Precambrian Geology and Tectonics Research
Above: Photograph of the Mavecure Inselbergs in eastern Colombia taken from the Inirida River. Inselbergs are made of ca. 1.5 Ga s-type granites (see Ibañez-Mejia and Cordani, 2019)
The ‘Precambrian’ remains one of the least explored yet most intriguing periods of Earth’s history. Encompassing approximately 88% of geologic time since the formation of our planet, the ‘Precambrian’ Eon saw the appearance of the first continents, the onset of plate tectonics, the construction and demise of multiple ‘supercontinents’ and the rise of atmospheric oxygen and life on Earth. Nevertheless, preservation biases in the rock record and the inherently low precision of most existing geochronology means that the timing of such important events remain highly controversial. Our lab has a keen interest in exploring the timescales and processes involved in the formation (and deformation) of Earth’s early continental lithosphere, to better understand the geochemical evolution of the terrestrial lithosphere and mantle.
Highlights
TECTONICS and crustal growth of the amazonian shield
The Amazonian Craton in northern South America is one of the largest Precambrian cratonic nuclei on Earth, yet it’s tectonic evolution and crustal growth history remain very poorly known. Some of my research has documented important characteristics of the Guyana Shield (northern half of the Amazonian Craton), such as the existence of a previously unrecognized Stenian-Tonian orogenic belt along its westernmost margin that has key implications for reconstructing Amazonia’s role during the formation of the Rodinia supercontinent. This orogenic belt, named the ‘Putumayo Orogen’ after Ibañez-Mejia et al. (2011), has been further documented in Ibañez-Mejia et al. (2015, 2018). Further research is underway to continue understanding the geology of the Putumayo Orogen and the Guyana Shield.
Evolution of the Chotanagpur Granite Gneiss complex (CGGC) of the indian shield
With collaborator Pulak Sengupta (Jadavpur U.) and his students Subham Mukherjee and Anindita Dey, we have completed several studies documenting the petrology, geochronology and isotope geochemistry of the CGGC. The CGGC is a polycyclic mobile belt pertaining to the ‘Central Indian Tectonic Zone’, an E-W–trending regional structure thought to be a suture along which major Indian blocks got stitched together during the Paleo- and Neoproterozoic. We have documented the provenance and petrogenesis of HT and UHT metasedimentary rocks in the CGGC (Dey et al., 2017, 2019) as well as the age, geochemistry, and source of orthogneisses and granitoids in the region (Mukherjee et al., 2017a, 2017b, 2019). Altogether, this research has better documented the importance of Stenian-Tonian tectonometamorphic events in the region, painting a clearer picture of how Greater India was assembled and participated in the Rodinia supercontinent.
Publications
AMAZONIAN SHIELD
Ibañez-Mejia, M., (2019) The Putumayo Orogen of Northwestern South America: a synthesis. Invited review to “The Geology of Colombia” book
Ibañez-Mejia, M., Cordani, U. (2019) Zircon U-Pb geochronology and Hf-Nd-O isotope geochemistry of the Paleo- to Mesoproterozoic Basement in the Westernmost Guyana Shield. Invited review to “The Geology of Colombia” book
Ibañez-Mejia, M., Bloch, E. M., & Vervoort, J. D. (2018). Timescales of collisional metamorphism from Sm-Nd, Lu-Hf and U-Pb thermochronology: A case from the Proterozoic Putumayo Orogen of Amazonia. Geochimica Et Cosmochimica Acta, 235, 103–126. http://doi.org/10.1016/j.gca.2018.05.017
Ibañez-Mejia, M., Pullen, A., Arenstein, J. Gehrels, G.E., Valley, J.W., Ducea, M.N., Mora, A.R., Pecha, M., Ruiz, J. (2015). Unraveling crustal growth and reworking processes in complex zircons from orogenic lower-crust: The Precambrian Putumayo Orogen of Amazonia. Precambrian Research 267, pp. 285-310. doi:10.1016/j.precamres.2015.06.014
Ibañez-Mejia, M., Ruiz, J., Valencia, V.A., Cardona, A., Gehrels, G., Mora, A. (2011). The Putumayo Orogen of Amazonia and its implications for Rodinia reconstructions: New U-Pb geochronological insights into the Proterozoic tectonic evolution of northwestern South America. Precambrian Research 191 (1-2), pp. 58-77. doi:10.1016/j.precamres.2011.09.005
Cardona, A., Chew, D., Valencia, V.A., Bayona, G., Mišković, A., Ibañez-Mejia, M. (2010). Grenvillian remnants in the Northern Andes: Rodinian and Phanerozoic paleo-geographic perspectives. Journal of South American Earth Sciences 29 (1), pp. 92-104.
INDIAN SHIELD
Mukherjee, S.†, Dey, A.†, Sanyal, S., Ibañez-Mejia, M., Sengupta, P. (in press) Geochemistry and U-Pb-Lu-Hf isotopes of zircon from Chotanagpur Granite Gneissic Complex (CGGC) granitoids: Implications for a Late Palaeoproterozoic continental arc. Contributions to Mineralogy and Petrology.
Dey, A.†, Karmakar, S., Ibañez-Mejia, M., Mukherjee, S. , Sanyal, S., Sengupta, P. (2019) Petrology and geochronology of a suite of pelitic granulites from parts of the Chotanagpur Granite Gneiss Complex, eastern India: Evidence for Stenian-Tonian reworking of a late Paleoproterozoic crust. Geological Journal
Mukherjee, S.†, Dey, A.†, Ibañez-Mejia, M., Sanyal, S., Sengupta, P. (2018). Geochemistry, U-Pb geochronology and Lu-Hf isotope systematics of a Suite of A-Type Granitoids from the Chotanagpur Granite Gneissic Complex (CGGC): Implications for Mesoproterozoic Crustal Extension in the East Indian Shield. Precambrian Research 305, pp. 40-63, doi: 10.1016/j.precamres.2017.11.018
Mukherjee, S.†, Dey, A.†, Sanyal, S., Ibañez-Mejia, M., Dutta, U., Sengupta, P. (2017). Petrology and U-Pb geochronology of zircon in a suite of charnokitic gneisses from parts of the Chotanagpur Granite-Gneiss Complex (CGGC): Evidence for reworking of a Mesoproterozoic basement during the formation of the Rodinia Supercontinent. Journal of the Geological Society of London
Dey, A.†, Mukherjee, S.†, Sanyal, S., Ibañez-Mejia, M., Sengupta, P. (2017). Deciphering Sedimentary provenance and timing of sedimentation from a suite of metapelites of the Chotanagpur Granite Gneissic Complex, India: Implications for Proterozoic tectonics in the East-Central part of the Indian Shield, in Mazumder, R. (Ed.): Sediment Provenance – Influences on Compositional Change from Source to Sink, Chapter 16, pp. 453-486, Elsevier