摘要
华北地台中部由山东半岛端部至晋西南地区近东西向的一个地带(北纬35°—38°及其左近),可以作为华北地台区燕山期岩浆活动的代表(图1)。 区内燕山期岩浆岩可归属两个岩区:鲁东岩区及华北中部岩区。前者又可分为两个带,即东部沿海带和沂沭裂谷带,后者分为鲁西带、南太行带和晋西南带。
The cross section from the Shandong Peninsula to Southwest Shanxi in the direction of east-west might be the representative of magmatic process during the Yanshan stage in the mid part of the North China platform. Two magmatic provinces could be subdivided in the area.One of the magmatic provinces is the Ludong province dominated by felsic rocks. The calc-alkaline series and alkalic rhyolite series are the most aboundant, and then the shoshonite series containing more alkaline developed in the Yishu rift secondary. The wide distribution of volcanic rocks and intrusive rocks on a large scale are of the important characters. The magmatic association in the area might result from the magmatism along the active continental margin.The rocks in the mid part of North China mainly consist of members bearing moderate silica including calc-alkaline series, shoshonite series and leuc-ite-bearing and nepheline-bearing peralkaline series. The ultrapotassic series, carbonatite and kimberlite are rare but of significance. The research of petrochemistry of the main series demonstrates that the alkalinity and the content of potassium increase from east to west. The magmatic association of this province shows that they were formed in the stable environment of continent. The magma of different series are probably not from the subduction of the Pacific Ocean plate towards the Asian continental margin, but related to the upwarping of mantle and expansion of the earth crust in the east part and to the subsidence and compression of mantle in the west part, which is caused by the compression event of the Pacific Ocean plate moving under the Asian continent. Therefore the Moho declines to the west, and the isothermal surface and the source region of magmas gradually became deeper from east to west.The calc-alkaline series gave way to the shoshonite series and paralka- line series while the upwarping of the mantle turned to the stage of rifting. As the mantle upwarped, the layer of partial melting rose from the top of the upper mantle to the lower earth crust. Magma caused by poorly partial melting are formed with more components of the lower melting point and are of higher alkalinity with the mobing-up of mantle materials along the rift,the source region of magmas arose and so did the alkalic solution formed in the deep part, which was absorbed subsequently by the magma generated in the lowercrust, thus the alkalic magmas being formed.The ultrapotassic,carbonatitic and kim-berlitic magmas from the deeper part of the mantle were emplaced when parts of previous partial melting of the earth crust consolidated.
出处
《吉林大学学报（地球科学版）》
EI
CAS
1984年第2期31-42,68,共13页
Journal of Jilin University：Earth Science Edition
