东秦岭造山带岩石圈热结构及断面模型

东秦岭岩石圈热结构热状态十分不均匀,沿断面可分成华北地块、北秦岭、南秦岭、扬子地块四大块,南秦岭为“热区”,北秦岭为“冷区”。商丹断裂带具８１．３ｍＷ／ｍ２高热流值,是南北秦岭的分界线,是多期构造运动的活动带,是扬子地块与华北地块的缝合带。加里东期扬子地块向华北地块俯冲碰撞,印支—燕山期俯冲板片由于“去层状化作用”断开下沉,软流圈上侵,岩石圈上地幔变薄。后国华北岩石圈下部插入扬子俯冲板片中形成穿插构造,商丹断裂带成为现今向南倾的走滑断裂带。中上地壳有不同时期的大规模逆冲推覆体,断块向南叠置;下地壳缩短成“漏斗”状下滑,地壳增厚造成东秦岭造山带现今独特复杂的岩石圈五层结构模型。

LITHOSPHERIC THERMAL STRUCTURE OF EAST QINLING OROGENIC BELT AND ITS TRANSVERSE SECTION MODEL

Lithospheric thermal structure of east Qinling orogenic belt is very nonuniform. This orogenicbelt may be divided into north China, north Qinling, south Qinling and Yangtze massives. The boundary between the south and the north Qinling massives is Shanghan fracture zone. It is a long-lived fracture zone with a geothermal current value of 81. 3mWm-2 and the suture cone between the Yangtze and the north China massives. South Qinling is a "hot district". while north Qiuling is a" cool district". In Caledonian epoch, the Yangtze tnassif was ran into subduction against the north China massif. In Indo-Chinese epoch, as a result of "delayerization", the subducting plate was broken and subdided, asthenosphere intruded ascendingly and lithospheric mantle thinned. Afterwards, Shangdan fracture zone became a strike-slip one with a dip to south because of the lower pat of the north China lithosphere inserting in the subdocting plate. Large-scale southward mppes occurred in the middle-upper crust in various ages. The lower crust was shortened and thickened, becoming a funnelform which resulted in the distinctive "five-layer structure model" of the east Qinling orogenic belt.