Hydrous Cr-bearing uvarovite garnets are rare in natural occurrences and belong to the ugrandite series and exist in binary solid solutions with grossular and andradite garnets. Here, we report the occurrence of hydro...Hydrous Cr-bearing uvarovite garnets are rare in natural occurrences and belong to the ugrandite series and exist in binary solid solutions with grossular and andradite garnets. Here, we report the occurrence of hydrous uvarovite garnet having Cr_(2)O_(3) upto 19.66 wt% and CaO of 32.12–35.14 wt% in the serpentinized mantle peridotites of Naga Hills Ophiolite(NHO), India. They occur in association with low-Cr diopsides. They are enriched in LILE(Ba, Sr), LREEs, with fractionating LREE-MREE [avg.(La/Sm)_(N) = 2.16] with flat MREE/HREE patterns [avg.(Sm/Yb)_(N) = 0.95]. Raman spectra indicate the presence of hydroxyl(OH^(–)) peaks from 3500 to 3700 cm^(-1). Relative abundances in fluid mobile elements and their close association with clinopyroxenes are suggestive of the formation of uvarovite garnets through low temperature metasomatic alteration of low-Cr diopsides by hydrothermal slab fluids. The high LREE concentration and absence of Eu anomaly in the garnet further attest to alkaline nature of the transporting slab dehydrated fluid rather the involvement of low-p H solution. The chemical characteristics of the hydroxyl bearing uvarovite hosted by the mantle peridotite of NHO deviate from the classical features of uvarovite garnet, and their origin is attributed to the fluid-induced metasomatism of the sub arc mantle wedge in a suprasubduction zone regime.展开更多
The ocean wave climate has a variety of applications in Naval defence.However,a long-term and reliable wave climate for the Indian Seas(The Arabian Sea and The Bay of Bengal)over a desired grid resolution could not be...The ocean wave climate has a variety of applications in Naval defence.However,a long-term and reliable wave climate for the Indian Seas(The Arabian Sea and The Bay of Bengal)over a desired grid resolution could not be established so far due to several constraints.In this study,an attempt was made for the simulation of wave climate for the Indian Seas using the third-generation wave model(3g-WAM)developed by WAMDI group.The 3g-WAM as such was implemented at NPOL for research applications.The specific importance of this investigation was that,the model utilized a“mean climatic year of winds”estimated using historical wind measurements following statistical and probabilistic approaches as the winds which were considered for this purpose were widely scattered in space and time.Model computations were carried out only for the deep waters with current refraction.The gridded outputs of various wave parameters were stored at each grid point and the spectral outputs were stored at selected locations.Monthly,seasonal and annual distributions of significant wave parameters were obtained by post-processing some of the model outputs.A qualitative validation of simulated wave height and period parameters were also carried out by comparing with the observed data.The study revealed that the results of the wave climate simulation were quite promising and they can be utilized for various operational and ocean engineering applications.Therefore,this study will be a useful reference/demonstration for conducting such experiments in the areas where wind as well as wave measurements are insufficient.展开更多
The present study of metabasalts was carried out to understand the mantle source and geodynamic setting of the Mahakoshal Group in the Central Indian Tectonic Zone.In this study,we present detailed field,petrography,a...The present study of metabasalts was carried out to understand the mantle source and geodynamic setting of the Mahakoshal Group in the Central Indian Tectonic Zone.In this study,we present detailed field,petrography,and whole rock geochemistry of the Mahakoshal metabasalts.The Mahakoshal metabasalts are sub-alkaline in nature and belong to the tholeiitic series of rocks.The variation in rareearth element patterns of metabasalts indicates the different degrees of partial melting at shallow as well as deeper depths.Further,Eu/Eu*varies from 0.8 to 1.1(except sample KP-144=0.3),Ce/Ce*varies from 0.97 to 1.05,showing no cerium anomaly,and Nb/Nb*ranges from 0.7 to 1.3(except KP-144=0.1).The magnesium number(Mg#)varies from 0.2 to 0.3,which is quite low,indicating the evolved nature of the metabasalts.The studied metabasalts show E-MORB to OIB-type affinities,which are placed in the trench-distal back-arc setting.The opening of the Mahakoshal Basin is due to retreating orogen in the accretionary orogen setting and is contemporaneous with the assembly of the Columbia Supercontinent(~2.1-1.8 Ga).Hence,field,petrographic,and geochemical signatures indicate that the Mahakoshal basin opened as a back-arc rift basin on the Bundelkhand Craton,and that metabasalts are derived from the mantle that underwent variable degrees of partial melting at different depths.展开更多
The present study focused on the estimation of submarine groundwater discharge(SGD)and the effects of nutrient fluxes due to the SGD process.The parameters of SGD such as magnitude,character,and nutrient flux in Punna...The present study focused on the estimation of submarine groundwater discharge(SGD)and the effects of nutrient fluxes due to the SGD process.The parameters of SGD such as magnitude,character,and nutrient flux in Punnakayal region of South East coast of India were evaluated using multiple tracers of groundwater inputs in 2019.It was found that the elevated values for the tracers in the study area,displayed a gradational change in the values as move from estuarine part to the offshore.Simultaneous occurrence of fresh and saline SGD is observed on the study sites.Also,indicated that the SGD fluxes ranged from 0.04 to 0.12 m^3 m^-2d^-1 at the estuary and0.03-0.15 m^3 m^-2d^-1at the groundwater site.A substantially increased value for 222 Rn activities is distinguished in the estuary to values over 312 dpm L^-1.Nutrient embellishments were generally greatest at locations with substantial meteoric elements in groundwater;however,the recirculation of saltwater through the geological formation could provide a way of transferring terrestrially-derived nutrients to the coastal zone at many places.展开更多
Phase equilibria modelling coupled with U–Pb zircon and monazite ages of garnet–cordierite gneiss from Vallikodu Kottayam in the Kerala Khondalite Belt,southern India are presented here.The results suggest that the ...Phase equilibria modelling coupled with U–Pb zircon and monazite ages of garnet–cordierite gneiss from Vallikodu Kottayam in the Kerala Khondalite Belt,southern India are presented here.The results suggest that the area attained peak P–T conditions of^900C at 7.5–8 kbar,followed by decompression to 3.5–5 kbar and cooling to 450–480C,preserving signatures of the partial melting event in the field of high to ultra-high temperature metamorphism.Melt reintegration models suggest that up to 35%granitic melt could have been produced during metamorphism at^950C.The U–Pb age data from zircons(~1.0–~0.7 Ga)and chemical ages from monazites(~540 Ma and^941 Ma)reflect a complex tectonometamorphic evolution of the terrain.The^941 Ma age reported from these monazites indicate a Tonian ultra-high temperature event,linked to juvenile magmatism/deformation episodes reported from the Southern Granulite Terrane and associated fragments in Rodinia,which were subsequently overprinted by the Cambrian(~540 Ma)tectonothermal episode.展开更多
The most pronounced effect of urbanisation on the microclimate of a region is the development of the Urban Heat Island （UHI）, which is the elevation of air temperature within the region with respect to adjoining rur...The most pronounced effect of urbanisation on the microclimate of a region is the development of the Urban Heat Island （UHI）, which is the elevation of air temperature within the region with respect to adjoining rural areas. There are many factors like coverage area, vegetation, soil moisture, street geometry, building materials, etc., which cause or modify the intensity of UI-II. The UHI in Kochi, a fast growing urban region in coastal South India, interlaced by a network of canals and wetlands which are part of the Vembanad Lake system, was investigated. The UHI during summer and winter periods were recorded through mobile traverses. The intensity of the heat island during summer was 2.2 K and during winter was 2.8 K. The heating and cooling rates in different locations within the region were also derived through stationary recorders installed at selected locations. The intensity of the UHI here is moderate compared to that observed in other cities in the region. It is inferred that the wetlands is controlling the intensity of the UHI here.展开更多
Himalayan leucogranites are important for understanding the tectonic evolution of collision zones in general and the causes of crustal melting in the Himalayan orogen in particular.This paper aims to understand the me...Himalayan leucogranites are important for understanding the tectonic evolution of collision zones in general and the causes of crustal melting in the Himalayan orogen in particular.This paper aims to understand the melt source and emplacement age of the leucogranites from Sikkim in order to decipher the deep geodynamic processes of the eastern Himalayas.Zircon U-Pb analysis of the Higher Himalayan Sequence(HHS)metamorphic core reveals a prolonged period of crustal melting between>33 Ma and ca.14 Ma.Major and trace element abundances are presented for 27 leucogranites from North Sikkim that are classified into two-mica and tourmaline leucogranite types.They are peraluminous in composition,characterized by high SiO2(70.91-74.9 wt.%),Al2O3(13.69-15.82 wt.%),and low MgO(0.13-0.74 wt.%).Elemental abundances suggest that Sikkim Himalayan leucogranites are derived from crustal melts.The two-mica leucogranites are derived from a metagreywacke source,whereas the tourmaline leucogranites are sourced from metapelitic sources,with inherited zircons indicating an HHS origin for both types.U-Pb zircon geochronology of the two mica leucogranites indicates ages of ca.19-15 Ma,consistent with crustal melting recorded in HHS gneisses from Darjeeling.Monazites from both the two-mica and tourmaline leucogranites yield a crystallization age of ca.15-14 Ma,coeval with movement on the Main Central Thrust and South Tibetan Detachment System which further provides constraints on the timing and mechanism of petrogenesis of leucogranites in the Sikkim Himalayas.展开更多
The paleo-temperature(Th)data from fluid inclusions are utilized for thermal history modelling using PetroMod software.Generally,bottom hole temperature(BHT)and vitrinite reflectance(Ro)measurements are widely used in...The paleo-temperature(Th)data from fluid inclusions are utilized for thermal history modelling using PetroMod software.Generally,bottom hole temperature(BHT)and vitrinite reflectance(Ro)measurements are widely used in petroleum system modelling(PSM)in the oil industry for calibration purposes.Th representing the minimum temperature of fluid entrapment estimated from fluid-inclusion study provides extra support to build the thermal models for PSM.Fluid inclusion parameters along with Rock-Eval pyrolysis analysis have been used to predict the maturity of oil in terms of API gravity as well as the maturity of source rocks respectively.Two exploratory wells RV-1(Mumbai Offshore Basin)and KK4C-A-1(Kerala-Konkan Offshore Basin),India were examined and the T_(h)from most of the fluid inclusions of wells RV-1 and KK4C-A-1 fell in the oil window range of 60-140℃suggesting thermal conditions favourable for oil generation in both of the wells.T_(h)of coeval aqueous inclusions along with the Hydrocarbon Fluid inclusions(HCFIs)was used to calibrate PSM.Vital parameters show that source rocks of well RV-1 are mature and that of well KK4C-A-1 are immature.Two sets of PSM are created in terms of generation and expulsion for the dry wells RV-1 and KK4C-A-1 and calibrated each well using fluid inclusion Th and BHT.From the fluid inclusion analysis method,it is evident that hydrocarbon generation happened in both wells and the paleo-temperature indicates that the formations of both wells were subjected to temperatures in the oil window range,even though it was designated as dry wells in the present scenario.The present study highlights the application of fluid inclusion paleo-temperature(Th)during calibration instead of commonly used methods.We could obtain desirable and accurate data output from PSM using T_(h) calibration.展开更多
Fluid inclusions represent the direct evidence of paleofluids and can provide valuable information on the evolution of sedimentary basins and oil-bearing strata.Hydrocarbon fluid inclusion(s)(HCFIs)are the vestiges of...Fluid inclusions represent the direct evidence of paleofluids and can provide valuable information on the evolution of sedimentary basins and oil-bearing strata.Hydrocarbon fluid inclusion(s)(HCFIs)are the vestiges of oil from the geological formations.The paper delineates the paleotemperature(T_(h))/oil window,the oil quality of HCFIs and Raman peaks corresponding to hydrocarbon species of HCFIs using fluid inclusion techniques,and source rock potential of hydrocarbon generation,thermal maturity,the quantity of organic matter,and the kerogen types obtained through Rock-Eval pyrolysis data from two dry wells RV-1 well of Mumbai offshore and KKD-1A well of Kerala-Konkan Basin.The present study compares the fluid inclusion parameters as well as the source rock geochemical characteristics of these two dry wells to address the scientific problem of the wells going dry.Further,evaluated whether the results agree with an earlier finding from a case study of two wells named KK4C-Al(Kerala-Konkan basin)and RV-1 well where only a few parameters such as temperature of homogenization(T_(h))&API gravity were utilised,and the chances of getting oil in the nearby areas of these two wells were reported.In the present study,the fluid inclusion parameters such as the palaeotemperature(T_(h)),API Gravity and Raman spectra were obtained from micron sized fluid inclusions at different depths for a quick assessment of nature of oil inclusions within the two dry wells.Along with fluid inclusion parameters,different source rock parameters obtained from Rock-Eval Pyrolysis analysis(secondary data)such as S1,S2,S3,(T_(max)),Hydrogen Index(HI),Oxygen Index(OI),Potential Yield(PY),Production Index(PI)and Total Organic Carbon Content(TOC)were also considered for a detailed source-rock evaluation of two wells(RV-1 and KKD-1A)and the results act as the supporting evidence to address the reason for the wells gone dry.Temperature of homogenisation(T_(h))of hydrocarbon Fluid Inclusion Assemblages(FIAs)from both the wells fall in the oil window(60-150℃)range indicating that there was a conducive thermal condition favourable for oil generation in these two basins.API gravity of oils in RV-1 well of Mumbai offshore(48-53)was lighter when compared to those in KKD-1A(18-22)of Kerala-Konkan basin.Raman spectra of HCFI samples could decipher important hydrocarbon species from RV-1 well samples.Raman spectra of KKD-1A well show less prominent peaks(broad)only.Pyrolysis data shows that Paleocene-Early Eocene source rocks of Panna formation of RV1 well are mature enough to generate hydrocarbons.On the other hand,Paleocene aged source rocks of Kasargod formation of KKD-1A well are immature.Source rock maturity therefore could be considered as crucial in hydrocarbon generation in these two wells even if oil-window was achieved.This study reports that,in RV-1 well,even though it is a dry well in a proven basin,the oil window,API gravity of oils and constituents from HCFIs of RV-1 well and the source-rock maturity opens up a demand for detailed exploration in nearby areas of RV-1 in the Mumbai offshore basin hopeful of finding a high-value prospect for oil,whereas the fluid inclusion studies in the HCFIs of KKD-1A well of Kerala-Konkan basin is showing only a minimal chance of oil generation that too of a heavy nature and the source rock immature characteristics suggesting only minimal generation of hydrocarbons.Due to the heaviness of the available oil in the KKD-1A well impedes migration.Our study suggests that there is no potential for finding oil in the nearby areas of KKD-1A well of Kerala-Konkan basin.展开更多
Land use and land cover change,perhaps the most significant anthropogenic disturbance to the environment,mainly due to rapid urbanization/industrialization and large scale agricultural activities.In this paper,an atte...Land use and land cover change,perhaps the most significant anthropogenic disturbance to the environment,mainly due to rapid urbanization/industrialization and large scale agricultural activities.In this paper,an attempt has been made to appraise land use/land cover changes over a century(19142007)in the Neyyar River Basin(L56 km;Area483.4 km2)in southern Keralaa biodiversity hot spot in Peninsular India.In this study,digital remote sensing data of the Indian Remote Sensing satellite series I-D(LISS III,20062007)on 1:50,000 scale,Survey of India(SOI)toposheet of 1914(1:63,360)and 1967(1:50,000)have been utilized to map various land use/land cover changes.Maps of different periods have been registered and resampled to similar geographic coordinates using ERDAS Imagine 9.0.The most notable changes include decreases in areas of paddy cultivation,mixed crops,scrub lands and evergreen forests,and increases in built-up areas,rubber plantations,dense mixed forests,and water bodies.Further,large scale exploitation of flood plain mud and river sand have reached menacing proportions leading to bank caving and cut offs at channel bends.Conservation of land and water resources forms an important aspect of ecosystem management in the basin.展开更多
In this paper we have synthesized the published and unpublished geochemical data on the Palaeoproterozoic mafic magmatism in the Indian Shield.Palaeoproterozoic mafic magmatism is widespread in the Indian Shield;it mo...In this paper we have synthesized the published and unpublished geochemical data on the Palaeoproterozoic mafic magmatism in the Indian Shield.Palaeoproterozoic mafic magmatism is widespread in the Indian Shield;it mostly emplaced as dyke intrusions within the cratons and south Indian granulite region and as intrusives/traps in the intra-cratonic basins and the Eastern Ghat Mobile Belt.展开更多
基金the funding received from the Science and Engineering Research Board (SERB), Govt. of India under GAP 3291funded by Ministry of Earth Science (MoES) with project reference number Mo ES/ P.O. (Seismic) 8 (09)-Geochron/2012。
文摘Hydrous Cr-bearing uvarovite garnets are rare in natural occurrences and belong to the ugrandite series and exist in binary solid solutions with grossular and andradite garnets. Here, we report the occurrence of hydrous uvarovite garnet having Cr_(2)O_(3) upto 19.66 wt% and CaO of 32.12–35.14 wt% in the serpentinized mantle peridotites of Naga Hills Ophiolite(NHO), India. They occur in association with low-Cr diopsides. They are enriched in LILE(Ba, Sr), LREEs, with fractionating LREE-MREE [avg.(La/Sm)_(N) = 2.16] with flat MREE/HREE patterns [avg.(Sm/Yb)_(N) = 0.95]. Raman spectra indicate the presence of hydroxyl(OH^(–)) peaks from 3500 to 3700 cm^(-1). Relative abundances in fluid mobile elements and their close association with clinopyroxenes are suggestive of the formation of uvarovite garnets through low temperature metasomatic alteration of low-Cr diopsides by hydrothermal slab fluids. The high LREE concentration and absence of Eu anomaly in the garnet further attest to alkaline nature of the transporting slab dehydrated fluid rather the involvement of low-p H solution. The chemical characteristics of the hydroxyl bearing uvarovite hosted by the mantle peridotite of NHO deviate from the classical features of uvarovite garnet, and their origin is attributed to the fluid-induced metasomatism of the sub arc mantle wedge in a suprasubduction zone regime.
文摘The ocean wave climate has a variety of applications in Naval defence.However,a long-term and reliable wave climate for the Indian Seas(The Arabian Sea and The Bay of Bengal)over a desired grid resolution could not be established so far due to several constraints.In this study,an attempt was made for the simulation of wave climate for the Indian Seas using the third-generation wave model(3g-WAM)developed by WAMDI group.The 3g-WAM as such was implemented at NPOL for research applications.The specific importance of this investigation was that,the model utilized a“mean climatic year of winds”estimated using historical wind measurements following statistical and probabilistic approaches as the winds which were considered for this purpose were widely scattered in space and time.Model computations were carried out only for the deep waters with current refraction.The gridded outputs of various wave parameters were stored at each grid point and the spectral outputs were stored at selected locations.Monthly,seasonal and annual distributions of significant wave parameters were obtained by post-processing some of the model outputs.A qualitative validation of simulated wave height and period parameters were also carried out by comparing with the observed data.The study revealed that the results of the wave climate simulation were quite promising and they can be utilized for various operational and ocean engineering applications.Therefore,this study will be a useful reference/demonstration for conducting such experiments in the areas where wind as well as wave measurements are insufficient.
文摘The present study of metabasalts was carried out to understand the mantle source and geodynamic setting of the Mahakoshal Group in the Central Indian Tectonic Zone.In this study,we present detailed field,petrography,and whole rock geochemistry of the Mahakoshal metabasalts.The Mahakoshal metabasalts are sub-alkaline in nature and belong to the tholeiitic series of rocks.The variation in rareearth element patterns of metabasalts indicates the different degrees of partial melting at shallow as well as deeper depths.Further,Eu/Eu*varies from 0.8 to 1.1(except sample KP-144=0.3),Ce/Ce*varies from 0.97 to 1.05,showing no cerium anomaly,and Nb/Nb*ranges from 0.7 to 1.3(except KP-144=0.1).The magnesium number(Mg#)varies from 0.2 to 0.3,which is quite low,indicating the evolved nature of the metabasalts.The studied metabasalts show E-MORB to OIB-type affinities,which are placed in the trench-distal back-arc setting.The opening of the Mahakoshal Basin is due to retreating orogen in the accretionary orogen setting and is contemporaneous with the assembly of the Columbia Supercontinent(~2.1-1.8 Ga).Hence,field,petrographic,and geochemical signatures indicate that the Mahakoshal basin opened as a back-arc rift basin on the Bundelkhand Craton,and that metabasalts are derived from the mantle that underwent variable degrees of partial melting at different depths.
基金the financial support by the Department of Science and Technology-SERB-ECRGovernment of India,New Delhi(Grant No:F:ECR/2018/001749)。
文摘The present study focused on the estimation of submarine groundwater discharge(SGD)and the effects of nutrient fluxes due to the SGD process.The parameters of SGD such as magnitude,character,and nutrient flux in Punnakayal region of South East coast of India were evaluated using multiple tracers of groundwater inputs in 2019.It was found that the elevated values for the tracers in the study area,displayed a gradational change in the values as move from estuarine part to the offshore.Simultaneous occurrence of fresh and saline SGD is observed on the study sites.Also,indicated that the SGD fluxes ranged from 0.04 to 0.12 m^3 m^-2d^-1 at the estuary and0.03-0.15 m^3 m^-2d^-1at the groundwater site.A substantially increased value for 222 Rn activities is distinguished in the estuary to values over 312 dpm L^-1.Nutrient embellishments were generally greatest at locations with substantial meteoric elements in groundwater;however,the recirculation of saltwater through the geological formation could provide a way of transferring terrestrially-derived nutrients to the coastal zone at many places.
基金funding from the Department of Science and Technology, Government of India(India) under the DST INSPIRE Faculty Scheme (Grant:DST/INSPIRE/04/2014/000221)
文摘Phase equilibria modelling coupled with U–Pb zircon and monazite ages of garnet–cordierite gneiss from Vallikodu Kottayam in the Kerala Khondalite Belt,southern India are presented here.The results suggest that the area attained peak P–T conditions of^900C at 7.5–8 kbar,followed by decompression to 3.5–5 kbar and cooling to 450–480C,preserving signatures of the partial melting event in the field of high to ultra-high temperature metamorphism.Melt reintegration models suggest that up to 35%granitic melt could have been produced during metamorphism at^950C.The U–Pb age data from zircons(~1.0–~0.7 Ga)and chemical ages from monazites(~540 Ma and^941 Ma)reflect a complex tectonometamorphic evolution of the terrain.The^941 Ma age reported from these monazites indicate a Tonian ultra-high temperature event,linked to juvenile magmatism/deformation episodes reported from the Southern Granulite Terrane and associated fragments in Rodinia,which were subsequently overprinted by the Cambrian(~540 Ma)tectonothermal episode.
文摘The most pronounced effect of urbanisation on the microclimate of a region is the development of the Urban Heat Island （UHI）, which is the elevation of air temperature within the region with respect to adjoining rural areas. There are many factors like coverage area, vegetation, soil moisture, street geometry, building materials, etc., which cause or modify the intensity of UI-II. The UHI in Kochi, a fast growing urban region in coastal South India, interlaced by a network of canals and wetlands which are part of the Vembanad Lake system, was investigated. The UHI during summer and winter periods were recorded through mobile traverses. The intensity of the heat island during summer was 2.2 K and during winter was 2.8 K. The heating and cooling rates in different locations within the region were also derived through stationary recorders installed at selected locations. The intensity of the UHI here is moderate compared to that observed in other cities in the region. It is inferred that the wetlands is controlling the intensity of the UHI here.
基金supported by Innovation in Science Pursuit for Inspired Research(INSPIRE)No.DST/INSPIRE Fellowship/2016/IF160729,。
文摘Himalayan leucogranites are important for understanding the tectonic evolution of collision zones in general and the causes of crustal melting in the Himalayan orogen in particular.This paper aims to understand the melt source and emplacement age of the leucogranites from Sikkim in order to decipher the deep geodynamic processes of the eastern Himalayas.Zircon U-Pb analysis of the Higher Himalayan Sequence(HHS)metamorphic core reveals a prolonged period of crustal melting between>33 Ma and ca.14 Ma.Major and trace element abundances are presented for 27 leucogranites from North Sikkim that are classified into two-mica and tourmaline leucogranite types.They are peraluminous in composition,characterized by high SiO2(70.91-74.9 wt.%),Al2O3(13.69-15.82 wt.%),and low MgO(0.13-0.74 wt.%).Elemental abundances suggest that Sikkim Himalayan leucogranites are derived from crustal melts.The two-mica leucogranites are derived from a metagreywacke source,whereas the tourmaline leucogranites are sourced from metapelitic sources,with inherited zircons indicating an HHS origin for both types.U-Pb zircon geochronology of the two mica leucogranites indicates ages of ca.19-15 Ma,consistent with crustal melting recorded in HHS gneisses from Darjeeling.Monazites from both the two-mica and tourmaline leucogranites yield a crystallization age of ca.15-14 Ma,coeval with movement on the Main Central Thrust and South Tibetan Detachment System which further provides constraints on the timing and mechanism of petrogenesis of leucogranites in the Sikkim Himalayas.
文摘The paleo-temperature(Th)data from fluid inclusions are utilized for thermal history modelling using PetroMod software.Generally,bottom hole temperature(BHT)and vitrinite reflectance(Ro)measurements are widely used in petroleum system modelling(PSM)in the oil industry for calibration purposes.Th representing the minimum temperature of fluid entrapment estimated from fluid-inclusion study provides extra support to build the thermal models for PSM.Fluid inclusion parameters along with Rock-Eval pyrolysis analysis have been used to predict the maturity of oil in terms of API gravity as well as the maturity of source rocks respectively.Two exploratory wells RV-1(Mumbai Offshore Basin)and KK4C-A-1(Kerala-Konkan Offshore Basin),India were examined and the T_(h)from most of the fluid inclusions of wells RV-1 and KK4C-A-1 fell in the oil window range of 60-140℃suggesting thermal conditions favourable for oil generation in both of the wells.T_(h)of coeval aqueous inclusions along with the Hydrocarbon Fluid inclusions(HCFIs)was used to calibrate PSM.Vital parameters show that source rocks of well RV-1 are mature and that of well KK4C-A-1 are immature.Two sets of PSM are created in terms of generation and expulsion for the dry wells RV-1 and KK4C-A-1 and calibrated each well using fluid inclusion Th and BHT.From the fluid inclusion analysis method,it is evident that hydrocarbon generation happened in both wells and the paleo-temperature indicates that the formations of both wells were subjected to temperatures in the oil window range,even though it was designated as dry wells in the present scenario.The present study highlights the application of fluid inclusion paleo-temperature(Th)during calibration instead of commonly used methods.We could obtain desirable and accurate data output from PSM using T_(h) calibration.
基金Department of Science and Technology(DST)through DST-INSPIRE Programme(DST/INSPIRE Fellowship/IF180169).
文摘Fluid inclusions represent the direct evidence of paleofluids and can provide valuable information on the evolution of sedimentary basins and oil-bearing strata.Hydrocarbon fluid inclusion(s)(HCFIs)are the vestiges of oil from the geological formations.The paper delineates the paleotemperature(T_(h))/oil window,the oil quality of HCFIs and Raman peaks corresponding to hydrocarbon species of HCFIs using fluid inclusion techniques,and source rock potential of hydrocarbon generation,thermal maturity,the quantity of organic matter,and the kerogen types obtained through Rock-Eval pyrolysis data from two dry wells RV-1 well of Mumbai offshore and KKD-1A well of Kerala-Konkan Basin.The present study compares the fluid inclusion parameters as well as the source rock geochemical characteristics of these two dry wells to address the scientific problem of the wells going dry.Further,evaluated whether the results agree with an earlier finding from a case study of two wells named KK4C-Al(Kerala-Konkan basin)and RV-1 well where only a few parameters such as temperature of homogenization(T_(h))&API gravity were utilised,and the chances of getting oil in the nearby areas of these two wells were reported.In the present study,the fluid inclusion parameters such as the palaeotemperature(T_(h)),API Gravity and Raman spectra were obtained from micron sized fluid inclusions at different depths for a quick assessment of nature of oil inclusions within the two dry wells.Along with fluid inclusion parameters,different source rock parameters obtained from Rock-Eval Pyrolysis analysis(secondary data)such as S1,S2,S3,(T_(max)),Hydrogen Index(HI),Oxygen Index(OI),Potential Yield(PY),Production Index(PI)and Total Organic Carbon Content(TOC)were also considered for a detailed source-rock evaluation of two wells(RV-1 and KKD-1A)and the results act as the supporting evidence to address the reason for the wells gone dry.Temperature of homogenisation(T_(h))of hydrocarbon Fluid Inclusion Assemblages(FIAs)from both the wells fall in the oil window(60-150℃)range indicating that there was a conducive thermal condition favourable for oil generation in these two basins.API gravity of oils in RV-1 well of Mumbai offshore(48-53)was lighter when compared to those in KKD-1A(18-22)of Kerala-Konkan basin.Raman spectra of HCFI samples could decipher important hydrocarbon species from RV-1 well samples.Raman spectra of KKD-1A well show less prominent peaks(broad)only.Pyrolysis data shows that Paleocene-Early Eocene source rocks of Panna formation of RV1 well are mature enough to generate hydrocarbons.On the other hand,Paleocene aged source rocks of Kasargod formation of KKD-1A well are immature.Source rock maturity therefore could be considered as crucial in hydrocarbon generation in these two wells even if oil-window was achieved.This study reports that,in RV-1 well,even though it is a dry well in a proven basin,the oil window,API gravity of oils and constituents from HCFIs of RV-1 well and the source-rock maturity opens up a demand for detailed exploration in nearby areas of RV-1 in the Mumbai offshore basin hopeful of finding a high-value prospect for oil,whereas the fluid inclusion studies in the HCFIs of KKD-1A well of Kerala-Konkan basin is showing only a minimal chance of oil generation that too of a heavy nature and the source rock immature characteristics suggesting only minimal generation of hydrocarbons.Due to the heaviness of the available oil in the KKD-1A well impedes migration.Our study suggests that there is no potential for finding oil in the nearby areas of KKD-1A well of Kerala-Konkan basin.
文摘Land use and land cover change,perhaps the most significant anthropogenic disturbance to the environment,mainly due to rapid urbanization/industrialization and large scale agricultural activities.In this paper,an attempt has been made to appraise land use/land cover changes over a century(19142007)in the Neyyar River Basin(L56 km;Area483.4 km2)in southern Keralaa biodiversity hot spot in Peninsular India.In this study,digital remote sensing data of the Indian Remote Sensing satellite series I-D(LISS III,20062007)on 1:50,000 scale,Survey of India(SOI)toposheet of 1914(1:63,360)and 1967(1:50,000)have been utilized to map various land use/land cover changes.Maps of different periods have been registered and resampled to similar geographic coordinates using ERDAS Imagine 9.0.The most notable changes include decreases in areas of paddy cultivation,mixed crops,scrub lands and evergreen forests,and increases in built-up areas,rubber plantations,dense mixed forests,and water bodies.Further,large scale exploitation of flood plain mud and river sand have reached menacing proportions leading to bank caving and cut offs at channel bends.Conservation of land and water resources forms an important aspect of ecosystem management in the basin.
基金supported by the grants from the Department of Science and Technology,Government of India to TR(SR/S4/ES-598/2011)and KVK(EMR/2014/000779)forms a part of CSIRES scheme to TR(21(1041)/17/EMR-Ⅱ)UGC-SAP scheme at the SRTM University(No.F.550/3/DRS-Ⅱ/2016/SAP-Ⅰ).
文摘In this paper we have synthesized the published and unpublished geochemical data on the Palaeoproterozoic mafic magmatism in the Indian Shield.Palaeoproterozoic mafic magmatism is widespread in the Indian Shield;it mostly emplaced as dyke intrusions within the cratons and south Indian granulite region and as intrusives/traps in the intra-cratonic basins and the Eastern Ghat Mobile Belt.
