Abstract:
The Habuqier gold deposit is a newly-discovered gold ore deposit in North Damao Banner, Inner Mongolia. In this paper, petrography, geochemistry, LA-MC-ICP-MS zircon U-Pb age and zircon Hf isotope compositions of the ore-related quartz diorite-porphyrite from the Habuqier gold ore district were studied. Zircon LA-MC-ICP-MS U-Pb dating shows that the weighted mean
206Pb/
238U age of zircons from the quartz diorite-porphyrite is 431.8±3.6Ma, indicating a lower Silurian crystallization age. Geochemically, the quartz diorite-porphyrite has moderate content of SiO
2, low K
2O, and high Na
2O, and magnesiumenrichment in composition (3.11%~4.79%), which indicate that it belongs to low K tholeiitic to calc-alkalineseries. Its A/NK ratios and A/CNK ratios range from 1.61 to 2.33 and 0.83 to 1.07, respectively, mainly belonging to metaluminous series. The trace element data of the rocks display enrichment of large ion lithophile elements (e.g., Ba, Rb, K and Sr) and light rare earth elements without significant Eu anomalies, and depletion of heavy rare earth elements, high field strength elements (e.g., Nb, Ta, and Ti). In situ Hf isotopic analyses show variable positive
εHf(
t) values ranging from +6.4 to +10.9, which correspond to relatively young two-stage Hf model ages ranging from 1014Ma to 718Ma. Therefore, based on these element, isotopic and geochronologic data, combined with data about the regional tectonic evolution and deposit geology, the authors hold that this gold deposit was associated with quartz diorite-porphyrite magmatic activities in the Early Silurian. The initial magma might have been derived from partial melting of a subducted oceanic crust which reacted with mantle wedge. Its tectonic setting was an island arc background that was produced by the Early Paleozoic underthrusting of the Paleo-Asian oceanic plate beneath the North China Craton.