The Deccan Volcanic Province (DVP), covering presently an area of 0.5 million km2, and estimated to be 2–3 times larger during the Upper Cretaceous-Paleocene, is one of the largest continental flood basalt provinces of the world. Its formation has been linked to the foundering of the Gondwanaland and Greater India’s northward drift, passing over the Reunion plume and eruption of over a million km3 of lava that apparently led to a mass extinction of global proportions. The DVP has thus been a major domain of scientific interest and study the world over. It had received attention since the 1830s, first from the army and civil service men of the British Raj and subsequently from the officers of the Geological Survey of India (GSI) founded in 1851, and academicians from a number of Indian Universities and research Institutions, often in collaboration with geologists from countries such as the UK, USA, Russia, France, Japan, Italy and others. Thus, studies of the DVP conducted for over 170 years, and especially in the last five decades, have provided a very large database that has led to a better understanding of the genesis and evolution of the this province and similar flood basalt provinces of the world. The DVP is thickest in the Western Ghats, forming many individual 400 m to 1650 m thick sections over some 700 km. The structural evolution of the lava sequence envisages a pre-uplift, thick (c. 2–3 km), lensoid pile of dense basalt that gradually sank into the crust by the end of the eruptive phase, followed by an uplift of the western margin of the Deccan due to both denudational-isostasy reasons and the associated geomorphological and structural evolution of the lava pile from Tertiary uplift and coastal flexure formation (the Panvel structure). Such an evolution has led to stresses that get accommodated along fractures in the pre-Deccan basement at varying depths and apparently provide the loci for seismicity observed over the province. The DVP is predominantly composed of quartz- and hypersthene-normative tholeiitic basalts in the plateau regions (Western Ghats and adjoining central and eastern parts, Malwa and Mandla). However, along the ENE-WSW-trending Narmada-Tapi rift zones, the N-S to NNW-SSE-trending Western coastal tract, the Cambay rift zone, and the Saurashtra and Kutch regions, the DVP shows considerable diversity in terms of structures, dyke swarms and dyke clusters, and intrusive and extrusive centres with diverse rock types. These include: primary picrite basalts and their differentiates (e.g., Botad, Dhandhuka, Wadhwan Jn., Pavagadh), granophyre-rhyolite intrusive ring-complexes and mixed basalt-rhyolite associations (e.g., Alech, Barda, Osham, Chogat-Chamardi, Mumbai Island, and others), carbonatite-nephelinite associations (Amba Dongar-Kawant), gabbro-anorthosite-nepheline syenite-syenite ring/layered complexes(e.g., Mt. Girnar, Mundwara, Phenai Mata), mantle-derived spinel peridotite-hosting melanephelinites and basanites (e.g. Dhrubya, Vethon and others in Kutch), besides scores of alkaline and lamprophyre dykes. Some of these complexes are associated with high gravity anomalies indicating dense plutonic bodies at depths. Flow morphological studies of the DVP have led to the recognition of two main types of flows, namely ‘a’a (typically forming simple, sheet flows) and pâhoehoe (typically forming compound, pahoehoe lobate flows) with transitions between them that result in mixed types. The ‘a’a types are largely single units found in the peripheral parts where thicknesses of the flow sequence range from a few meters to a few tens of meters. The compound pâhoehoe flows contain many units or lobes and are largely found in the thicker sections of Western Ghats, and also in the central parts of the province. The flow sequences of the Western Ghats (c. 400 m to 1650 m thick and spread over an area of400 km × 100 km along the N-S tract from north of Nasik to Belgaum) have been mapped and correlated using flow morphology, petrology and selected trace elements (Sr, Ba, Zr, Y and Ti) and Sr- isotopes. Such a combination of geochemical characters, constrained further by altitude and magnetic polarity (chrons 30N-29R-29N) have led to the delineation of the flow sequences from north to south into a Deccan Basalt Group, comprising three Subgroups from the base to the top, namely the Kalsubai, Lonavala and Wai Subgroups, with twelve (12) formations in total, each formation containing many flows. Giant plagioclase basalts (GPBs) and bole beds of diverse origin (intertrappean sediments, weathered basalt or tuffs with baking effects) have been found in many flow sequences of the DVP, especially in the Western Ghats and contiguous plateau regions, and these interflow units help in subregional-scale mapping and also provide insights into magma chamber processes and eruptive breaks in the volcanic cycles. Field and geochemical studies of some twenty-three (23) flow sequences (10 from Western Ghats, five from central India and eight from eastern India) by several groups have enabled correlation of some formations of the Western Ghats such as the Ambenali (crustally uncontaminated) and Poladpur (contaminated) over long distances (c. 400–700 km) to Toranmal, Mhow, Chikaldara, Jabalpur and other sections. However, these formations occur at different stratigraphie elevations at these places and also differ in some isotopic characters (e.g. 206Pb/204Pb). Such features have cast doubts on long distance travel of flows from a single source and led to suggestions of multiple source areas (vents and dykes) as also inferred from the two zones of compositional diversity mentioned above. Based on detailed field, petrological and geochemical characters including isotopic data and Ar-Ar ages, dyke swarms and clusters in the Narmada-Tapi and western coastal tracts have been shown to belong to two groups: (1) The randomly oriented group between Pune and Nasik as possible feeders to the lava flow sequences of the Western Ghats and (2) Some of the dykes from the east-west-oriented Narmada-Tapi swarm, attributed to active N-S extension during the flood basalt episode, and showing chemical affinities to the lower and middle formations (Jawhar, Igatpuri, Neral, Thakurwadi, Bhimashankar, Khandala). A wide variety of petrographic types of basalts have been observed in the DVP attesting to the diverse crystallisation and differentiation of the different magma types during transport and in magma chambers. Based on petrographic and mineralogical data from a number of thick sections, it has been inferred that minerals such as olivine (Fo90–Fo20), clinopyroxenes (diopsidic augite, augite, subcalcic augite and pigeonite), plagioclase (An84–An30) and opaque oxides including spinels show considerable variations depending upon the tholeiitic or alkaline character of the host magma and its degree of evolution. Secondary minerals, especially zeolites such as heulandite and stilbite, are found in all the ten formations of the Western Ghats whereas merlionite and analcite are only found in the Khandala Formation. Other ten species are of variable abundance are found in the ten formations of the Western Ghats and other areas. Zeolite zonation in DVP suggested earlier has not been substantiated by recent studies, instead multigeneration of secondary minerals in cavities is attributed to late hydrothermal activity from Paleocene to early Miocene.

中文翻译：

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印度德干火山省 (DVP)：回顾

德干火山省 (DVP) 目前覆盖面积 50 万平方公里，估计在上白垩统-古新世期间面积增加 2-3 倍，是世界上最大的大陆洪水玄武岩省之一。它的形成与冈瓦纳大陆和大印度向北漂移的沉没有关，经过留尼汪岛的羽流和超过一百万平方公里的熔岩喷发，显然导致了全球范围内的大规模灭绝。因此，DVP 已成为科学兴趣和研究世界的主要领域。自 1830 年代以来，它首先受到英国统治的军队和公务员的关注，随后受到成立于 1851 年的印度地质调查局 (GSI) 的官员以及来自一些印度大学和研究机构的院士的关注，经常与来自英国、美国、俄罗斯、法国、日本、意大利等国家的地质学家合作。因此，对 DVP 进行了 170 多年的研究，特别是在过去的 50 年中，提供了一个非常大的数据库，使人们更好地了解该省和世界上类似洪水玄武岩省的起源和演变。 . DVP 在西高止山脉最厚，在大约 700 公里的范围内形成了许多单独的 400 m 至 1650 m 厚的部分。熔岩序列的结构演化设想了一个前隆起、厚（约 2-3 公里）、透镜状的致密玄武岩堆，在喷发阶段结束时逐渐沉入地壳，由于剥蚀均衡的原因以及第三纪隆起和海岸弯曲形成（Panvel 结构）熔岩堆的相关地貌和结构演化，德干河西缘隆起。这种演变导致应力沿着前德干基底中不同深度的裂缝得到调节，显然为全省观测到的地震活动提供了位置。DVP 主要由高原地区（西高止山脉和毗邻的中部和东部地区，马尔瓦和曼德拉）的石英和超硬质拉斑玄武岩组成。然而，沿着 ENE-WSW 走向的 Narmada-Tapi 裂谷带、NS 到 NNW-SSE 走向的西部沿海地区、Cambay 裂谷带以及 Saurashtra 和 Kutch 地区，DVP 在构造、岩脉群和岩脉簇、侵入和喷出中心以及不同岩石类型方面表现出相当大的多样性。这些包括：原生苦英岩玄武岩及其分化岩（例如，Botad、Dhandhuka、Wadhwan Jn.、Pavagadh）、花岗岩-流纹岩侵入环复合体和混合玄武岩-流纹岩组合（例如，Alech、Barda、Osham、Chogat-Chamardi、Mumbai岛等）、碳酸岩-霞石组合（Amba Dongar-Kawant）、辉长岩-斜长岩-霞石-正长岩-正长岩环/层状复合体（例如，Mt. Girnar、Mundwara、Phenai Mata）、地幔衍生的尖晶石橄榄岩-托管黑斑岩和 basanites（例如 Dhrubya、Vethon 和 Kutch 的其他人），此外还有许多碱性和斑岩岩脉。这些复合体中的一些与表明深部致密深成体的高重力异常有关。DVP 的流动形态研究导致人们认识到两种主要类型的流动，即 'a'a（通常形成简单的片状流）和 pâhoehoe（通常形成复合，pahoehoe lobate 流），它们之间的过渡导致混合类型。'a'a 类型主要是在流动序列的厚度范围从几米到几十米的外围部分中发现的单个单元。复合 pâhoehoe 流包含许多单元或裂片，主要位于西高止山脉的较厚部分以及该省的中部地区。西高止山脉的流动序列（c. 400 m 到 1650 m 厚，沿着从 Nasik 以北到 Belgaum 的 NS 道分布在 400 km × 100 km 的区域内）已经使用流动形态学、岩石学和选定的微量元素（Sr、Ba、Zr、Y 和Ti)和Sr-同位素。这种地球化学特征的组合，进一步受到高度和磁极（年代数 30N-29R-29N）的限制，导致从北到南的流动序列被划定为一个德干玄武岩群，包括从底部到顶部的三个亚群，即 Kalsubai、Lonavala 和 Wai 子群，共有十二 (12) 个地层，每个地层包含许多流。在 DVP 的许多流动序列中发现了巨大的斜长石玄武岩 (GPB) 和不同来源的岩床（圈层沉积物、风化玄武岩或具有烘焙效应的凝灰岩），尤其是在西高止山脉和毗连的高原地区，这些互流单元有助于进行次区域尺度的测绘，还有助于深入了解岩浆房过程和火山循环中的喷发中断。几个小组对大约二十三 (23) 个流动序列（10 个来自西高止山脉，5 个来自印度中部，8 个来自印度东部）进行了实地和地球化学研究，已经能够将西高止山脉的一些地层，例如 Ambenali（地壳未受污染) 和 Poladpur（受污染）长距离（约 400-700 公里）到 Toranmal、Mhow、Chikaldara、Jabalpur 和其他部分。然而，这些地层出现在这些地方的不同地层高程，并且在某些同位素特征（例如206Pb/204Pb）上也不同。这些特征使人们对来自单一来源的水流的长距离传播产生了怀疑，并提出了多个源区（喷口和堤坝）的建议，这也是从上述两个组成多样性区域推断出来的。根据详细的野外、岩石学和地球化学特征，包括同位素数据和 Ar-Ar 年龄，Narmada-Tapi 和西部沿海地区的岩墙群和簇已被证明属于两个组：（1）Pune 和Nasik 可能是西高止山脉熔岩流序列的馈源，以及 (2) 一些来自东西向的 Narmada-Tapi 群的堤坝，归因于洪水玄武岩事件期间活跃的 NS 延伸，并显示出与下层和中层（Jawhar、Igatpuri、Neral、Thakurwadi、Bhimashankar、Khandala）。在 DVP 中观察到了各种各样的玄武岩岩相类型，证明了不同岩浆类型在运输过程中和岩浆房中的不同结晶和分化。根据多个厚剖面的岩石学和矿物学数据，推断橄榄石 (Fo90-Fo20)、单斜辉石（透辉辉石、辉石、亚钙辉石和变辉石）、斜长石（An84-An30）和不透明氧化物等矿物包括尖晶石在内的岩浆显示出相当大的变化，这取决于宿主岩浆的拉斑或碱性特征及其演化程度。次生矿物，尤其是沸石，如沸石和辉沸石，在西高止山脉的 10 个地层中均有发现，而墨长石和方沸石仅在坎达拉地层中发现。在西高止山脉和其他地区的 10 个地层中发现了其他 10 个物种的丰度可变。早先提出的 DVP 中的沸石分带尚未得到最近研究的证实，相反，洞穴中的多代次生矿物归因于从古新世到中新世早期的晚期热液活动。