Geochronology, geochemistry and Sr-Nd-Pb-Hf isotopes of the Early Jurassic granodiorite from the Sankuanggou intrusion, Heilongjiang Province, Northeastern China: Petrogenesis and geodynamic implications

• Published in: Lithos 2018-01, Vol.296-299, p.113-128
• Main Authors: Deng, Ke, Li, Qiugen, Chen, Yanjing, Zhang, Cheng, Zhu, Xuefeng, Xu, Qiangwei
• Format: Article
• Language: English
• Subjects: CAOB; Mesozoic granitoids; Sankuanggou skarn Fe-Cu deposit; Sr-Nd-Pb-Hf isotopes; Zircon U–Pb age
• ISSN: 0024-4937; 1872-6143
• DOI: 10.1016/j.lithos.2017.10.016

Mesozoic granitoid rocks represent a volumetrically component of the Northeastern (NE) China and preserve useful information about the tectonomagmatic history of this region. The Sankuanggou intrusion associated with skarn Fe-Cu deposit in the Duobaoshan ore field within NE China primarily consists of granodiorite with minor alkali-feldspar granite and diorite, which intrudes the Ordovician Duobaoshan Formation in the region. Zircon LA-ICP-MS U–Pb geochronology and whole-rock geochemistry, and Sr-Nd-Pb-Hf isotope analysis were performed on the Sankuanggou intrusion to investigate the petrogenesis and geodynamic implications. Zircon U–Pb dating of magmatic zircons from the granodiorite rock suggests that the intrusion was emplaced in the Early Jurassic (177±1 Ma). Geochemically, it belongs to the metaluminous to slightly peraluminous high-K calc-alkaline I-type granitoids with a narrow range of SiO2 concentration (65.73–67.33 wt.%), high Ba, Sr, LREE and LILE contents and low abundance of Rb, Y, HREE and HFSE. All of these studied samples have homogeneous initial isotope traits with (87Sr/86Sr)i ranging from 0.70415 to 0.70423, εNd(t) of +3.6 to +4.0, (206Pb/204Pb)i=17.933–18.458, (207Pb/204Pb)i=15.520–15.587 and (208Pb/204Pb)i=37.523–38.087, and zircon εHf(t) values varying from +4.8 to +9.9. These results, combined with the previous data, demonstrate that the Sankuanggou granitoids were formed by partial melting of the pre-existing juvenile crust in an extensional regime related to the post-collisional setting following the closure of the CAOB rather than previously proposed continental arc setting related to Paleo-Pacific or the Mongol–Okhotsk subduction, although their potential influence should not be dismissed. •The Sankuanggou granodiorite was emplaced in 177±1Ma.•The granodiorite originated from partial melting of a juvenile crust.•The granodiorite was formed in an extensional setting.