40Ar/39Ar geochronology and geochemistry of the Central Saurashtra mafic dyke swarm: insights into magmatic evolution, magma transport, and dyke-flow relationships in the northwestern Deccan Traps

Geochemistry of Deccan Tholeiite Flows and Dykes of Elephanta Island: Insights into the Stratigraphy and Structure of the Panvel Flexure Zone, Western Indian Rifted Margin

“…TiO 2 and Al 2 O 3 contents in augite and ferroaugite are low (0-2.6 wt.% TiO 2 and 0.6-5.9 wt.% Al 2 O 3 ). The pyroxenes of the Elephanta rocks analyzed in this study lie within the field defined by the pyroxenes of Deccan rocks [53][54][55][56] (Figure 5b). Equilibration temperatures of groundmass clinopyroxenes and pigeonites in the Elephanta flows and dykes, based on the two-pyroxene geothermometer of [57], range from~1100 to 900 • C. Similar temperatures (1113-924 • C) are obtained for groundmass pigeonites using the algorithm of [58].…”

Geochemistry and 40Ar/39Ar geochronology of the Nandurbar‐Dhule mafic dyke swarm: Dyke‐sill‐flow correlations and stratigraphic development across the Deccan flood basalt province

“…Other radio‐isotopic dates of dykes in the Narmada‐Satpura‐Tapi region are few but 66.9–64.5 Ma dyke ages (K‐Ar and 40 Ar/ 39 Ar) reported by Bhattacharji et al () and a 65.6 Ma ( 40 Ar/ 39 Ar) age by Sheth, Duncan, Chandrasekharam, and Mahoney () fall within the time period indicated by our new dating results. A ~3–4 Myr minimum duration of dyke emplacement is also known for the Central Saurashtra mafic dyke swarm (which includes the 62 km long Sardhar dyke; Cucciniello et al, ).…”

“…Before we discuss the geochemical correlations of individual dykes to the lava flows of the Deccan Traps, it is necessary to evaluate how homogeneous in chemical‐isotopic composition the individual dykes are. Examples of regional Deccan dykes showing lateral homogeneity or heterogeneity have been discussed by Bondre et al (), Ray et al (), Sheth et al (), Sheth et al (), Vanderkluysen et al (), and Cucciniello et al (). The 79‐km‐long Sakri‐Dhule‐Parola dyke shows very contrasting compositions in samples SDPD1 (isotopically Mahabaleshwar‐like, with ε Nd (t) = +3.0, Zr/Nb = 12.23, Ba/Y = 3.05) and the much more highly crustally contaminated SDPD2 (Jawhar‐Igatpuri‐like, with ε Nd (t) = −7.1, Zr/Nb = 17.37, Ba/Y = 5.87).…”

“…Geochemical data have been used successfully in stratigraphic correlation of widely separated sections in the Deccan Traps, and include Sr‐Nd‐Pb isotopes (not modified by fractional crystallization) and alteration‐resistant trace elements (thus excluding Rb and K, and also Ba and Sr for highly weathered samples; e.g., Beane et al, ; Chandrasekharam et al, ; Devey & Lightfoot, ; Lightfoot et al, ; Lightfoot & Hawkesworth, ; Mahoney et al, ; Peng et al, ; Peng et al, ; Sheth, Mahoney, & Chandrasekharam, ). The same data have been used in evaluating dyke‐flow correlations (e.g., Bondre et al, ; Cucciniello et al, ; Sheth et al, ; Sheth et al, ; Vanderkluysen et al, ). Lavas of many Western Ghats formations show significant overlap in binary plots, particularly of the major elements, but they show distinctive characteristics of primitive mantle‐normalized multi‐element patterns (e.g., Mahoney et al, ; Peng et al, ; Sheth et al, ; Sheth et al, ).…”

“…These are the ENE‐WSW‐trending Narmada‐Tapi dyke swarm, in the region of the Narmada and Tapi rivers and the intervening Satpura mountains (e.g., Bhattacharji, Chatterjee, Wampler, Nayak, & Deshmukh, ; Ray et al, ; Sant & Karanth, ), the NNW‐SSE‐trending Coastal dyke swarm, on the Konkan plain between the western Indian coast and the Western Ghats escarpment (e.g., Dessai & Viegas, ; Hooper, Widdowson, & Kelley, ; Sheth et al, ; Widdowson, Pringle, & Fernandez, ), and the Nasik‐Pune dyke swarm east of the Western Ghats escarpment, with more randomly oriented dykes than the other two (e.g., Bondre, Hart, & Sheth, ; Vanderkluysen et al, ). Abundant tholeiitic dykes also outcrop in the Saurashtra peninsula in the northwestern Deccan (Figure ), forming a westerly extension of the Narmada‐Tapi dyke swarm (Auden, ; Cucciniello, Demonterova, Sheth, Pande, & Vijayan, ; Sheth et al, ). Additional Deccan tholeiitic dykes outcrop in east‐central India between the outcrop areas of the Deccan and the Early Cretaceous (~115 Ma) Rajmahal Traps (Chalapathi Rao et al, ; Kent, Saunders, Kempton, & Ghose, ).…”