Petrographical Studies on the Peridotite in the Horoman Region at the Southerr end of the Hidaka Mountain Range, Hokkaido
Petrographical Studies on the Peridotite in the Horoman Region at the Southerr end of the Hidaka Mountain Range, Hokkaido
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北海道日高山脉南端霍罗马地区橄榄岩的岩相研究
DOI：
10.5575/geosoc.59.111
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发表时间：
1953
期刊：
影响因子：
--
通讯作者：
S. Igi
中科院分区：
文献类型：
--
作者：
S. Igi
在北海道，沿沿着两条平行的构造带，即Kamuikotan带和日高带，分布着许多超镁铁质火成岩体。这些构造带构成了北海道的地质骨干，被认为是白垩纪造山运动的产物，称为“日高造山运动”。认为日高带可能是造山深核，而鸭颈丹带可能是向西的逆冲推覆带。两个构造带的超镁铁质火成岩具有许多共同特征。但在它们身上也观察到了截然不同的特征，对比最明显的特征之一是，Kamuikotan带的超镁铁质岩石几乎全部被蛇纹化，另一方面，这些岩石在日高带总是处于未蚀变的橄榄岩状态。在日高构造带南端的霍罗曼地区，有该构造带最大的橄榄岩侵入体。该橄榄岩的造岩矿物具有定向排列的特点，因此，岩体的各个部位都有明显的流动结构或层状结构。从这些流动结构的排列来看，似乎在橄榄岩体的中心存在一个大的圆顶结构，如图1所示，该橄榄岩体中有多种岩相，如纯橄榄岩相、辉石橄榄岩相、斜长石橄榄岩相等，各岩相的发育与流动结构相一致，因此，在悬崖中，由不同种类的岩相交替所引起的明显现象似乎清楚地表明是分层。（图1），- 它们在每个相的矿物沉积层如下：1.,橄榄石-（深棕色尖晶石）2.，橄榄石-斜方辉石-单斜辉石-（浅棕色尖晶石）3.，橄榄石-斜方辉石-单斜辉石-（绿色尖晶石）4.，橄榄石-单斜辉石-斜长石-（黑色尖晶石）每种矿物的光学特征见表1。本文描述了各岩相的岩石学特征，作为进一步发展对霍罗曼橄榄岩体认识的基础。进一步的研究，特别是关于侵入构造的研究，将由本作者的合作者在不久的将来发表。
In Hokkaido, there are many ultra-mafic igneous bodies along the two parallel tectonic zones which are named the Kamuikotan zone and the Hidaka zone respectively., These tectonic zones compose the geological back-bone of Hokkaido, and are regarded as the product of a Cretaceous orogenic movement which is called "Hidaka Orogeny"., It is believed that the Hidaka zone may be an orogenic deep core and the Kamuikotan zone its westward over-thrusting zone., Many common characters have been noticed in the ultra-mafic igneous rocks of both tectonic zones., But contrasting features have also been observed in them., One of the most contrasted features is that the ultra-mafic rocks of the Kamuikotan zone are almost wholly serpentinized, on the other hand, those rocks are always in the unaltered peridotitic state in the Hidaka zone., In the Horoman region, at the southern end of the Hidaka tectonic zone, occurs the largest peridotite intrusive mass of the zone., The rock-forming minerals of this peridotite have an orientated arrangement, so the flow structure or layered structure are well marked in all parts of the mass., Judging from the arrangement of these flow structures, it seems that a large dome structure has existed at the centre of this peridotite mass, as presented in Fig 1., There are various kinds of rock facies in this peridotite mass, such as dunitic, pyroxene-peridotitic, and plagioclase-peridotitic facies etc., and each rock facies is developed in accordance with the flow structure., So, in a cliff, obvious appearance caused by the alternation of different kinds of rock facies seem clearly to be stratifications., (Plate 1)., -And their mineralassemblodges in each facies follow., 1., Olivine -(dark brown spinel) 2., Olivine -rhombic pyroxene-monoclinic pyroxene-(light brown spinel) 3., Olivine -rhombic pyroxene-monociinic pyroxene -(green spinel) 4., Olivine -monoclinic pyroxene-plagioclase-(black spinel) Optical characters of each mineralare given in Table 1., In this paper, the writer described the petrographical characters of each rock facies as a basis for further development of the knowledge about the Horoman peridotite mass., Further studies, especially concerning the intrusive tectonics, will be published in the near future by collaborators of the present writer.,