40Ar–39Ar analysis of phlogopite in the Horoman Peridotite Complex, Hokkaido, Japan and implications for its origin
40Ar–39Ar analysis of phlogopite in the Horoman Peridotite Complex, Hokkaido, Japan and implications for its origin
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日本北海道 Horoman 橄榄岩杂岩中金云母的 40Ar–39Ar 分析及其起源意义
DOI：
10.1046/j.1440-1738.2001.00290.x
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发表时间：
2001
期刊：
影响因子：
1.5
通讯作者：
S. Arai
中科院分区：
文献类型：
--
作者：
I. Kaneoka;N. Takahashi;S. Arai
对产于日本北海道的霍罗曼橄榄岩杂岩中的斜长二辉橄榄岩中金云母进行了~（40）Ar-~（39）Ar分析，得到其坪年龄为20.6 ± 0.5 Ma，其变质流体的Ar同位素比值接近大气。年龄谱略呈马鞍形，意味着金云母在一定深度形成过程中有一些过量的40 Ar掺入。由于金云母被推断为在橄榄岩体的折返过程中形成于脉和/或岩脉中，因此可能有地下水和海水的交代流体参与了金云母在地壳环境中的形成。一个斜长二辉橄榄岩的全岩样品的40 Ar-39 Ar年龄为129 Ma，金云母从其中分离出来，是霍罗曼橄榄岩杂岩的主要岩性的代表，表明存在过量的40 Ar。因此，年龄没有地质意义。
Abstract 40Ar–39Ar analysis of phlogopite separated from a plagioclase lherzolite of the Horoman Peridotite Complex, Hokkaido, Japan, has yielded a plateau age of 20.6 ± 0.5 Ma in an environment where the metamorphic fluid was characterized by an almost atmospheric Ar isotopic ratio. The age spectrum is slightly saddle‐shaped, implying some incorporation of excess 40Ar during the formation of the phlogopite at a depth. As the phlogopite has been inferred to have formed in veins and/or interstitials during exhumation of the peridotite body, metasomatic fluids, to which ground‐ and sea water might have contributed, were probably involved in the formation of phlogopite in the crustal environment. A total 40Ar–39Ar age of 129 Ma of a whole rock sample of the plagioclase lherzolite, from which the phlogopite was separated and is representative of the main lithology of the Horoman Peridotite Complex, indicates the occurrence of excess 40Ar. Hence, the age has no geological meaning.