Hydrous melting in mantle wedge and magmatism in subduction zones

 Factors controlling magmatism in subduction zones and location of volcanic arcs are explored through variable H2O and pressure-experiments on peridotite, primitive magnesian andesite, and basaltic andesite under the supervision of T.L. Grove at the MIT Experimental Petrology Laboratory. Our studies indicate that an H2O-rich fluid, formed by dehydration of hydrous minerals in the subducted oceanic lithosphere, rises into the overlying mantle wedge and causes flux melting that continues to shallow mantle depths (< 30 km). The resulting melts segregate at the top of the wedge and pass through the crust where they differentiate and follow distinctive SiO2 enrichment paths at low FeO/MgO. Further details are available at the MIT Petrology Research > Subduction-zone magmas web-page.

  1. Grove, T.L., Till, C.B., Lev, E., Chatterjee, N. and Medard, E. (2010) Reply to comment on "Global systematics of arc volcano position". Nature, 468, E7-E8. doi:10.1038/nature09155
  2. Grove, T.L., Till, C.B., Lev, E., Chatterjee, N. and Medard, E. (2009) Kinematic variables and water transport control the formation and location of arc volcanoes. Nature, 459/4, 694-697. doi:10.1038/nature08044
  3. Grove, T.L., Chatterjee, N., Parman, S.W. and Medard, E. (2006) The influence of H2O on mantle wedge melting. Earth and Planetary Science Letters, 249, 74-89. doi:10.1016/j.epsl.2006.06.043
  4. Grove, T.L., Baker, M., Price, R.C., Parman, S.W., Elkins-Tanton, L.T., Chatterjee, N. and Muentener, O. (2005) Magnesian andesite and dacite lavas from Mt. Shasta, northern California: products of fractional crystallization of H2O-rich mantle melts. Contributions to Mineralogy and Petrology, 148, 542-565. doi:10.1007/s00410-004-0619-6
  5. Grove, T.L., Elkins-Tanton, L., Parman, S.W., Chatterjee, N., Muentener, O. and Gaetani, G.A. (2003) Fractional crystallization and mantle-melting controls on calc-alkaline differentiation trends. Contributions to Mineralogy and Petrology, 145, 515-533. doi: 10.1007/s00410-003-0448-z
  6. Other relevant publications.
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Depth of post-shield alkalic reservoir, East Maui, Hawaii

 Post-shield alkalic lavas account for about 1% of the lavas on Hawaiian Islands. In eastern Maui, these lavas erupted on top of the voluminous shield-stage tholeiitic lavas as the island of Maui migrated northwestward with the Pacific plate beyond the Hawaiian plume axis. The alkalic lavas in East Maui belong to an older Kula and a younger Hana series. The latter erupted predominantly from vents near the Haleakala summit and along the southwest rift zone forming a series of cinder cones. Alkalic lava from Kolekole cinder cone on the southwest rift near the Haleakala crater have transitional compositions between Kula and Hana lavas. They predominantly consist of ankaramitic picro-basalts with reverse- or cyclic-zoned clinopyroxene (Fig. A) and olivine (Fig. B) phenocrysts that indicate magma mixing during formation. Calculated pressures of equilibrium between phenocryst-rims and their host lava corresponding with the minimum depths of the alkalic magma reservoirs are between 4.4 and 11.2 kb. The alkalic magma reservoirs at Kolekole may thus extend deep into the spinel lherzolite field of the upper mantle.

  1. Chatterjee, N. and Bhattacharji, S. (2010) Geological and Geochemical Studies of Kolekole Cinder Cone, Southwest Rift Zone, East Maui, Hawaii. In: Ray, J., Sen, G., Ghosh, B. (eds.) "Topics in Igneous Petrology, A Tribute to Professor Mihir K. Bose", Springer, Dordrecht Heidelberg London New York, p. 95-113. doi:10.1007/978-90-481-9600-5_5
  2. Chatterjee, N., Bhattacharji, S. and Fein, C. (2005) Depth of alkalic magma reservoirs below Kolekole cinder cone, Southwest Rift zone, East Maui, Hawaii. Journal of Volcanology and Geothermal Research, 145, 1-22. doi:10.1016/j.jvolgeores.2005.01.001
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Origin of Proterozoic anorthosite massifs of eastern India

 Large anorthosite massifs are common in the Proterozoic granulite complexes of eastern India. The Bengal Anorthosite was emplaced at 1550 ± 2 Ma contemoraneously with a phase of high-grade metamorphism at the eastern margin of the Chotanagpur Gneissic Complex (CGC). It was subsequently overprinted by Grenvillian metamorphism at 947 ± 27 Ma. Small bodies of late Paleoproterozoic to early Mesoproterozoic anorthosite of different generations associated with metamorphosed layered mafic-ultramafic sequences also occur in the CGC. The Bengal Anorthosite massif is morphologically different from the smaller anorthositic bodies. Surface and subsurface mineralogical and geochemical investigations indicate cyclic layering with depth in the massif that is possibly related to derivation and emplacement of melt in discrete batches. Sub-parallel, E-W oriented, discontinuous lenses of metabasite occur within and outside the anorthosite massif. Field evidence indicates that the metabasites and the anorthosite are coeval, but chemical compositions suggest that they are not comagmatic. Geochemical characteristics indicate a mantle origin for the anorthosite and a lower crustal origin for the metabasites.

The Balugaon Anorthosite was emplaced at 983.0 ± 2.5 Ma in the Chilka Lake region of the Eastern Ghats Belt (EGB) after fabric-defining Grenvillian metamorphism. Orientation of granulitic foliation at the margin of the massif, and primary joints and flow layers in the massif indicate that the anorthosite was probably emplaced through forceful injection of the anorthositic diapir in the granulite terrain.

  1. Chatterjee, N., Crowley, J.L., Mukherjee, A. and Das, S. (2008) Geochronology of the 983 Ma Chilka Lake Anorthosite, Eastern Ghats Belt, India: implications for pre-Gondwana tectonics. Journal of Geology, 116, 105-118. doi: 10.1086/528901
  2. Chatterjee, N., Crowley, J.L. and Ghose, N.C. (2008) Geochronology of the 1.55 Ga Bengal anorthosite and Grenvillian metamorphism in the Chotanagpur gneissic complex, eastern India.Precambrian Research,161, 303-316. doi:10.1016/j.precamres.2007.09.005
  3. Ghose, N.C., Chatterjee, N., Mukherjee, D., Kent, R.W. and Saunders, A.D. (2008) Mineralogy and geochemistry of the Bengal Anorthosite massif in the Chotanagpur Gneissic Complex at the eastern Indian shield margin. Journal of Geological Society of India, 72, 263-277. article
  4. Ghose, N.C. and Chatterjee, N. (2008) Petrology, tectonic setting and source of dykes and related magmatic bodies in the Chotanagpur Gniessic Complex, Eastern India. In: Srivastava, R.K., Sivaji, Ch., Chalapathi Rao, N.V. (eds.) "Indian Dykes", Narosa Publishing House, New Delhi, p. 471-493. ISBN:978-81-7319-877-9
  5. Mukherjee, D., Ghose, N.C. and Chatterjee, N. (2005) Crystallization history of a massif anorthosite in the eastern Indian shield margin based on borehole lithology. Journal of Asian Earth Sciences, 25/1, 77-94. doi:10.1016/j.jseaes.2004.01.012
  6. Ghose, N.C., Mukherjee, D. and Chatterjee, N. (2005) Plume generated Mesoproterozoic mafic-ultramafic magmatism in the Chotanagpur mobile belt of Eastern Indian shield margin. Journal of Geological Society of India, 66, 725-740. article
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The role of basaltic magmatism in intra-cratonic basin development

 Basaltic sills and lava flows (~1.88 Ga) are commonly intercalated with sediments in the lower part of the sedimentary sequence in the intra-cratonic, mid-Proterozoic Cuddapah basin of southern India. At the surface, these sills appear concentric with the arcuate western and southwestern margins of the basin. A positive gravity anomaly at the center of the concentric sills indicates a large lopolithic cupola that probably originated through mantle upwelling during the early part of the basin's history.

Dikes and dike swarms in NW-SE and NE-SW orientations intrude the Archean crust surrounding the basin. The doleritic dikes are composed of tholeiites and alkali basalts, and their differentiates. The trace element characteristics of these dikes are different from those of the basaltic sills inside the basin. The dikes are closer in composition to some dikes in the Napier Complex of East Antarctica that was juxtaposed to the Cuddapah region in Gondwana. However, accurate age data are not available to support correlation of dikes between the Cuddapah region and the Napier Complex.

  1. Chatterjee, N. and Bhattacharji, S. (2001) Petrology, geochemistry and tectonic settings of the mafic dikes and sills associated with the evolution of the Proterozoic Cuddapah Basin of South India. Proceedings of Indian Academy of Sciences (Earth and Planetary Sciences), 110/4, 433-453. doi:10.1007/BF02702905
  2. Chatterjee, N. and Bhattacharji, S. (1998) Formation of Proterozoic Tholeiite intrusives in and around Cuddapah Basin, South India and their Gondwana Counterparts in East Antarctica; and Compositional Variation in their Mantle Sources. Neues Jahrbuch für Mineralogie Abhandlungen, 174/1, 79-102. doi:10.1127/njma/174/1998/79
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Textural study of peridotite xenoliths

 A new method using digital back-scattered electron and X-ray images is applied for textural analysis of peridotite xenoliths from kimberlite pipes in South Africa. We determine modal amounts and average grain sizes of each mineral in the thin section without resorting to ellipsoidal approximations of grain boundaries, and investigate the spatial relationship of mineral pairs. The observed distributions can be explained by a model in which harzburgitic residues produced by large extents of partial melting are formed at shallow depths (~100 km) and high temperatures (~1500° C) that descend to greater depths (~160 km) where cooling (~1100° C) causes clinopyroxene and garnet to exsolve from orthopyroxene. It is proposed that the thermal history may have been imposed in an Archaean subduction zone.

  1. Saltzer, R.L., Chatterjee, N. and Grove, T.L. (2001) The spatial distribution of garnets and pyroxenes in mantle peridotites: pressure-temperature history of peridotites from the Kaapvaal craton. Journal of Petrology, 42/12, 2215-2229. doi:10.1093/petrology/42.12.2215
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