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Documentation of shock features in impactites from the Dhala impact structure, India
Author(s) -
Pati Jayanta Kumar,
Poelchau Michael H.,
Reimold Wolf Uwe,
Nakamura Norihiro,
Kuriyama Yutaro,
Singh Anuj Kumar
Publication year - 2019
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/maps.13369
Subject(s) - impact structure , geology , shock metamorphism , shock (circulatory) , metamorphic rock , meteorite , lithology , zircon , geochemistry , impact crater , mineralogy , seismology , astrobiology , medicine , physics
The fundamental approach for the confirmation of any terrestrial meteorite impact structure is the identification of diagnostic shock metamorphic features, together with the physical and chemical characterization of impactites and target lithologies. However, for many of the approximately 200 confirmed impact structures known on Earth to date, multiple scale‐independent tell‐tale impact signatures have not been recorded. Especially some of the pre‐Paleozoic impact structures reported so far have yielded limited shock diagnostic evidence. The rocks of the Dhala structure in India, a deeply eroded Paleoproterozoic impact structure, exhibit a range of diagnostic shock features, and there is even evidence for traces of the impactor. This study provides a detailed look at shocked samples from the Dhala structure, and the shock metamorphic evidence recorded within them. It also includes a first report of shatter cones that form in the shock pressure range from ~2 to 30 GP a, data on feather features (FFs), crystallographic indexing of planar deformation features, first‐ever electron backscatter diffraction data for ballen quartz, and further analysis of shocked zircon. The discovery of FF s in quartz from a sample of the MCB ‐10 drill core (497.50 m depth) provides a comparatively lower estimate of shock pressure (~7–10 GP a), whereas melting of a basement granitoid infers at least 50–60 GP a shock pressure. Thus, the Dhala impactites register a strongly heterogeneous shock pressure distribution between <2 and >60 GP a. The present comprehensive review of impact effects should lay to rest the nonimpact genesis of the Dhala structure proposed by some earlier workers from India.