摘要
按照自然出露情况,丹凤岩群东段可以划分为商南─丹凤段和商镇─高桥段。研究证明,商南─丹凤段中侵入岩的出露面积大于变质地层。变质地层的变质级达角闪岩相;原岩主要是陆源碎屑岩和泥灰岩,有少量的灰岩和基性火山岩。而商镇—高桥段全部由侵入岩组成。这两段的侵入岩构成了完整的正序岩浆演化序列,包括了钙碱性系列中从基性端元到酸性端元的几乎全部岩石类型,明显地具有活动陆缘型岩石组合。商镇—高桥段的塑性变形明显地弱于商南—丹凤段。在后一段的郭家沟剖面,辉长质变晶超糜棱岩带宽度达几百米,变形强度达深层次的辉石相。
According to natural occurrence, the east segment of Danfeng Group may be divided into Shangnan-Danfeng segment and Shangzheng-Gaoqiao segment. The research demostrates that the occurrence area ofintrusive rocks is larger than that of metamerphic strata in Shangnan-Danfeng segment. Metamorphic grade ofthe metamorphic strata reaches amphibole factes, and the original rocks should be mainly terregenaous elasticsedimentary rocks, marlite and a few of limestone and basic volcanic rock. Shangzhen-Gaoqiao segment consists completely of intrusive rocks. Intrusive rocks in the both segments constitute completely normal magmaevolution series, which include nearly all the rock types of calci-alkalic series from basic to acidend and evidently show rock association of active continenal margin type, the extent of ductile deformation inShangzheng-Gaoqiao segment is obviously weaker than that in Shangnann-Danfeng segment. The width ofgabbroic metacrystalline ultramylonite belt reaches hundreds of meters in Guojiagou section of the latter segment and the deformation intensity reaches pyroxene factes of deep layer. Similarly, they experenced universally static recrystalization and zoned crenal ation stage after ductile deformation. In the view of the facts asmentioned-above, the content of Danfeng group should only refers to the minor metamorphic strata in Shangnan-Danfeng segment.
基金
地矿部"八五"秦巴重点科研项目
关键词
丹凤岩群
侵入岩带
变质地层
侵入岩
Danfeng group
deformation intrusive rocks
metamophic strata