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Small degree of partial melting on peridotites and gabbros from the upper mantle.

来自上地幔的橄榄岩和辉长岩有小程度的部分熔融。

基本信息

批准号：
03640663
负责人：
NIIDA Kiyoaki
金额：
$ 1.28万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1992
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-03640663/
关键词：
UPPER MANTLE PERIDOTITE PARTIAL MELTING GABBRO MELTING EXPERIMENT SOLIDUS AMPHIBOLE MAGMA CHANNEL 幌満カンラン岩体

项目摘要

Gabbroic layers and pockets are commonly found in upper mantle-derived peridotites (e.g., gabbros in the Horoman peridotite complex, Japan; mafic layers in the Ronda peridotites). There is a general consensus that gabbros in association with the mantle-derived peridotites do not show any co-genetic relationships in chemical compositions as residues and the partially fused melts. Effects of small melts on the modification of the gabbros as well as peridotites were investigated in this research.(1) H2O-undersaturated solidus of MORB pyrolite locates at a pressure of 28 kb at T=1000ﾟC and at a temperature of 1075ﾟC between P=18 and 23 kb. This solidus coincides with the stability limit of pargasitic amphibole in MORB pyrolite composition and the location of solidi can be controlled by the Na2O+K2O content of peridotites.(2) 10 kb H2O-undersaturated solidus of the Horoman gabbro was determined near T=950ﾟC from the sandwich-type melting experiments. The maximum temperature stability of pargasitic amphibole in gabbros occurs at T=1075ﾟC under P=10 kb, which is approximately 50ﾟC higher than that for MORB pyrolite. It is clear that the amphibole can be an agent controlling the decomposition and modification on hydrated peridotites under the P-T conditions near solidus.(3) Effect of small amounts of melt on peridotites is observable near magma channels in the upper mantle-derived peridotites, where a replacement can be generated during small degree of partial melting of the wall peridotites as well as melt addition from the channel.

辉长岩层和袋状岩通常存在于上地幔衍生的橄榄岩中（如日本霍罗曼橄榄岩杂岩中的辉长岩，隆达橄榄岩中的基性层）。普遍认为，辉长岩与幔源橄榄岩在化学成分上不存在共成关系，如残留物和部分熔融体。研究了小熔体对辉长岩和橄榄岩变质的影响。(1) MORB软锰矿在温度为1075 ~ 18 ~ 23 kb之间，温度为1075 ~ 1000℃时，压力为28 kb。该固形物符合MORB软锰矿组成中寄生角闪洞的稳定极限，固形物的位置可由橄榄岩的Na2O+K2O含量控制。(2)在T=950 oc附近，通过夹心式熔融实验测定了霍罗曼辉长岩的10 kb h2o欠饱和固相。辉长岩中寄生角闪洞在P=10 kb条件下的最大温度稳定性为T=1075ºC，比MORB软锰矿高约50ºC。在固相附近的P-T条件下，角闪孔可能是控制水合橄榄岩分解和变质的一种剂。(3)上地幔源橄榄岩的岩浆通道附近存在少量熔体对橄榄岩的影响，壁面橄榄岩的部分小程度熔融和通道的熔体加入可产生替代作用。