| The Jiao Dong W-Nb-Ta ore district is a newly discovered rare metal deposit associated with leucogranite-pegmatite systems. Through field geological surveys, the authors identified a biotite monzogranite porphyry intrusion in this district, characterized by intense silicification, chloritization, and malachitization. Based on detailed petrographic studies, electron probe microanalysis (EPMA) was conducted on chlorite within the biotite monzogranite porphyry from the Jiao Dong district to constrain its physicochemical formation conditions and assess the porphyry mineralization potential. The chlorite in the biotite monzogranite porphyry is identified as typical Fe-Mg chlorite, formed at temperatures ranging from 177 to 211°C, indicative of biotite alteration by medium- to low-temperature fluids. The chlorite exhibits AlIV values ranging from 1.01 to 1.30, Fe2+/(Fe2++Mg2+) ratios between 0.64 and 0.77, Cr/Ti ratios from 0.02 to 27.13, oxygen fugacity (fO2) values from -38.6 to -34.0, and sulfur fugacity (fS2) values from -13.3 to -10.8. Compared to chlorite from the propylitic alteration zones of typical porphyry deposits in Tibet, the chlorite in the biotite monzogranite porphyry from the Jiao Dong district is characterized by higher AlIV, Fe2+/(Fe2++Mg2+), and sulfur fugacity, as well as moderate temperature, Cr/Ti ratios, and oxygen fugacity. These characteristics suggest a certain potential for porphyry copper mineralization. |