Trace element and He-Ar isotopic evidence of pyrite for the source of ore-forming fluids in the Jinqingding gold deposit, eastern Shandong Province

Abstract：The Jinqingding gold deposit with identified reserves of more than 50t is currently the largest lode gold deposit in terms of single vein gold resources and is also a superlarge gold deposit located in the middle part of the Muping-Rushan gold belt in Jiaodong; nevertheless, the genetic type and source of ore-forming fluids in the gold deposit constitute a problem that needs urgent solution. A study of trace elements and REE compositions and features of gold-bearing pyrite from No. Ⅱ ore body of the Jinqingding gold deposit reveals that the pyrite displays hydrothermal characteristics with Co/Ni ratios from 2.317 to 11.734 (7.17 on average). The HFSE indicates that the ore-forming fluid originally belonged to the F-rich system and generally evolved into the Cl-rich system at the chief metallogenic stage, and the distribution patterns of REE shows that the source of matallogenic materials was not mainly from Mesozoic Kunyunshan monzonitic granite. According to an analysis of the characteristic parameters (3He/4He=0.1~2.2 Ra（0.60 Ra on average）)，40Ar/36Ar =462.7~1507.5（831 on average），it is considered that the source of matallogenic materials was mainly derived from the lower crust and was contaminated by meteoric water during the intrusion，and the mantle fluids were involved in the metallogenic process.