川南雷波地区梅树村组凝灰质硅质岩的发现及其地质意义

袁永盛; 吴亮; 唐烽; 张耀堂; 李文辉; 王万能; 张宏辉; 张光旭; 赵见波

doi:10.12090/j.issn.1006-6616.2025106

川南雷波地区梅树村组凝灰质硅质岩的发现及其地质意义

doi: 10.12090/j.issn.1006-6616.2025106

袁永盛^{1, 2,},
吴亮^{1, 2, ,},
唐烽^3,,
张耀堂^{1, 2,},
李文辉^{1, 2,},
王万能^{1, 2,},
张宏辉^{1, 2,},
张光旭^4,,
赵见波^{1, 2,}

1.
中国地质调查局昆明自然资源综合调查中心, 云南昆明
2.
中国地质学会热液型金铜多金属矿成矿规律与有效勘查技术创新基地, 云南昆明
3.
中国地质科学院地质研究所
4.
贵州省古生物与古环境全省重点实验室

基金项目: 中国地质调查局项目（DD202308404）；中国地质调查局项目（DD20220987）；国家自然科学基金项目编号（42172035）

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出版历程
- 收稿日期: 2025-08-06
- 修回日期: 2025-12-09
- 录用日期: 2025-12-26
- 预出版日期: 2026-11-12

Discovery of tuffaceous siliceous rocks inthe Meishucun Formation, Leibo area,southern Sichuan,and its geological significance

yongsheng yuan^{1, 2
,},
Liang WU^{1, 2
, ,},
feng tang^3
,,
YaoTang ZHANG^{1, 2
,},
WenHui LI^{1, 2
,},
WanNeng WANG^{1, 2
,},
HongHui ZHANG^{1, 2
,},
guangxu zhang^4
,,
JianBo ZHAO^{1, 2
,}

1.
Kunming General Survey of Natural Resources Center, CGS
2.
Innovation Base for Metallogenic Regularity and Effective Exploration Technology of Hydrothermal Gold-Copper Polymetallic Deposits，Geological Society of China
3.
Institute of Geology，Chinese Academy of Geological Sciences
4.
Guizhou Provincial Key Laboratory of Paleontology and Paleoenvironment

Funds: The Geological Survey Projects of the China Geological Survey(DD202308404);The Geological Survey Projects of the China Geological Survey(DD20220987);The National Natural Science Foundation of China(42172035)

摘要

摘要: 确定火山灰的岩石类型、沉积时代和构造背景，可为区域地层对比、成矿事件和沉积环境转变研究提供重要依据。川南雷波地区梅树村组底部发现了3层凝灰质硅质岩，对其开展了锆石U-Pb测年、微量元素和Hf同位素测试。结果显示，凝灰质硅质岩锆石U-Pb谐和年龄为539.3±2.7 Ma，ε_Hf(t)值为−1.2~2.9，二阶段模式年龄T_DM2为1312~1567 Ma。根据区域上埃迪卡拉纪—寒武纪之交的火山沉积记录，认为凝灰质硅质岩的锆石U-Pb年龄为梅树村组底部的时代厘定提供了年代学约束，对应寒武纪纽芬兰世幸运期，与全球寒武系底界推荐年龄基本一致。区域地层对比表明，将川南−滇东地区埃迪卡拉系—寒武系界线置于梅树村组待补段与灯影组界面处更为合理。同期广泛分布的凝灰岩层反应了这一时期全球构造运动的等时性，为盆地演化研究提供了可对比的等时面。结合扬子地区在埃迪卡拉纪—寒武纪过渡时期的盆地演化和成矿特征，该年龄较好地限定了川南−滇东地区磷块岩开始沉积的时间，并将川南地区兴凯运动Ⅰ幕活动最强烈的时期约束在~539 Ma。锆石微量元素及Hf同位素分析表明，凝灰质组分具有流纹质特征，成岩物质主要来自新生下地壳的部分熔融，岩浆可能形成于岩浆弧环境；凝灰岩的形成可能与冈瓦纳大陆碰撞拼合或周缘微板块向冈瓦纳大陆俯冲碰撞有关。通过对凝灰质硅质岩形成时代和地球化学特征的研究，深化了扬子地块埃迪卡拉纪—寒武纪过渡期火山物质属性、来源与构造环境认识，为埃迪卡拉系—寒武系界线厘定、磷块岩沉积时限以及盆地演化过程解析提供重要年代学证据。
- 扬子地区 /
- 梅树村组 /
- 凝灰质 /
- 锆石U-Pb年龄 /
- Hf同位素
Abstract: [Objective] By determining the rock type, deposition age, and tectonic background of volcanic ash, foundational constraints can be provided for studies on regional stratigraphic correlation, metallogenic events, and sedimentary environment transformation. [Methods] Three layers of waxy yellow tuffaceous siliceous rocks were found at the bottom of the Meishucun Formation in the Leibo area of southern Sichuan. Zircon U-Pb dating, along with zircon trace element and Hf isotope tests were conducted on the tuffaceous siliceous rocks. [Results] The results indicates that the zircon U-Pb concordant age is 539.3±2.7 Ma, ε_Hf (t) values ranging from -1.2 to 2.9, and a two-stage model age (T_DM2) between 1312 and 1567 Ma. [Conclusion] Through the comparison of volcanic sedimentary records across the Ediacaran-Cambrian transition period, the age of the Meishucun Formation is determined to be the Fortunian stage of the Cambrian Newfoundland Series. The age align closely with the recommended global Cambrian Series boundary age. It is more reasonable to position the Ediacaran-Cambrian boundary in the southern Sichuan-eastern Yunnan region at the interface between the Daibu member of the Meishucun Formation and the Dengying Formation. The widely distributed tuffaceous layers from the same period indicating the synchronous nature of global tectonic movements at this time. This provides an isochronous surface for comparative studies of basin evolution. By analyzing the Yangtze region's basin evolution and metallogenic effects during the Ediacaran-Cambrian transition, the age provides a clear limitation on the beginning of phosphorite deposition in the southern Sichuan-eastern Yunnan area. The activity of the Xingkai Movement's first episode in southern Sichuan is constrained to about 539 Ma. Through the analysis of zircon trace elements and Hf isotopes, it is indicated that the tuffaceous composition is rhyolitic, and the material is mainly formed by partial melting of juvenile lower crust. It is likely that the magma formed in a magmatic arc environment. The formation of tuff in this region may be related to the collision and amalgamation with the Gondwana continent or the subduction and collision of surrounding microplates towards Gondwana.
- Yangtze region /
- Meishucun Formation /
- tuffaceous /
- zircon U-Pb age /
- Hf isotope