Exceptional Multi Stage Mineralization of Secondary Minerals in Cavities of Flood Basalts from the Deccan Volcanic Province, India

Abstract

Flood basalts of the Deccan Volcanic Province erupted between about 67.5 to 60.5 Ma ago and reached a thickness of up to 3500 m. The main part consists of compound and simple lava flows with a tholeiitic composition erupted within 500,000 years at about 65 Ma. Within the compound lava flows, vesicles and cavities are frequent. They are filled by secondary minerals partly of well development and large size. This study presents data on the secondary mineralization including detailed field descriptions, optical, cathodoluminescence and SEM microscopy, X-ray diffractometry, fluid inclusions, C and O isotope analyses, and Rb-Sr and K-Ar geochronology. The investigations indicate a multistage precipitation sequence with three main stages. During stage I clay minerals and subsurface filamentous fabrics (SFFs), of probably biogenic origin, formed after the lava flows cooled down near to the Earth’s surface. In stage II, first an assemblage of calcite (I) and zeolite (I) (including mordenite, heulandite, and stilbite) as well as plagioclase was overgrown by chalcedony, and finally a second calcite (II) and zeolite (II) generation developed by burial metamorphism by subsequent lava flows. Stage III is characterized by precipitation of a third calcite (III) generation together with powellite and apophyllite from late hydrothermal fluids. Rb-Sr and K-Ar ages of apophyllite indicate a large time span for stage III. Apophyllite formed within different time intervals from the Paleogene to the early Miocene even within individual lava flows at certain localities. From the Savda/Jalgaon quarry complex, ages cluster at 44–48 Ma and 25–28 Ma, whereas those from the Nashik area are 55–58 Ma and 21–23 Ma, respectively.

Posteruptive Thermal History of the Proterozoic Basaltic North Shore Volcanic Group of the Midcontinent Rift: Evidence from K/Ar Data of Celadonite

“…In the continental flood basalts of the Parana basin, Rb/Sr ages of celadonite (81-107 Ma) are also younger than the eruption age (127-137 Ma) indicating a time interval and a long duration of alteration between eruption and formation of celadonite [80]. Using K/Ar and Rb/Sr data on apophyllite, Ottens et al [20] determined a time interval of 24 myrs for a late hydrothermal formation of apophyllite from Savda in the Deccan Volcanic Province (India) following burial metamorphism. Środoń et al [81] report K/Ar ages of celadonite in the 500 m thick Volvyn-Brest Ediacaran continental flood basalts and distinguish two superimposed alteration processes: The Ediacaran hydrothermal alteration event related to meteoric water and the later Caledonian and/or Variscan potassic alteration.…”

“…It is also reported in the flood basalts from the Deccan Traps Volcanic Province by Ottens al. [20] as first rim-forming mineral in cavities. It also occurs in the Tertiary basalts of the Lessini Mountains of northern Italy where it is assumed to have crystallized during the deuteric cooling stage from a residual fluid with H 2 O and fluids [21].…”

Mineralogy, Geochemistry and Genesis of Agate—A Review

“…Several investigations indicated the participation of residual magmatic fluids in the agate formation and the heating of meteoric fluids, which are necessary for the alteration of the rocks and the release of silica and other chemical elements forming secondary minerals (e.g., [22,24,37]). However, in certain occurrences such as the Paraná Continental Flood Basalt Province, Brazil or the Deccan Trap Province, India strong indications were found that the agate formation took place remarkably later than the emplacement of the surrounding volcanic host rocks [76][77][78].…”

“…Furthermore, several organic phases were detected in agates such as carbonaceous material, solid bitumen or disordered graphite-like substances [35,[44][45][46]. Carbonates (especially calcite), iron oxides/hydroxides and clay minerals are the most frequent and present in more or less all types of agates, whereas minerals of the zeolite group are typical phases in volcanic agates [1,15,49,78]. It is noteworthy, that certain chemical elements may be present in different chemical compounds in the same agate.…”

Investigations of Structural and Residual Trapping Phenomena during CO2 Sequestration in Deccan Volcanic Province of the Saurashtra Region, Gujarat

“…e massive basalt layer should act as caprock due to its fault-free and thick enough layer so that it can act as an impermeable seal [7]. e mineral composition of the Deccan basalts is dominated by the Pyroxene, Plagioclase, and Olivine mineral groups [11,[14][15][16][17]. Basalt rock formation consists mainly of the divalent cation like Ca 2+ , Mg 2+ , and Fe 2+ , which is advantageous in forming the secondary minerals.…”