From Donghai County of Jiangsu Province to Rongcheng County of Shandong Province on the southern border of the Sulu orogen, there exposes an ultramafic belt, accompanied with an ultrahigh-pressure metamorphic zone. It...From Donghai County of Jiangsu Province to Rongcheng County of Shandong Province on the southern border of the Sulu orogen, there exposes an ultramafic belt, accompanied with an ultrahigh-pressure metamorphic zone. It can be further divided into the Xugou belt (the northern belt), and the Maobei-Gangshang belt (the southern belt). One grain of diamond has been discovered from the Zhimafang pyrope peridotite in the southern belt using the heavy mineral method. The diamond grain is 2.13 mm × 1.42 mm × 0.83 mm in size and weighs 9.4 mg. The occurrence of the diamond suggests that the Zhimafang pyrope peridotite xenolith is derived from the lithospheric upper mantle. The tectonic emplacement mechanism of the pyrope peridotite xenoliths in granite-gneisses is obviously different from those in kimberlite. The Sulu orogen was located on the active continental margin of the Sino-Korean craton in the Neoproterozoic. The relatively cold and water-bearing oceanic crustal tholeiite slab subducted beneath the lithospheric mantle of the Sino-Korean craton, and partly melted to produce granitic magma and water-bearing fluids. The magma and fluids pierced through and fractured the overlying lithospheric mantle, and ascended to the crustal level together with the ultramafic mantle fragments as xenoliths.展开更多
Garnet is one of the most significant minerals in metamorphic rocks, that provides key information on prograde, peak-metamorphic and retrograde parts of the pressure-temperature （PT） path. Such results require a det...Garnet is one of the most significant minerals in metamorphic rocks, that provides key information on prograde, peak-metamorphic and retrograde parts of the pressure-temperature （PT） path. Such results require a detailed knowledge of its different growth domains. For iron-poor compositions, the cathodoluminescence （CL） microscopy is an important and often overlooked method and allows to identify the internal structures of all garnet grains in one thin section within only a few seconds. The advantage of the CL-microscope is to deliver low magnification images in true color, not only of garnet but also, for instance, of other rock forming silicates, carbonates, sulfates, etc., of metamorphic, but also of sedimentary and magmatic origin, using polished thin sections. Internal structures of grossular from Mexico and pyrope from the Italian Alps were characterized and visualized by CL-microscopy. The different growth domains were additionally studied using CL-spectra and electron microprobe （EMP） analysis. Grossular shows a patchy zonation in its core while in mantle and rim zones oscillatory zoning is observed. It contains zones of anomalous birefringence, zones of orange and bluish luminescence and zones lacking luminescence. Different but low amounts of the activator elements Mn2＋ and Eu2＋ are responsible for the orange and bluish luminescent domains. Pyrope is also characterized by oscillatory growth zones, shows a dull luminescent core with a change of crystal morphology during growth, and displays an increase of brightness from core towards rim--the outermost rim, however, is lacking luminescence. The different luminescent zones are characterized by different amounts of Dy3＋, Tb3＋, Sm3＋ and Sm2＋ as activator elements. Because of slow diffusion rates of activators such as the REEs Sm, Dy and Tb, it can be still possible to visualize possible prograde and/or peak pressure stage growth domains of garnet, even if later high temperature events may have homogenized the major element profiles. Such domains may help to identify respective assemblages of mineral inclusions, and hence these results can represent an integral part of a detailed PT path. Thus the CL-information can be used as an important pathfinder prior to supplementary investigations, as for instance EMP, ion probe, mineral or fluid inclusion studies.展开更多
We calculated thermo-elastic properties of pyrope（Mg3Al2Si3O12） at mantle pressures and temperatures using Ab initio molecular dynamic simulation.A third-order Birch-Murnaghan equation at a reference temperature of ...We calculated thermo-elastic properties of pyrope（Mg3Al2Si3O12） at mantle pressures and temperatures using Ab initio molecular dynamic simulation.A third-order Birch-Murnaghan equation at a reference temperature of 2 000 K fits the calculations with bulk modulus,K0=159.5 GPa,K0＇=4.3,V0=785.89 A3,Grüneisen parameter,γ0=1.15,q=0.80,Anderson Grüneisen parameter δT=3.76 and thermal expansion,α0=2.93×10^-5 K^-1.Referenced to room temperature,where V0=750.80 A3,γ0 and α0 become 1.11 and 2.47×10^-5 K^-1.The elastic properties of pyrope are found to be nearly isotropic at transition zone conditions.展开更多
In kersantite and spessartite dikes of Chetlas Kamen＇ in Central Timan among accessory garnets, that are rather rare in lamprophyres, there was discovered few and for the first time high-majorite pyrope garnet with m...In kersantite and spessartite dikes of Chetlas Kamen＇ in Central Timan among accessory garnets, that are rather rare in lamprophyres, there was discovered few and for the first time high-majorite pyrope garnet with majorite minal Mg3Fe2[SiO4]3 （26-42%）, similar to majorite garnet originating from a meteorite. Majorite discovered in Coorara meteorite is very rare in the terrestrial rocks. As it is shown, there is 18% pyroxene admixture in original analysis of maj orite that is why a surplus of S i appeared in its formula. In rocks, where majorite garnet was found, there are also revealed microcrystalline diamonds.展开更多
In the last decade,researchers have been particularly interested in IIa CLIPPIR type diamonds,which differ in composition and physical characteristics from diamonds of peridotite related"P"and eclogite relat...In the last decade,researchers have been particularly interested in IIa CLIPPIR type diamonds,which differ in composition and physical characteristics from diamonds of peridotite related"P"and eclogite related"E"generations.Moore(Moore,2009)sought them as mantle kimberlite related megacrysts,but light C isotopy and chemical features needs special explanation.展开更多
Volatile components in diamonds, associated garnet (pyrope), and olivine from two extremely rare xenoliths of diamondiferous peridotites recovered from the Udachnaya kimberlite pipe in Yakutia, Russia, were analyzed b...Volatile components in diamonds, associated garnet (pyrope), and olivine from two extremely rare xenoliths of diamondiferous peridotites recovered from the Udachnaya kimberlite pipe in Yakutia, Russia, were analyzed by gas chromatography–mass spectrometry (GC–MS) using a Focus DSQ II Series Single Quadrupole GC–MS (Thermo Scientific, USA). These xenoliths are pyrope lherzolite and pyrope dunite based upon compositions of coexisting minerals. Unlike the pyrope lherzolite, which contained pyrope with moderate calcium (Ca)-component content (about 15 mol%), the dunite contained subcalcic chromium (Cr)-pyrope with low Ca-component content (less than 10 mol%). All investigated minerals contained dominating hydrocarbons and their derivatives represented by aliphatic (paraffins, olefins), cyclic (naphthenes, arenes), oxygenated (alcohols, ethers), and heterocyclic (dioxanes, furans) hydrocarbons;nitrogenated, chlorinated, and sulfonated compounds;carbon dioxide (CO2);and water (H2O). The relative concentration (rel%) of total hydrocarbon was 79.7 rel% for diamonds, 69.1 rel% for garnet, and 92.6 rel% for olivine, with a general amount of components ranging from 161 to 206. New data on volatiles in diamonds, associated garnet, and olivine suggest the presence of a wide spectrum of hydrocarbons along with nitrogen (N2), CO2, and H2O in some upper mantle areas.展开更多
In this paper we present summation of thirteen year’s investigation of the all diamond-bearing structures of Mongolia. Four gold and diamond-bearing astropipe structures of exemplified by the Agit Khangay, Khuree Man...In this paper we present summation of thirteen year’s investigation of the all diamond-bearing structures of Mongolia. Four gold and diamond-bearing astropipe structures of exemplified by the Agit Khangay, Khuree Mandal, Bayan Khuree and Tsenkher astropipes of Mongolia. Detailed geological and gas-geochemical investigation of the diamond and gold-astropipe structures show that diamond genesis is an expression of collision of the lithospheric mantle with the explosion process initiated in an impact collapse meteor crater.展开更多
The Dalnyaya kimberlite pipe（Yakutia,Russia） contains mantle peridotite xenoliths（mostly Iherzolites and harzburgites） that show both sheared porphyroclastic（deformed） and coarse granular textures,together with ...The Dalnyaya kimberlite pipe（Yakutia,Russia） contains mantle peridotite xenoliths（mostly Iherzolites and harzburgites） that show both sheared porphyroclastic（deformed） and coarse granular textures,together with ilmenite and clinopyroxene megacrysts.Deformed peridotites contain high-temperature Fe-rich clinopyroxenes,sometimes associated with picroilmenites,which are products of interaction of the lithospheric mantle with protokimberlite related melts.The orthopyroxene-derived geotherm for the lithospheric mantle beneath Dalnyaya is stepped similar to that beneath the Udachnaya pipe.Coarse granular xenoliths fall on a geotherm of 35 mWm-2 whereas deformed varieties yield a 45 mWm-2）geotherm in the 2-7.5 GPa pressure interval.The chemistry of the constituent minerals including garnet,olivine and clinopyroxene shows trends of increasing Fe~#（=Fe/（Fe＋Mg））with decreasing pressure.This may suggest that the interaction with fractionating protokimberlite melts occurred at different levels.Two major mantle lithologies are distinguished by the trace element patterns of their constituent minerals,determined by LA-ICP-MS.Orthopyroxenes,some clinopyroxenes and rare garnets are depleted in Ba,Sr,HFSE and MREE and represent relic lithospheric mantle.Re-fertilized garnet and clinopyroxene are more enriched.The distribution of trace elements between garnet and clinopyroxene shows that the garnets dissolved primary orthopyroxene and clinopyroxene.Later high temperature clinopyroxenes related to the protokimberlite melts partially dissolved these garnets.Olivines show decreases in Ni and increases in Al,Ca and Ti from Mg-rich varieties to the more Fe-rich,deformed and refertilized ones.Minerals showing higher Fe~#（0.11-0.15） are found within intergrowths of low-Cr ilmenite-clinopyroxene-garnet related to the crystallization of protokimberlite melts in feeder channels.In P-f（O_2） diagrams,garnets and Cr-rich clinopyroxenes indicate reduced conditions at the base of the lithosphere at-5 log units below a FMQ buffer.However,Cr-poor clinopyroxenes,together with ilmenite and some Fe-Ca-rich garnets,demonstrate a more oxidized trend in the lower part of lithosphere at-2 to 0 log units relative to FMQ.Clinopyroxenes from xenoliths in most cases show conditions transitional between those determined for garnets and megacrystalline Cr-poor suite.The relatively low diamond grade of Dalnyaya kimberlites is explained by a high degree of interaction with the oxidized protokimberlite melts,which is greater at the base of the lithosphere.展开更多
文摘From Donghai County of Jiangsu Province to Rongcheng County of Shandong Province on the southern border of the Sulu orogen, there exposes an ultramafic belt, accompanied with an ultrahigh-pressure metamorphic zone. It can be further divided into the Xugou belt (the northern belt), and the Maobei-Gangshang belt (the southern belt). One grain of diamond has been discovered from the Zhimafang pyrope peridotite in the southern belt using the heavy mineral method. The diamond grain is 2.13 mm × 1.42 mm × 0.83 mm in size and weighs 9.4 mg. The occurrence of the diamond suggests that the Zhimafang pyrope peridotite xenolith is derived from the lithospheric upper mantle. The tectonic emplacement mechanism of the pyrope peridotite xenoliths in granite-gneisses is obviously different from those in kimberlite. The Sulu orogen was located on the active continental margin of the Sino-Korean craton in the Neoproterozoic. The relatively cold and water-bearing oceanic crustal tholeiite slab subducted beneath the lithospheric mantle of the Sino-Korean craton, and partly melted to produce granitic magma and water-bearing fluids. The magma and fluids pierced through and fractured the overlying lithospheric mantle, and ascended to the crustal level together with the ultramafic mantle fragments as xenoliths.
文摘Garnet is one of the most significant minerals in metamorphic rocks, that provides key information on prograde, peak-metamorphic and retrograde parts of the pressure-temperature （PT） path. Such results require a detailed knowledge of its different growth domains. For iron-poor compositions, the cathodoluminescence （CL） microscopy is an important and often overlooked method and allows to identify the internal structures of all garnet grains in one thin section within only a few seconds. The advantage of the CL-microscope is to deliver low magnification images in true color, not only of garnet but also, for instance, of other rock forming silicates, carbonates, sulfates, etc., of metamorphic, but also of sedimentary and magmatic origin, using polished thin sections. Internal structures of grossular from Mexico and pyrope from the Italian Alps were characterized and visualized by CL-microscopy. The different growth domains were additionally studied using CL-spectra and electron microprobe （EMP） analysis. Grossular shows a patchy zonation in its core while in mantle and rim zones oscillatory zoning is observed. It contains zones of anomalous birefringence, zones of orange and bluish luminescence and zones lacking luminescence. Different but low amounts of the activator elements Mn2＋ and Eu2＋ are responsible for the orange and bluish luminescent domains. Pyrope is also characterized by oscillatory growth zones, shows a dull luminescent core with a change of crystal morphology during growth, and displays an increase of brightness from core towards rim--the outermost rim, however, is lacking luminescence. The different luminescent zones are characterized by different amounts of Dy3＋, Tb3＋, Sm3＋ and Sm2＋ as activator elements. Because of slow diffusion rates of activators such as the REEs Sm, Dy and Tb, it can be still possible to visualize possible prograde and/or peak pressure stage growth domains of garnet, even if later high temperature events may have homogenized the major element profiles. Such domains may help to identify respective assemblages of mineral inclusions, and hence these results can represent an integral part of a detailed PT path. Thus the CL-information can be used as an important pathfinder prior to supplementary investigations, as for instance EMP, ion probe, mineral or fluid inclusion studies.
基金supported by the US NSF (No. EAR0809397)NERC (Nos. NER/T/S/2001/00855, NER/O/S/2001/01227)+1 种基金computer facilities provided by NERC at University College Londonthe UK National Supercomputing Service (Hec-tor)
文摘We calculated thermo-elastic properties of pyrope（Mg3Al2Si3O12） at mantle pressures and temperatures using Ab initio molecular dynamic simulation.A third-order Birch-Murnaghan equation at a reference temperature of 2 000 K fits the calculations with bulk modulus,K0=159.5 GPa,K0＇=4.3,V0=785.89 A3,Grüneisen parameter,γ0=1.15,q=0.80,Anderson Grüneisen parameter δT=3.76 and thermal expansion,α0=2.93×10^-5 K^-1.Referenced to room temperature,where V0=750.80 A3,γ0 and α0 become 1.11 and 2.47×10^-5 K^-1.The elastic properties of pyrope are found to be nearly isotropic at transition zone conditions.
文摘In kersantite and spessartite dikes of Chetlas Kamen＇ in Central Timan among accessory garnets, that are rather rare in lamprophyres, there was discovered few and for the first time high-majorite pyrope garnet with majorite minal Mg3Fe2[SiO4]3 （26-42%）, similar to majorite garnet originating from a meteorite. Majorite discovered in Coorara meteorite is very rare in the terrestrial rocks. As it is shown, there is 18% pyroxene admixture in original analysis of maj orite that is why a surplus of S i appeared in its formula. In rocks, where majorite garnet was found, there are also revealed microcrystalline diamonds.
基金supported by the RFBR grant 19-05-00788supported by the Ministry of Science and Higher Education of the Russian Federation
文摘In the last decade,researchers have been particularly interested in IIa CLIPPIR type diamonds,which differ in composition and physical characteristics from diamonds of peridotite related"P"and eclogite related"E"generations.Moore(Moore,2009)sought them as mantle kimberlite related megacrysts,but light C isotopy and chemical features needs special explanation.
基金supported by the Russian Science Foundation (RSF-14-17-00602P)the Russian Foundation for Basic Research (RFBR-18-05-00761)a Russian Federation State Research Subsidy
文摘Volatile components in diamonds, associated garnet (pyrope), and olivine from two extremely rare xenoliths of diamondiferous peridotites recovered from the Udachnaya kimberlite pipe in Yakutia, Russia, were analyzed by gas chromatography–mass spectrometry (GC–MS) using a Focus DSQ II Series Single Quadrupole GC–MS (Thermo Scientific, USA). These xenoliths are pyrope lherzolite and pyrope dunite based upon compositions of coexisting minerals. Unlike the pyrope lherzolite, which contained pyrope with moderate calcium (Ca)-component content (about 15 mol%), the dunite contained subcalcic chromium (Cr)-pyrope with low Ca-component content (less than 10 mol%). All investigated minerals contained dominating hydrocarbons and their derivatives represented by aliphatic (paraffins, olefins), cyclic (naphthenes, arenes), oxygenated (alcohols, ethers), and heterocyclic (dioxanes, furans) hydrocarbons;nitrogenated, chlorinated, and sulfonated compounds;carbon dioxide (CO2);and water (H2O). The relative concentration (rel%) of total hydrocarbon was 79.7 rel% for diamonds, 69.1 rel% for garnet, and 92.6 rel% for olivine, with a general amount of components ranging from 161 to 206. New data on volatiles in diamonds, associated garnet, and olivine suggest the presence of a wide spectrum of hydrocarbons along with nitrogen (N2), CO2, and H2O in some upper mantle areas.
文摘In this paper we present summation of thirteen year’s investigation of the all diamond-bearing structures of Mongolia. Four gold and diamond-bearing astropipe structures of exemplified by the Agit Khangay, Khuree Mandal, Bayan Khuree and Tsenkher astropipes of Mongolia. Detailed geological and gas-geochemical investigation of the diamond and gold-astropipe structures show that diamond genesis is an expression of collision of the lithospheric mantle with the explosion process initiated in an impact collapse meteor crater.
基金supported by RBRF grants:05-05-64718,11-0500060,11-05-91060-PICS,16-05-00860the projects 77-2,65-03,02-05 UIGGM SD RAS and ALROSA Stock Company
文摘The Dalnyaya kimberlite pipe（Yakutia,Russia） contains mantle peridotite xenoliths（mostly Iherzolites and harzburgites） that show both sheared porphyroclastic（deformed） and coarse granular textures,together with ilmenite and clinopyroxene megacrysts.Deformed peridotites contain high-temperature Fe-rich clinopyroxenes,sometimes associated with picroilmenites,which are products of interaction of the lithospheric mantle with protokimberlite related melts.The orthopyroxene-derived geotherm for the lithospheric mantle beneath Dalnyaya is stepped similar to that beneath the Udachnaya pipe.Coarse granular xenoliths fall on a geotherm of 35 mWm-2 whereas deformed varieties yield a 45 mWm-2）geotherm in the 2-7.5 GPa pressure interval.The chemistry of the constituent minerals including garnet,olivine and clinopyroxene shows trends of increasing Fe~#（=Fe/（Fe＋Mg））with decreasing pressure.This may suggest that the interaction with fractionating protokimberlite melts occurred at different levels.Two major mantle lithologies are distinguished by the trace element patterns of their constituent minerals,determined by LA-ICP-MS.Orthopyroxenes,some clinopyroxenes and rare garnets are depleted in Ba,Sr,HFSE and MREE and represent relic lithospheric mantle.Re-fertilized garnet and clinopyroxene are more enriched.The distribution of trace elements between garnet and clinopyroxene shows that the garnets dissolved primary orthopyroxene and clinopyroxene.Later high temperature clinopyroxenes related to the protokimberlite melts partially dissolved these garnets.Olivines show decreases in Ni and increases in Al,Ca and Ti from Mg-rich varieties to the more Fe-rich,deformed and refertilized ones.Minerals showing higher Fe~#（0.11-0.15） are found within intergrowths of low-Cr ilmenite-clinopyroxene-garnet related to the crystallization of protokimberlite melts in feeder channels.In P-f（O_2） diagrams,garnets and Cr-rich clinopyroxenes indicate reduced conditions at the base of the lithosphere at-5 log units below a FMQ buffer.However,Cr-poor clinopyroxenes,together with ilmenite and some Fe-Ca-rich garnets,demonstrate a more oxidized trend in the lower part of lithosphere at-2 to 0 log units relative to FMQ.Clinopyroxenes from xenoliths in most cases show conditions transitional between those determined for garnets and megacrystalline Cr-poor suite.The relatively low diamond grade of Dalnyaya kimberlites is explained by a high degree of interaction with the oxidized protokimberlite melts,which is greater at the base of the lithosphere.
