Emplacement age and isotope geochemistry of Sung Valley alkaline-carbonatite complex, Shillong Plateau, northeastern India; implications for primary carbonate melt and genesis of the associated silicate rocks

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doi: 10.1016/j.lithos.2004.09.017
Author(s): Srivastava, Rajesh K.; Heaman, Larry M.; Sinha, Anup K.; Sun Shihua
Author Affiliation(s): Primary:
Banaras Hindu University, Igneous Petrology Laboratory, Varanasi, India
University of Alberta, Canada
Chinese Academy of Sciences, China
Volume Title: Lithos (Oslo)
Source: Lithos (Oslo), 81(1-4), p.33-54. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0024-4937 CODEN: LITHAN
Note: In English. 92 refs.; illus., incl. 6 tables, geol. sketch map
Summary: The early Cretaceous (Albian-Aptian) Sung Valley ultramafic-alkaline-carbonatite complex is one of several alkaline intrusions that occur in the Shillong Plateau, India. This complex comprises calcite carbonatite and closely associated ultramafic (serpentinized peridotite, pyroxenite and melilitolite) and alkaline rocks (ijolite and nepheline syenite). Field relationship and geochemical characteristics of these rocks do not support a genetic link between carbonatite and associated silicate rocks. There is geochemical evidence that pyroxenite, melilitolite and ijolite of the complex are genetically related. Stable (C and O) and radiogenic (Nd and Sr) isotope data clearly indicate a mantle origin for the carbonatite samples. The carbonatite εNd (+0.7 to +1.8) and εSr (+4.7 to +7.0) compositions overlap the field for Kerguelen ocean island basalts. One sample of ijolite has Nd and Sr isotopic compositions that also plot within the field for Kerguelen ocean island basalts, whereas the other silicate-carbonatite samples indicate involvement with an enriched component. These geochemical and isotopic data indicate that the rocks of the Sung Valley complex were derived from and interacted with an isotopically heterogeneous subcontinental mantle and is consistent with interaction of a mantle plume (e.g. Kerguelen plume) with lithosphere. A U-Pb perovskite age of 115.1±5.1 Ma obtained for a sample of Sung Valley ijolite also supports a temporal link to the Kerguelen plume. The observed geochemical characteristics of the carbonatite rocks indicate derivation by low-degree partial melting (∼0.1%) of carbonated mantle peridotite. This melt, containing a substantial amount of alkali elements, interacted with peridotite to form metasomatic clinopyroxene and olivine. This process could progressively metasomatize lherzolite to form alkaline wehrlite. Abstract Copyright (2005) Elsevier, B.V.
Year of Publication: 2005
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 05 Petrology, Igneous and Metamorphic; Absolute age; Alkalic composition; Asia; Australasia; Australia; Basalts; Broken Ridge; Bunbury Australia; C-13/C-12; Carbon; Carbonatites; Carbonatitic composition; Chemical composition; Complexes; Cretaceous; Dates; Emplacement; Flood basalts; Igneous rocks; Ijolite; India; Indian Ocean; Indian Peninsula; Intrusions; Isotope ratios; Isotopes; Jurassic; Kerguelen Plateau; Leg 120; Leg 183; Major elements; Mantle; Meghalaya India; Melilitolite; Melting; Mesozoic; Middle Cretaceous; Naturaliste Plateau; Nepheline syenite; Northeastern India; O-18/O-16; ODP Site 1136; ODP Site 1137; ODP Site 1138; ODP Site 1141; ODP Site 1142; ODP Site 749; ODP Site 750; Ocean Drilling Program; Oxides; Oxygen; Perovskite; Plutonic rocks; Pyroxenite; Rajmahal-Sylhet Province; Shillong Plateau; Sm/Nd; Stable isotopes; Sung Valley Complex; Syenites; Trace elements; U/Pb; Ultramafic composition; Ultramafics; Upper Jurassic; Volcanic rocks; Western Australia; Whole rock
Coordinates: N253400 N253500 E0921000 E0920500
Record ID: 2007015643
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands