黑龙江科洛杂岩变形特征、阶段和意义

The Deformation Features, Phases and Significance of Keluo Complex in Nenjiang Area, Heilongjiang Province

兴蒙造山区东段的科洛地区,自古亚洲洋关闭之后,经历了复杂的多阶段陆内变形,每一期变形都具有不同的机制,均是中国东北中生代以来板块边缘重要构造事件的反映。三叠纪中晚期,科洛杂岩经历了上盘指向NNE方向的韧性挤压变形,相关变形分布在整个科洛杂岩地区,大量低角度石英拉伸线理以及A型褶皱枢纽均指示了松嫩地块NNE向的运动,科洛杂岩也在此时形成。科洛杂岩并不是松嫩地块的基底,而是中生代构造事件的变质产物,该期事件不是古亚洲洋关闭后的造山带伸展,而与来自东侧和南侧的挤压有关。晚侏罗世-早白垩世科洛地区左行韧性走滑是蒙古-鄂霍茨克洋的关闭所致,其变形集中在科洛杂岩的西部边界剪切带上。白垩纪时科洛杂岩受到伸展构造的改造,以一系列向南东倒伏、走向NNE-SSW的相似褶皱为特征,褶皱的倒伏向不随位置的变化而改变,其伸展不是典型的变质核杂岩。新生代科洛杂岩又受到了近SN向的挤压,发生区域性的宽缓褶皱变形。

Keluo complex,located in the eastern part of the Great Xing’an Range,has undergone multistage andcomplicated intraplate deformation events after the closure of the Paleoasian Ocean.Each phase of the deformation hasdifferent mechanisms,reflecting various plate marginal tectonic events after the Mesozoic in NE China.In the LateTriassic,Keluo complex experienced the top-to-the NNE pervasive ductile compression.Both nearly horizontal quartzstretching lineations and hinges of“A”type folds indicated that the Songnen block moved to the NNE and the complexformed at the same time.So the complex formed during the Mesozoic tectonic event rather than the basement of theSongnen block.This event was not the post-orogenic extension related to the closure of Paleoasian Ocean,but wasrelated to the southern and eastern compression on the Songnen Block.During the Late Jurassic to Early Cretaceous,aphase of sinistral ductile shearing was triggered by the closure of the Mongolia?Okhotsk Ocean.The strain concentratedin the western border of the complex.In the Cretaceous,Keluo complex was superposed by an extension deformationevent,yielding a series of similar folds whose strike is NNE-SSW with the axial surface inclined to the SE.Thedeformation type suggested that it was not a typical metamorphic core complex.In the Cenozoic,Keluo complex wasinfluenced by the S-N trending compression,broad and gentle regional folds were formed.