华北地块东南缘中生代侵入杂岩中所含榴辉岩类包体矿物微量元素地球化学特征及其意义

Geochemical characteristics for trace element of mineral in eclogite inclusions separated out of Mesozoic intrusive complex from southeastern margin of North China Block and its significances

华北地块东南缘中生代侵入杂岩中所含榴辉岩类包体中矿物的分析结果表明,组成榴辉岩类包体的各矿物之间元素的分配在榴辉岩相变质阶段已经达到了化学平衡;石榴石中Al、Fe、Mn,单斜辉石中Na、Mg、Ca,角闪石中Na、Mg、Fe等主量元素含量与其全岩之间均呈良好的正相关,受全岩成分制约;石榴石明显富集HREE、贫LREE,单斜辉石相对富集LREE、MREE、贫HREE,两者轻、重稀土含量呈相互消长的互补关系,石榴石和单斜辉石中分别富集Y、Sr,Ga和过渡族元素Sc、Ti、V、Cr、Co等含量较高,其含量受全岩成分控制;金红石中稀土元素的含量很少,Fe、Al、Mg、Ca、Mn、Nb、Ta、Cr和Zr含量相对较高,Rb、Sr、Ba含量极低,部分微量元素(如Nb、Cr、Fe、V、W等)含量与其原岩有继承和对应关系;部分原生或/和退变角闪石的REE配分模式分别与单斜辉石和石榴石相似,过渡族金属元素等的含量与石榴石、单斜辉石和全岩具有一定的相关性,角闪石容纳Na、K、Sr、Rb、Ba等元素的能力较强,其成分除受全岩成分的制约外,石榴石、单斜辉石对其形成也有影响。榴辉岩类包体与其寄主中生代侵入杂岩中部分高价态/高场强元素(HFSE)和重稀土元素(HREE)呈相互消长的关系。榴辉岩的形成与扬子地块和华北地块之间的俯冲-碰撞作用有关。

The test results of minerals in eclogite inclusions separated out of Mesozoic intrusive complex from southeastern margin of North China indicate that the distribution of element between minerals in eclogite inclusions got up to chemical equilibrium at eclogite facies metamorphic stage.The major element components,such as Al,Fe and Mn in garnet;Na,Mg and Ca in clinopyroxenes;Na,Mg and Fe in amphiboles,appear strong positive correlation with its total rock and restricted by the composition of its total rock.Garnets are markedly enriched with HREE,and depleted LREE,whereas clinopyroxene are relatively enriched with LREE and MREE,and depleted HREE.The content of LREE and HREE in garnets and clinopyroxenes emerge complementary relation with mutual growth and decline.Garnets enriched with Y,while clinopyroxenes enriched with Sr,both have higher Ga and transition group element（Sc,Ti,V,Cr,Co,etc.）,respectively,and controled by the composition of its total rock.Rutiles have anything of REE and lowest Rb,Sr and Ba,while have higher Fe,Al,Mg,Ca,Mn,Nb,Ta,Cr and Zr,and the components of some trace elements（e.g.Nb,Cr,Fe,V,W,etc.）inherited the original matter which dominant are mafic rock.Some protogene amphiboles are similar clinopyroxenes and retrogressive amphiboles are similar garnets on chondrite-nomalized REE patterns.Transition group element content in amphiboles are interdependency with garnets,clinopyroxenes and total rock.The amphiboles have better capability for admission with Na,K,Sr,Rb,Ba,etc,and its content influence by garnets,clinopyroxenes and total rock.Some high electrovalency element or/and high field strength element and HREE emerge the decrease and increase between eclogite inclusions and its host Mesozoic intrusive complex.The eclogite could be resulted from the subduction-collision action between the Yangtze Block and the North China Block.