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.
Citations
More filters
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
References
More filters
01 Jan 1989
TL;DR: In this article, trace-element data for mid-ocean ridge basalts and ocean island basalts are used to formulate chemical systematics for oceanic basalts, interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone.
Abstract: Summary Trace-element data for mid-ocean ridge basalts (MORBs) and ocean island basalts (OIB) are used to formulate chemical systematics for oceanic basalts. The data suggest that the order of trace-element incompatibility in oceanic basalts is Cs ≈ Rb ≈ (≈ Tl) ≈ Ba(≈ W) > Th > U ≈ Nb = Ta ≈ K > La > Ce ≈ Pb > Pr (≈ Mo) ≈ Sr > P ≈ Nd (> F) > Zr = Hf ≈ Sm > Eu ≈ Sn (≈ Sb) ≈ Ti > Dy ≈ (Li) > Ho = Y > Yb. This rule works in general and suggests that the overall fractionation processes operating during magma generation and evolution are relatively simple, involving no significant change in the environment of formation for MORBs and OIBs. In detail, minor differences in element ratios correlate with the isotopic characteristics of different types of OIB components (HIMU, EM, MORB). These systematics are interpreted in terms of partial-melting conditions, variations in residual mineralogy, involvement of subducted sediment, recycling of oceanic lithosphere and processes within the low velocity zone. Niobium data indicate that the mantle sources of MORB and OIB are not exact complementary reservoirs to the continental crust. Subduction of oceanic crust or separation of refractory eclogite material from the former oceanic crust into the lower mantle appears to be required. The negative europium anomalies observed in some EM-type OIBs and the systematics of their key element ratios suggest the addition of a small amount (⩽1% or less) of subducted sediment to their mantle sources. However, a general lack of a crustal signature in OIBs indicates that sediment recycling has not been an important process in the convecting mantle, at least not in more recent times (⩽2 Ga). Upward migration of silica-undersaturated melts from the low velocity zone can generate an enriched reservoir in the continental and oceanic lithospheric mantle. We propose that the HIMU type (eg St Helena) OIB component can be generated in this way. This enriched mantle can be re-introduced into the convective mantle by thermal erosion of the continental lithosphere and by the recycling of the enriched oceanic lithosphere back into the mantle.
19,221 citations
TL;DR: In this paper, a system was presented whereby volcanic rocks may be classified chemically as follows: Subalkaline Rocks:A.B. Tholeiitic basalt series:Tholeitic picrite-basalt; tholeiite, tholeitic andesite; dacite; rhyolite.
Abstract: A system is presented whereby volcanic rocks may be classified chemically as follows:I. Subalkaline Rocks:A. Tholeiitic basalt series:Tholeiitic picrite-basalt; tholeiite; tholeiitic andesite.B. Calc-alkali series:High-alumina basalt; andesite; dacite; rhyolite.II. Alkaline Rocks:A. Alkali olivine basalt series:(1) Alkalic picrite–basalt; ankaramite; alkali basalt; hawaiite; mugearite; benmorite; trachyte.(2) Alkalic picrite–basalt; ankaramite; alkali basalt; trachybasalt; tristanite; trachyte.B. Nephelinic, leucitic, and analcitic rocks.III. Peralkaline Rocks:pantellerite, commendite, etc.
6,269 citations
Book•
01 Jan 1966
TL;DR: In this article, the authors define di-and ring silicates: olivine group humite group zircon sphene (titanite) garnet group, vesuvianite sillimanite, mullite, andalusite, kyanite topaz staurolite, chloritoid epidote group lawsonite, pumpellyite melilite group beryl, cordierite, tourmaline axinite.
Abstract: PART 1 ORTHO: Di- and ring silicates: olivine group humite group zircon sphene (titanite) garnet group, vesuvianite sillimanite, mullite, andalusite, kyanite topaz staurolite, chloritoid epidote group lawsonite, pumpellyite melilite group beryl, cordierite, tourmaline axinite. PART 2 CHAIN SILICATES: pyroxene group wollastonite sapphirine amphibole group. PART 3 SHEET SILICATES: mica group stilpnomelane pyrophyllite chlorite serpentine clay minerals apophyllite prehnite. PART 4 FRAMEWORK SILICATES: feldspar group silica minerals nepheline group petalite, leucite sodalite group cancrinite - vishnevite, scapolite analcite, zeolite group. PART 5 NON-SILICATES: oxides hydroxides sulphides sulphates carbonates phosphates halides
5,387 citations
TL;DR: The International Mineralogical Association's approved amphibole nomenclature has been revised to simplify it, make it more consistent with divisions generally at 50%, define prefixes and modifiers more precisely, and include new amphibole species discovered and named since 1978, when the previous scheme was approved.
Abstract: The International Mineralogical Association's approved amphibole nomenclature has been revised to simplify it, make it more consistent with divisions generally at 50%, define prefixes and modifiers more precisely, and include new amphibole species discovered and named since 1978, when the previous scheme was approved. The same reference axes form the basis of the new scheme and most names are little changed, but compound species names like tremolitic hornblende (now magnesiohornblende) are abolished, as are crossite (now glaucophane or ferroglaucophane or magnesioriebeckite or riebeckite), tirodite (now manganocummingtonite), and dannemorite (now manganogrunerite). The 50% rule has been broken only to retain tremolite and actinolite as in the 1978 scheme; the sodic-calcic amphibole range has therefore been expanded. Alkali amphiboles are now sodic amphiboles. The use of hyphens is defined. New amphibole names approved since 1978 include nyboite, leakeite, kornite, ungarettiite, sadanagaite, and cannilloite. All abandoned names are listed. The formulae and source of the amphibole end-member names are listed and procedures outlined to calculate Fe (super 3+) and Fe (super 2+) where not determined by analysis.
3,510 citations