Morphology and chemistry of olivine phenocrysts of Mangamate Tephra, Tongariro Volcanic Centre, New Zealand
Morphology and chemistry of olivine phenocrysts of Mangamate Tephra, Tongariro Volcanic Centre, New Zealand
复制标题
新西兰汤加里罗火山中心 Mangamate Tephra 橄榄石斑晶的形态和化学
DOI：
--
复制
发表时间：
1991
期刊：
影响因子：
--
通讯作者：
A. Palmer
中科院分区：
文献类型：
--
作者：
S. L. Donoghue;R. Stewart;A. Palmer
Mangamate Tephra [MT]的四个成员，爆发于c。在汤加里罗山和鲁阿佩胡山环形平原的火山碎屑岩序列中可以识别，并且在形态和矿物学上与来自鲁阿佩胡山的下伏安山质火山碎屑岩不同。Mangamate火山灰主要由灰色的角石质火山砾组成，与鲁阿佩胡山的较老和较年轻的浮石火山砾形成强烈对比。三个MT成员含有镁橄榄石（fo 75 -88）。确定了两种橄榄石习性。[I]型非骨架（颗粒状或多面体）橄榄石是薄片上的半自形等长至板状晶体，仅出现在Waihohonu火山岩段中。[II]型骨架橄榄石是自形拉长，不完整的晶体与中空的内部和漏斗和H形链形态。他们被发现在Poutu Lapilli，Waihohonu Lapilli和Oturere Lapilli成员。[II]型骨架橄榄石，以前没有在北岛中部火山岩中报道，...
Abstract Four members of Mangamate Tephra [MT], erupted c. 10,000 years bp from Mt Tongariro, are identifiable in tephra sequences of both the Mt Tongariro and Mt Ruapehu ring plains, and are morphologically and mineralogically distinct from underlying andesitic tephras derived from Mt Ruapehu. Mangamate Tephra comprises dominantly grey angular lithic lapilli units, contrasting strongly with older and younger, distinctly pumiceous lapilli units from Mt Ruapehu. Three members of MT contain forsteritic olivine (fo75–88). Two olivine habits are identified. Type [I] non-skeletal (granular or polyhedral) olivines are subhedral equant to tabular crystals in thin section and occur only in Waihohonu Lapilli Member. Type [II] skeletal olivines are euhedral elongate, incomplete crystals with hollow interiors and hopper and H-shaped chain morphologies. They are found in Poutu Lapilli, Waihohonu Lapilli and Oturere Lapilli members. Type [II] skeletal olivines, not previously reported in Central North Island tephras, ...