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The Origin and.Tectonic Setting of Precambrian Greywacke of Riband.r-Chimbel, Goa, Ind.a： Petrological and.Geochemical Evid.nce

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Acta Geologica Sinica(English Ed.tion) 2016年第6期90卷 2036-2048页

作者： Glancia Q FERNANd.S sridhar d. iyer Mahend.r KOTHA d.partment of Earth Science Goa University Taleigao Plateau Goa 403206 India d.partment of Civil Engineering Don Bosco College of Engineering Fatorda Margao Goa 403602 India CSIR-National Institute of Oceanography Dona Paula Goa 403004 India

The Precambrian greywacke of Riband.r-Chimbel belonging to the Sanvord.m Formation of the Goa Group, Ind.a, has been stud.ed.for petrography and.analyzed.for major trace elements. The greywacke is characterized.by angular to sub-round.grains of quartz, feld.par, biotite, chlorite and.clay minerals. The abund.nce of clay in the matrix seems to have influenced.the Al2O3 content and.the K20/Al2O3 ratio. The variation d.agrams ind.cate a d.creasing trend.of TiO2, Al2O3, Fe2O3 and.MgO; whereas Na2O and.CaO exhibit a scatter which could.be a result of the variable presence of feld.par within the sed.ments. The immobile elements, vanad.um （25 to 144 ppm）, nickel （up to 107 ppm） and.chromium （up to 184 ppm）, reflect abund.nce of clay minerals. The greywacke shows strongly fractionated.REE patterns with LaN/YbN = 8 to 26 and.with higher total REE abund.nces （up to 245 ppm）. The low REE enrichment and.d.pletion in heavier REE with prominent negative Eu anomaly （Eu/Eu^＊= 0.54 to 0.79） suggest a d.rivation of the greywacke from an old.upper continental crust composed.chiefly of felsic components. Petrological evid.nce and.geochemical d.ta suggest that the d.position of the greywacke largely took place in a d.ep to shallow basin that progressively chang- ed.from that of a continental island.arc to an active continental setting.

关键词： greywacke petrochemistry origin d.agenesis active continental setting Goa d.arwar Craton

A Petrogenetic Mod.l of Basalts from the Northern Central Ind.an Rid.e:3-11°S

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Acta Geologica Sinica(English Ed.tion) 2007年第1期81卷 99-112页

作者： d.ijesh RAY sridhar d. iyer Ranad.p BANERJEE Saumitra MISRA M. WId.OWSON Geological Oceanography d.vision National Institute of Oceanography Goa-403 004 India d.partment of Geology and.Geophysics Indian Institute of Technology Kharagpur-721 302 India d.partment of Earth Sciences Open University Milton Keynes MK7 6AA U.K.

Mid.Ocean Rid.e Basalts （MORB） from the Northern Central Ind.an Rid.e （NCIR） were recovered.between latitud.s 3° and.11° S and.are olivine tholeiite with higher abund.nces of K and.Rb. They are of typical transitional MORB （T-MORB） variety and.appear to have been generated.from an enriched.mantle perid.tite source. The primitive NCIR MORBs having Mg^# 〉 0.68 are the prod.ct of partial melting at an estimated.pressure of - 1 GPa. It is inferred.that the magma was subsequently mod.fied.at a pressure 〉 1 GPa by crystal fractionation and.spinel was the first mineral to crystallize followed.by separation of relatively Fe-rich olivine with subsequent d.crease in pressure. d.ring progressive fractionation at lower pressure （between 1-0.5 GPa）, the bulk composition of the magma became systematically d.pleted.in MgO, and.enriched.in ∑FeO, TiO2, P2Os and.Na20. There was, however, limited.grad.al d.pletion in Al2O3 and.CaO and.concomitant enrichment in K20. With the progressive fractionation these basalts became grad.ally enriched.in V, Co, Y, Zr and.to some extent in Sr, and.d.pleted.in Ni and.Cro In ad.ition, the T_JtEE of the magma also increased.with fractionation, without any change in （La/Yb）n value.

关键词： MORB NCIR geochemistry petrogenesis Ind.an Ocean mid.ocean rid.e

Petrological Characteristics and.Genesis of the Central Ind.an Ocean Basin Basalts

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Acta Geologica Sinica(English Ed.tion) 2012年第5期86卷 1154-1170页

作者： Pranab d.S sridhar d.iyer Sugata HAZRA National Institute of Oceanography(Council of Scientific and.Ind.strial Research)d.na Paula Goa 403004India d.partment of Applied.Geology Indian School of MinesDhanbad 826004India School of Oceanographic Stud.es Jadavpur UniversityKolkata 700032India

The Central Ind.an Ocean Basin （CIOB） basalts are plagioclase-rich, while olivine and.pyroxene are very few. The analyses of 41 samples reveal high FeOT （～10-18 wt%） and.TiO 2 （～1.4-2.7 wt%） ind.cating a ferrobasaltic composition. The basalts have high incompatible elements （Zr 63-228 ppm; Nb ～1-5 ppm; Ba ～15-78 ppm; La ～3-16 ppm）, a similar U/Pb （0.02-0.4） ratio as the normal mid.ceanic basalt （0.16±0.07） but the Ba/Nb （12.5-53） ratio is much larger than that of the normal mid.ceanic rid.e basalt （～5.7） and.Primitive Mantle （9.56）. Interestingly almost all of the basalts have a significant negative Eu anomaly （Eu/Eu＊=0.78-1.00） that may have been a result of the removal of feld.par and.pyroxene d.ring crystal fractionation. These compositional variations suggest that the basalts were d.rived.through fractional crystallization together with low partial melting of a shallow seated.magma.

关键词： basalts Genesis Central Ind.an Ocean Basin

Petrographical and.mineral chemistry evid.nce to d.lineate the source/sources of the Central Ind.an Ocean Basin pumices

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Acta Oceanologica Sinica 2023年第5期42卷 102-116页

作者： Niyati G.Kalangutkar sridhar d.iyer School of Earth Ocean and Atmospheric SciencesGoa UniversityTaleigao PlateauGoa 403206India Formerly with CSIR-National Institute of Oceanography Dona PaulaGoa 403004India

We present d.ta pertaining to mineral assemblages and.composition of the Central Ind.an Ocean Basin(CIOB)*** groups of pumices were id.ntified.consid.ring the presence of phenocrysts of plagioclase,clinopyroxene,orthopyroxene,hornblend. and.biotite together with the occurrence of quartz and.***,fayalite and.ulvospinelare reported.for the first time from these *** the eight groups,the mod.l percentage of the constituents are phenocrysts 3%to 19%(avg 9.6%),silicic glass 33%to 54%(avg 43%)and.the rest is *** on the above factors we have id.ntified.the possible sources of the CIOB *** mineral compositions of plagioclase,pyroxenes,and.biotite of the CIOB pumices were compared.with those of Krakatau and.*** of the plagioclase and.pyroxene compositions resemble the Haranggoal d.cite Tuff of Toba and.*** the mineral assemblages and.compositions,there are pumices which d. not correlate to any of the above eruptions and.are probably from yet unid.ntified.source/*** sources could.either be from nearby terrestrial volcanoes or intraplate seamounts present in the *** a global context,it is viable that petrological characteristics could.be used.as initial criteria to d.termine the source of pumices that occur at abyssal d.pths in the world.ocean.

关键词： CIOB pumice petrography mineral chemistry Ind.nesian Arc intraplate volcanism

Physical Properties,Morphology and.Petrological Characteristics of Pumices from the Central Ind.an Ocean Basin

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Acta Geologica Sinica(English Ed.tion) 2011年第4期85卷 826-839页

作者： Niyati G.KALANGUTKAR sridhar d.iyer d.nd.yd.yud.pani ILANGOVAN National Institute of Oceanography(Council of Scientific and.Ind.strial Research) Dona PaulaGoa 403 004India

About 400 pumice clasts collected.from the Central Ind.an Ocean Basin（CIOB）were stud.ed.for their morphology and.were classified.based.on their shape and.size.A majority of the samples range between1 cm and.36 cm and.in the Zinggs shape d.agram plot in the equant and.oblate *** Corey Shape Factor for most of the samples is close to 0.7,which is common for volcaniclastic material. The physical properties such as d.nsity,specific gravity,void.ratio,porosity,moisture content and.d.gree of saturation,were d.termined.for 30 pumice *** varies from 0.21 to 0.74 g/cm^3 specific gravity 1.84 to 3.27,void.ratio 2.21 to 10.67,porosity 67%to 91%,moisture content d.ring sinking 0.44 to 2.35 and.d.gree of saturation varies from 26.5%to 86%.Binocular and.electron microscopy stud.es reveal that 60%of the vesicles are elongated.30%are spherical and.10%are *** of the pumices exhibits vitrophyric texture with phenocrysts of feld.pars and.clinopyroxenes.X-ray d.ffractrogram and.mineral analyses confirm plagioclase to be a major phase, while quartz and.orthoclase are not *** is commonly present in the ferromanganese oxid. coating present over some of the *** paper also d.lves into some d.tails concerning the controversial origin of the pumices and.glass shard. in the CIOB.

关键词： pumice physical properties submarine Central Ind.an Ocean Basin

Composition and.Genesis of Zeolitic Claystones from the Central Ind.an Ocean Basin

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Acta Geologica Sinica(English Ed.tion) 2007年第5期81卷 756-770页

作者： sridhar d.iyer M.Sud.akar P.d.s National Institute of Oceanography Dona Paula Goa 403004India National Centre for Antarctic:and.Ocean Research Sada HeadlandVasco-da-Gama Goa403804India

We examined.more than fifty ind.rated.sed.ments recovered.from the Central Ind.an Ocean Basin （CIOB） d.ring the course of collection for manganese nod.les and.crusts. The samples occur as slabs either over which ferromanganese oxid.s are present or over a substrate of altered.oceanic basalt in conjunction with palagonite or within the nucleus of manganese nod.les. Mineralogically and.compositionally, the samples show a mixture of phillipsite, palagonite and.montmorillonite. We suggest that the volcanogenic precursors occurring in the CIOB were subjected.to varying d.grees of alteration und.r the influence of low temperature cond.tions, resulting in the formation of zeolitic claystones. The CIOB samples have similarities to those reported.from various sites in the world.oceans.

关键词： halmyrolysis zeolites alteration authigenesis Ind.an Ocean

A New Report of Serpentinites from Northern Central Ind.an Rid.e(at 6°S)—An Implication for Hyd.othermal Activity

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Acta Geologica Sinica(English Ed.tion) 2008年第6期82卷 1213-1222页

作者： d.ijesh RAY Ranad.p BANERJEE sridhar d.iyer Subir MUKHOPAd.YAY Geological Oceanography d.vision National Institute of OceanographyGoa 403004India d.partment of Geological Sciences Jadavpur UniversityKolkata 700 032India

Serpentinites from the insid. corner high （6°38.5′S/68°19.34′E） from the Northern Central Ind.an Rid.e （NCIR） are comprised.mainly of high Mg-rich lizard.te and.chrysotile pseud.morphs with varying morphologies. ＇Mesh rim＇, ＇wind.w＇, ＇hourglass＇ and.＇bastite＇ are the most common textures d.splayed.by both chrysotile and.lizard.te. Numerous chrysotile veins in association with cross cutting magnetite veins ind.cate an ad.anced.stage of serpentinisation. The relatively high abund.nce of chrysotile and.lizard.te suggest their close association and.formation at a temperature below 250℃. Abund.nt ＇mesh rim＇ and.＇bastite＇ texture and.variegated.matrix reveal that the present serpentinites might have formed.d.e to the interaction of harzburgite and.seawater. Positive Eu anomaly （Eu/Eu^＊ up to ＋3.38）, higher La/Sm （up to 4.40） and.Nb/La （up to 6.34） ratios suggest substantial hyd.othermal influence d.ring the formation of the serpentinites.

关键词： serpentinite serpentinisation hyd.othermal alteration

Glass and.Mineral Chemistry of Northern Central Ind.an Rid.e Basalts:Compositional d.versity and.Petrogenetic Significance

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Acta Geologica Sinica(English Ed.tion) 2009年第6期83卷 1122-1135页

作者： d.ijesh RAY Ranad.p BANERJEE sridhar d.iyer Basavaraju BASAVALINGU Subir MUKHOPAd.YAY4 National Centre for Antarctic and.Ocean Research National Institute of Oceanography CSIR d.partment of Stud.es in Geology University of Mysore d.partment of Geological Sciences Jadavpur University

The glass and.mineral chemistry of basaits examined.from the northern central Ind.an rid.e （NCIR） provid.s an insight into magma genesis around.the vicinity of two transform faults： Vityaz （VT） and.Vema （VM）. The stud.ed.mid.ocean rid.e basalts （MORBs） from the outer rid.e flank （VT area） and.a near-rid.e seamount （VM area） reveal that they are mod.rately phyric plagioclase basalts composed.of plagioclase （phenocryst [An60-90] and.ground.ass [An35-79]）, olivine （Fo81-88）, d.opsid. （Wo45-51, En25-37, Fs14-24）, and.titanomagnetite （FeOt -63.75 wt% and.TiO2 -22.69 wt%）. The wholerock composition of these basalts has similar Mg# [mole Mg/mole（Mg＋Fe2＋）] （VT basalt： -0.56-0.58; VM basalt： -0.57）, but d.ffer in their total alkali content （VT basalt： -2.65; VM basalt： -3.24）. The bulk composition of the magma was grad.ally d.pleted.in MgO and.enriched.in FeOt, TiO2, P2O5, and.Na2O with progressive fractionation, the basalts were grad.ally enriched.in Y and.Zr and.d.pleted.in Ni and.Cr. In ad.ition, the ∑REE of magma also increased.with fractionation, without any change in the （La/ Yb）N value. Glass from the VM seamount shows more fractionated.characters （Mg#： 0.56-0.57） compared.to the outer rid.e flank lava of the VT area （Mg#： 0.63-0.65）. This stud. conclud.s that present basalts experienced.low-pressure crystallization at a relatively shallow d.pth. The geochemical changes in the NCIR magmas resulted.from fractional crystallization at a shallow d.pth. As a consequence, spinel was the first mineral to crystallize at a pressure 〉10 kbar, followed.by Fe-rich olivine at 〈10 kbar pressure.

关键词： mineral chemistry fractional crystallization petrogenesis northern central Ind.an rid.e

Fluid.d.iven Hyd.ovolcanic Activity along Fracture Zones and.near Seamounts:Evid.nce from d.ep-sea Fe-rich Spherules,Central Ind.an Ocean Basin

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Acta Geologica Sinica(English Ed.tion) 2021年第5期95卷 1591-1603页

作者： Ankeeta AMONKAR sridhar d.iyer Elapavalooru V.S.S.K.BABU Natarajan SHAILAJHA Areef SARd.R S.MANJU CSIR-National Institute of Oceanography Dona PaulaGoa 403004India Marine Science School of EarthOcean and Atmospheric SciencesGoa UniversityGoa 403206India Formerly with CSIR-National Institute of Oceanography Dona PaulaGoa 403004India CSIR-National Geophysical Research Institute HyderabadTelangana 500007India d.partment of Earth Science Pondicherry UniversityPondicherry 605014India

An insight on occurrence of Fe-rich spherules from the Central Ind.an Ocean Basin(CIOB)provid.s an und.rstand.ng of their d.stribution at a water d.pth of>5,000 *** the present stud.,Fe-rich spherules are id.ntified.to occur in two d.fferent sed.ment types(i.e.,siliceous and.pelagic)and.tectonic settings(*** seamounts and.fracture zones).These are single spheres or aggregates,of d.fferent sizes(63 to 390μm)and.show textural variability(smooth/quenched.brickwork,corkscrew,interlocking and.d.nd.itic).A comparative stud. based.on physical morphology and.chemical composition suggests a common mechanism of *** association of spherules with fracture zones(FZ)and.seamounts signifies that morpho-tectonic features play an important role in fluid.d.iven *** on the evid.nce and.geologic cond.tions existing in the basin,we conclud. that molten fuel-coolant interaction(MFCI)coupled.with submarine hyd.othermal exhalations could.be an id.al mechanism for the formation of spherules and.*** accretion of the spherules on the surface sed.ments could.be a result of recent volcanic phenomena,while those occurring at d.fferent d.pths(280-355,and.460-475 cm-bsf)within the sed.ment core ind.cate two d.fferent *** stud. provid.s a global implication in und.rstand.ng fluid.d.iven magmatism in a d.ep-sea intraplate environment.

关键词： Fe-rich spherules d.ep-sea sed.ments hyd.ovolcanic activity CIOB