Geologic and Petrologic re-examination of the "Hayachine Tectonic Belt"

本文对川井、釜石地区早钦构造带及其周围的基性-超基性岩的地层学、地质构造和地球化学性质进行了重新研究。研究结果如下：1.在河合地区，古生代岩石从上到下分为早千杂岩（Nakadake蛇纹岩、Kagura杂岩和Koguro组;奥陶纪-志留纪？），药师川组（奥陶纪？-志留纪）和小田越组（志留纪）。在釜石地区，它被划分为早知复合体（Kentosan复合体和岩仓山复合体;志留纪？），千城垣组（泥盆纪）、高川组（石炭纪）和栗林组（二叠纪）。2.早池构造带东缘带的地质构造以逆断层和逆褶皱为特征，向东延伸。相反，在西部边缘带，它以逆断层和不对称褶皱为特征，向西Fergenz。因此，“早知构造带”似乎形成了一个背斜。早钦杂岩的基性岩和奥长花岗岩的化学性质与大洋玄武岩或大洋斜长花岗岩相似.早知杂岩形成于奥陶纪或志留纪，为洋壳，上覆志留纪厚层陆源沉积。志留纪及以后，“早知构造带”为被动陆缘，晚侏罗世可能形成了一个广泛的背斜，它沿被动陆缘沿着由逆断层将南、北方北上地块分隔开来。背斜带被称为“早川构造带”。

Stratigraphy,geologic structure and geochemical nature of the basic to ultrabasic rocks in and around the "Hayachine Tectonic Belt" in the Kawai and Kamaishi district are re-examined. The results of the investigation are as follows:1. In the Kawai district, the Palaeozoic rocks are divided, in ascending order, into the Hayachine Complex (Nakadake Serpentinite, Kagura Complex and Koguro Formation; Ordovi-cian-Silurian ?), Yakushigawa Formation (Ordovician?-Silurian) and Odagoe Formation (Silurian). In the Kamaishi district, it is divided into the Hayachine Complex (Kentosan Complex and Iwakurayama Complex; Silurian ?), Senjyogataki Formation (Devonian), Kogawa Formation (Carboniferous)and Kuribayashi Formation (Permian).2. Geologic structure in the eastern marginal zone of the "Hayachine Tectonic Belt" is characterized by reverse faults and overterned folds with eastward Fergenz. On the contrary, in the western marginal zone it is characterized by reverse faults and asymmetric folds with westward Fergenz. Thus the "Hayachine Tectonic Belt" seems to form an anticlinorium.3. The chemical nature of the basic rocks and trondhjemites of the Hayachine Complex is similar to that of oceanic basalt of oceanic plagiogranite.4. The Hayachine Complex was formed as an oceanic crust in Ordovician or Silurian time, and is overlain by thick terrigenous sediments of Silurian age. On and after the Silurian, the "Hayachine Tectonic Belt" was a site of passive margin, then, probably in the late jurassic, a broad anticline was formed in the zone, which separated from the Southern and Northern Kitakami Massif by reverse faults, along the passive margin. The anticlinal zone is called the "Hayachine Tectonic Belt".