Geodynamics-Evolution of Sutures/Shallow Mantle Boundaries

Broad Objectives: Imaging shallow mantle layering and terrane boundaries in the Precambrian Provinces of India utilizing P-to-s (Ps) and S-to-p (Sp) converted waves and their authentication through information theoretic approaches.  

Research Activities:

The group focuses mainly on integrated researches in the emerging areas of seismology, petrophysics, geochemistry and geodynamics. Recently the group has added other dimensions by way of introducing to environmental pollution and paleoclimate researches.  Some of the recent findings of the group are highlighted below:

  1. The Southern Granulite Province of India has witnessed at least seven tectonothermal episodes during its evolution. Therefore the surface geological features are obliterated due to overprint of one episode with the other. This has led to the proposition of several models that are contradictory to each other. During 2014-15, our group developed innovative approaches towards unambiguous detection of a geosuture within the Southern Granulite Province of India, where sudden jump in Moho depths (Figure-1) coupled with differing average crustal compositions and field occurrences of deformed alkaline rocks and carbonatites (Figure-2) are documented in the region.

Figure-1 Pms arrivals (P-to-s mode conversion from Moho).Inset shows the key map.

Figure-2 Distribution of Vp/Vs values across the eastern and western segments showing distinctness in average crustal composition. The distributions of alkaline rocks and carbonatites (star) and anorthosites (diamonds) are shown. Broken lines in different colors represent major shear/fault zones in the region. A geosuture is demarcated by the white dashed line based on a jump in the Moho depth and distinct Vp/Vs values. See also Figure-1.  

   The vivid depth images with a step in Moho and differing crustal compositions across the blocks, together with occurrence of alkali syenites and other rock types reminiscent of collision, enable to demarcate the unambiguous presence of a geosuture in the region. The approach adopted is first of its kind in India.

  1. Ringwoodite is a high-pressure form of mineral olivine [(Mg,Fe)2SiO4]. The actual sampling of this mineral as impurities within the Juína diamond from Brazil opens up a wide variety of new research areas related to the planet earth that are highlighted in our study (Current Science, 2014). We discussed the observed discrepancies between the seismological and mineralogical Claypeyron slopes in the light of terrestrial occurrence of ringwoodite.

  2. Based on the stable isotope evidence, we report for the first time occurrence of ~ 2.7 Ga old Archean cap carbonates from the Dharwar Supergroup of southern India. An in-depth analysis of carbon isotope data from Dharwar Craton reveals preservation of their pristine character. The dolomitic member of Marikanive area comprising the Vanivilas Formation are characterized by highly depleted δ13C value and merit as the Indian example of ca. 2.7 Ga old cap carbonate. This finding can be of great importance for supercontinent reconstruction (see Current Science, 2015).

  3. The contents of toxic Cr(VI) in surface and groundwater samples of Hyderabad City were not estimated by any researchers earlier. Lead is another toxic heavy metal that causes severe ailment beyond the permissible limit. Therefore in collaboration with the city based St. Pious X Degree & PG College for Women, we measured the contents of Cr(VI) and Pb in water samples collected from different lakes and groundwater bodies using a spectrophotometer. The results reveal that the studied water bodies and aquifers are contaminated to variable degrees and pose serious threat to the ecosystem. In view of low geochemical baseline values for chromium and lead, the origin of heavy metal contamination is inferred to be anthropogenic. Higher incidences of ailments such as chronic skin diseases, diarrhea and acute renal failure amongst the city population of Hyderabad are perhaps indicative of Cr6+ ingestion. Likewise, high Pb content in the blood samples of the city population is indicative of initiation of Pb poisoning. This collaborative societal research received wide media coverage following its publication in the prestigious journal "Pollution" in 2015 (see News papers such as The Hindu, Eenadu and Sakshi, dated March 20, 2015 for more details).

Ongoing Projects:

Project Title

Project Number

Evolution of Sutures/Shallow Mantle Boundaries

MLP-6509-28 (BPK)

Making of the Precambrian sutures of the Indian Shield

INDEX (PSC-0204) (BPK)


Staff

Name

Designation

Dr. D. S. Ramesh

Currently on deputation to IIG, Mumbai as Director

Mr. P. A. Raju

Technical Assistant