Eocene calc-alkaline volcanic rocks related to Cenozoic episodic magmatism during Neo-Tethyan subduction, Tarom–Hashtjin Belt, NW Iran

IF 1.4 4区地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS

Mineralogy and Petrology Pub Date : 2024-07-24 DOI:10.1007/s00710-024-00865-2

Ashraf Torkian, Tanya Furman, Ibrahim Tale Fazel, Nayer Ajalli

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Abstract

The Eocene Rasht-Abad volcanic rocks are located in the Alborz-Azerbaijan magmatic belt (including the Tarom-Hashtjin province) of NW Iran. Those are mainly mafic to intermediate with calc-alkaline affinities, comprising andesite, andesite-basalt, trachy-andesite, and dacite. Clinopyroxene ranging in composition from diopside to augite is the most significant mafic mineral of the basic rocks. Aluminum partitioning between tetrahedral and octahedral sites shows that those crystalized at low pressure. Ferric iron of clinopyroxene also indicates high oxygen fugacity for formation of crystal. Geothermobarometry using clinopyroxene-melt equilibrium calculations constrains the crystallization temperature and pressure of this mineral as 1100–1200 °C and 2–6 kbar. Ce/Pb values of the mafic lavas are lower than values expected for mantle-derived melts but do not support crustal contamination. Co-existing basalt to trachyandesite lavas display parallel and tight REE patterns that suggest these rocks originated from a common mantle source or parental magma. Tectonomagmatic discrimination diagrams and mineral compositions are consistent with the host volcanic rocks having the characteristics of continental margin arcs. Geochemical data are consistent with the parental magma of mafic-intermediate rocks of Rasht-Abad area being derived from a typical subcontinental lithospheric mantle which was enriched by subducted slab-derived fluids and melts during tectonic events in the active continental margin. The data support a model of Eocene flare-up magmatism associated with rollback of a flattened slab.

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伊朗西北部塔罗姆-哈什津带始新世钙碱性火山岩与新生代新泰西俯冲过程中的偶发岩浆活动有关

始新世的拉什特-阿巴德火山岩位于伊朗西北部的阿尔伯兹-阿塞拜疆岩浆岩带（包括塔罗姆-哈什津省）。这些火山岩主要是黑云母岩到中间岩，具有钙碱性，包括安山岩、安山岩-玄武岩、闪长岩-安山岩和英安岩。基性岩中最重要的黑云母矿物是霞石，其成分从透辉石到辉石不等。四面体和八面体位点之间的铝分配显示，这些矿物是在低压下结晶的。霞石的铁质也表明晶体的形成具有较高的富氧性。利用clinopyroxene-熔融平衡计算得出的地球热压测定法将这种矿物的结晶温度和压力限制在1100-1200 °C和2-6千巴。黑云母熔岩的Ce/Pb值低于地幔熔体的预期值，但不支持地壳污染。同时存在的玄武岩和闪长岩熔岩显示出平行和紧密的 REE 模式，表明这些岩石源自共同的地幔源或母岩浆。构造地貌判别图和矿物成分与具有大陆边缘弧特征的主火山岩一致。地球化学数据表明，拉什特-阿巴德地区的岩浆岩母岩来自典型的次大陆岩石圈地幔，该地幔在活动大陆边缘的构造事件中被俯冲板块衍生的流体和熔体富集。这些数据支持与扁平板块回滚有关的始新世爆发岩浆活动模型。

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来源期刊

Mineralogy and Petrology 地学-地球化学与地球物理

CiteScore

2.60

自引率

0.00%

发文量

审稿时长

1 months

期刊介绍： Mineralogy and Petrology welcomes manuscripts from the classical fields of mineralogy, igneous and metamorphic petrology, geochemistry, crystallography, as well as their applications in academic experimentation and research, materials science and engineering, for technology, industry, environment, or society. The journal strongly promotes cross-fertilization among Earth-scientific and applied materials-oriented disciplines. Purely descriptive manuscripts on regional topics will not be considered. Mineralogy and Petrology was founded in 1872 by Gustav Tschermak as "Mineralogische und Petrographische Mittheilungen". It is one of Europe''s oldest geoscience journals. Former editors include outstanding names such as Gustav Tschermak, Friedrich Becke, Felix Machatschki, Josef Zemann, and Eugen F. Stumpfl.