Late Mesozoic low-P/high-T metamorphism preceding emplacement of Cretaceous granitic rocks in the Gosaisho-Takanuki district, Abukuma metamorphic belt
Late Mesozoic low-P/high-T metamorphism preceding emplacement of Cretaceous granitic rocks in the Gosaisho-Takanuki district, Abukuma metamorphic belt
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阿武隈变质带五西庄-高贯地区白垩纪花岗岩侵位前的晚中生代低磷/高温变质作用
DOI：
10.1111/j.1440-1738.1993.tb00083.x
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发表时间：
1993
期刊：
影响因子：
1.5
通讯作者：
Hiroyuki Nemoto
中科院分区：
文献类型：
--
作者：
M. Tagiri;H. Sato;Eiji Matsumura;Hiroyuki Nemoto
Abukuma变质带中部由两个地质单元组成，即Gosaisho群和Takanuki群。尽管Gosaisho群和Takanuki群的变形方式不同，但它们的岩相显示出逐渐的过渡。在这两个群中，早期的区域低压(超过3kb)变质作用已被接触变质作用叠加。区域变质作用的P/T条件的证据记录在装甲矿物的岩芯中。根据变质镁铁矿、变质泥质岩和变质钙质硅质片岩的矿物边缘组合和变质泥质岩的石墨化程度，划分了变质带。斜长石、钙角闪石和石榴石的矿物核心化学随变质程度的增加而变化，表明戈赛什群的区域变质作用发生在红柱石稳定场的高压区。Takanuki变质岩在构造上被Gosaisho群覆盖，并经历了区域变质作用，条件在硅酸铝三重点附近过去，蓝晶石已经结晶。两组接触晕均发育于中白垩世花岗岩侵入体周围。接触变质作用期间，岩心上发育有斜长石、钙角闪石、石榴石等边缘。区域变质作用始于侏罗纪硅质岩沉积后，继而为中白垩世接触变质作用。
The central part of Abukuma metamorphic belt consists of two geologic units, the Gosaisho Group and the Takanuki Group. Although the deformation styles differ between the Gosaisho and the Takanuki Groups, their rock facies show a gradual transition. In both Groups early regional low-pressure (over 3 kb) metamorphism has been overprinted by contact metamorphism. Evidence for the P/T condition of the regional metamorphism is recorded in cores of armored minerals. Metamorphic zones have been defined on mineral rim assemblages of meta-mafite, meta-pelite and meta-calc-siliceous schist and on the degree of graphitization of meta-pelite. The mineral-core chemistry of plagioclase, Ca-amphibole and garnet changes with increasing metamorphic grade, and indicates that the regional metamorphism of the Gosaisho Group took place in a high pressure region of the andalusite stability field. The Takanuki metamorphic rocks are structurally overlain by the Gosaisho Group and have undergone regional metamorphism whose conditions have passed near the triple point of Al-silicates and kyanite has crystallized. The contact aureoles in both groups are developed around middle Cretaceous granitic intrusions. Rims of plagioclase, Ca-amphibole and garnet overgrew on the mineral-cores during the contact metamorphism. The regional metamorphism began after the sedimentation of Jurassic chert and was succeeded by the contact metamorphism in the middle Cretaceous.