Origin and Metamorphism of Corundum‐Rich Metabauxites at Mt. Ismail in the Southern Menderes Massif, SW Turkey
Origin and Metamorphism of Corundum‐Rich Metabauxites at Mt. Ismail in the Southern Menderes Massif, SW Turkey
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土耳其西南部门德雷斯地块南部伊斯梅尔山富刚玉变铝土矿的成因和变质作用
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发表时间：
2012
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通讯作者：
M. Moazzen
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作者：
M. Aydoğan;M. Moazzen
富镁变质辉石，发现在西北翼的东北-西南走向的等斜卧褶皱在山。Ismail，被封闭在晚白垩世时代的厚层平台型大理石中，围绕着Menderes Massif（土耳其西南部）南部的多变质核心系列。观察到的变质层位为典型的石香肠状结构，横向延伸到c。3公里，1至5米厚。 这些岩石的主要矿物组合为方解石（1050模态%）、氯云母（1030模态%）、白色云母（珍珠云母、白云母）、一水硬铝石、铁-钛氧化物（钛铁矿、钛铁矿、金红石）和针铁矿、褐铁矿、黄铁矿、电气石（黑云母、黑云母）作为次要相。全岩化学分析和矿物组合表明，变质铝土矿的共生矿物为高铝。一些矿物（如绿帘石和珍珠云母）显示出很大的成分变化，反映了岩溶铝土矿的初始化学不均匀性。野外观察、微量元素富集系数、Cr、Zr、Ga和Ni等元素的浓度以及少量的不动元素都表明，所研究的富镁变铝土岩可归类为岩溶铝土岩，更可能是中间火成岩或泥质母岩风化的产物，类似于中陶里德斯（Seydi Zahehir地区）的岩溶牛尿铝土矿，可能年龄相似（Cenomanian-Turonian）。在构造-变质演化方面，所研究的富镁变质辉石在500 - 600°C和500-600 kbar压力下发生区域变质，这是Barrovian变质作用的结果，称为“主门德里斯变质作用”，与中始新世期间从伊兹密尔-安卡拉缝合线到门德里斯台地上的蛇绿岩仰冲有关。
The corundum‐rich metabauxites, found at the northwest limb of an NE–SW‐trending isoclinal recumbent fold at Mt. Ismail, are enclosed in thick‐bedded platform‐type marbles of Late Cretaceous age, surrounding the polymetamorphic core series in the southern part of the Menderes Massif (SW Turkey). The metabauxite horizons observed as typically boudine‐like structure, extend laterally over c. 3 km and are 1 to 5 m thick. These rocks have dominant mineral assemblages of corundum (∼50 modal %), chloritoid (∼30 modal %), white mica (margarite, muscovite), diaspore, Fe–Ti‐Oxides (ilmenite, ilmenohematite, rutile), and goethite, limonite, pyrite, tourmaline (uvite, schorl) as minor phases. Chemical analyses of whole rock samples and the mineral assemblage indicate that coexisting minerals of metabauxites are highly aluminous. A number of minerals (e.g. chloritoid and margarite) display a large compositional variation reflecting the initial chemical inhomogenetiy of the karstbauxites. The field observations, trace‐element accumulation coefficients, concentration of elements such as Cr, Zr, Ga and Ni and low amounts of immobile elements all suggest that the studied corundum‐rich metabauxites can be classified as karstbauxites, and are more likely to be a product of weathering of intermediate igneous or argillaceous parental rocks, similar to the karstic Tauric bauxites in the Central Taurides (Seydi şehir region) and probably are similar in age (Cenomanian–Turonian). In respect of tectono‐metamorphic evolution, the studied corundum‐rich metabauxites were regionally metamorphosed at ∼5–6 kbar pressure and 500–600°C as a consequence of the Barrovian metamorphism referred to as the ‘Main Menderes Metamorphism’ related to the ophiolitic obduction onto the Menderes platform from the Izmir–Ankara Suture during the Middle Eocene.