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References (1)
- Publisher
- Wiley
- Copyright
- © 2016 Geological Society of China
- ISSN
- 1000-9515
- eISSN
- 1755-6724
- DOI
- 10.1111/1755-6724.12924
- Publisher site
- See Article on Publisher Site
Abstract
ACTA GEOLOGICA SINICA (English Edition) Vol. 90 Supp. 1 July 2016 http://www.geojournals.cn/dzxben/ch/index.aspx http://mc.manuscriptcentral.com/ags Shaik A Rashid and Naqeebul Islam, 2016. Geochemical Characteristics of Proterozoic Mafic Dykes from the Bomdila Group of Rocks, NE Lesser Himalaya, India. Acta Geologica Sinica (English Edition), 90(supp. 1): 122. Geochemical Characteristics of Proterozoic Mafic Dykes from the Bomdila Group of Rocks, NE Lesser Himalaya, India Shaik A Rashid and Naqeebul Islam Department of Geology, Aligarh Muslim University, Aligarh -202002, India The mafic dykes from the Paleoproterozoic Bomdila melting of a common source; however, the plots may shifts Group of metasedimentary rocks, Arunachal Pradesh, NE horizontally to higher X-axis values because of crystal Lesser Himalaya, India have been analyzed for major and fractionation (Feigenson et al., 1983; Rosey et al., 1992; trace elements geochemistry essentially to understand their Bradshaw et al., 1993). A broad positive linear pattern is petrogenesis. The mafic rocks are basaltic in composition exhibited by the Bomdila mafic rocks in (La/Yb) vs. (La) N N and show continental tholeiitic nature. The important diagram, indicating that they were formed by different characters such as low magnesium numbers (mostly < 60) degrees of melting of a source with similar (La/Yb) ratios. and Sr as well as negative Eu anomalies of the Bomdila Lower degree of melting resulted the samples with higher mafic rocks suggest that fractional crystallization has (La) and (La/Yb) whereas samples with lower (La) and N N N played a role in the generation of these rocks. The uniform (La/Yb) have formed by higher degree of melting. CaO/Al O ratio with increasing FeO /MgO further The strong enrichment of LREE and LIL elements in the 2 3 indicates that olivine and plagioclase were the main Bomdila tholeiites relative to primordial mantle indicate fractionating phases. The fractionation of olivine and their derivation from an enriched mantle source (Weaver pyroxene from the primitive magmas in the evolution of and Tarney, 1983). On Nd-Ce, Zr-Nb bivariate plots, the these mafics is also evident from the diagram FeO / mafic samples always fall on enriched side in the diagram. (FeO +MgO) – Al O . However, a large variation in The high LREE/HREE and low Nb, P and Ti together with 2 3 incompatible element ratios (e.g., La/Yb, Zr/Y, Ti/Y, Zr/ high and variable Fe/Mg ratio of Bomdila mafics indicate Nb) in the mafic rocks cannot be explained by crystal that the source was enriched through a hydrous silicate melt fractionation alone. These variations probably represent phase. Typical continental tholeiitic nature, overall low Mg different degree of partial melting from a common source numbers with chemical features indicating the involvement and also reflect the enriched mantle source characteristics. of fractional crystallization are consistent with the The mafic samples plotted on (La/Yb) vs. (La) further geochemical signatures of other such volcanics from Chail, N N support the inference that these rocks evolved by different Juthogh, Vaikrita and Garhwal regions (Ahmad and Bhat, degrees of partial melting of a mantle source. In general, on 1987; Bhat and LeFort, 1992) that exist in the NW Lesser this type of plot, a linear relationship will be defined by the Himalaya. samples if they are derived by different degrees of partial * Corresponding author. E-mail: rashidamu@hotmail.com
Journal
Acta Geologica Sinica (English Edition) – Wiley
Published: Oct 1, 2016