Petrological evidences of impact-induced shock metamorphism in the basement granitoids and rhyolitic melt breccia of Mohar area, Shivpuri district, Madhya Pradesh

Roy, Madhuparna; Kumar, Sanjeev; Pandey, Pradeep; Bhairam, C. L.; Parihar, P. S.

doi:10.1007/s12594-014-0143-x

Cited by 8 publications

(7 citation statements)

References 7 publications

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“…It is established from the subsurface data that the structure, with a 7.5 km diameter, is that of a simple crater without a central uplift, as no granitic basement rocks have been intercepted at shallow depths in any of the boreholes drilled at the center of the mesa. The basement granite as well as the melt breccia bear signatures of shock metamorphism, with the latter possibly having been derived by the shock melting of the former (Roy et al 2014).…”

Section: Geologymentioning

confidence: 99%

“…It is generally shocked, with rusty red feldspar and chalky white opaque quartz in the bore hole cores (figure 5a) and is microscopically characterized by highly deformed feldspars (figure 5b) and a wide variety of shock metamorphic features that leave indelible marks on quartz, feldspar, biotite, zircon and apatite (Roy et al 2014). The rock comprises medium grains of highly deformed, dark red, toasted feldspars, quartz with rampant planar deformation features (PDF)-like structures, heterogeneous anisotropism or melt veining, biotite/chlorite showing kink banding and accessory zircon and apatite exhibiting planar deformation feature.…”

Section: Basement Granitementioning

confidence: 99%

“…During the course of subsurface uranium exploration in this structure, the geoscientists of Atomic Minerals Directorate for Exploration and Research observed the presence of voluminous melt rock (melt breccia) beneath the mesa, which is the surface manifestation of the structure. Petrological study of drill core samples brought to light unequivocal and rampant evidences of shock metamorphic features in the melt breccia as well as the basement granitoids underlying it (Roy et al 2014). The shock metamorphic features comprise planar deformation features (PDF)-like structures in quartz, feldspar, apatite and zircon, toasted, diaplectic, ladder-textured feldspars, selectively shock-melted feldspars, ballen quartz and melt-veined quartz.…”

Section: Introductionmentioning

confidence: 99%

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Mineral shock signatures in rocks from Dhala (Mohar) impact structure, Shivpuri district, Madhya Pradesh, India

et al. 2017

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A concrete study combining optical microscopy, Raman spectroscopy and X-ray diffractometry, was carried out on subsurface samples of basement granite and melt breccia from Mohar (Dhala) impact structure, Shivpuri district, Madhya Pradesh, India. Optical microscopy reveals aberrations in the optical properties of quartz and feldspar in the form of planar deformation feature-like structures, lowered birefringence and mosaics in quartz, toasting, planar fractures and ladder texture in alkali feldspar and near-isotropism in bytownite. It also brings to light incidence of parisite, a radioactive rare mineral in shocked granite. Raman spectral pattern, peak positions, peak widths and multiplicity of peak groups of all minerals, suggest subtle structural/crystallographic deviations. XRD data further reveals minute deviations of unit cell parameters of quartz, alkali feldspar and plagioclase, with respect to standard αquartz, high-and low albite and microcline. Reduced cell volumes in these minerals indicate compression due to pressure. The c 0 /a 0 values indicate an inter-tetrahedral angle roughly between 120 o and 144 o , further pointing to a possible pressure maxima of around 12 GPa. The observed unit cell aberration of minerals may indicate an intermediate stage between crystalline and amorphous stages, thereby, signifying possible overprinting of decompression signatures over shock compression effects, from a shock recovery process.

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Section: Geologymentioning

confidence: 99%

Section: Basement Granitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mineral shock signatures in rocks from Dhala (Mohar) impact structure, Shivpuri district, Madhya Pradesh, India

et al. 2017

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“…The impact breccia has a variable thickness, with a maximum of 200 m (Roy et al. 2014) and occurs both as vesicular to nonvesicular rock. Melt breccia contains clasts of basement granites.…”

Section: Introductionmentioning

confidence: 99%

“…The monomict granitoid breccia comprises fractured and extensively brecciated country rock (predominantly granitoids). The impact breccia has a variable thickness, with a maximum of 200 m (Roy et al 2014) and occurs both as vesicular to nonvesicular rock. Melt breccia contains clasts of basement granites.…”

Section: Introductionmentioning

confidence: 99%

Evidence for shock provides insight into the formation of the central elevated area in the Dhala impact structure, India

Agarwal

Kumar

Joshi

et al. 2020

Meteorit & Planetary Scien

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The central elevated area is a postimpact morphological landmark in the otherwise flat eroded remnant of the Dhala impact structure, India. Its base is the Bundelkhand granitic complex followed by beds of Dhala and Kaimur Formations. The beds of the Dhala and Kaimur Formation present typical sedimentary textures and structures such as cross-bedding. The grains are angular, sorting is moderate to poor, and brittle-ductile deformation of the protolith is still preserved in some grains. This reveals a short distance of transport. Detailed microscopy and U-stage measurements confirm planar deformational features (PDFs) oriented (0001) and {10-13} in few quartz grains. Based on these facts, it is suggested that the quartz with PDFs was shocked, ejected out of the crater, and deposited near the crater cavity. Reworking of the ejecta blanket redeposited these quartz grains to their present location. Relatively few shocked grains in the rocks favor a postimpact fluvial process over impact resurge.

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Characteristic landforms and geomorphic features associated with impact structures: Observations at the Dhala structure, north‐central India

Singh

Pati

Sinha

et al. 2021

Earth Surf Processes Landf

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Geomorphological study of some of the just more than 200 known terrestrial impact structures has demonstrated that despite extensive degradation, important geomorphological keys, such as drainage pattern, topographic signatures, erosional landforms, and depositional features, can still be assessed. They can provide possible indicators to assist in the recognition of further impact structures, especially on Precambrian shields and cratonic landmasses. This study documents the surface features and landforms of the Paleoproterozoic, about 11 km diameter Dhala impact structure in India. The Dhala structure has an estimated age that is constrained stratigraphically between 1.7 and 2.5 Ga. This structure is deeply eroded, and barely has a morphological resemblance to other known terrestrial or extraterrestrial impact structures.We have analyzed the operative surface-forming processes for the Dhala area.We demand to continue the in-depth study of all terrestrial impact structures, especially the pre-Paleozoic ones, so that geomorphological criteria can be rigorously constrained and applied in conjunction with a priori remote sensing and field data to support the identification of new structures prior to their ultimate confirmation using diagnostic evidence of shock metamorphism.

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Petrological evidences of impact-induced shock metamorphism in the basement granitoids and rhyolitic melt breccia of Mohar area, Shivpuri district, Madhya Pradesh

Cited by 8 publications

References 7 publications

Mineral shock signatures in rocks from Dhala (Mohar) impact structure, Shivpuri district, Madhya Pradesh, India

Mineral shock signatures in rocks from Dhala (Mohar) impact structure, Shivpuri district, Madhya Pradesh, India

Evidence for shock provides insight into the formation of the central elevated area in the Dhala impact structure, India

Characteristic landforms and geomorphic features associated with impact structures: Observations at the Dhala structure, north‐central India

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