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Journal ArticleDOI

Mineralogical and chemical characteristics of newer dolerite dyke around Keonjhar, Orissa: Implication for hydrothermal activity in subduction zone setting

17 Jun 2014-Journal of Earth System Science (Springer India)-Vol. 123, Iss: 4, pp 887-904

AbstractThe 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.

Topics: Mafic (58%), Amphibole (50%)

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Journal ArticleDOI
Abstract: We report eight new Pb-Pb baddeleyite ages and paleomagnetic results on a series of hitherto unknown Neoarchean NNE-SSW trending mafic dyke swarms intruding the Paleoarchean basement rocks in the Singhbhum craton, eastern India. Being the most dominant dyke swarms in the region, they occur over the entire Singhbhum craton with an areal distribution extending to about 30,000 km 2 . Of the eight dyke samples analysed across the entire dyke swarm, six were emplaced at 2762.4 ± 2.0 Ma (weighted mean of 6 dyke ages), two with similar strike directions, yielded older and younger ages of 2800.2 ± 0.7 Ma and 2752.0 ± 0.9 Ma respectively. The older 2800.2 ± 0.7 Ma dyke event appears to be coeval with several other magmatic events reported earlier from the Singhbhum craton. Emplacement of dacite tuffs within the Malaigiri basin, on the southern margin of the craton, the Budhapal and Rengali granite from the south-western and southern parts of the craton, along with the Temperkola granite activity and associated acid volcanics in the western part of the craton, and perhaps the Mayurbhanj granite (fine-grained phase) are also contemporaneous, suggesting a fairly wide spread thermal event in the region at this time. Well defined craton-wide magmatic events contemporaneous to the 2762.4 ± 2.0 Ma Singhbhum dyke activity have been reported from the Pilbara. The younger 2752.0 ± 0.9 Ma age dyke event occurring in the Singhbhum is also know from the eastern Pilbara. An older event at 2783 ± 1.2 Ma (Gaborone-Kanye-Plantation Porphyry-Derdepoort-Modipe episode) was identified in the Kaapvaal craton. Comparison of paleomagnetic data obtained on the Singhbhum Neoarchean dyke swarms with the Pilbara and Kaapvaal data, show all these continents were located at steep latitudes and could have been proximal to each other during this time. If Pilbara and Kaapvaal formed supercraton Vaalbara during the Neoarchean time, we propose Singhbhum with similar Archean geology could also have had its ancestry in the same supercraton.

63 citations


Journal ArticleDOI
Abstract: We report the first key paleopole as a result of paleomagnetic study on a precisely dated 1765.3 ± 1.0 Ma WNW-ESE trending dyke swarm from Singhbhum Craton. This pole has been used in this study to propose the paleogeographic reconstruction of India with Baltica Craton and North China Craton. Incremental alternating field (AF) and thermal demagnetization, isolated high coercivity components with north to north-westerly declination and shallow negative inclination from 9 sampling sites which are representing different individual dykes. The primary origin of the ChRM is supported by the positive baked contact test. The WNW-ESE trending dykes yield a mean paleomagnetic direction with a declination = 329.2° and an inclination = −22.8° (k = 31.6; α95 = 9.3°). The positive bake contact test proves the primary nature of remanence. The pole position of Singhbhum Craton at 1765 Ma is 45°N, 311°E (dp = 5.2 and dm = 9.9). Paleogeographic reconstruction at ca. 1770 Ma, supported by geological, tectonic and metallogenic evidences indicate that the Baltica Craton and India linkage can be stable for at least ∼370 Ma (∼1770–1400 Ma). There is also reasonable evidence in support of India-North China Craton spatial proximity at ∼1770 Ma.

22 citations


Journal ArticleDOI
01 Apr 2019-Lithos
Abstract: Evidences of Mesoarchean crustal reworking are not very common in geological records, being only found from Precambrian terrains like Kaapvaal and Pilbara Cratons where it is preserved as anorogenic/post-collisional granitic activity of 3–3.2 Ga age. The present study focuses on a granitoid unit of similar age, found near the eastern margin of the Precambrian Singhbhum Craton of eastern India. This ellipsoidal, N-S trending, well-foliated granite-gneiss body is found within the polydeformed, metasedimenatry rocks of Singhbhum Group, belonging to the North Singhbhum Mobile Belt. LA-ICP MS U-Pb analysis of zircon grains from one sample give crystallization ages ranging from 3079.4 ± 6.8 Ma to 3115 ± 10 Ma. These rocks hereby dubbed as “Bangriposi Granite Gneiss”, are composed of quartz, alkali feldspar, ferroan biotite (Fe/Fe + Mg: 0.7–0.9), titanite, illmenite, hastingsite, apatite, and numerous U-Th-REE- bearing accessory phases. They have high SiO2 (67–77 wt%) and Na2O + K2O (8.19–9.01 wt%), low CaO (0.35–1.5 wt%), MgO (0.05–0.36 wt%) and shows enrichment of Nb, Rb, Zr, Y, Th, and REEs, and depletion of Cr, Ni, U, with high FeOt/FeOt + MgO (~0.9), Ga/Al (2.04–3.51), (La/Yb)N (6.5–13), and low Eu/Eu* (0.11–0.47). Geochemically and mineralogically they are categorized as metaluminous to weakly peraluminous (A/CNK: 0.9–1.1) ferro-potassic alkali feldspar granites. These rocks show unequivocal affinities towards ‘A-type” granites and from geochemical evidences it is suggested that the parent magma was produced in response to crustal anatexis under low fO2 with P-T estimates of ~900 °C and 7–8 kbar. Geochemical modelling has revealed that the probable source was lower crustal amphibolites belonging to the Paleoarchean Older Metamorphic Group, which suffered low degrees (5–15%) of melting. Negative ƐNd values (−0.5 to −1.5) are also in favour of reworking of older crust and their Nd isotopic signature bears similarities with other coeval anatectic granites. Bangriposi Granite-Gneiss, along with Mayurbhanj Granite and Bonai Granite, represent a major phase of Mesoarchean anorogenic/post-collisional granitic activity in Singhbhum Craton, indicating the onset of its stabilization. Similar Mesoarchean crustally reworked felsic units are encountered in Pilbara and Kaapvaal cratons suggesting a possibility of correlation with the hypothesized “Vaalbara” supercontinent.

18 citations


Journal ArticleDOI
Abstract: This paper provides new mineralogical and morphological characterizations of calcic amphiboles from hydrothermally altered dolerites from France to discuss their potential to contain naturally occurring asbestos (NOA) and to release elongated mineral particles corresponding to asbestos fibers, or asbestos-like fibers, into the air. The calcic amphiboles were characterized using electron microprobe analysis, scanning and transmission electron microscopy. The results underline that fibrous occurrences of actinolite and ferro-actinolite regularly occur in hydrothermally altered dolerites, both in the groundmass and in quartz veins. In the groundmass, actinolitic amphiboles crystallize at the expense of magmatic clinopyroxenes and are rarely fibrous. Conversely, actinolite and ferro-actinolite fibers from quartz veins are potentially asbestiform to clearly asbestiform. The identification of quartz veins in hydrothermally altered dolerites is, therefore, an important parameter which should draw attention to the possible presence of asbestiform actinolite fibers. The mineralogical characterization of such veins as well as the estimation of their thickness and density is an important point to consider during studies involving NOA issues. Moreover, the degree of weathering of the dolerites, which directly affects the ability of non-asbestiform actinolite crystals to dissociate into very thin fibers, regarded as cleavage fragments instead of as asbestos, is also a key parameter to consider. Hydrothermally altered dolerites are common rocks likely to be exploited by the quarrying industry to produce aggregates or to be affected by construction works. Due to the abundance of actinolite fibers that they may contain locally, these rocks become priority targets to be monitored in terms of geological characterization and airborne fiber emission to ensure the protection of populations and workers.

8 citations


Cites background from "Mineralogical and chemical characte..."

  • ...Calcic amphiboles corresponding to actinolitic hornblendes, actinolites and ferro-actinolites are regularly described in doleritic dykes affected by recrystallizations under greenschist facies conditions (e.g., Offler 1984; Barton and Van Bergen 1984; Rose and Bird 1994; Oliver and McAlpine 1998; Hanson et al. 2004; Day and Springer 2005; Rigopoulos et al. 2010; Shibuya et al. 2010; Sengupta et al. 2014; Mäkitie et al. 2014)....

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Journal ArticleDOI
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.

6 citations


References
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01 Jan 1989
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.

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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.

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Journal ArticleDOI
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.

3,319 citations