Precambrian tectono-magmatic evolution of the western margin of the Yangtze block, South China: evidence from zircon U-Pb-Lu-Hf isotopes, REE and trace elements of Yuanmou-Miyi complexes

ABSTRACT

Here new evidence of the isotope geochronology and the geochemistry from the Yuanmou-Miyi complexes reveal the Precambrian tectono-magmatism geodynamic process in the study area. The Yangtze Block basement with 1.81- ~1.77 Ga and negative ε_Hf(t) values of −7.8 to −0.7 corresponded to the assembly of the Columbia-supercontinent. However, the rifting magmatic event of ~ 1.70 Ga, which caused the continental crust extension-thinning in the study area, may exert influence on the subduction-magmatism in the Grenvillian period. The Yuanmou-Miyi complexes of 1.19- ~1.00 Ga are characterized by (La/Sm)_N＞1, depletion in HFSEs, negative anomalies of Nb-Ta, and enrichment of LILEs, which show a genetic link with the subduction-magmatism. The temporal tendency that the magmatism from Yuanmou to Miyi gradually became younger, may be responsible for the subducting direction. The subduction caused the reactivation of the Anninghe-Lvzhijiag fault zone, and created the rupture windows of the subduction slab, leading to upwelling of the deep magma. These granitoids were derived from the partial melting of the mantle wedge, while the small-scale gabbro dikes intruded into the granitoids were likely spillover products from the asthenosphere mantle melts through the rupture windows.

KEYWORDS:

• Yuanmou-Miyi complexes
• isotope geochronology
• REE-trace elements
• subduction magmatism
• Grenvillian period
• Yangtze block

Highlights

1. A few of the gabbro dikes might be spillover products from the asthenospheric mantle melts.

2. The magmatism of 19 to ~00 Ga may be derived from a subduction-related setting;

3. The subduction provided a path for magma emplacement along the faults and ruptured slab windows;

4. The granitoids were derived from the partial melting of the mantle wedge.

Acknowledgments

We are thankful for the suggestions provided by Prof. Christopher J. Eastoe. Dr. Robert J. Stern of the chief editor and review experts put forward very pertinent and valuable suggestions for revision.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2023.2255649

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [42072096].