Understanding the genesis of ore-bearing and ore-barren adakitic rocks: insights from geochronology and geochemical analysis of the Tuncang intrusion and enclaves along the South Tan-Lu Fault
Feng Zi, Wenzhou Xiao, Mabrouk Sami, Chenguang Zhang, Fenquan Xie, Ye Liu, Shuanglian Li
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引用次数: 0
Abstract
The relationships between metallogenic capacity and geochemical features of adakitic rocks along the South Tan-Lu Fault (STLF) remain unclear. In this study, the ore-barren adakitic rocks (Tuncang, Guandian and Wawuliu) exhibit higher K2O/Na2O ratios and lower Sr/Y ratios than the ore-bearing adakitic rocks (Chuzhou and Shangyaopu). These differences strongly suggest that the ore-barren adakitic rocks originated from the thickened lower continental crust (LCC), whereas the ore-bearing adakitic rocks were derived from oceanic slabs. Notably, the Tuncang granite exhibits higher Y/Yb and (Ho/Yb)N ratios than the Guandian granodiorite and Wawuliu intrusion. Accordingly, we suggest that the Tuncang granite likely originated from a delaminated eclogitic LCC, whereas the Guandian and Wawuliu intrusions were derived from a thickened basaltic LCC sources. The occurrence of diorite and gabbro mafic microgranular enclaves (MMEs) within the Tuncang granite strongly suggests a magma-mixing process. Considering their MgO contents and εNd(t) and (87Sr/86Sr)i values, we suggest that the gabbro MMEs were likely derived from an enriched mantle source previously metasomatized by subduction-related components and that the diorite MMEs were subsequently formed by magma mixing. Due to the slightly younger ages of the ore-bearing adakitic rocks, we propose a model in which the ore-barren adakitic rocks formed through LCC delamination at 130 Ma and the ore-bearing adakitic rocks formed through oceanic slab remelting at 125 Ma. Consequently, the exploration of Cu–Au mineralization along the STLF should focus on younger oceanic slab-derived adakitic rocks.
期刊介绍:
The International Journal of Earth Sciences publishes process-oriented original and review papers on the history of the earth, including
- Dynamics of the lithosphere
- Tectonics and volcanology
- Sedimentology
- Evolution of life
- Marine and continental ecosystems
- Global dynamics of physicochemical cycles
- Mineral deposits and hydrocarbons
- Surface processes.