespread attention to this mineral in recent years.However,research on this type of polyhalite has focused mainly on the aspects,such as the mineral development characteristics and genetic types,etc.Studies focusing on high-resolution analyses of the sedimentary characteristics and evolution of the surrounding strata and its control on the formation of polyhalite are rare.Therefore,in this study,microfacies and high-precision sequence stratigraphy analyses were carried out using core data of the continuous coring target interval of well CXD1.Fourteen microfacies types were identified and divided into six microfacies associations representing different sedimentary facies zones with different energy and environmental characteristics ranging from restricted to evaporative platform.On this basis,according to the vertical development of microfacies,stratigraphic thickness and typical diagnostic interfaces,four fourth-order sedimentary sequences and multiple fifth-order cycles within them were defined.The results implied that the primary polyhalite associated with salt in the northeast Sichuan Basin was obviously affected and controlled by sea level fluctuations.Specifically,it developed mainly in the superposition period between the end of regressions in the fourth-order sequences and transgressions of the fifth-order cycles.The evaporative condition in the former provided an important basis for the formation of polyhalite;however,the external seawater replenishment provided by the latter was the necessary condition.

关 键 词：沉积微相 层序地层 沉积控矿 杂卤石 下三叠统 川东北 

分 类 号：P619.211[天文地球—矿床学]