CHRISTIAN KOEBERL
Articles written in Journal of Earth System Science
Volume 121 Issue 1 February 2012 pp 91-108
Mineral chemistry of lava flows from Linga area of the Eastern Deccan Volcanic Province, India
Sohini Ganguly Jyotisankar Ray Christian Koeberl Theodoros Ntaflos Mousumi Banerjee
Several basaltic lava flows have been identified in the study area in and around Linga, in the Eastern Deccan Volcanic Province (EDVP) on the basis of distinctly developed structural zones defined by primary volcanic structures such as columnar joints and vesicles. These basaltic lava flows are spatially distributed in four different sectors, viz., (i) Bargona–Gadarwara (BG) sector (ii) Shikarpur–Linga (SL) sector (iii) Arjunvari–Survir Hill (AS) sector and (iv) Kukrachiman–Morand Hill (KM) sector. A threetier classification scheme has been adopted for the characterization and classification of individual lava flows. Each lava flow consists of a Lower Colonnade Zone (LCZ) overlain by the Entablature Zone (EZ) and Upper Colonnade Zone (UCZ). The LCZ and UCZ grade into a distinct/indistinct Lower Vesicular Zone (LVZ) and Upper Vesicular Zone (UVZ), respectively. The LCZ and UCZ of the flows are characterized by columnar joints while the EZ is marked by multi-directional hackly jointing. The geometry of different joint patterns corresponds to different styles of cooling during solidification of lava flows. Detailed petrographic studies of the investigated lava flows reveal inequigranular phenocrystal basalts characterized by development of phenocrystal phases including plagioclase, clinopyroxene and olivine, whereas groundmass composition is marked by tiny plagioclase, clinopyroxene, opaque mineral and glass. Electron microprobe analyses indicate that the olivine has a wide range ∼Fo22 to Fo66 revealing a wide spectrum of compositional variation. Pyroxene compositions are distinctly designated as Quad pyroxenes. Phenocrystal pyroxenes are mostly diopsidic, while the groundmass pyroxenes mainly correspond to augite with a minor pigeonite component. Pyroxene phenocrysts are characterized by a prominent Tienrichment. Phenocrystal plagioclase grains are calcic (An52.7$–$An72.9), whereas groundmass plagioclase are relatively sodic (An39.2$–$An61.6). Groundmass opaque minerals are characteristically found to be Ti–magnetite/ilmenite/pyrophanite. Pyroxene thermometry reveals a temperature span of 850° to 1280°C for the studied lavas while olivine–clinopyroxene thermometry yields a temperature range from 1040°$–$1160°C. The variation of temperature for the lava flows is ascribed to their normal cooling history after eruption.
Volume 131 All articles Published: 23 July 2022 Article ID 0163 Research article
PAYEL DEY JYOTISANKAR RAY JANISAR M SHEIKH SURESH C PATEL CHRISTIAN KOEBERL AVIPSHA CHAKRABORTY
Multivariate statistical analysis involving hierarchical clusters was carried out for basaltic samples
(and associated units) from Khandwa (21°49'N, 76°21'E). ‘Highly significant’ or ‘significant’ linear correlation
coefficient values (
$\bf{Highlights}$
$\bullet$ Multivariate statistical analysis from a portion of eastern Deccan volcanic province deciphers distinctive nature of crystallization.
$\bullet$ Cluster patterns indicate distinct ‘bulk level of crystallization’ and ‘ultimate crystallization’ for the lavas.
$\bullet$ Rapid quenching of dyke rocks only allows them to crystallize up to the bulk level.
$\bullet$ Ambient temperature controls bulk level of crystallization for the lavas.
Volume 131 All articles Published: 28 September 2022 Article ID 0210 Research article
PAYEL DEY JYOTISANKAR RAY JANISAR M SHEIKH SURESH C PATEL CHRISTIAN KOEBERL SIMRAN DUTTA
Continental flood basalts of the world are represented either by picrobasalt/picrite layers (with abundant growth of olivine) or by (almost) olivine-depleted tholeiite basalts. We have taken a case study from the olivine-depleted basaltic rocks from Khandwa (21°49'N: 76°21'E) Eastern Deccan Volcanic Province. Our research shows that recent cooling experiments (available in the literature) involving a dry basalt and construction of some selected binary major element variation diagrams (entailing lever rules) can explain (and quantify) the insignificant level (${\sim}$2–4%) of olivine crystallization (${\sim}$olivine decadence) in tholeiite basalts. Such decadent olivine retains a skeletal crystallographically-oriented geometry. We contemplate that our simplistic model of olivine decadence can be extended to other flood basalt provinces of the world as well.
$\bf{Highlights}$
$\bullet$ First-time cogent model of olivine decadence in Deccan basalts
$\bullet$ Integration of newly obtained experimental data and binary variation diagrams
$\bullet$ Petrographic support validates the model
$\bullet$ Model can be extended to other continental Flood basalts
Volume 132, 2023
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