内蒙古莫力达瓦旗哈达阳构造混杂岩地质特征及发现的意义

GEOLOGY OF THE HADAYANG TECTONIC MELANGE IN INNER MONGOLIA:Discovery significance

哈达阳构造混杂岩出露于嫩江黑河构造带之中.根据区域地质背景及构造混杂岩中岩块地质及地球化学特征,划分了基质、原地岩块及异地岩块3部分.基质主要为绿帘黑云绿泥构造片岩.原地岩块主要有绿帘黑云绿泥构造片岩及可能来自海沟外缘缓坡的砾岩.异地岩块主要有角闪石岩、混染闪长岩及变酸性火山岩.角闪石岩及混染闪长岩岩石地球化学特征表明,其形成于与消减作用相关的边缘海扩张环境,而变酸性火山岩具有岛弧钙碱性火山岩特征.上述特征说明,哈达阳构造混杂岩与板块俯冲消减-碰撞作用相关.沿红山梁、哈达阳直达依克特一带出露的古生代地层彼此之间均为断块接触,认为在该沿线存在一条早石炭世末的构造混杂岩带.哈达阳构造混杂岩的发现为正确认识嫩江黑河构造带性质,正确分析构造带结构都具有重要意义.

The Hadayang tectonic melange is outcropped in the Nenjiang-Heihe tectonic belt. According to its regionalgeological setting and rock geological and geochemical characteristics, the tectonic melange is divided into three parts：matrix, autochthonous blocks and allochthonous blocks. The matrix is dominated by epidote-biotite-chlorite tectonic schist.The autoehthonous blocks are composed of epidote-chlorite-biotite tectonic schist and possible conglomerates from outerslope of trench. The allochthonous blocks are mainly hornblendite, hybrid diorite and meta-acidic volcanic rocks. Thelithogeochemical characteristics show that the hornblendite and hybrid diorite were formed in a marginal ocean expansionenvironment related to subduction, while the meta-acidic volcanic rocks have the characteristics of island arc calc-alkalinevolcanic rocks. The characteristics above indicate that the Hadayang tectonic melange is related to the subduction-collisionof plates. Combined with the feature that glaucophane appears in the Early Carboniferous recta-acidic volcanic rocks ofHongsanliang area and Paleozoic strata outcropped along the Hongsanliang-Hadayang-Yikete area are fault contactrelationship between each other, the authors conclude that there is a tectonic melange belt of late Early Carboniferous alongthis line. The discovery of Hadayang tectonic melange belt is of important significance for understanding the Nenjiang-Heihe tectonic belt and its structure.