| 混积岩中重矿物形貌学特征及物源意义 |
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| 引用本文： | 李红,李飞,龚峤林,曾楷,邓嘉婷,王浩铮,苏成鹏.混积岩中重矿物形貌学特征及物源意义[J].沉积学报,2021,39(3):525-539. |
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| 作者姓名： | 李红 李飞 龚峤林 曾楷 邓嘉婷 王浩铮 苏成鹏 |
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| 作者单位： | 1.西南石油大学地球科学与技术学院，成都 610500 |
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| 基金项目： | 国家自然科学基金41872119, 41502115四川省科技计划项目20YYJC1185 |
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| 摘 要： | 混积岩能够同时提供碳酸盐沉积以及陆源碎屑物质供给两方面的线索，在沉积动力学、古地理学、古气候学以及物源示踪等领域受到越来越多的关注。需要注意的是，受颗粒性质、滨海水动力条件、风化和成岩作用等因素影响，混积岩中陆源碎屑含量不稳定且粒径普遍偏细，亚稳定—不稳定重矿物会发生不同程度丢失，因而一些反映原始陆源碎屑构成的物源分析方法可能不适用。在研究中以四川盆地北部米仓山地区不同剖面仙女洞组混积岩中粉砂级碎屑组分为对象，对不同沉积环境下的重矿物组成、形貌特征（粒径、延长系数和磨圆度）、风化侵蚀和成岩状况进行了初步探索。结果显示:滨岸环境下的陆源碎屑含量最高，混积台地边缘陆源碎屑含量明显减少，同时易风化重矿物比例降低。另一方面，混积台地边缘稳定重矿物中的碎屑锆石粒径和延长系数与滨岸环境相比明显变小，且同一级别延长系数下锆石磨圆变好。此外，研究还发现沿汉南—米仓山地区存在较为连续的浅水高能鲕粒滩和古杯—微生物丘（礁）相带。这些证据表明沧浪铺期汉南古陆已经发育并向盆地内部提供物源。川北地区下寒武统是四川盆地油气勘探的重要接替层位，理清沧浪铺期物源方向对认识上扬子北部寒武纪早期古地理格局具有较大价值。
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| 关 键 词： | 沧浪铺期 四川盆地 物源分析 汉南古陆 锆石 |
| 收稿时间： | 2020-07-02 |
Morphological Characteristics and Provenance Significance of Heavy Minerals in the Mixed Siliciclastic-carbonate Sedimentation: A case study from the Xiannüdong Formation,Cambrian (Series 2), northern Sichuan |
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| LI Hong,LI Fei,GONG QiaoLin,ZENG Kai,DENG JiaTing,WANG HaoZheng,SU ChengPeng.Morphological Characteristics and Provenance Significance of Heavy Minerals in the Mixed Siliciclastic-carbonate Sedimentation: A case study from the Xiannüdong Formation,Cambrian (Series 2), northern Sichuan[J].Acta Sedimentologica Sinica,2021,39(3):525-539. |
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| Authors: | LI Hong LI Fei GONG QiaoLin ZENG Kai DENG JiaTing WANG HaoZheng SU ChengPeng |
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| Institution: | 1.School of Geoscience and Technology, Southwest Petroleum University, Chengdu 610500, China2.Division of Key Laboratory of Carbonate Reservoirs of CNPC, Southwest Petroleum University, Chengdu 610500, China3.Research Institute of Exploration and Development, SINOPEC Southwest Branch Company, Chengdu 610041, China |
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| Abstract: | The mixed siliciclastic-carbonate rocks can provide clues for understanding both the carbonate sedimentation and the sources of terrigenous particles. Accordingly， these rocks have received increasingly attention in the fields of studies on sedimentary dynamics， paleogeography， paleoclimatology， and provenance analysis. It should be noted that， affected by the nature of the particles， as well as the hydrodynamic， weathering， and diagenetic conditions， the content of the terrigenous fractions in the mixed siliciclastic-carbonate rocks is changeable and the particle size is generally small. Metastable-unstable heavy minerals may be lost during the weathering and diagenetic processes in varying degrees. Therefore， some traditional provenance analysis methods to indicate the source of original terrestrial compositions may not be applicable. In this work， systemic petrological and morphological studies were conducted on silt-sized heavy minerals in the mixed siliciclastic-carbonate systems of Lower Cambrian （Stage 3） in the Hannan-Micangshan area. The composition， morphological （grain size， elongation， and roundness）， weathering and diagenetic characteristics of heavy minerals in different sedimentary environments have been preliminarily explored. The results show that the percentage of terrigenous particles in the coastal environments was much higher than those of the shelf margins， and the proportion of easily weathered heavy minerals also decreases in the rimmed shelf. On the other hand， the particle size and elongation of detrital zircon in the stable heavy minerals on the platform margin are markedly smaller than those in the coastal environment， and the roundness of zircon becomes better under the same level of elongation. In addition， this study also found that there were relatively continuous shallow-water， high-energy ooid shoals and archaeocyath-microbial mounds developed along the Hannan-Micangshan area. These evidence indicates that the Hannan Massif had being developed during the Cambrian Age 3 and could provide large amounts of terrigenous material to the northern Upper Yangtze area. The Lower Cambrian of the northern Sichuan Basin is a potential replacement for oil and gas exploration in the Sichuan Basin. It is of great value to clarify the provenance of the Canglangpuian for understanding the Early Cambrian paleogeography of the northern Upper Yangtze area of the South China Block. |
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