Carbon Enrichment in the Lithospheric Mantle:Evidence from the Melt Inclusions in Mantle Xenoliths from the Hainan Basalts

It is generally believed that the lithospheric mantle and the mantle transition zone are important carbon reservoirs.However,the location of carbon storage in Earth's interior and the reasons for carbon enrichment remain unclear.In this study,we report CO_(2)-rich olivine-hosted melt inclusions in the mantle xenoliths of late Cenozoic basalts from the Penglai area,Hainan Province,which may shed some light on the carbon enrichment process in the lithospheric mantle.We also present a detailed petrological and geochemical investigation of the late Cenozoic basalts and mantle xenoliths from northern Hainan Island.The collected samples of late Cenozoic Hainan Island basalts belong to both alkaline and subalkaline series,showing fractionated REE patterns with high(La/Yb)_(N)values of 3.52–11.77,which are typical for OIB.Based on Al-in-olivine thermometry,the temperatures estimated for the mantle xenoliths can be divided into two groups.One group has temperatures of less than 1050℃,and the other group has temperature ranging from 1050℃to 1282℃.Clinopyroxene(La/Yb)_(N)–Ti/Eu and clinopyroxene Ca/Al–Mg^(#)diagrams indicate that the mantle peridotite experienced metasomatism from both silicate and carbonate melts.Melt inclusions in the olivine of mantle xenoliths include(1)CO_(2)bubble–rich melt inclusions;(2)multiphase melt inclusions(glass+CO_(2)bubble+daughter minerals);(3)pure glass melt inclusions.Magnesite is a daughter mineral in the olivine-hosted melt inclusions,which could be interpreted as a secondary mineral formed by the interactions of CO_(2)-rich fluids with an olivine host,due to post-entrapment effects.The glasses in olivine-hosted melt inclusions have high SiO_(2)contents(60.21–77.72 wt%).Our results suggest that a considerable amount of CO_(2)-rich melt inclusions are captured in the lithospheric mantle during metasomatism.The lithospheric mantle can therefore act as is a‘carbon trap',with much CO_(2)being absorbed by the lithospheric mantle in this way.

Application of Hydrothermal Diamond Anvil Cell to Homogenization Experiments of Silicate Melt Inclusions

The homogenization of silicate melt inclusions （SMIs）,small droplets of silicate melt trapped in magmatic minerals,is an important component of petrogenetic and magmatic research.Conventional homogenization experiments on SMIs use microscope-mounted heating stages capable of producing high temperatures at 1 atm and cold-seal high-pressure vessels.Heating stages are generally used for SMIs with low internal pressures and allow in situ observations of the homogenization processes.In contrast,cold-seal high-pressure vessels are generally used to heat SMIs that have high internal pressures,although the homogenized SMIs can only be observed after quenching in this approach.Here we outline an alternative approach that uses a hydrothermal diamond anvil cell （HDAC） apparatus to homogenize SMIs.This is the only current method wherein phase changes in high-internal-pressure SMIs can be observed in situ during homogenization experiments,which represents an advantage over other conventional methods.Using an HDAC apparatus prevents high-internal-pressure SMIs from decrepitating during heating by elevating their external pressure,in addition to allowing in situ observations of SMIs.The type-V HDAC that is currently being used has a shorter distance between the sample chamber and the observation window than earlier types,potentially enabling continuous observation of the processes involved in heating and SMI homogenization through an objective lens with a long working distance.Homogenization experiments using HDAC require that a number of steps,including HDAC preparation,sample preparation,sample loading,preheating,and formal heating,be carefully followed.Homogenization experiments on SMIs within granite samples from the Jiajika pegmatite deposit （Sichuan,China） are best performed using an HDAC-based approach,because the elevated proper external pressure of these SMIs,combined with a short heating duration,helps to suppress material leakage and any reactions within the SMIs,in addition to allowing in situ observations during homogenization experiments.Furthermore,using the HDAC approach has other benefits：heating rates can be precisely controlled,wafer oxidization can be prevented,and samples can be subjected to in situ microbeam analysis.In summary,homogenization using HDAC provides more reliable results than those obtained using conventional heating equipment.Future developments will include improvements to the quenching method and temperature controls for the HDAC apparatus,thereby improving the utility of this approach for SMI homogenization experiments.

Liquid immiscibility recorded in melt inclusions within corundum from alkaline basalt,Changle area,Shandong province,Eastern China

Abundant melt-and fluid inclusions occur in corundum megacrysts of alkaline basalt from the Changle area,Shandong province,eastern China.One type of melt inclusions,i.e.muhiphase melt inclusions(glass+bubbles+daughter minerals)were identified,which occur along growth zones of host corundum megacrysts.Microthermometry and laser Raman microprobe analysis were performed on the melt inclusions.The bubbles within the melt inclusions are confirmed to be CO_2-rich phase and the daughter minerals are probably silicates,such as augite and okenite.The results of high temperature homogenization experiment strongly suggest that two immiscible melts,i.e.a H_2O-and CO_2-rich melt and an anhydrous and CO_2-poor melt were trapped by melt inclusions in corundum megacryst.

Magma Evolution Processes in the Southern Okinawa Trough:Insights from Melt Inclusions

The Okinawa Trough is an initial back-arc basin that is influenced by the subduction of the Philippine Sea Plate and develops on the continental crust.The Okinawa Trough is a natural laboratory for the study of basin evolution,magmatism,and crustmantle processes in the early stage of back-arc spreading.Melt inclusions are small droplets of magma that are captured during the mineral crystallization process and can record the geochemical composition changes during magma evolution.In this study,the geochemical compositions of melt inclusions in host plagioclases of two volcanic rock samples at Station nos.9-1 and 9-2 from the southern Okinawa Trough are systematically analyzed.Based on previous studies,the origin and evolution of magma and the introduction of subducting materials in the study area are discussed.Results show that melt inclusions are characterized by the relative enrichment of large-ion lithophile elements,depletion of high-field-strength elements,and slight enrichment of rare earth elements.Indeed,the subduction of the Philippine Sea Plate introduced sediment-derived melts and fluids into the magma source area of the southern Okinawa Trough.Subsequently,4%to 5%partial melting of the hydrated mantle produces basaltic magma.The melt inclusions of andesite and dacite investigated in this study were formed by fractional crystallization of basaltic magma.Finally,the crystallization of plagioclase,pyroxene,and magnetite occurred during the late stage of magma evolution.The temperature-pressure data show that the melt inclusions in plagioclase have two capture periods:one is at temperatures above 1250℃and the other is at temperatures between 1180℃and 1200℃.The capture pressure of the inclusions at temperatures between 1180℃and 1200℃is between 5.6 kPa and 6.1 kPa,corresponding to the depth of 15–17 km below the seafloor.The geochemical characteristics of major and trace elements in inclusions show that the samples from two stations(i.e.,9-1 and 9-2)have similar or identical magma source areas.However,the crystallization differentiation reflected by inclusions in sample 9-1 is more obvious than that in sample 9-2.The inclusions were captured during magma evolution and were not contaminated by crustal materials.

Study on the Physical and Chemical Conditionsof Ore Formation of Hetai Ductile Shear Zone-Hosted Gold Deposit and Discovery of Melt Inclusions

The Hetai ductile shear zone-hosted gold deposit occurs in the deep-seated fault mylonite zone of the Sinian-Silurian metamorphic rock series. In this study there have been discovered melt inclusions, fluid-melt inclusions and organic inclusions in ore-bearing quartz veins of the ore deposit and mylonite for the first time. The homogenization temperatures of the various types of inclusions are 160℃, 180-350℃, 530℃ and 870℃ for organic inclusions, liquid inclusions, two-phase immiscible liquid inclusions and melt inclusions, respectively. Ore fluid is categorized as the neutral to basic K\++-Ca\+\{2+\}-Mg\+\{2+\}-Na\++-SO\+\{2-\}\-4-HCO\+-\-3-Cl\+- system. The contents of trace gases follow a descending order of H\-2O>CO\-2>CH\-4> (or <) H\-2>CO>C\-2H\-2>C\-2H\-6>O\-2>N\-2. The concentrations of K\++, Ca\+\{2+\}, SO\+\{2-\}\-4, HCO\+-\-3, Cl\+-, H\-2O and C\-2H\-2 in fluid inclusions are related to the contents of gold and the Au/Ag ratios in ores from different levels of the gold deposit.This is significant for deep ore prospecting in the region. Daughter minerals in melt inclusions were analyzed using SEM. Quartz, orthoclase, wollastonite and other silicate minerals were identified. They were formed in different mineral assemblages. This analysis further proves the existence of melt inclusions in ore veins. Sedimentary metamorphic rocks could form silicate melts during metamorphic anatexis and dynamic metamorphism, which possess melt-solution characteristics. Ore formation is related to the multi-stage forming process of silicate melt and fluid.

Heating Stage Experimental Study of Melt Inclusions in Feldspars from Three Holocene Eruptions of Changbaishan Tianchi Volcano

There occurred several eruptions from Changbaishan Tianchi volcano in Holocene, and at least three of them were believed to be true according to the formal studies. The products of three eruptions were yellow comenditic pumice of - 5000a B.P. （Eruption Ⅰ ）, gray comenditic pumice and pyroclastic flow of - 1000a B.P. （ Eruption II, i.e. the millennium explosive eruption）, black trachy pumice and welded tuff of - 300a B.P. （ Eruption Ⅲ ） respectively. There were a large number of melt inclusions found in phenocrysts, which differ in size and color. The Leitz 1350 heating stage experiments for melt inclusions in host feldspars from three Holocene eruptions of Changbaishan Tianchi volcano imply that there were little differences between the homogenization temperatures of melt inclusions from Eruptions Ⅰ and Ⅲ, whereas it was rather complicated for Eruption H, i.e. there might be two kinds of melt with different homogenization temperature periods, which gave the evidence for the assumption that the explosive millennium eruption of Tianchi volcano was triggered by injection and mixing of two different magmas. The experimental results also indicate that （ 1 ） small melt inclusion is easy to be homogenized, while the large one, especially the one with lots of daughter crystals, is rather difficult to be homogenized; （2） homogenization temperature closely correlates with the size of melt inclusion within host crystal, with the temperature point switching from high heating rate to low heating rate, and correlates with whether it is the first time to obtain homogenization as well; and （3） a melt inclusion can get different homogenization temperatures when it is repeatedly heated. Even more, the next homogenization temperature is usually higher than the former one, which testifies the phenomenon that hydrogen migration occurs during repeated heating.

Magma Mixing as a Trigger for Sulphide Saturation in the UG2 Chromitite(Bushveld):Evidence from the Silicate and Sulphide Melt Inclusions in Chromite

It is of great importance to understand the origin of UG2 chromitite reefs and reasons why some chromitite reefs contain relatively high contents of platinum group elements（PGEs： Os, Ir, Ru, Rh,Pt, Pd） or highly siderophile elements（HSEs： Au, Re, PGE）. This paper documents sulphide-silicate assemblages enclosed in chromite grains from the UG2 chromitite. These are formed as a result of crystallisation of sulphide and silicate melts that are trapped during chromite crystallisation. The inclusions display negative crystal shapes ranging from several micrometres to 100 μm in size.Interstitial sulphide assemblages lack pyrrhotite and consist of chalcopyrite, pentlandite and some pyrite. The electron microprobe data of these sulphides show that the pentlandite grains present in some of the sulphide inclusions have a significantly higher iron（Fe） and lower nickel（Ni） content than the pentlandite in the rock matrix. Pyrite and chalcopyrite show no difference. The contrast in composition between inter-cumulus plagioclase（An_（68）） and plagioclase enclosed in chromite（An_（13））, as well as the presence of quartz, is consistent with the existence of a felsic melt at the time of chromite saturation.Detailed studies of HSE distribution in the sulphides and chromite were conducted by LA-ICP-MS（laser ablation-inductively coupled plasma-mass spectrometry）, which showed the following.（Ⅰ） Chromite contained no detectable HSE in solid solution.（Ⅱ） HSE distribution in sulphide assemblages interstitial to chromite was variable. In general, Pd, Rh, Ru and Ir occurred dominantly in pentlandite, whereas Os,Pt and Au were detected only in matrix sulphide grains and were clearly associated with Bi and Te.（Ⅲ）In the sulphide inclusions,（a） pyrrhotite did not contain any significant amount of HSE,（b） chalcopyrite contained only some Rh compared to the other sulphides,（c） pentlandite was the main host for Pd,（d）pyrite contained most of the Ru, Os, Ir and Re,（e） Pt and Rh were closely associated with Bi forming a continuous rim between pyrite and pentlandite and（f） no Au was detected. These results show that the use of ArF excimer laser to produce high-resolution trace element maps provides information that cannot be obtained by conventional（spot） LA-ICP-MS analysis or trace element maps that use relatively large beam diameters.

The 2010 Merapi Eruption： An Overview of Melt Inclusion and Geochemical Data

To characterize the magma that gave rise to explosive eruptions of Merapi volcano in October-November 2010, melt inclusions and juvenile components fiom the eruption deposits have been analyzed. Major-element compositions of whole-rocks were analyzed by X-ray fluorescence and trace elements, including the Rare Earth Elements by inductively coupled plasma mass spectrometry. Melt inclusions and the host minerals were analyzed using energy-dispersive X-ray spectroscopy and CO2 and H20 in melt inclusions, and their associated bubbles, were analyzed using laser Raman spectrometry. The compositions of the whole-rock eruption products are basaltic and esite that slightly sifting of SiO2 and K20 composition to previous eruption products, whereas the melt inclusions in pyroxene, plagioclase and hornblende are dacite to rhyolite, likely trapped mainly during late stages of crystallization of the magma. The most high volatile content in the melt inclusion are CO2 and H2O which appear strong Raman peaks for CO2 in the gas bubbles indicate abundances on high levels of CO2. Interpretation of result from a long-term flux of CO2 into the reservoir, either derived from more mafic magmas at depth or from reaction of magma in the reservoir with limestone and it may indicate that volcanic outgassing rates far exceed the amounts that can be supplied magmas.

Geochemistry of mafic rocks and melt inclusions and their implications for the heat source of the 14.0°S hydrothermal field, South Mid-Atlantic Ridge

Fresh rocks sampled from the 14.0°S hydrothermal field of the South Atlantic Ridge can be divided into two categories: olivine-gabbro and basalt. The olivine-gabbro is composed mainly of three types of minerals: olivine, clinopyroxene and plagioclase, while a multitude of melt inclusions occur in the plagioclase phenocrysts of the basalts. We analyzed the whole-rock, major and trace elements contents of the basalts, the mineral chemistry of phenocrysts and melt inclusions in the basalts, and the mineral chemistry of olivine-clinopyroxene-plagioclase in the olivine-gabbro, then simulated magma evolution within the crust using the COMAGMAT program. The whole-rock geochemistry shows that all the basalts exhibit typical N-MORB characteristics. In addition, the mineral chemistry characteristics of the olivine-gabbro(low-Fo olivine, low-Mg# clinopyroxene, high-Ti O2 clinopyroxene, low-An plagioclase), show that strong magma differentiation occurred within the crust. Nevertheless, significant discrepancies between those minerals and phenocrysts in the basalts(high-Fo olivine, high-An plagioclase) reflect the heterogeneity of magma differentiation. High Mg#(≈0.72) melt inclusions isobaric partial crystallization simulations suggest that the magma differentiation occurred at the depth shallower than 13.03 km below the seafloor, and both the vertical differentiation column shows distinct discrepancies from that of a steady-state magma chamber. Instead, a series of independent magma intrusions probably occurred within the crust, and their corresponding crystallized bodies, as the primary high-temperature thermal anomalies within the off-axis crust, probably act as the heat source for the development of the 14.0°S hydrothermal system.

Characteristics of melt inclusions in skarn minerals from Fe, Cu(Au) and Au(Cu) ore deposits in the region from Daye to Jiujiang

A vast amount of the melt inclusions and fluid-melt inclusions have been found in skarn minerals from Fe, Cu(Au) and Au(Cu) ore deposits distributed from Daye to Jiujiang along the Yangtze River besides vapor-liquid inclusions. The melt inclusions are many and varied in shape. They mainly consist of crystallized silicate phases (Csi), iron phases (Fe), amorphous silicate phases (Asi) and vapor (V) with different volume percentages, and some of them contain several crystallized silicate phases. These melt inclusion sizes are commonly (10—46) × (6—15) μm2. A difference between the fluid-melt inclusions and melt inclusions is that the liquid phase appears in the former and their homogenization temperatures are lower than the latter. We measured the homogenization temperatures of the melt inclusions, fluid-melt inclusions and fluid inclusions in ten thin sections from eight ore deposits on Leitz microscope heating stage 1350 which was made in Germany. Forty-eight homogenization temperature values have been obtained. Among them, thirty-nine values are homogenization temperatures of the melt inclusions in garnet and pyroxene from skarns, two values are homogenization temperatures of fluid-melt inclusions, others belong to the fluid inclusions. Melt inclusions in garnet and pyroxene have homogenization temperatures of 890—1115°C. Fluid-melt inclusions have homogenization temperatures of 745—750°C. Homogenization temperatures of fluid inclusions are between 580°C and 675°C. The average of thirtynine homogenization temperatures for the melt inclusions is 1029.9°C. We think studied skarns to be magmatic genesis on the basis of available data relative to the characteristic features of phase states within the melt inclusions and the fluid melt inclusions and their homogenization temperatures.

Fluid-melt Inclusions in Fluorite of the Huanggangliang Skarn Iron-Tin Deposit and Their Significance to Mineralization

For the first time, fluid-melt inclusions are found in fluorite of the Huanggangliang skarn iron-tin deposit (HSID). The fluorite was formed in the main stage of mineralization, named the hydro-skarnization stage. The inclusions contain various components such as Fe, Mg and Cr from deep sources. The melts of primary inclusions are mainly Ca- and F-rich and those of secondary inclusions tend to become Si-rich. During this evolution process, the melts and iron daughter minerals decreased and even vanished. These facts reveal that the evolution of the primary mineralizing fluids and the differentiation of the fluids and melts are the main factors leading to the deposition of Fe, Sn and other elements. This discovery confirms the magmatic genesis of the HSID and has filled in the gaps in the research of magmatogenic skarn deposits and furnished new methods for such research. Furthermore, it has enlarged the scope of the research on fluid inclusions.

Si-and alkali-rich melt inclusions in minerals of mantle peridotites from eastern China:Implication for lithospheric evolution

Minerals of spinel- and garnet-facies mantle xenoliths entrained in Cenozoicbasalts from eastern China (North China, Northeastern China and Southeastern China coastal area)contains lots of melt inclusions. Studies on these melt inclusions show that the glass inclusionsare rich in SiO_2 (60%—68%) and alkalis (K_2O+Na_2O = 5%—11%, especially for K_2O) as well asvolatiles such as H_2O and CO_2 (2%—7%), which belong to dacites and andesites of the high-K calcicalkali series rocks with few shoshonites. High Al and Ca diopside in melt inclusion is the productof melt crystallization at high temperature and pressure, rather than the product ofdevitrification. Results show that these K-rich (in general K_2O 】 3%) intermediate-acidic silicatemelt inclusions have characteristics of continent without a genetical link to host basalts and theirphenocrystic minerals. Thus, these trapped melt inclusions represent melts of Mesozoic lithosphericmantle-crust interaction and imply that the continental lithospheric mantle beneath eastern Chinahad undergone fragmentation and recreation processes during the Mesozoic and Cenozoic periods. Thisresult undoubtly provides important implication for the evolution of sub-continental lithospherebeneath eastern China. We propose that these Si- and alkalis-rich melts should be responsible forthe mantle chemical heterogeneity underneath eastern China.

Petrogenesis of Songshugou dunite body in the Qinling orogenic belt, Central China: Constraints from geochemistry and melt inclusions

The Songshugou dunite body, which occupies an area of about 20 km2, is the largest ultramafic massif in the eastern Qinling orogenic belt, Central China. The major compo-nent of this body is dunitic rocks including mylonitic dunite and coarse-grained dunite; they oc-cupy about 95 vol% of the total body. Petrography, mineral composition, major and trace ele-ments and primitive melt inclusions have been investigated in this paper; all revealed that this dunite body is the product of melt-rock interaction by porous percolation flow. In comparison with dunite sills or veins in harzburgite from the basal part of Oman ophiolite, this dunite body is characterized by lower contents of Al2O3, CaO and HREE but higher content of highly incom-patible elements and Zr and Hf. The LREE enriched patterns and primitive mantle normalized spidergrams of trace elements are also different from the Oman dunite. Combining with melt in-clusions observed in olivines, we conclude that this dunite body is the product of large- scale porous percolation flow of high-MgO melts within depleted mantle peridotites. The high-MgO magma, in essence, was most probably produced at the hot head of an upwelling mantle plume. The occurrence of the Songshugou dunite body is closely associated with the activity of mantle super-plume in Neo-Proterozoic era in the Yangtze Craton.

Inclusions in melting process of titanium and titanium alloys

This paper summarizes melting methods of titanium and titanium alloy, such as vacuum arc melting(VAR) and electron beam cold hearth melting(EBCHM), and the related inclusions formed when using these melting methods. Low-density inclusions are resulted from contamination of air, and high-density inclusions are caused by refractory elements. The formation process of inclusions was analysed. The removal mechanism of different kinds of inclusions was specified. Low-density inclusions are removed mainly by resolving. This is a comprehensive process containing reaction diffusion. The resolving rate of high-density inclusions is so low that these inclusions are mainly removed by sedimentation. The experiments and physical models of inclusions are detailed. In various melting methods, vacuum arc melting is prominent. However, this method cannot remove inclusions effectively, which usually results in repeat melting. Electron beam cold hearth melting has the best ability of removing inclusions. These results can provide instructions to researchers of titanium and titanium alloys.

Analysis of chemical composition of melt inclusion of beryl in pegmatite and discovery of zinc-spinel by electronic probe

The compositions of daughter mineral of melt inclusion in beryls, which are from pegmatites of Keketuhai in Xinjiang and Mufushan in Hunan, have been analyzed by electronic probe. Ten kinds of mineral, such as beryl, zinc-spinel, mica, quartz, magnetite, etc., which consist of different mineral associations have been identified. The zinc-spinel existing in two dif-

Lithogeochemistry of Volcanic Rocks and Hosted Melt Inclusions in Wudalianchi,Heilongjiang,China

Wudalianchi（五大连池） volcanoes are famous Quaternary ones with fairly good volcanic landscape in Northeast China.The volcanic rocks are phonotephrite,tephri-phonolite,trachyandesite,and basaltic trachyandesite with SiO2 contents of 47.3 wt.%-54.2 wt.%.The characteristic of high K2O content in Wudalianchi volcanic rocks suggests that they probably share a common potassic magma source.The magma evolutions of Wudalianchi volcanic rocks are similar,while the new eruption prod-ucts of Laoheishan（老黑山） and Huoshaoshan（火烧山） volcanoes are slightly more evolved than the old eruption materials,i.e.,the magma of the new eruptions in 1719-1721 from the above two volcanoes is the evolved magma in underground chamber.The main phenocrysts of Wudalianchi volcanic rocks are olivines,clinopyroxenes,and some characteristic K-rich leucites.The various-shaped melt inclu-sions are found in olivine phenocrysts from new eruption products of Laoheishan and Huoshaoshan volcanoes.By electron microprobe（EMP） analyzing,the contents of SiO2 and total alkali show a wide range,suggesting that the pre-eruptive magma was probably more complicated,or the melt inclusions were rather unhomogeneous.On the basis of EMP results,it is believed that the sulfur degassing rate from this new eruption was much higher than that of the millennium eruption of Tianchi（天池） volcano,while the chlorine degassing rate was a magnitude lower than that of Tianchi volcano.

Effect of interaction of refractories with Ni-based superalloy on inclusions during vacuum induction melting

This study documents laboratory-scale observation of the interactions between the Ni-based superalloy FGH4096 and refractories.Three different crucibles were tested—MgO,Al2O3,and MgO–spinel.We studied the variations in the compositions of the inclusions and the alloy–crucible interface with the reaction time using scanning electron microscopy equipped with energy dispersive X-ray spectroscopy and Xray diffraction.The results showed that the MgO and MgO–spinel crucibles form MgO-containing inclusions(Al–Mg oxides and Al–Mg–Ti oxides),whereas the inclusions formed when using the Al2O3 crucible are Al2O3 and Al–Ti oxides.We observed a new MgAl2O4 phase at the inner wall of the MgO crucible,with the alloy melted in the MgO crucible exhibiting fewer inclusions.No new phase occurred at the inner wall of the Al2O3 crucible.We discuss the mechanism of interaction between the refractories and the Ni-based superalloy.Physical erosion was found to predominate in the Al2O3 crucible,whereas dissolution and chemical reactions dominated in the MgO crucible.No reaction was observed between three crucibles and the Ti of the melt although the Ti content(3.8wt%)was higher than that of Al(2.1wt%).

RESEARCH ON THE COMPOSITION OF MINERAL MELT INCLUSIONS IN VOLCANIC ROCK SERIES IN THE GREAT WALL STATION AREA, KING GEORGE ISLAND, ANTARCTICA

Ⅰ. INTRODUCTION The Great Wall Station area is located in the Fildes Peninsula, King George Island. The strata are composed mainly of basaltic and basah-andesitic lavas, pyroclastic rocks and pyroclastic-sedimentary rocks. This volcanic rock series shows the characteristics of typical island-arc volcanic rocks. From below upwards five rock units may be distinguished: (Ⅰ) the Jasper Hill Member, (Ⅱ)the Agate Beach Mem-

Sulfide-melt inclusions in mantle xenoliths from the Changbaishan district,Jilin province,China

Mantle xenoliths are common in the Cenozoic basalts of the Changbaishan District,Jilin Province,China.Sulfide assemblages in mantle minerals can be divided into three types:isolated sulfide grains,sulfide-meh inclusions and filling sulfides in fractures.Sulfide-meh inclusions occur as single-phase sulfides,sulfide-silicate melt,and CO_2-sulfide-silicate melt inclusions. Isolated sulfide grains are mainly composed of pyrrhotite,but cubanite was found occasionally.Sulfide-meh inclusions are mainly composed of pontlandite and MSS,with small amounts of chalcopyrite and talnakhite.The calculated distribution coefficient K_(D3)for lherzolite are similar to that of mean experimental value.The bulk sulfides in lherzolite were in equilibrium with the enclosing minerals, indicating immiscible sulfide melts captured in partial melting of upper mantle.Sulfide in fractures has higher Ni/Fe and(Fe+Ni)/S than those of sulfide melt inclusions.They might represent later metasomatizing fluids in the mantle.Ni/Fe and(Fe+Ni)/S increase from isolated grains,sulfide inclusions to sulfides in fractures.These changes were not only affected by temperature and pressure,hut by geochemistry of Ni,Fe and Cu,and sulfur fugacity as well.

Glass melt inclusion in clinopyroxene from Linqu Cenozoic basalt,Shandong Province,China

Cenozoic basalts from the Linqu County, Shandong Province, China entrain some clinopy- roxene crystals, of which many contain abundant glass melt inclusions. These melt inclusions are ex- tremely irregular in shape with most grain sizes in a range of 10-50 μm and coexist with low-Mg# olivines, labradorites and Ca-rich potassium feldspars. In-situ major and trace element analyses show that the glass melt inclusions are high in alkalis (Na2O+K2O > 10 wt%), SiO2 (>54 wt%), CaO and FeO (>4 wt%), but low in MgO (Mg# < 20), and have LREE enrich- ments ((Ce/Yb)cn = 11.6-16.4) and apparently posi- tive Eu anomalies (Eu/Eu* > 2), thus having phonoli- tic compositions. The compositional features of cli- nopyroxene crystals, glass melt inclusions and their coexistent minerals suggest that these melt inclu- sions were exotic melts in clinopyroxenes trapped prior to their entrainment in the host basalt. The dis- covery of these melt inclusions provides a new ap- proach to further investigating the evolution of Meso- zoic lithospheric mantle beneath the southeastern North China Craton.