Mineralogical and chemical characteristics of newer dolerite dyke around Keonjhar, Orissa: Implication for hydrothermal activity in subduction zone setting
TL;DR: The newer dolerite dykes around Keonjhar within the Singbhum Granite occur in NE-SW, NW-SE and NNE-SSW trends as mentioned in this paper.
Abstract: The newer dolerite dykes around Keonjhar within the Singbhum Granite occur in NE–SW, NW–SE and NNE–SSW trends. The mafic dykes of the present study exhibit several mineralogical changes like clouding of plagioclase feldspars, bastitisation of orthopyroxene, and development of fibrous amphibole (tremolite–actinolite) from clinopyroxene, which are all considered products of hydrothermal alterations. This alteration involves addition and subtraction of certain elements. Graphical analyses with Alteration index and elemental abundances show that elements like Rb, Ba, Th, La and K have been added during the alteration process, whereas elements like Sc, Cr, Co, Ni, Si, Al, Fe, Mg and Ca have been removed. It is observed that in spite of such chemical alteration, correlation between major and trace elements, characteristic of petrogenetic process, is still preserved. This might reflect systematic Alteration (addition or subtraction) of elements without disturbing the original element to element correlation. It has also been established by earlier workers that the evolution of newer dolerite had occurred in an arc-back arc setting which may also be true for newer dolerites of the present study. This is evident from plots of pyroxene composition and whole rock composition of newer dolerite samples in different tectonic discrimination diagrams using immobile elements. The newer dolerite dykes of the Keonjhar area may thus be considered to represent an example of hydrothermal activity on mafic rocks in an arc setting.
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TL;DR: In this article, the authors reported eight new Pb-Pb baddeleyite ages and paleomagnetic results on a series of hitherto unknown NNE-SSW trending mafic dyke swarms intruding the Paleoarchean basement rocks in the Singhbhum craton, eastern India.
89 citations
TL;DR: In this article, the authors reported the first key paleopole as a result of paleomagnetic study on a precisely dated 1765, which was used in this study to propose the paleogeographic reconstruction of India with Baltica Craton and North China Craton.
35 citations
TL;DR: The Bangriposi Granite Gneiss as discussed by the authors is composed of quartz, alkali feldspar, ferroan biotite (Fe/Fe+Mg: 0.7-0.9), titanite, illmenite, hastingsite, apatite, and numerous U-ThREE bearing accessory phases.
27 citations
TL;DR: The Singhbhum Craton in eastern India is host to at least seven sets of mafic dyke swarms and the dykes range in composition from basalt to andesite and have transitional tholeiitic to calc-alkaline affinities as discussed by the authors.
14 citations
TL;DR: In this article, the authors investigated the petrography and geochemistry of 19 NNE-SSW to NE-SW trending dolerite dykes in two sectors in the northern and southwestern part of Bahalda town, Odisha, India.
Abstract: The mafic dyke swarm, newer dolerite dykes (NDDs) intrudes the Archaean Singbhum granite of the Singhbhum craton, eastern India. The present investigation focuses on the petrography and geochemistry of 19 NNE–SSW to NE–SW trending NDDs in two sectors in the northern and south-western part of Bahalda town, Odisha, Singhbhum. Chondrite normalised rare earth element (REE) patterns show light REE (LREE) enrichment among majority of the 13 dykes while the remaining six dykes show a flat REE pattern. Critical analyses of some important trace element ratios like Ba/La, La/Sm, Nb/Y, Ba/Y, Sm/La, Th/La, La/Sm, Nb/Zr, Th/Zr, Hf/Sm, Ta/La and Gd/Yb indicate that the dolerite dykes originated from a heterogeneous spinel peridotite mantle source which was modified by fluids and melts in an arc/back arc setting. REE modelling of these dolerite dykes were attempted on LREE-enriched representative of NDD which shows that these dykes might have been generated by 5–25% partial melting of a modified spinel peridotite source which subsequently suffered around 30% fractional crystallisation of olivine, orthopyroxene and clinopyroxene. The reported age of ~2.75–2.8 Ma seems to be applicable for these dykes and this magmatism appears to be contemporaneous with major scale anorogenic granitic activity in the Singhbhum craton marking a major event of magmatic activity in eastern India.
11 citations
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TL;DR: In this paper, the geochemical properties of Newer Dolerite dykes were investigated in the context of possible tectonic setting, and the authors made attempts to classify these dykes according to their trace and REE composition.
Abstract: Copyright © 2012 by The Geochemical Society of Japan. belong to different generations (Saha et al., 1973). The geochemical characters of these dykes are strikingly uniform over a long period of time (Bose, 2008; Mallick and Sarkar, 1994). Bose (2008) suggested that Newer Dolerite dykes generated through partial melting of subcontinental mantle which in turn was metasomatised. Mir et al. (2010) documented geochemical characteristics of these dykes similar to those of back arc extension basalts (BABB). In the studied area shear fractures which appears to act as pathways of these mafic intrusives have two dominant trends NE-SW and E-W and a subsidiary NW-SE trends. This might suggest that stress system have not an uniform direction over a long period, but it changed orientation with time. The geochemical classification of these dykes and their linking to possible tectonic settings have not yet been reported by earlier workers. In the present work, attempts have been made to classify these dykes according to their trace and REE composition. The genesis of different chemical types of Newer Dolerite dykes has been discussed in the perspective of possible tectonic setting.
9 citations
"Mineralogical and chemical characte..." refers background in this paper
...Similar orthopyroxene bearing dolerite dyke has been reported from Chaibasa area of Singhbhum region (Sengupta and Ray 2012) where co-existence of bastitised orthopyroxenes, anorthitic plagioclase and clinopyroxene has been explained as product of contamination of granitic country rock and mafic…...
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...Although reports on mineralogical alteration in Proterozoic mafic dykes of India are fairly common (Mallikharjuna Rao et al. 2005; Sengupta and Ray 2012), detailed studies on behaviour of major trace elements during such alterations have hardly been attempted....
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...In Singbhum region, newer dolerite dykes exhibit mineralogical and chemical compositions which point towards emplacement in an arc setting in which hydrothermal activity and alteration are common features during emplacement (Sengupta and Ray 2012)....
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...Geochemical signatures of subduction related processes in a back arc setting in newer dolerite dykes of Singbhum pluton have been reported by several workers (Bose 2008; Mir et al. 2010; Sengupta and Ray 2012)....
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01 Jan 2013
TL;DR: Newer Dolerite dykes (NDD) traverses the Singhbhum Granitoid Complex (SGC) in distinct orientations viz., NNE-SSW, NNW-SSE and E-W as discussed by the authors.
Abstract: Newer Dolerite Dykes (NDD) traverses the Singhbhum Granitoid Complex (SGC) in distinct orientations viz., NNE-SSW, NNW-SSE and E-W, among which the NNE-SSW trend is the most dominant. These dykes are subalkaline in nature and show compositional variation from basalt through basaltic andesite to andesite. The relationship shown by various oxides against MgO is consistent with fractional crystallization of a mafic magma. Variations in major elements, particularly SiO2, Al2O3, CaO, TiO2 contents, and CaO/TiO2 and Al2O3/TiO2 ratios in the studied dykes indicates that their Ca and Al are held in the residual mantle phases such as clinopyroxene, plagioclase, spinel and garnet. Low Ni and highly variable Cr values suggest that olivine and clinopyroxene fractionation controlled the abundances of Ni and Cr in these rocks. The high (La/Yb)N and (Gd/Yb)N in combination with relatively low HREE abundance of the Newer Dolerites dykes suggest that they may have formed by low degrees of partial melting of a garnet bearing source. The higher Th/Zr, Rb/Y, Ba/Nb and Ba/Th ratios of these dykes suggest that their mantle source was enriched/ metasomatised by slab derived fluids. Their geochemical characteristics particularly Ti/Y, Zr/Y, Th/Nb, Ba/Nb, La/Nb, (La/Sm)PM are similar to subduction zone basalts that occur along the plate margin. The enriched LREE-LILE and depletion of high-field strength elements (HFSE) especially Nb, P and Ti and detectable slab-derived components of the studied dykes are all features typical for subduction zone-related petrogenesis.
6 citations
"Mineralogical and chemical characte..." refers background in this paper
...It appears from previous works that the newer dolerites were evolved in arc-back arc setting (Bose 2008; Mir et al. 2010, 2013)....
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...It has also been demonstrated that newer dolerites show geochemical signatures similar to those of back-arc basaltic rocks (Mir et al. 2011, 2013)....
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...Several workers have suggested a subduction zone related origin of these newer dolerite dykes of Singhbhum region (Bose 2008; Mir et al. 2010, 2011, 2013)....
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01 Jan 1990
TL;DR: In this paper, high vesicular and glassy pillow basalts from the sunken oceanic island at Ocean Drilling Program Site 706 in the Indian Ocean show variable alteration and the addition of secondary zeolite facies clay minerals.
Abstract: Highly vesicular and glassy pillow basalts from the sunken oceanic island at Ocean Drilling Program Site 706 in the Indian Ocean show variable alteration and the addition of secondary zeolite facies clay minerals. The mineralogical changes reflect chemical additions of K, Rb, Cs, Li, Si, Sc, Fe, and possibly Sr, Pb, Tl, Au, Pt, and Rh. The elements Ca, Mg, Mn, Ni, and possibly Na, Ba, U, and Ir were removed, but the rare earth elements as well as the elements Zr, Nb, Y, Ti, Al, V, Th, and probably P and Hf were immobile. The data for Cr, Cu, Zn, Bi, Pd, and Ru show large variations, indicating that they were probably mobile; whether they were generally added or removed could not be ascertained, however. The chemical additions and removals are similar to the low-temperature changes observed in ocean-floor basalts near the seawater-seafloor interface. The large, though nonpervasive, chemical changes reflect the effects of alteration caused by seawater percolating down through easily altered glass-rich basalts. They imply that a low-temperature alteration zone similar to the zone in the recharge portion of the ocean-floor (ridge) hydrothermal system also occurs on oceanic islands.
5 citations
"Mineralogical and chemical characte..." refers background or methods in this paper
...Greenough et al. (1990) have documented quantitatively, the effects of alteration on hotspot basalts from sunken oceanic island in the Indian Ocean....
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...In order to document quantitatively the effects of alteration on newer dolerites of the study area, we are following the methods adopted by Greenough et al. (1990)....
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Journal Article•
TL;DR: An ultramafic body flanked on either side by tholeiitic dolerite occurs as a minor intrusion in the Singhbhum granite, southwest of Keshargaria (22°36' : 85°56').
Abstract: An ultramafic body flanked on either side by tholeiitic dolerite occurs as a minor intrusion in the Singhbhum granite, southwest of Keshargaria (22°36' : 85°56'). The ultramafic body varies from pyroxene-rich harzburgite to olivine-rich poikilitic harzburgite, the latter being conspicuous in the central part of the intrusion. A crude planar structure defined by enstatite crystals is developed towards the contact walls. The constituent mafic silicates, arranged in paragenetic order, are: forsteritic olivine, enstatite, diopsidic augite (malacolite), phlogopite and plagioclase, the last three phases appear to represent intracummulus crystallisation. The central part of the intrusion is relatively enriched in olivine whereas the marginal parts are in an advanced stage of differentiation relative to the central zone, indicated by lower Mg/Fe and Ba/Rb ratios in the former. This spatial variation in degree of differentiation is considered to have been induced during flowage of the crystal-iquid mush. The ultramafic intrusion is non-uniform in chemical and mineralogical compositions and does not represent unaltered mantle material. The significant deviation from the mantle composition is in higher aluminium and ferric iron and lower magnesium in the investigated peridotite. The Keshargaria ultramafic body which is one of several such bodies associated with the Newer Dolerite intrusions, represents a stage of fractionation of mantle derived magma.
3 citations
"Mineralogical and chemical characte..." refers background in this paper
...The mafic dyke swarm, popularly known as the newer dolerite suite, traverses the Precambrian Singbhum granitic complex in the districts of Singbhum, Keonjhar and Mayurbhanj in eastern India (Dunn 1929; Jones 1934; Krishnan 1936; Dunn and Dey 1942; Saha 1948, 1952; Saha et al. 1972, 1973)....
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