斯洛伐克西喀尔巴阡山脉Veporic单元榴辉岩相变质镁铁岩

IF 1 4区 地球科学 Q4 GEOSCIENCES, MULTIDISCIPLINARY
M. Janák, Š. Méres, L. Medaris, Jr.
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引用次数: 2

摘要

西喀尔巴阡山脉Veporic单元变质岩与榴辉岩密切相关,记录了复杂的P-T演化过程,包括高压变质作用的影响。所研究的变超镁铁石化学性质与辉石岩相似,具有细至中粒结构,主要由橄榄石和角闪石组成,并含有少量石榴石、正辉石、尖晶石、绿泥石、钛铁矿和碳酸盐。高压矿物组合为石榴石(XMg = 0.46 ~ 0.47) +橄榄石(XMg = 0.71 ~ 0.73) +低铝正辉石(XMg = 0.77 ~ 0.78);Al = 0.02 ~ 0.03 apfu) +钛铁矿+绿泥石(XMg = 0.87 ~ 0.89) + cr尖晶石。富铬尖晶石极有可能是前hp变质期的遗留物,可能是岩浆成因。采用石榴石-正辉石Fe-Mg交换温度计、al -in-正辉石气压计和SiO2-TiO2 - Al2O3-FeO-MgO-CaO-H2O体系的热力学模拟计算表明,变质的峰值条件为2.4±0.4 GPa和702±20℃。随后的减压和退变记录为铝直辉石的形成,al尖晶石和角闪石的复合体(角闪石)取代石榴石,cr尖晶石转变为al尖晶石,并在基体中形成丰富的角闪石。因此,除了伴生榴辉岩的证据外,Veporic单元的变质铁质岩石也为西喀尔巴阡山脉前高山基底的高压变质提供了证据,这种高压变质最有可能发生在Variscan时代。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Eclogite facies metaultramafite from the Veporic Unit (Western Carpathians, Slovakia)
Metaultramafic rocks closely associated with eclogites in the Veporic unit of the Western Carpathians record a complex P–T evolution, including the effects of high-pressure (HP) metamorphism. The investigated metaultramafite is chemically similar to pyroxenite, has a fineto medium-grained texture, is composed predominantly of olivine and amphibole, and contains minor amounts of garnet, orthopyroxene, spinel, chlorite, ilmenite and carbonates. The highpressure mineral assemblage is garnet (XMg = 0.46–0.47) + olivine (XMg = 0.71–0.73) + low-Al orthopyroxene (XMg = 0.77–0.78; Al = 0.02–0.03 apfu) + ilmenite + chlorite (XMg = 0.87–0.89) + Cr-spinel. Chromium-rich spinel is most likely a relict from the pre-HP metamorphic stage, possibly of magmatic origin. Calculations using a garnet– orthopyroxene Fe–Mg exchange thermometer, Al-in-orthopyroxene barometer, and thermodynamic modelling in the system SiO2–TiO2– Al2O3–FeO–MgO–CaO–H2O indicate that the peak conditions of metamorphism reached 2.4±0.4 GPa and 702±20 °C. Subsequent decompression and retrogression is recorded by the formation of aluminous orthopyroxene, replacement of garnet by symplectites of Al-spinel and amphibole (hornblende), transformation of Cr-spinel to Al-spinel and formation of abundant amphibole in the matrix. Metaultramafic rocks in the Veporic unit thus provide evidence, in addition to that from associated eclogites, for high-pressure metamorphism in the pre-Alpine basement of the Western Carpathians, which is most likely of Variscan age.
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来源期刊
Geologica Carpathica
Geologica Carpathica 地学-地球科学综合
CiteScore
2.40
自引率
23.10%
发文量
26
审稿时长
>12 weeks
期刊介绍: GEOLOGICA CARPATHICA covers a wide spectrum of geological disciplines including geodynamics, tectonics and structural geology, volcanology, stratigraphy, geochronology and isotopic geology, karstology, geochemistry, mineralogy, petrology, lithology and sedimentology, paleogeography, paleoecology, paleobiology and paleontology, paleomagnetism, magnetostratigraphy and other branches of applied geophysics, economic and environmental geology, experimental and theoretical geoscientific studies. Geologica Carpathica , with its 60 year old tradition, presents high-quality research papers devoted to all aspects not only of the Alpine-Carpathian-Balkanian geoscience but also with adjacent regions originated from the Mediterranean Tethys and its continental foreland. Geologica Carpathica is an Official Journal of the Carpathian-Balkan Geological Association.
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