Petrogenesis and tectonic implications of the Early Cretaceous syenogranite in Huanggangliang area, southern Great Hinggan Range: Evidence from zircon U−Pb ages, petrogeochemistry and Sr−Nd−Pb isotopes

Objective A large area of granitoids had been developed in the huanggangliang tin-iron mining and its surrounding area in the southern Great Hinggan Range. Thus, the study on its diagenetic age, petrogenetic type and source of diagenetic and ore-forming materials provides important insights to the mechanism of Early Cretaceous collision orogeny in this area and its relationship with mineralization.

Methods Samples were collected from the Huanggangliang tin−iron mining area and its surrounding areas in the southern Great Hinggan Range for petrography, zircon U−Pb geochronology, rock geochemistry, and Rb−Sr, Sm−Nd, Pb isotope studies.

Results  The crystallization ages of these samples range from 141.9 Ma to 139.1 Ma, which was formed during the Early Cretaceous and was about 3 Ma earlier than the mineralization age. The rocks are belong to high potassium calcium alkaline A−type granites with characteristics of high silicon, low aluminum, low magnesium, high potassium and low sodium. The ratios of (⁸⁷Sr/⁸⁶Sr)_i and ¹⁴³Nd/¹⁴⁴Nd are 0.70031~0.70543 and 0.512572~0.512636, respectively, the value of ε_Nd (t) is 0.07~ 1.18, and the Nd isotope model age T_DM2 ranges from 926 Ma to 838 Ma.

Conclusions The diagenetic materials of the Huanggangliang skarn tin−iron deposit were separated from the depleted mantle in Neoproterozoic, and experienced crustal contamination during ascending emplacement process. The southern Great Hinggan Range area experienced high−angle subduction of the Paleo−Pacific Ocean plate after post−collisional extension of the Mongol−Okhotsk Ocean closure.