Diopsidites from a Neoproterozoic–Cambrian suture in southern India

Abstract

We report the occurrence and characteristics of diopsidite dykes and veins from the Palghat-Cauvery Suture Zone (PCSZ) marking the boundary between the Archaean Dharwar craton to the north and the Proterozoic Madurai Block to the south, which is considered as a trace of the Cambrian Gondwana suture zone in southern India. The diopsidites are composed predominantly of coarse crystals of diopside [Mg no. (100 Mg/(Mg+Fe tot )) up to 89] surrounded by retrograde calcic amphibole, plagioclase and phlogopite with accessory titanite and calcite. The major, trace and rare earth element characteristics of the diopside crystals suggest their formation in a subduction zone setting. We correlate the petrogenesis of the diopsidites with the tectonics associated with the subduction and closure of the Neoproterozoic Mozambique Ocean prior to the final collisional assembly of the Gondwana supercontinent in Cambrian.

Clinopyroxenites (diopsidites) and metabasites from the East Sarmatian Orogen, East European Craton

“…Thus, we assume that the temperatures of the Voronezh Crystalline Massif diopsidite formation occurred at temperature from 600°C (veinlets) to 800°C (dykes). The circulation of Ca-enriched fluids within subduction-related setting has been reported in previous studies (Jan and Howie, 1981;Yang, 2006;Python et al, 2007Python et al, , 2011Bach and Klein, 2009;Santosh et al, 2010;Akizawa et al, 2011). The amphibolites adjacent to the diopsidites were subjected to diopsidization.…”

“…12), Sr and LREE (Fig. Both the lower crust (Santosh et al, 2010;Akizawa et al, 2011) and upper mantle Akizawa and Arai, 2014) diopsidites exhibit similar petrographic and mineralogical characteristics, indicating their genetic coherence. Python et al (2007) suggested that seawater penetrated down to the mantle and provided the source for Ca, Sr and LREE.…”

“…Genetic models of clinopyroxenite formation include the following: (1) magmatic crystallization from the melt (e.g. Ishiwatari et al, 2006;Dantas et al, 2007;Dilek et al, 2008), (2) metamorphism/metasomatism (Grégoire et al, 2000; or (3) metasomatic processes in suprasubduction zones Bach and Klein, 2009;Santosh et al, 2010;Akizawa et al, 2011). In the case of large masses of pyroxenites associated with other magmatic suites including gabbros and peridotites, a magmatic origin is well established.…”

“…(a, b) Chondrite-and primitive-mantle-normalized (afterSun and McDonough, 1989) trace and REE patterns for clinopyroxenes from the diopsidite rocks in the Vorontsovka terrane. The shaded area represents data on clinopyroxene in diopsidites of Oman ophiolite and that of southern India is fromSantosh et al (2010).Table 5. Major (wt.% oxide) and trace (ppm) element contents of studied…”

“…Profile across the thickest part of the diopsidite dyke and host amphibolites. Data for diopsidites (shaded fields) of southern India are fromSantosh et al (2010) and those of Oman ophiolite are fromPython et al (2007). Samples were collected from the centre of dyke to margins.…”