The Chalk hills of Salem complex also called Salem mafic and ultramafic complex (SMUC), occurs in northern part of Cauvery suture zone (CSZ), southern granulite terrane (SGT), India with the lithological sequence of ultramafic cumulates, mafic intrusions of gabbros and amphibolites with quartzo-feldspathic veins and ultrapotassic dykes. Recently the complex has been described as Neoproterozoic Alaskan-type. The Ti- rich gabbros are in association with serpentinized dunites and pyroxenites in the form of several intrusions at various locations of the complex. The petrography of these gabbros shows sub-alkaline to alkaline in nature with mineralogy of two pyroxenes and plagioclases of calcicsodic assemblages along with magnetite-titanomagnetite-ilmenite (Ti-spinels). The whole rock geochemistry indicates that they are tholeiitic in nature with enrichment of LILE (Rb, Ba, Th, Sr) and depletion of HFSE (Nb, Ta, Ti) with reference to N-MORB. The mineral chemistry of clinopyroxenes from these gabbros show slightly higher Mg# (0.68–0.80), TiO 2 (0.40–0.73 wt%) with lower Al 2 O 3 (4.4–5.5 wt%), Na 2 O (0.53–0.94 wt%) and Cr 2 O 3 (0.1–0.17 wt%) contents. The orthopyroxenes also show low Al 2 O 3 (1.4–2.3 wt%), Cr 2 O 3 (up to 0.13 wt%), and relatively higher MgO (17.11–21.79 wt%). The Ti- bearing oxides (ilmenites) of these gabbros are characterized by higher contents of TiO 2 (38–51 wt%) and FeO (46–56 wt%), similar to that of Ti-Fe rich Alaskan- type of mafic rocks. On various tectonic discrimination diagrams of whole rock and clinipyroxene mineral chemistry of these gabbros reveal that they are derived from subduction related components of arc magmas of titanium rich, evolved through the process of high degree of crystal fractionation. From the two-pyroxene thermometry, the temperature of formation of these gabbros are determined as 893–1014°C and the clinopyroxene barometry results variable pressures of 8–13 kbars. The tectonic setting with the available age relationships from the complex suggest these intrusions are syntectonic and co-genetic of late emplacements along with the ultramafics during Neoproterozoic subduction events. Such occurrences of high Ti- bearing gabbros are common in many Alaskan- type of complexes like Neoproterozoic Arabian Nubian Shield and other parts of the world.

中文翻译：

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来自印度南部塞勒姆白垩山的高钛辉长岩：新元古代阿拉斯加型进化过程中的共同遗传起源

塞勒姆杂岩群的白垩山也称为塞勒姆镁铁质和超镁铁质杂岩体（SMUC），发生在印度南部麻粒岩（SGT）Cauvery缝合带（CSZ）北部，具有超镁铁质堆积、辉长岩和镁铁质侵入体的岩性序列。具有石英长石脉和超钾质岩脉的角闪岩。最近，该复合体被描述为新元古代阿拉斯加型。富含 Ti 的辉长岩与蛇纹石化的单质岩和辉石岩在复合体的不同位置以几种侵入体的形式存在。这些辉长岩的岩相学显示出亚碱性到碱性的性质，具有两种辉石的矿物学和钙钠钙石组合的斜长石以及磁铁矿 - 钛磁铁矿 - 钛铁矿（Ti 尖晶石）。整个岩石地球化学表明它们是拉斑岩，相对于 N-MORB，它们富含 LILE（Rb、Ba、Th、Sr）和耗尽 HFSE（Nb、Ta、Ti）。来自这些辉长岩的单斜辉石的矿物化学显示出略高的 Mg# (0.68–0.80)、TiO 2 (0.40–0.73 wt%) 和较低的 Al 2 O 3 (4.4–5.5 wt%)、Na 2 O (0.53–0.94 wt%) %) 和 Cr 2 O 3 (0.1–0.17 wt%) 含量。斜方辉石还显示出低 Al 2 O 3 (1.4–2.3 wt%)、Cr 2 O 3 (高达 0.13 wt%) 和相对较高的 MgO (17.11–21.79 wt%)。这些辉长岩的含钛氧化物（钛铁矿）的特点是 TiO 2 (38-51 wt%) 和 FeO (46-56 wt%) 含量较高，类似于富含 Ti-Fe 的阿拉斯加型基性岩. 在这些辉长岩的全岩和斜辉石矿物化学的各种构造判别图上显示，它们来源于富钛弧形岩浆的俯冲相关成分，通过高度的晶体分馏过程演化而来。根据双辉石温度测定法，这些辉长岩的形成温度确定为 893-1014°C，单辉石气压测定法得出的可变压力为 8-13 kbar。具有来自该复合体的可用年龄关系的构造环境表明，这些侵入是新元古代俯冲事件期间晚期侵位与超基性岩的同构造和共生的。这种高含钛辉长岩在许多阿拉斯加类型的杂岩中很常见，例如新元古代阿拉伯努比亚地盾和世界其他地区。