Mineralogy and 40Ar/39Ar geochronology of orangeites (Group II kimberlites) from the Damodar Valley, eastern India

Ray W. Kent; Simon P. Kelley; Malcolm S. Pringle

doi:10.1180/002646198547701

Mineralogy and ⁴⁰Ar/³⁹Ar geochronology of orangeites (Group II kimberlites) from the Damodar Valley, eastern India

Ray W. Kent^*, Simon P. Kelley, Malcolm S. Pringle

^*Corresponding author for this work

School of Geosciences

Research output: Contribution to journal › Article › peer-review

Abstract

A suite of ultramafic-mafic alkaline igneous rocks in the Damodar Valley, eastern India, contains carbonate, phosphate and titanate minerals that are not characteristic or common in minettes or lamproites, but are typical of orangeites (Group II kimberlite) from southern Africa. Phlogopite grains from the Damodar alkaline rocks yield mean ⁴⁰Ar/³⁹Ar ages of 116.6±0.8 Ma, 113.5±0.5 Ma and 109.1±0.7 Ma (1σ errors) using laser dating techniques. These ages are similar to the Rb-Sr ages of African orangeites, which lie mostly in the range 121 to 114 Ma. Prior to this study, only one possible occurrence of orangeite (the ∼820 m.y.-old Aries pipe. Western Australia) was known outside the Kaapvaal craton and its environs. If the Damodar alkaline rocks are bona fide orangeites, it is likely that they were generated at depths of >150 km, within the stability field of diamond.

Original language	English
Pages (from-to)	313-323
Number of pages	11
Journal	Mineralogical Magazine
Volume	62A
Issue number	PART 3
DOIs	https://doi.org/10.1180/002646198547701
Publication status	Published - 1 Jan 1998

Keywords

Ar/Ar
Craton
Diamond
Group II kimberlite
Orangeite

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title = "Mineralogy and 40Ar/39Ar geochronology of orangeites (Group II kimberlites) from the Damodar Valley, eastern India",

abstract = "A suite of ultramafic-mafic alkaline igneous rocks in the Damodar Valley, eastern India, contains carbonate, phosphate and titanate minerals that are not characteristic or common in minettes or lamproites, but are typical of orangeites (Group II kimberlite) from southern Africa. Phlogopite grains from the Damodar alkaline rocks yield mean 40Ar/39Ar ages of 116.6±0.8 Ma, 113.5±0.5 Ma and 109.1±0.7 Ma (1σ errors) using laser dating techniques. These ages are similar to the Rb-Sr ages of African orangeites, which lie mostly in the range 121 to 114 Ma. Prior to this study, only one possible occurrence of orangeite (the ∼820 m.y.-old Aries pipe. Western Australia) was known outside the Kaapvaal craton and its environs. If the Damodar alkaline rocks are bona fide orangeites, it is likely that they were generated at depths of >150 km, within the stability field of diamond.",

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N2 - A suite of ultramafic-mafic alkaline igneous rocks in the Damodar Valley, eastern India, contains carbonate, phosphate and titanate minerals that are not characteristic or common in minettes or lamproites, but are typical of orangeites (Group II kimberlite) from southern Africa. Phlogopite grains from the Damodar alkaline rocks yield mean 40Ar/39Ar ages of 116.6±0.8 Ma, 113.5±0.5 Ma and 109.1±0.7 Ma (1σ errors) using laser dating techniques. These ages are similar to the Rb-Sr ages of African orangeites, which lie mostly in the range 121 to 114 Ma. Prior to this study, only one possible occurrence of orangeite (the ∼820 m.y.-old Aries pipe. Western Australia) was known outside the Kaapvaal craton and its environs. If the Damodar alkaline rocks are bona fide orangeites, it is likely that they were generated at depths of >150 km, within the stability field of diamond.

AB - A suite of ultramafic-mafic alkaline igneous rocks in the Damodar Valley, eastern India, contains carbonate, phosphate and titanate minerals that are not characteristic or common in minettes or lamproites, but are typical of orangeites (Group II kimberlite) from southern Africa. Phlogopite grains from the Damodar alkaline rocks yield mean 40Ar/39Ar ages of 116.6±0.8 Ma, 113.5±0.5 Ma and 109.1±0.7 Ma (1σ errors) using laser dating techniques. These ages are similar to the Rb-Sr ages of African orangeites, which lie mostly in the range 121 to 114 Ma. Prior to this study, only one possible occurrence of orangeite (the ∼820 m.y.-old Aries pipe. Western Australia) was known outside the Kaapvaal craton and its environs. If the Damodar alkaline rocks are bona fide orangeites, it is likely that they were generated at depths of >150 km, within the stability field of diamond.

KW - Ar/Ar

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Mineralogy and ⁴⁰Ar/³⁹Ar geochronology of orangeites (Group II kimberlites) from the Damodar Valley, eastern India

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Keywords

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