花岗岩体生长方式及构造运动学、动力学意义——以东秦岭造山带核部花岗岩体为例

 岩体的生长方式可概括为中心式、偏心式、侧向式、不规则式、中心多点式。它们可提供反演区域构造动力学特点的信息。非极性生长可能暗示,在岩浆生成与上升定位的有限的时、空间范围内,上下圈层之间相对运动不大;有规律的极性生长很可能揭示了上下圈层之间有相对运移。秦岭造山带核部某些晋宁期H 型花岗岩体具南北向极性生长特点,反映了构造块体垂直造山带方向的运动特点;加里东-海西期很多H 型花岗岩体生长呈侵位中心东移的极性生长,揭示了秦岭杂岩平行造山带的侧向运移及剪刀状双向俯冲的板块构造动力学特点。

GROWTH PATTERNS OF GRANITOID PLUTONS AND THEIR IMPLICATIONS FOR TECTONICS, KINEMATICS AND DYNAMICS:EXAMPLES FROM GRANITOID PLUTONS IN THE CORE OF THE QINLING OROGENIC BELT,CHINA

Granitoid plutons generally consist of units, sequences or small plutons, so they have growth patterns and process. We define the growth patterns as distribution characteristics of units, sequences and plutons and the growth process as time, volume and rate of growth. This paper focuses on the growth patterns and divides them into central, accentric lateral, irregular and multi-central growth, a study of the growth patterns providing information of tectonic dynamics. Non-pole(central)growing patterns may imply that relative motion between different-level tectonic blocks is not strong in the finite time-space scale from the magma source to the emplacement levels. However, pole growth patterns with regular migration of emplacement centers may be a mark of existence of movement between different levels in continent and mantle. In the core of the Qinling orogenic belt, for example, the growth of the Jining granitoid plutons was characterized by N-S lateral growing, implying tectonic kinematics parallel to the subduction direction. i.e. perpendicular to the belt. In contrast, the growth of the plutons in Calidonian Variscian was characterized by lateral or accentric growth with the eastward migration of granite emplacement center, indicating, together with other evidences, a large-scale parallel-orogen westward lateral flow of the Qinling complex. The dynamics was characterized by lateral extrusion caused by two-side subduction in a scissors form. This study may reveal a lateral motion of blocks between two plates during oblique subduction-collision from point to plane. In general, growth patterns with migration of emplacement centers may be more developed in granitoid plutons generated from action between continent, mantle and ocean crust. This paper shows that a study of granite growth patterns and their relations to the tectonic dynamic background and to reaction of ocean crust, continental crust and mantle not only enriches the contents of pluton study, but also provids new information on plate tectonics and continent dynamics, so it should be paid more attention.