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首页> 外文期刊>Lithos: An International Journal of Mineralogy, Petrology, and Geochemistry >Petro-geochemistry, Sr-Nd isotopes and Ar-40/Ar-39 ages of fractionated alkaline lamprophyres from the Mount Girnar igneous complex (NW India): Insights into the timing of magmatism and the lithospheric mantle beneath the Deccan Large Igneous Province
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Petro-geochemistry, Sr-Nd isotopes and Ar-40/Ar-39 ages of fractionated alkaline lamprophyres from the Mount Girnar igneous complex (NW India): Insights into the timing of magmatism and the lithospheric mantle beneath the Deccan Large Igneous Province

机译：石油地球化学，SR-ND同位素和Ar-40 / Ar-39岁的分级碱性乳液从吉尔诺伊山（NW印度）（NW印度）：洞察岩浆广告中的时序和Deccan大火省下方的岩石

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摘要

Mount Gimar is one of the most conspicuous alkaline complexes (gabbro-diorite-syenite-lamprophyre), which intrude some of the earliest erupted basalts (ca. 69 Myr) of the Deccan Large Igneous Province (Deccan LIP) in the Kathiawar plateau of NW India. Petrography, bulk-rock geochemistry, Sr and Nd isotopes and Ar-40/Ar-39 mineral ages of fractionated (Mg#: 36.3-43.6) lamprophyre dykes (younger intrusives) are reported from two widely separated domains from Mt. Gimar. Petrography and mineral chemistry reveal that major mineral assemblages (pargasite and kaersutite varieties of amphibole, diopside, biotite and feldspar) in the lamprophyres are pristine and devoid of alteration. The lamprophyres belong to the alkaline variety in general and the camptonite - monchiquite series in particular. The bulk-rock major and trace elements of the Girnar lamprophyres display very good correlation with each other and also with those of associated rocks (syenites, diorites and gabbros) which support their genetic relationship. Trace-element ratios do not evidence crustal contamination and reveal derivation of the lamprophyres from partial melting of a lithospheric mantle source significantly modified by interaction with asthenospheric-derived melts, and resembles other alkaline rocks from the Deccan LIP in this regard. Initial( 87)Sr/Sr-86 (0.7052-0.7053) and Nd-143/Nd-144 (0.5125-0.5127) of the Girnar lamprophyres and associated rocks such as syenite, diorite and gabbro are tightly clustered and further attest to their derivation from a cogenetic parental melt. Their positive sNd, values (+0.8 to +3.4) require a mantle source that has experienced moderate long-term depletion of light rare-earth elements. Neoproterozoic/Early Cambrian depletedmantle (T-DM) Nd model ages of similar to 414-588 Myr are closer to the timing of break-up of the Rodinia supercontinent as well as coincide with the Ediacaran-Cambrian Malagasy orogeny. Ar-40/Ar-39 dating of three mineral separates (amphibole and biotite) from the lamprophyres gave precise plateau ages of 65.9 = 03 Myr to 66.1 +/- 0.4 Myr demonstrating that the emplacement of the Mt. Girnar igneous complex was close to the Cretaceous-Paleogene boundary. The emplacement of a range (110 Myr to 68.5 Myr) of other spatially related alkaline as well as silicic plutonic complexes, such as the Mundwara, Sarnu-Dandali, and Barda complexes prior to the main flood basalt event at ca. 66.0-65.1 Myr, highlights the role of extensional events in pre-existing rift/fault zones preceding the plume-lithosphere interaction in the Deccan LIP. (C) 2020 Elsevier B.V. All rights reserved.
机译：Mount Gimar是最引人注目的碱性综合体（Gabbro-Diorite-Syenite-Lamprophyre）之一，它侵入了在Kathiawar高原的Deccan大火植物（Deccan Lip）的一些最早爆发的沼泽地（CA.69 Myr）。印度。据报道，分级（Mg＃：36.3-43.6）的两种广泛分离的结构域，散流，岩石地球化学，Sr和Nd同位素和Ar-40 / Ar-39矿物老年矿物老年人的含量。岩画和矿物化学揭示了林普罗斯中主要矿物组合（旁吡酯，锥形，生物烟灰岩和长桥）是原始的并且没有改变。林普罗斯通常属于碱性品种，特别是Camppiquite系列。 Girnar LamproShyres的体积岩石主要和微量元素与支持其遗传关系的相关岩石（Syenites，Diorites和Gabbros）彼此呈现非常好的相关性。痕量元素比不是证据存在的地壳污染，并揭示裂解岩石晶体的偏移，通过与哮喘衍生的熔体相互作用显着改性，并且在这方面类似于来自甲板唇的其他碱性岩石。初始（87）SR / SR-86（0.7052-0.7053）和ND-143 / ND-144（0.5125-0.5127）的GIRNAR LAM膀胱和相关岩石如Syenite，Diorite和Gabbro是紧密聚集的，并进一步证明它们的衍生物来自泌尿病的祖父融化。它们的阳性SND，值（+0.8至+3.4）需要一种壮观的轻度稀土元素的中等长期消耗的地幔源。 NeoProteroZoic /早期寒武纪脱绒型（T-DM）类似于414-588 MYR的型号更加接近罗西尼亚超镇的分解的时间，以及与埃德拉曼 - 寒武纪马达糖洋葱巧克力重合。来自林膀胱的三种矿物分离的Ar-40 / Ar-39约会，从林百瑞斯进行了精确的平台年龄65.9 = 03 Myr至66.1 +/- 0.4 Myr，证明了Mt.Girnar Igneous Complex的施加接近白垩纪 - 古近界。其他空间相关碱性和硅质型复合物的范围（110 MYR至68.5 MYR），例如MUNDWARA，SARNU-DANDALI和BARDA复合物，如CA的主要洪水玄武岩事件前。 66.0-65.1 MYR，突出了在Deccan唇部羽毛球圈相互作用之前的存在预先存在的裂口/断层区中的扩展事件的作用。 （c）2020 Elsevier B.V.保留所有权利。

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