Petrological features and tectonic significance of the Ordovician in Duobaoshan ore district,northern Heilongjiang
Huang Yongwei1, Liu Yang1, Wang Xichen2, Wang Lin1, Liu Jinying3, Yang Jiquan4, Wang Baoquan4, Xu Xiumei4
1. China University of Geosciences, Beijing 100083;
2. Management of Central Geological Exploration Fand, Ministry of Land and Resources, Beijing 100045;
3. Beijing Exploration and Technique Engineering Corp. Ltd., Beijing 100080;
4. Bureau of Geology and Exploration of Heilongjiang Province, Harbin 151000
The Ordovician was well developed in Duobaoshan ore district, northern Heilongjiang province,in which the volcanic rocks were source layers of Cu-Mo ore deposits.The paper described briefly the biostratigraphy and sedimentary features of the Ordovician, and explored the petrochemical characteristics of the volcanic rocks.The volcanic series consisted of andisite and subordinate acidic rocks,which attached,generally,to the talc-alkaline,with part of tholeiitic series.The volcanics of the early cycle (the Wolihe Formation) were characterized with relatively lower K,La and Eu negative anomaly,which meant an island arc in continental margin, and in position far from the continent,the arc showed some property of oceanic island-arc.In later cycle (eruptive period of the Duobaoshan Formation), the arc migrated westwards and became, partly,Andean-type arc,or a transitional situation between the continent marginal arc and Andean-type arc.The regional tectonic evolution was reconstructed,which indicated the oceanis crust of the Xing-Meng Ocean subducted eastwards beneath the Jiamusi Block,and the Early Paleozoic structural line was NNW-orientation.In Late Paleozoic the regional evolution was constrained by the northwestward subduction, so the structural line was NE-striking.