Indo–Chinese Magmatic Activity in the Duobaoshan District of Heilongjiang Province and Its Geological Significance

Abstract

AbstractThe Duobaoshan ore concentration area, located in Nenjiang County of Heilongjiang Province, is an important porphyry Cu‐Mo ore concentration area in China, which is characterized by complex magmatic activities and multi‐phase overprinting metallogenesis. On the basis of field geological observation, systematic sampling, in‐lab analysis and the metallogenic regularity in the Xiang'an‐Mongolian metallogenic belt, this work carried out high‐precision dating and geochemical analysis on the Yuejin, 173‐kilometer and Wolihedingzi rock bodies. These rock bodies are renamed monzonitic granite and their consistent age (238 Ma) show that they were formed not in Variscan but in Indosinian. Therefore, it is inferred that the ore spots formed in the potassium silicate and sericite alteration zones of the rock mass also belong to Indosinian. In addition, we collected granodiorite from the Tongshan mining pit, and its zircon age is 223.1±2.8 Ma and the Cu content of the sample is high. The Tongshan mineralization is inferred to undergo the superimposition of Indosinian diagenetic mineralization. The age of the granodiorite porphyry related to copper‐molybdenum mineralization in the Xiaoduobaoshan area is 222.1±5.5 Ma, and the earlier age of granodiorite is 471.8±7.4 Ma, indicating that the initial magmatic activities belong to the Duobaoshan porphyry system in the Caledonian period. The geochemical characteristics of the Indosinian rock samples show continental arc features, with reference to tectonic‐magmatic activities of the whole Daxing'anling area. We consider that the magmatic activities and mineralization of the Indosinian period are affected by the southward subduction of Okhotsk Ocean since Late Permian. By combining the mineralization rules of Daxinganling area and the structural systems of Duobaoshan ore concentration area, we divide two rock‐mineralization belts in this area including the Yuejin‐Duobaoshan‐Tongshan belt and 173‐kilometer‐Xiaoduobaoshan‐Wolihedingzi belt, which are distributed nearly parallel along the NW‐trending fractures and show similar geotectonic settings and the timing of the magmatic activities. It is favorable for discovering porphyry Cu‐Mo deposits in these two metallogenic belts, especially in the Yuejin, 173‐kilometer and Wolihedingzi areas where less research work has been made.