黑龙江北部多宝山矿区奥陶系的岩石特征和构造意义

黑龙江北部多宝山矿区广泛发育奥陶系，因含有铜、钼矿源层而受到地质界的注意.本文概述了其生物地层和沉积特征，重点探讨了其火山岩的岩石化学特征.该套火山岩总体上属钙碱性系列，部分（主要是酸性岩）可能属拉斑玄武岩系.下旋回（窝里河组）火山岩以相对低K、La和Eu负异常为特征，总体属大陆边缘岛弧，局部显示出大洋岛弧安山岩的性质.上旋回（多宝山组）的弧则属大陆边缘岛弧与安第斯型山弧的过渡类型，部分地区可能有安第斯型山弧发育.分5个阶段重塑了该区奥陶纪大地构造演化，早古代洋壳向东偏北消减于布列亚一佳木斯地块之下，因后退式的消减而火山弧向西偏南迁移，构造线方向为北北西向.

Petrological features and tectonic significance of the Ordovician in Duobaoshan ore district,northern Heilongjiang

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.