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首页> 外文期刊>Contributions to Mineralogy and Petrology >Ar-40/Ar-39 geochronology, geochemistry and petrology of volcanic rocks from the Simav Graben, western Turkey
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Ar-40/Ar-39 geochronology, geochemistry and petrology of volcanic rocks from the Simav Graben, western Turkey

机译：土耳其西部Simav Graben火山岩的Ar-40 / Ar-39地质年代，地球化学和岩石学

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摘要

Major and trace element compositions with Sr-Nd isotopic ratios, as well as Ar-Ar radiometric ages of the Miocene volcanic rocks from the Neogene units around Simav region (western Anatolia), are used to discuss the genetic relationship between (1) high-voluminous Lower-Middle Miocene high-potassic, calc-alkaline (HKCA) and (2) Middle Miocene small-voluminous high-MgO shoshonitic-ultrapotassic (SHO-UK) magmatic units in the region. All the HKCA rocks, including basaltic to rhyolitic (and granitic) samples, share similar trace element characteristics (enrichments of LILE and LREE and depletions in HFSE as a common feature of orogenic magmatic rocks), with subtle differences in their Sr-87/Sr-86((i)) ratios (basalts and rhyolites similar to 0.708, dacites similar to 0.710). Most of the samples of the high-MgO SHO-UK group are classified as shoshonite and latite, with some lamproites, sharing similar geochemical features with the other ultrapotassic rocks of the Mediterranean. All the rock groups have similar and high abundances of incompatible trace elements, and radiogenic Sr. Geochemical modeling of the trace element and isotopic ratios of the samples reveals that both the SHO-UK and HKCA groups were derived from a common mantle source which had been highly metasomatized and enriched by continental materials during partial subduction of the crustal metamorphic slices in a continental collision setting. The geochemical variations of these rocks were mainly controlled by source characteristics (such as heterogeneity) and variable degrees of partial melting and subsequent effects of fractional crystallization, with low degrees of crustal contamination. The HKCA series were derived by higher degrees of partial melting of the lithospheric mantle source than the SHO-UK rocks. The HKCA rocks then underwent two-stage fractional crystallization (clinopyroxene-dominated followed by feldspar-dominated fractionating mineral assemblages) to form the high-K calc-alkaline basalt to rhyolite series, whereas the SHO-UK rocks experienced comparatively little fractional crystallization. A tectonic scenario involving the rapidly extending and thinning of orogenic crust is compatible with the time-dependent compositional variation of the magmatic rocks.
机译：使用具有Sr-Nd同位素比的主要和微量元素组成，以及来自Simav地区（西安纳托利亚西部）新近纪单元的中新世火山岩的Ar-Ar辐射年龄，来讨论（1）高该地区有大量的中下新世高钾钙碱性（HKCA）和（2）中新世中小镁高含量的镁铁质钾盐超低钾（SHO-UK）岩浆单元。所有HKCA岩石，包括玄武质到流纹岩（和花岗质）样品，都具有相似的痕量元素特征（LILE和LREE的富集以及HFSE中的损耗是造山岩浆岩的共同特征），其Sr-87 / Sr有细微差别-86（（i））比率（玄武岩和流纹岩相似，为0.708，dacites近似为0.710）。高MgO SHO-UK组的大多数样品被分类为shoshonite和latite，带有一些斑岩，与地中海的其他超钾盐岩具有相似的地球化学特征。所有岩石组都具有相似且高含量的不相容微量元素，并且放射成因的Sr.样品的微量元素和同位素比的地球化学模型显示，SHO-UK和HKCA组均来自相同的地幔源。在大陆碰撞环境中，部分地壳变质带俯冲过程中，大陆物质高度交化和富集。这些岩石的地球化学变化主要受烃源特征（如非均质性）和部分熔融程度的变化以及随后部分结晶的影响（地壳污染程度较低）的控制。 HKCA系列是由于岩石圈地幔源的部分熔融程度高于SHO-UK岩石而得出的。然后，HKCA岩石经历了两个阶段的分步结晶（由斜发rox为主，然后由长石为主的分馏矿物组合）形成高K钙碱性玄武岩至流纹岩系列，而SHO-UK岩石经历了相对较少的分步结晶。涉及造山壳迅速扩展和变薄的构造场景与岩浆岩随时间变化的成分变化是相容的。

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