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Acta Oceanologica Sinica 2023年第5期42卷 93-101页

作者： durbar ray Anil L.Paropkari CSIR-National Institute of Oceanography Dona PaulaGoa 403004India Retired Chief Scientist CSIR-National Institute of OceanographyGoa 403004India

We report the mineralogy and geochemistry of hydrothermal sulphide from the crater of a volcanic high near 18°36.4′S of the Central Lau Spreading *** 1990s,that volcanic structure was reported active and sulphide samples were collected by MIR submersible.A section of a chimney-like structure from the crater-floor was studied *** Fe-depleted sphalerites,and Co-depleted pyrites in that chimney were similar to those commonly found in low to moderate temperature(<300℃)sulphides from sediment-starved hydrothermal *** analyses of three parts of that chimney section showed substantial enrichment of Zn(18%–20%)and Fe(14%–27%)but depletion of Cu(0.8%–1.3%).In chondrite-normalized rare earth element-patterns,the significant negative Ce-anomalies(Ce/Ce*=0.27–0.39)and weakly positive Eu-anomalies(Eu/Eu*=1.60–1.68)suggested sulphide mineralisation took place from reduced low-temperature *** depleted concentration of lithophiles in this sulphide indicates restricted contribution of sub-ducting plate in genesis of source fluid as compared to those from other parts of Lau Spreading *** mineralogy and bulk composition of subsamples across the chimney section suggests barely any alteration of fluid composition and/or mode of mineralisation occurred during its growth.

关键词： Central Lau Spreading Center hydrothermal sulphide mineralogy geochemistry

Geochemistry of volcanic glass from Mahanadi offshore region,eastern continental margin of India:Constraints on the contribution of latest Toba super-eruption

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Acta Oceanologica Sinica 2024年第2期43卷 111-119页

作者： Muralidhar Kocherla durbar ray Manavalan Satyanarayanan Hilda Joao Virsen Gaikwad PB Ramamurty CSIR-National Institute of Oceanography Dona Paula 403004GoaIndia CSIR-National Geophysical Research Institute Uppal RoadHyderabad 500007India

The tephra layers in multiple sediment cores from the offshore region of the Mahanadi basin in the northern Bay of Bengal were investigated for possible volcanic sources. The glass shards from those tephra layers were studied for size distribution, texture, and elemental geochemistry to establish chronostratigraphic markers for regional and global Quaternary correlation. The textural features of fine-grained(silty) volcanic glasses suggest the distal source of these tephra deposits. Major element composition with elevated SiO_(2) contents ranging between75%–76% and dominance of K_(2)O(> 4.5%) over CaO(< 0.9%) suggest ashes have originated from siliceous rhyolitic melts, similar to the petrographic composition of tephra from the Toba volcano. The bulk trace element compositions of the same glass shards were comparable with those reported in the youngest Toba tephra reported elsewhere. Likewise, the LREE-dominated chondrite normalized REE profiles of tephra from the Mahanadi basin closely resemble the characteristic REE patterns in Toba ash from other parts of the Indian Ocean and thus confirmed the contribution of the youngest Toba super-eruption for this ash layers.

关键词： Mahanadi basin Bay of Bengal volcanic glass glass morphology glass-chemistry

Mineralogical and geochemical variation in hydrothermal sulfides from Vienna Woods field,Manus Basin,Papua New Guinea：constraints on their evolution

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Acta Oceanologica Sinica 2018年第4期37卷 22-33页

作者： ray durbar BANERJEE Ranadip MAZUMDER Aninda PAROPKARI Anil L. MUKHOPADHYAY Subir BALAKRISHNAN Srinivasan CSIR-National Institute of Oceanography Dona Paula Goa 403004 India Department of Geological Sciences Jadavpur University Kolkata 700032 India Department of Earth Sciences Pondicherry University Puducherry 605014 India

Polymetallic sulfides from two hydrothermal chimneys and talus deposit from the Vienna Woods field of Manus Basin were studied for mineralogy,elemental composition,and S-isotope ratio to understand their *** factors including the nature of source fluid,mineral paragenesis,and related geochemical processes have been *** and elemental concentration of Cu and Fe-rich large chimney at the central part of this hydrothermal field was completely different from the smaller Zn-rich peripheral chimney and Fe-rich talus deposit,suggesting the variable degree of alterations generate physico-chemically different source fluids responsible for these hydrothermal ***,S-isotope ratios also indicate chemically diverse fluids and different modes of precipitation were involved in their *** mineral zonings and associated elemental and isotopic compositions within individual deposit confirm paragenetic shifts were involved during their growth process.

关键词： Manus Basin hydrothermal chimney talus geochemistry mineralogy

Microtexture and Distribution of Minerals in Hydrothermal Barite-Silica Chimney from the Franklin Seamount, SW Pacific: Constraints on Mode of Formation

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Acta Geologica Sinica(English Edition) 2014年第1期88卷 213-225页

作者： durbar ray Dalayya KOTA Pranab DAS L.Surya Prakash V.D.KHEDEKAR Anil L.PAROPKARI Abhay V.MUDHOLKAR CSIR-National Institute of Oceanography Indian School of Mines

An extinct hydrothermal barite-silica chimney from the Franklin Seamount of the Woodlark Basin, in the southwestern Pacific Ocean, was investigated for mineral distribution and geochemical composition. Six layers on either side of the orifice of a chimney show significant disparity in color, mineral assemblage and major element composition. Electron microscope（SEM） images reveal that the peripheral wall of the chimney is composed of colloform silica, suggesting that incipient precipitation of silica-saturated hydrothermal fluid initiated the development of the chimney wall. Intermediate layers, between the exterior wall and the inner fluid-orifice, dominate with barite and sulfides. Low Sr-to-Ba ratios（SrO/BaO = 0.015–0.017） indicate restricted fluid-seawater mixing, which causes relatively high-temperature formation of the intermediate layers. Whereas the innermost layer bordering the chimney orifice is characterized by more silica and a higher Sr-to-Ba ratio（SrO/BaO = 0.023）, could have formed due to a paragenetic shift from a high-temperature active phase to a cooler waning stage of formation. A paragenetic shift is also probably responsible for the change in mineral formation mechanism that resulted in the textural variation of barite and colloform silica developed during different growth phases of this barite-silica chimney.

关键词： mineralogy oceanography geochemistry Franklin seamount barite-silica chimney