Crustal structure and Paleozoic metallogenic tectonic setting of the Duobaoshan ore district, NE China

Abstract

The Duobaoshan ore district has the largest Early Paleozoic porphyry Cu (Mo) deposit in Northeast China, located along the suture zone between the Xing’an and Songnen blocks. The crustal structure and mineralization in this district are key factors in the reconstruction of the Early Paleozoic setting of the Central Asian Orogenic Belt (CAOB). However, the locations and deep structure of the Hegenshan–Heihe suture zone remain unclear. The new seismic data collected in this study present transparent reflection features and bright spots associated with mineralization, and the westward-dipping reflection in the upper mantle beneath the west of the Sunwu County is a key seismological evidence of a relict ancient subduction belt between the Xing’an and Songnen blocks. The collected geochemical data show that Paleozoic granites (485–471.5 Ma) are enriched with large-ion lithophile elements, such as Rb, Ba, Sr, and LREE (light rare earth element) but depleted of high-field-strength elements, such as Nb, Ta, and Ti, suggesting a subduction-related island arc setting. The major outcome of this research is the identification of the fine crustal structure of the Duobaoshan ore district, which can help in identifying the relict subduction of the Paleo-Asian Ocean and restricting the most plausible suture location of the Xing’an and Songnen blocks to the west of the Sunwu County, moreover, Paleozoic magmatism and mineralization in the Duobaoshan ore district are found to be associated with subduction.