Kuangchan zonghe liyong (Feb 2023)
The C-H-O Isotopic Composition and Significance of Spodumene for Redamen Pegmatite Type Rare Metal Deposit in Western Sichuan
Abstract
The Redamen rare metal deposit is located in the south western part of Keeryin pegmetite typed ore field in western Sichuan. It is a special deposit in the aspects of surrounding rock, element mineralization zoning and distance. The ore with different elevation (3540~3830 m) of the same vein and the same orebody is systematically collected, spodumene single mineral is selected to analyze the C-H-O isotope composition and features of inclusions in different minerals.The inclusions in minerals are mainly liquid-rich inclusions. The salinity of the inclusions in spodumene is 8%~20%, and the homogenization temperature is 180~330℃. The inclusions belong to the ore-forming fluid with medium-low salinity and medium-high temperature. The inclusions in quartz have salinity of 0%~8%, homogenization temperature of 150~240℃, and belong to low salinity and low temperature fluid. The results of C-H-O isotope test show that the δD/‰ of spotamene in the Redamen rare metal deposit ranges from -97.5 to -104.7 (average of -102.8). Compared with the Lijiagou deposit in the southeast of the ore field, the δD/‰ of spodumene is obviously smaller, with the δ18OH2O/‰ ranging from -0.34 to 2.88 (average of 1.032). However, it is basically consistent with the main metallogenic period of spodumene in Lijiagou deposit, indicating that the ore-forming fluid of late mineralization (that is, the main metallogenic period of spodumene) is mixed with meteoric water. The δ13CV-PDB/‰ of spodumene in the Redamen rare metal deposit ranges from -10 to -16.6, with an average of -12.7, indicating that the carbon source in the main mineralization period (spodumene formation period) has a mixed nature of magmatic system and meteoric precipitation system, which is related to the low temperature alteration of magmatic mantle source (granite, mantle multi-phase system) and may be mixed with CO2 generated by the decarboxylation of deposited organic materials. Through the study of mineral C-H-O isotopes and fluid inclusions, the source and evolution process of ore-forming fluids were further clarified.
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