Abstract Deccan Traps (DT) volcanism and the Chicxulub bolide impact have been suggested as potential triggers of the Cretaceous–Paleogene boundary (KPB) mass extinction. Recently published geochronology has established a timeline for the main basaltic sequence of the DT, showing that the majority of eruptions occurred within 700–800 kyr spanning the KPB. Silicic to alkaline magmatism linked to the DT, spatially associated with the Narmada lineament in central India, has been long known but not as well studied. Previous geochronology of some of the felsic magmatic centers has yielded dates that span many millions of years, making their temporal relationship with DT volcanism uncertain. We present zircon U-Pb ages from the Alech, Barda, Girnar, Rajula and Phenai Mata silicic–alkaline complexes, in addition to a series of trachytes on the coastal plain near Mumbai. While the trachytes are ∼64 Ma and mark the continental breakup of India ∼1.5 Myr after the main phase of DT eruptions, the silicic-alkaline complexes were all emplaced coevally with the main phase of DT volcanism ca. 66.2-65.7 Ma. Initial eHf in zircons (+10 to -20), whole-rock 87Sr/86Sr (0.702439-0.760932) and eNd (+1.11 to -35.7) for all five intrusive complexes suggest a hybrid origin involving juvenile sources as well as significant assimilation of older continental crust. Recognition that the silicic-alkaline complexes are coeval with basaltic magmatism and associated with a significant thermal imprint on the crust in and near the Narmada rift sedimentary strata supports the hypothesis that outgassing of organic-rich sediments may have contributed to the end-Maastrichtian warming and biologic crisis.

中文翻译：

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与德干圈闭溢流玄武岩同步的广泛硅质和碱性岩浆作用，印度

摘要 德干圈闭 (DT) 火山作用和希克苏鲁伯火流星撞击被认为是白垩纪-古近系边界 (KPB) 大规模灭绝的潜在触发因素。最近发表的地质年代学已经为 DT 的主要玄武岩序列建立了时间表，表明大部分喷发发生在跨越 KPB 的 700-800 kyr 内。与 DT 相关的硅质至碱性岩浆作用，在空间上与印度中部的纳尔马达 (Narmada) 构造有关，早已为人所知，但并未得到充分研究。一些长英质岩浆中心以前的地质年代学已经产生了跨越数百万年的日期，使得它们与 DT 火山活动的时间关系不确定。我们展示了来自 Alech、Barda、Girnar、Rajula 和 Phenai Mata 硅-碱性复合物的锆石 U-Pb 年龄，除了孟买附近沿海平原上的一系列粗面。虽然粗面约为 64 Ma，标志着 DT 喷发主阶段后印度大陆分裂 1.5 Myr，但硅-碱性复合物都与 DT 火山活动的主阶段同时侵位。66.2-65.7 毫安。锆石的初始 eHf（+10 至 -20）、全岩 87Sr/86Sr（0.702439-0.760932）和 eNd（+1.11 至 -35.7）所有五个侵入复合体表明混合起源涉及幼年来源以及显着的同化较旧的大陆地壳。