experimental reactions of amphibolite with boron bearing aqueous fluids at 200 mpa implications for tourmaline stability and partial melting in mafic rocks reactions between hornblende plagioclase amphibolite and acidic and alkaline b bearing aqueous fluids have been investigated by experiments at 475 600 c and 200 mpa at 600 c hornblende calcic plagioclase react to form tourmaline danburite clinopyroxene quartz in acidic fluids containing 0 5 1 0 wt b2o3 tourmaline is precipitated directly from acidic fluids and the reaction is driven by neutralization of fluids by na ca derived from the breakdown of reactant solids the concentration of b2o3 in fluids needed to stabilize tourmaline increases as ph increases above approximately 6 0 and tourmaline is unstable in alkaline fluids ph approximately 6 5 7 0 regardless of b concentration in addition to acid base relations tourmaline stability is favored by comparatively higher activity coefficients for al species in acidic fluids the concentrations of al and si in fluid increase with alkalinity with the eventual production of felsic borosilicate melts through partial melting of the plagioclase component of the amphibolite in seeded experiments tourmaline also contributes components to melt partial melting is evident in the range 500 525 c at 200 mpa in experiments with 8wt b2o3 in fluid as na2b4o7 the experimental results are applied primarily to metasomatic reactions between mafic rocks and borate fluids derived from granitic magmas but tourmaline stability and partial melting in mafic regional metamorphic systems are also discussed briefly

alkali free tourmaline in the system mgo al2o3 b2o3 sio2 h2o abstract an end member of the tourmaline series with a structural formula mg 2 al al 6 bo 3 3 si 6 o 18 oh 4 has been synthesized in the system mgo al 2 o 3 b 2 o 3 sio 2 h 2 o where it represents the only phase with a tourmaline structure our experiments provide no evidence for the substitutions al mg h mg 2h b h si and alal mgsi and we were not able to synthesize a phase mg aluminobuergerite characterized by mg in the 3a site and a strong oh deficiency reported by rosenberg and foit 1975 the alkali free tourmaline has a vacant 3a site and is related to dravite by the al for na mg substitution it is stable from at least 300 c to about 800 c at low fluid pressures and 100 excess b 2 o 3 and can be synthesized up to a pressure of 20 kbars at higher temperatures the tourmaline decomposes into grandidierite or a boron bearing phase possibly related to mullite b mullite quartz and unidentified solid phases or the tourmaline melts incongruently into corundum liquid depending on pressure in the absence of excess b 2 o 3 tourmaline stability is lowered by about 60 c tourmaline may coexist with the other mgo al 2 o 3 b 2 o 3 sio 2 h 2 o phases forsterite enstatite chlorite talc quartz grandidierite corundum spinel b mullite cordierite and sinhalite depending on the prevailing ptx conditions the 3a vacant tourmaline has the space group r3m with a 15 90 a c 7 115 a and v 1557 0 a 3 however these values vary at room temperature with the pressure temperature conditions of synthesis by 0 015 a in a 0 010 a in c and 4 0 a 3 in v probably as a result of mgal order disorder relations in the octahedral positions despite these variations intensity calculations support the assumed structural formula refractive indices are n o 1 631 2 n e 1 610 2 n 0 021 the infrared spectrum is intermediate between those of dravite and elbaite the common alkali and calcium deficiencies of natural tourmalines may at least partly be explained by miscibilities towards 3a vacant end members the apparent absence of 3a vacant tourmaline in nature is probably due to the lack of fluids that carry boron but no na or ca

boron and lithium in high grade rocks and minerals from the wawa kapuskasing region ontario there is no preferential partitioning of boron among the principal rock forming minerals in high grade rocks of the kapuskasing structural zone ksz and the wawa domal gneiss region wdg lithium is strongly concentrated in biotite and other ferromagnesian minerals but does not show consistent partitioning between these and the sialic minerals the distribution of b and li within a rock may be studied using an alpha track image which shows that the inconsistencies in partitioning may be largely attributed to disturbance of mineral equilibria by postmetamorphic low grade alteration that deposited b and li boron has similar concentrations in all the rock types studied although it is an incompatible element that elsewhere accumulates in pegmatites lithium concentrations are low in the anorthositic rocks but are otherwise very variable in some but not all rocks higher than usual b and li can be attributed to introduction during alteration boron occurs at low concentrations 2 3 ppm throughout both the k

the influence of tectonic deformation on some geochemical properties of coals a possible indicator of outburst potential abstract nearly all outburst prone coal is known to have been tectonically deformed in fault and fold zones which underwent one or more episodes of strong structural deformation the physical properties of deformed coal such as strength coefficient and rate of gas desorption have been broadly studied and used to predict outbursts in the past however it can be difficult to reliably determine these physical coefficients from core sampling operations because the coal can be inadvertently pulverized during drilling the development of a new index which predicts the outburst potential of coal seams and is not influenced by sampling procedures could be beneficial to mining safety technology tectonic deformation may not only affect the original physical structure of a coal but also may bring about changes in chemical properties any chemical property with the potential to identify outburst prone coal must also be stable and independent of the physical changes imposed by drilling most of the chemical characteristics of coal display no obvious difference between normal undeformed coal which is not subject to outbursts and deformed coal however recent studies have shown that the chloroform extract yield is a very good geochemical index for differentiating these coals nineteen coal samples from five mines experiencing outbursts in the pingdingshan coalfield henan china were analyzed their mean maximum vitrinite reflectance in oil ranges from 0 97 to 1 28 all of the samples were prepared to 180 m 80 mesh us and subsamples were extensively extracted with chloroform in a soxhlet apparatus at 75 c the mean extract yield of the 10 deformed coals is 1 45 whereas that of the nine normal coals is 0 44 we conclude that deformed coal has a higher chloroform extract yield than equivalent coal which has not been tectonically disturbed chloroform extraction therefore can be used to recognize deformed coal and the potential to undergo further deformation chloroform extract yield is an accepted measure of the hydrocarbon generating potential of coals and other rocks the results presented here therefore suggest that tectonic deformation may modify the hydrocarbon generating potential of coals the adsorption of soluble organic matter expelled during and following tectonic deformation onto enhanced surface areas may have contributed to the higher extract yields of the deformed coal

redetermination and reevaluation of compositional variations in metamorphosed sediments of the littleton formation new hampshire in a study of metamorphosed pelites of the devonian aged littleton formation new hampshire shaw 1954 found little evidence for large scale compositional change other than devolatilization because his data are still used for such studies we have reanalyzed his original samples using more precise methods and for additional elements to provide a more useful data set since shaw s study remapping in new hampshire has shown that 21 samples from the original set of 67 appear to be from underlying silurian formations the new data for the remaining 46 littleton samples show statistically unambiguous differences between sample sets in average concentration ratios to al2o3 or tio2 for several elements on a loss on ignition free basis the data do not however show systematic compositional differences as a function of metamorphic grade variations in element concentrations within sample sets of low medium and high metamorphic grade are as large or larger than differences in average concentrations between pairs of sample sets this renders the method of comparing average compositions intrinsically insensitive even to substantial compositional change during metamorphism we find no compelling evidence in support of metamorphic gain or loss of the elements we studied but taken at face value the statistical uncertainties would allow considerable gain or loss of most elements during metamorphism of littleton pelites further detailed sampling would be required to determine whether the samples of each metamorphic grade are representative and to interpret the compositional variations and differences accurately in terms of metamorphic element mobility on the one hand and inheritance from the heterogeneous sedimentary protolith on the other

boron in chert and precambrian siliceous iron formations abstract in order to assess the importance of siliceous sediments as a sink for oceanic b and to determine the effect of diagenesis on the mobilization of b samples were analysed from chert nodules bedded cherts and siliceous banded iron formations from a variety of sedimentary environments and geologic ages boron analyses on bulk samples were made by prompt gamma neutron activation analysis the distribution of b in rocks was mapped using track methods nodular phanerozoic cherts typically contain 50 150 ppm b and bedded cherts somewhat less the b is initially concentrated in tests of silica secreting organisms but some is lost in early diagenesis as silica progressively recrystallises to quartz banded iron formation silica of archean and proterozoic age usually contains

source and partitioning of b and sn in the cornubian batholith of southwest england abstract emplacement of the variscan s type cornubian batholith initiated the formation of the historical world class sn and cu deposits and extensive tourmalinisation of southwest england the hypothesis is tested that the sn and tourmaline mineralisation were wholly formed by magmatically derived hydrothermal fluids with no requirement for a contribution from the stripping of country rocks by circulating hydrothermal fluids from simple geochemical modelling sufficient sn concentrations to match those in the main 90 of granite outcrop biotite granites average of 23 mg kg and to produce the large sn deposits can be derived by partial melting of pre granite southwest england crust at geologically realistic levels of partial melting 30 fractionation 10 to 50 and melt aqueous fluid partitioning assumed to be 6 wt of the mass of the granite batholith in contrast insufficient b 700 mg kg or b concentrations found in many of the granites we conclude that tourmaline in the biotite granites was formed from magmatically derived hydrothermal fluids which emanated as a result of first and possibly second boiling an additional source of b for the hydrothermal fluids may have been the devolatilisation of stoped blocks of country rock mudstones these findings provide fundamental constraints on the evolution of the cornubian batholith which is used as a model for a large number of sn provinces worldwide

contrasting behaviour of boron during crustal anatexis the study of volatile elements in crustal anatectic terranes may provide information about the role of fluid flow and fluid pathways during high temperature metamorphism we have studied the distribution of li and b in two migmatitic areas the pena negra anatectic complex central spain and the migmatites and leucogranites associated with the ronda peridotites southern spain they represent two contrasting cases in the behaviour of volatiles particularly b during anatexis the pena negra migmatites are dominated by diatexites where it is possible to distinguish granitic leucosomes melanosomes metric to decimetric leucogranitic segregates and decimetric to metric sillimanite rich restitic enclaves all lithologies are characterized by low b concentrations mean values 30 ppm and b is enriched in melanosomesrrestites with respect to leucosomesrleucogranites this may be due to the fact that a notable proportion of b can reside in restitic sillimanite b concentrations in leucosomes and leucogranites can be explained by closed system anatexis at ronda metatexitic and diatexitic migmatites underlie the ronda peridotites and diatexite and leucogranite dikes intrude the peridotites diatexites underlying the peridotites are characterized by cordierite q biotite garnet as ferromagne sian phases with rare or absent tourmaline low b contents 10 ppm and cordierite garnet leucosomes leucogranite dikes have high b concentrations mean valuef 400 ppm with tourmaline being a common and sometimes the most abundant ferromagnesian phase a genetic relationship between diatexites and leucogranites is strongly suggested by the presence of dikes of diatexites intruding the bottom of the peridotites we conclude that b in the leucogranites may stem from the dissolution of tourmaline originally present in the metasediments or infiltration of b rich aqueous fluids into the anatectic zone according to recent experimental work textures in some tourmaline rich ronda leucogranites suggest initial b o 23 contents in the melt higher than the present measured concentrations preliminary experimental results presented in this paper propose that this difference is not due to water activities in the melt rapid crystallization of the melts following undercooling may explain the existence of abundant euhedral tourmaline in leucogranites with low aluminium saturation index asis molar al o r caoq na oq k o and relatively low b contents q 2001 elsevier science b v all rights 23 2 2 reserved

the impact of tectonic deformation upon coal seams in the south wales coalfield uk observations on the nature and appearance of coal seams which were deformed during the late carboniferous variscan orogeny have been made over several years within a number of opencast coal sites located across the south wales coalfield the deformation of coal seams was dominated by brittle failure and subsequent movement along fracture planes examination of hand specimens and smaller scale samples using a scanning electron microscope reveals the presence of two distinct types of small scale tectonic fracture markings within deformed coals striated fracture surfaces with prominent ridges and grooves can bear a superficial resemblance to shatter cones in appearance but are unique to coal in their tectonic setting and appear to have formed by static shear failure whereas strongly polished fracture surfaces result from movement across fracture planes deformed coal seams are also affected by distinctive large scale tectonic fracture sets the extent of fracturing within coal seams can be assessed using different techniques including measuring fracture frequency directly performing various strength and hardness tests making relatively simple subjective assessments on the appearance of the coal or monitoring the size distribution of the coal product by applying some of these methods within working opencast sites it can be shown that large amounts of abnormally fractured coal were formed along coal based thrust flats or detachments but that the distribution of fractured coal along detached seams is rarely homogeneous enhanced fracturing often occurred in association with the localised thickening of seams along small scale thrusts or within coal duplexes variable seam thicknesses and pockets of structurally thickened coal are seen as the most efficient means by which the presence and location of significant amounts of fractured coal can be predicted from borehole evidence during prospecting

instantaneous outbursts in underground coal mines an overview and association with coal type instantaneous outbursts in underground coal mines have occurred in at least 16 countries involving both methane ch4 and carbon dioxide co2 the precise mechanisms of an instantaneous outburst are still unresolved but must consider the effects of stress gas content and physico mechanical properties of the coal other factors such as mining methods e g development heading into the coal seam and geological features e g coal seam disruptions from faulting can combine to exacerbate the problem prediction techniques continue to be unreliable and unexpected outburst incidents resulting in fatalities are a major concern for underground coal operations gas content thresholds of 9 m 3 t for ch4 and 6 m 3 t for co2 are used in the sydney basin to indicate outburst prone conditions but are reviewed on an individual mine basis and in mixed as situations data on the sorption behaviour of bowen basin coals from australia have provided an explanation for the conflicting results obtained by coal face desorption indices used for outburst proneness assessment a key factor appears to be different desorption rates displayed by banded coals which is supported by both laboratory and mine site investigations dull coal bands with high fusinite and semifusinite contents tend to display rapid desorption from solid coal for a given pressure drop the opposite is true for bright coal bands with high vitrinite contents and dull coal bands with high inertodetrinite contents consequently when face samples of dull fusinite or semifusinite rich coal of small particle size are taken for desorption testing much gas has already escaped and low readings result the converse applies for samples taken from coal bands with high vitrinite and or inertodetrinite contents in terms of outburst potential it is the bright vitrinite rich and the dull inertodetrinite rich sections of a coal seam that appear to be more outburst prone this is due to the ability of the solid coal to retain gas even after pressure reduction creating a gas content gradient across the coal face sufficient to initiate an outburst once the particle size of the coal is reduced rapid gas desorption can then take place c 1998 elsevier science

late quaternary sediment dating and quantification of lateral sediment redistribution applying230thex a study from the eastern atlantic sector of the southern ocean high resolution records of the natural radionuclide230th were measured in sediments from the eastern atlantic sector of the antarctic circumpolar current to obtain a detailed reconstruction of the sedimentation history of this key area for global climate change during the late quaternary high resolution dating rests on the assumption that the230thex flux to the sediments is constant short periods of drastically increased sediment accumulation rates up to a factor of 8 were determined in the sediments of the antarctic zone during the climate optima at the beginning of the holocene and the isotope stage 5e by comparing expected and measured accumulation rate of230thex lateral sediment redistribution was quantified and vertical particle rain rates originating from the surface water above were calculated we show that lateral contributions locally were up to 6 5 times higher than the vertical particle rain rates at other locations only 15 of the expected vertical particle rain rate were deposited

kerguelen plateau quaternary late pliocene palaeoenvironments from diatom silicoflagellate and sedimentological data abstract gravity cores from the south kerguelen plateau contain sections representing two quaternary intervals 1

eight glacial cycles from an antarctic ice core the antarctic vostok ice core provided compelling evidence of the nature of climate and of climate feedbacks over the past 420 000 years marine records suggest that the amplitude of climate variability was smaller before that time but such records are often poorly resolved moreover it is not possible to infer the abundance of greenhouse gases in the atmosphere from marine records here we report the recovery of a deep ice core from dome c antarctica that provides a climate record for the past 740 000 years for the four most recent glacial cycles the data agree well with the record from vostok the earlier period between 740 000 and 430 000 years ago was characterized by less pronounced warmth in interglacial periods in antarctica but a higher proportion of each cycle was spent in the warm mode the transition from glacial to interglacial conditions about 430 000 years ago termination v resembles the transition into the present interglacial period in terms of the magnitude of change in temperatures and greenhouse gases but there are significant differences in the patterns of change the interglacial stage following termination v was exceptionally long 28 000 years compared to for example the 12 000 years recorded so far in the present interglacial period given the similarities between this earlier warm period and today our results may imply that without human intervention a climate similar to the present one would extend well into the future

antarctic sea ice and palaeoproductivity variation over the last 156 000 years in the indian sector of southern ocean abstract antarctic sea ice plays a vital role in global climate via its impact on ocean circulation biological productivity and co2 partitioning between the ocean and the atmosphere however very little is known about its past history especially in the southwestern indian sector of the southern ocean so we here provide new quantitative records of winter sea ice concentration wsic and duration wsid sea surface temperatures sst and productivity in sediment core sk 200 33 55 s 45 e from the permanently open ocean zone over the last 156 000 years the new records combined with regional records indicate that the hydrological structures migrated northward by a few degrees of latitude during all glacial periods with the southern antarctic circumpolar current front reaching the core site the antarctic polar front located at 46 s and the winter sea ice wsi probably extending to 49 s in contrast hydrological fronts and wsi edge migrated poleward by a couple of degrees of latitude during the early holocene and last interglacial comparison to sst and wsi records from different sectors of the so suggests higher amplitude variations in wsi in the atlantic sector as compared to the indian and western pacific sectors over the last glacial interglacial cycle which we attribute to the presence of the weddell gyre transporting far to the north the sea ice produced in the weddell sea the new records also suggest a drop in productivity in the pooz during glacial periods probably related to greater wsi extent and reduced growing season

pegmatite wallrock interactions black hills south dakota progressive boron metasomatism adjacent to the tip top pegmatite abstract interaction between country rock and fluids derived from the tip top pegmatite has resulted in a series of boron enriched assemblages between unaltered quartz mica schist to the pegmatite contact is a succession of four mineral assemblages 1 1 quartz biotite potassium feldspar assemblage q b k which consists essentially of the original metamorphic silicate assemblage plus anomalously high amounts of modal tourmaline 2 2 quartz biotite tourmaline assemblage q b t 3 3 tourmaline quartz muscovite assemblage t q m 4 4 tourmaline quartz assemblage t q alkali elements cs rb k li sio 2 and ba show a decrease from the q b k assemblage to the t q assemblage a1 2 o 3 ga b total fe and zn increase moderately from the q b k assemblage to the t q assemblage the mineral chemistries also change considerably the mg mg fe 2 ratios in biotites range from 0 54 to 0 50 in samples from the q b k assemblage to 0 39 in the q b t assemblage the range in tourmaline end member components from the q b k assemblage to the t q assemblage is as follows q b k dravite 63 schorl 23 elbaite 05 buergerite 09 t q dravite 23 schorl 37 elbaite 17 buergerite 23 observed variations in mineral assemblage and whole rock chemistry within the alteration zone appear to a first approximation to be a function of b 2 o 3 boron metasomatism and k 2 o alkali leaching the breakdown of feldspar and biotite may be approximated by reactions 2hcl 2 k na alsi 3 o 8 ai 2 k na cl al 2 sio 5 5sio 2 h 2 o and 2 annite sio 2 5al 2 sio 5 2nacl 6h 3 bo 3 ai 2 tourmaline 2kcl 7h 2 o the alteration zone may represent either a single episode b cs li rb enriched fluid or multiple episodes b zn mn fluid and cs li rb fluid of pegmatite fluid schist interactions in both situations b in the aqueous fluid from the pegmatite reacts with the schist breaking down sheet silicate traps for cs rb li and k and forming tourmaline rich assemblages

modern distribution of diatoms in sediments from the george v coast antarctica abstract currently little information exists concerning high frequency climate change in the antarctic data that are essential to gaining a more complete understanding of global climate change sediments from the george v coast continental margin potentially contain a high resolution record of the late holocene the relatively high rate of sedimentation 3 mm year and the presence of laminated intervals which contain undisturbed sequences make these sediments valuable for future downcore work in order to utilize diatom assemblages as proxies of paleoclimatic and paleoceanographic parameters a preliminary study of the surface sediment distribution of diatoms from the george v coast continental margin was completed nitzschia curta van heurck hasle and nitzschia kerguelensis o meara hasle present great potential for tracking the holocene retreat of ice across the continental shelf of this region concentrations of n curta an ice related form decreases in an offshore direction whereas n kerguelensis an oceanic species associated with circumpolar flow displays an increase in sediments offshore the genus thalassiosira cleve displays a clear association with areas of open water primary production as has been noted in others parts of the antarctic downcore variability in relative abundance of this genus will be useful in understanding the history of sea ice versus open water production on the george v coast shelf in contrast the distribution of chaetoceros ehrenberg resting spores appears to be more complex but may be related to the position of the stationary ice edge associated with the annual minimal extent of sea ice finally an understanding of the downcore variability of thalassiothrix antarctica schimper ex karsten a species which is very abundant in the laminated sections of the sediment cores will have to rely on studies of its distribution in other areas of the antarctic as it is sparsely distributed along the george v coast today

reappraisal of sea ice distribution in atlantic and pacific sectors of the southern ocean at 18 000 yr bp the question of the distribution of winter and summer sea ice cover during the last glacial maximum 18 000 yr bp is important in climatic modelling of the glacial world we have now compared satellite derived 5 yr monthly averages of per cent summer sea ice cover in the atlantic and pacific sectors of the southern ocean with the distribution of reported sedimentological indicators of sea ice cover at the sediment water interface these data strongly suggest that sediment type cannot be used to identify summer sea ice limits neither in recent sediments nor in sediments of the last glacial maximum rather the data seem to indicate that sediment type can be used to identify spring sea ice limits for these two time intervals

diatom distribution and paleoceanographic reconstruction in the southern ocean present and last glacial maximum abstract diatom assemblage and preservational data are used to reconstruct paleoceanographic conditions at the last glacial maximum 18 000 yrs bp in the southern ocean from these data the following points can be made about the last glacial maximum in this region 1 contraction and slight northern shift of the belt of well preserved diatoms appears to be related to the northward shift of late spring early summer sea ice cover 2 presence of open ocean though poorly preserved diatom assemblages to the south of this belt strongly suggest that during many summers large areas of the southern ocean were ice free 3 the distribution of thenitzschia kerguelensis factor both in surface sediments and at the last glacial maximum indicates that the gyre systems particularly the weddell gyre were intensified during glacial times 4 although data are sparse in the higher latitude south atlantic there is an indication that the weddell polynya also existed during glacial times although it was shifted a few degrees northward

a coupled approach to simulate initiation of outbursts of coal and gas model development an outburst of coal and gas is a major hazard in underground coal mining it occurs when certain conditions of coal stress strength and gassiness are met the outburst is recognized as a two step process i e initiation and development each step has its own characteristics and requires different approaches in numerical modeling as a first step the initiation process of the outburst is numerically simulated with a coupled simulator the simulator models the deformation and failure of a coal seam adsorption and desorption of gas and flow of gas and water in coal the simulator is developed by linking and sequentially executing two numerical codes flac3d and comet3 flac3d is a widely used commercial code designed for engineering mechanics computation while comet3 is a well established code to model gas and water production from desorption controlled reservoirs in this paper these two codes are linked and sequentially executed through coupling modules including a user designed c module and several modules developed with the build in fish language in flac3d these coupling modules are used to transfer relevant data between the codes a simple example to simulate the initiation of the outburst is also presented in this paper to demonstrate the capability of the coupled simulator

geochemical modeling of low melt fraction anatexis in a peraluminous system the pena negra complex central spain abstract a study was made of the chemical fractionation associated with four cases of anatectic segregation of low melt fraction cordieritic granites from migmatized meta greywackes the aims of the study were to 1 reveal the fractionation patterns of major and trace elements 2 compare the major element chemistry of leucogranites and the quantitative behavior of source minerals during anatexis inferred by mass balance adjustment with available experimental data for peraluminous systems and 3 discuss the behavior of trace elements in crustal melting by comparing the chemically determined composition of leucogranites with the results of three fractionation models two of these assume a perfect diffusive behavior of trace elements within residual solids but they use a different set of distribution coefficients the third assumes a perfect nondiffusive behavior in relation to their source rocks the leucogranites are strongly depleted in li transition elements and light rare earth elements but enriched in k2o sio2 and ba the k rb ratio in leucogranites is higher than in sources and reaches values typical of high grade metamorphism mass balance analysis using the anatexis mixing model shows that the chemistry of cordierite leucogranites is compatible with its having originated by closed system water undersaturated anatexis on previously migmatized meta greywackes leaving a residue enriched in cordierite plus biotite and exhausted in k feldspar biotite melts congruently unless important amounts of sillimanite were also present in the source compared with experimental melts obtained from sources with the same chemical composition but with a different femic mineralogy biotite sillimanite instead of cordierite biotite the pena negra leucogranites are richer in k2o and mgo with a lower fe fe mg ratio the differences in magnesium are believed to result from the changes in the mineral assemblage of the source rocks however the differences in potassium contents are still not well understood the behavior of trace elements during anatexis cannot be modeled by trace element fractionation equations because of the sluggish diffusion kinetics of trace elements at the temperature of anatexis making the melting rate of minerals greater than the diffusion rate of trace elements within minerals the behavior of trace elements essentially consists in following that of the minerals containing them

airflow disturbance induced by coal mine outburst shock waves a case study of a gas outburst disaster in china abstract we explore the magnitude of airflow disturbance in mine roadways induced by gas outburst shock waves outburst shock wave propagation in the near field of the outburst source is established and simulated in three dimensions using fluent the effects in connected but distal roadways are represented by a simplified one dimensional network model and solved by flowmaster a mesh based parallel code coupling interface mpcci is applied to couple the three dimensional near source model and the one dimensional distal model the coupled model is verified by theoretical analysis and against observations from a coal and gas outburst incident comprising 2887 tonnes of coal that occurred in the jiulishan coal mine china and general characteristics of outburst events explored simulations demonstrate that airflow disturbance induced by outburst shock waves in the coal mine is principally controlled by the shock wave overpressure and fan pressure provided by the main fan of these the shock wave overpressure exerts the dominant impact the larger the shock wave overpressure the more rapid the decrease of airflow in the roadway branches and the larger the ultimate airflow decrease furthermore the arrival time of the minimum air flow rate is delayed when the fan pressure is large the ability to resist airflow disturbance is enhanced and the area subject to countercurrent flow is reduced the initial air flow rate and the restored air flow rate show less correlation with the shock wave overpressures however they are both significantly affected by the pressure of the main fan this work presents a novel approach for the study of airflow disturbance in underground ventilation networks in coal mines caused by coal and gas outbursts and provides guidance for the design of outburst prevention facilities

diatom evidence for late holocene climatic events in granite harbor antarctica downcore diatom data from a deep basin in granite harbor antarctica provide new high resolution information concerning changes in oceanographic and depositional processes that have occurred during approximately the last 1250 years the influence of global scale climatic change during the time of the medieval warm period and possibly the little ice age is revealed by long term changes in floral assemblages as recorded by changes in the relative concentration of nitzschia cylindrus the diatom data suggest that granite harbor experienced less annual ice and pack ice cover during both these periods possibly because of higher temperatures during the medieval warm period and stronger offshore winds during the little ice age the sedimentary record reveals several distinct short lived events in which nearly monospecific blooms of corethron criophilum and chaetoceros spp occurred possibly the result of strong stabilization of the upper water column and were most likely a response to regional rather than global conditions although short lived these events may play a significant role in the delivery of organic carbon and biogenic silica to the seafloor

constraining coalbed methane reservoir petrophysical and mechanical properties through a new coal structure index in the southern qinshui basin northern china implications for hydraulic fracturing structurally deformed coal sdc influences not only gas outbursts during coal mining but also coalbed methane cbm production different sdcs have different mechanical strengths and physical properties the structurally constrained petrophysical and mechanical properties of a cbm reservoir from the southern qinshui basin sqb northern china have been investigated by using a coal structure index csi the csi was established as a quantitative criterion for the deformation of sdcs based on surface conditions and blockiness using the data of 783 coring samples from 109 cbm wells the results show that undeformed coal and slight brittle sdcs are dominant in the sqb with ductile sdcs distributed locally both compressive strength and tensile strength decline exponentially with increasing csi average avg coal structure is a crucial factor for coal seam fracturing with an increasing csi avg the major fracture length will first increase to the maximum of 266 m at a csi avg of 45 and then decrease rapidly however branch fractures are independent of the csi avg the major fracture height attained a minimum of 4 39 m at a csi avg of 40 and then slowly increased therefore slightly brittle sdcs should be beneficial for fracturing at least for high rank coals the presence of variable sdcs can have a considerable impact on cbm reservoir petrophysical and mechanical properties finally a csi model that strives to establish the relation between structure deformation and cbm reservoir physical and mechanical properties in coal is expected to effectively guide hydraulic fracturing

mineral leucosome trace element partitioning in a peraluminous migmatite a laser ablation icp ms study abstract low pressure peraluminous migmatites from the pena negra complex central spain stayed partially molten for 5 10 ma until the latest hercynian deformations allowed the segregation of melt as discordant leucosome veins due to long residence within its source the melt had time enough to equilibrate with residual phases other than accessories included within major refractory minerals we estimated crystal melt partition coefficients as the concentration ratios between leucosome samples appearing to be pure melts and mesosome minerals which were analyzed for trace elements with a laser probe coupled to an icp mass spectrometer our data reveal that when biotite is stable li rb cs tl sc v cr ni nb and ta become strongly compatible the role of biotite in fractionating y th u and the ree is insignificant cordierite strongly fractionates li and be and also has some effect on the hree and u garnet produces extreme fractionation of sc y and the hree the ree partition coefficients for ferromagnesian silicates increase with the atomic number this effect being progressively more important through biotite cordierite and garnet k feldspar strongly fractionates ba and pb but plays a secondary role to biotite for rb and cs k feldspar fractionation does not change the lree hree ratio but plagioclase fractionation produces a significant decrease in the lree hree ratio both feldspars greatly fractionate sr and eu monazite fractionation produces a dramatic depletion in ree th and u as well as a decrease in the lree hree and th u ratios apatite also fractionates the ree although in contrast with monazite it increases the lree hree ratio and does not affect the th u ratio zircon fractionation like apatite and garnet produces a strong depletion in the hree and a concomitant increase in the lree hree ratio in contrast with monazite zircon fractionation causes the th u ratio to increase

late quaternary sea ice history in the indian sector of the southern ocean as recorded by diatom assemblages abstract a modern analog technique mat5201 31 has been applied to fossil diatom assemblages to provide down core estimates of february sea surface temperatures ssts and of sea ice duration over the past 220 000 years at 56 40 s 160 14 e at the core location sea ice progression lagged the sst drop by 1 ka at interglacial glacial transitions and sea ice retreat was almost synchronous to the sst increase at glacial interglacial terminations sea ice increased continuously during glacial periods to reach its maximum extent at the end of glacial times although ssts were almost constant during glacials this indicates that ssts are the major parameter determining the advance and retreat of sea ice at transitions but that the sea ice advance during glacial conditions may be related to positive feedbacks of the ice on albedo air temperature and meridional wind stress the strong correlation r 0 75 between sea ice duration at the core location and the vostok co2 record argues for a control of antarctic sea ice extent on atmospheric co2 concentration via the modification of the ocean to atmosphere gas balance

reappraisal of antarctic seasonal sea ice at the last glacial maximum we used modern analog technique applied to antarctic diatoms to quantitatively reconstruct seasonal sea ice extent at the last glacial maximum winter maximum sea ice limit occurred around 48 s in the atlantic and western indian sectors around 55 s in the eastern indian and western pacific sectors and around 58 60 s in the eastern pacific sector of the southern ocean summer maximum sea ice extents during the last ice age and today are similar which contradicts climap s findings this implies a reduced summer albedo feedback of the southern hemisphere and a greater transfer of heat and moisture from the ocean to the atmosphere than shown by previous qualitative studies

accumulation of biogenic and lithogenic material in the pacific sector of the southern ocean during the past 40 000 years the 230th normalization technique was applied to surface sediments and down core records from the pacific sector of the southern ocean between 120 w and 170 w in order to reconstruct vertical rain rates corrected for lateral redistribution of sediment preserved rain rates of opal organic carbon and biogenic ba all indicate that biological productivity south of the antarctic polar front apf was much lower than today during the last glacial maximum lgm probably in response to increased ice cover however by analogy with modern opal fluxes south of the acc we show that year round ice cover is not a prerequisite for very low rates of opal accumulation available records from north of the apf indicate little to no change in opal export in contrast to records from the indian and atlantic sectors which show enhanced opal export north of the apf during the lgm glacial records from north of 66 s in the pacific all show lithogenic fluxes that were greater than today but significantly lower than lithogenic fluxes in the glacial atlantic and indian sectors together these new records from the pacific sector show that during the lgm the three basins of the southern ocean were significantly more differentiated than today the observed inter basin distribution of lithogenic fluxes and opal burial and the presumed geographical distribution of increased dust input to the southern ocean during the lgm are consistent with an atlantic indian pacific gradient in the degree of iron stimulated diatom productivity within the zone lying between the apf and the subantarctic front previous studies which focused primarily on the atlantic sector may have overestimated the glacial increase in the strength of the biological pump in the southern ocean

diatom distribution in southern ocean surface sediments atlantic sector implications for paleoenvironmental reconstructions abstract a study of 230 surface sediment samples collected in the atlantic sector of the southern ocean between the southernmost weddell sea and the subtropical zone documents the modern distribution of diatoms revealing patterns of paleoenvironmental significance estimations of diatom valves per gram dry sediment display numbers of 50 200 106 in the zone of high opal burial located between the mean position of the winter sea ice edge and the polar front and maximum values of greater than 200 106 in the near shore sedimentary basins off the antarctic peninsula lowest diatom concentrations and assemblages strongly affected by dissolution were encountered in the weddell basin despite alteration of the diatom assemblages prior to their incorporation into the sediment record the biogeographic distribution and the abundance pattern of most of the 35 studied diatom species shows a close relationship with the surface hydrography water temperature these relationships can be used to estimate past surface water temperatures based on statistical treatments of the assemblages or on simple relations of species occurrences in the geological record another close link occurs between the distribution of sea ice and sea ice related diatoms

the biogeography of major diatom taxa in southern ocean sediments 2 open ocean related species diatoms from 228 southern ocean core top sediment samples were examined to determine the geographic distributions of 32 major diatom species taxa preserved in the sediments of three zonally distinct regions sea ice open ocean and the tropical subtropical in the first of three papers 14 species taxa occurring in the region where sea ice covers the ocean surface on an annual basis are geographically documented comparisons are drawn between the diatom abundances on the sea floor sea ice parameters annual duration and concentration in february and september and february sea surface temperature such parameters are commonly used in reconstructing past oceanographic conditions in the sea ice and open ocean zones analysis of the geographic patterns and sea surface parameter correlations reveals species specific distributions regulated primarily by sea ice coverage and sea surface temperature which support the use of diatom remains for the estimation of these past seasurface environmental parameters comparison with reliable accounts of the 14 species from the sediments or plankton also provides the first glimpses into species specific ecology and habitat linkages d 2005 elsevier b v all rights reserved

diatom distributions in northern north pacific surface sediments and their relationship to modern environmental variables abstract the quantitative analysis of diatom assemblages preserved in 52 samples from the bellingshausen and the amundsen seas provides the first comprehensive view on the distribution of diatoms in surface sediments of the eastern and central pacific sector of the southern ocean on a latitudinal transect along 120 w diatom valve accumulation rates ar reach maximum values 8 10 108 valves m 2 yr 1 in a zone extending over ca 900 km between the antarctic polar front and the maximum average winter sea ice extent and exceed those ars obtained from an eastern transect along 90 w by one order of magnitude lowest diatom concentrations 1 3 106 valves g 1 were encountered in sediments of the sea ice zone affected by winter and summer sea ice the accumulation rate pattern of the most abundant diatom fragilariopsis kerguelensis 50 abundance in 47 samples mirrors the pattern of the total diatom valve ar and the biogenic silica bsi ar making f kerguelensis the major contributor to the bsi preserved at the sea floor relative abundances of diatom species and species groups were statistically compared with a selection of environmental variables such as the mean summer sea surface temperature and salinity mean annual surface nutrient concentration nitrate phosphate silicon mean annual water column stratification mixed layer depth in summer and mean summer and winter sea ice concentrations polynomial canonical redundancy analysis rda revealed the biogeographic distribution of diatom species had the strongest relationship with summer sea surface temperature ssst out of the nine tested environmental variables this relationship accounted for 69 6 of the total variance of the diatom distribution with 29 7 explained by the first gradient significantly correlated to ssst with r2 0 941 and 15 6 explained by the second gradient correlated to both summer and winter sea ice and silicon concentration azpeitia tabularis hemidiscus cuneiformis and roperia tesselata were associated with warmer water conditions 4 c whereas fragilariopsis curta f separanda f rhombica and thalassiosira gracilis were correlated with cold ssst confirming these environmental relationships is crucial for the development of reference data sets used in quantitative estimations of palaeoclimatic and palaeoceanographic conditions with statistical methods this new data set represents the first modernised treatment of diatom remains from the se pacific ocean and generally supports the use of a circum polar database for the determination of summer sst sea ice and potentially biogenic silica distribution of the southern ocean back into the late quaternary

new tools for the reconstruction of pleistocene antarctic sea ice abstract based on the quantitative analysis of diatom assemblages preserved in 274 surface sediment samples recovered in the pacific atlantic and western indian sectors of the southern ocean we have defined a new reference database for quantitative estimation of late middle pleistocene antarctic sea ice fields using the transfer function technique the detrended canonical analysis dca of the diatom data set points to a unimodal distribution of the diatom assemblages canonical correspondence analysis cca indicates that not only winter sea ice wsi but also summer sea surface temperature ssst represent the most prominent environmental variables that control the spatial species distribution to test the applicability of transfer functions for sea ice reconstruction in terms of concentration and occurrence probability we applied four different methods the imbrie and kipp method ikm the modern analog technique mat weighted averaging wa and weighted averaging partial least squares wapls using logarithm transformed diatom data and satellite derived 1981 2010 sea ice data as a reference the best performance for ikm results was obtained using a subset of 172 samples with 28 diatom taxa taxa groups quadratic regression and a three factor model ikm d172 28 3q resulting in root mean square errors of prediction rmsep of 7 27 and 11 4 for wsi and summer sea ice ssi concentration respectively mat estimates were calculated with different numbers of analogs 4 6 using a 274 sample 28 taxa reference data set mat d274 28 4an 6an resulting in rmsep ranging from 5 52 4an to 5 91 6an for wsi as well as 8 93 4an to 9 05 6an for ssi wa and wapls performed less well with the d274 data set compared to mat achieving wsi concentration rmsep of 9 91 with wa and 11 29 with wapls recommending the use of ikm and mat the application of ikm and mat to surface sediment data revealed strong relations to the satellite derived winter and summer sea ice field sea ice reconstructions performed on an atlantic and a pacific southern ocean sediment core both documenting sea ice variability over the past 150 000 yr mis 1 mis 6 resulted in similar glacial interglacial trends of ikm and mat based sea ice estimates on the average however ikm estimates display smaller wsi and slightly higher ssi concentration and probability at lower variability in comparison with mat this pattern is a result of different estimation techniques with integration of wsi and ssi signals in one single factor assemblage by applying ikm and selecting specific single samples thus keeping close to the original diatom database and included variability by mat in contrast to the estimation of wsi reconstructions of past ssi variability remain weaker combined with diatom based estimates the abundance and flux pattern of biogenic opal represents an additional indication for the wsi and ssi extent

enhancement of gas drainage efficiency in a special thick coal seam through hydraulic flushing abstract coal seam gas is a kind of precious energy but it also will be a terrible disaster in coal mining if not well controlled underground coal seam gas drainage is one of the most effective methods for lowering the risk of gas disaster however it is difficult to extract gas in many coal seams with low permeability especially in tectonic coal seams which were severely crushed or even pulverized by tectonism the key to improving the gas drainage efficiency is stress relief and permeability increase there are many conventional technologies to improve the gas drainage efficiency of a single coal seam but they are inoperative on the special thick coal seam with a soft mylonitic tectonic coal sub layer at the lower part in this paper to enhance gas drainage in this coal seam we presented a hydraulic flushing gas drainage technology numerical simulation was conducted to analyze the stress evolution plastic damage permeability changes and gas drainage of the coal after hydraulic flushing further abundant field experiments were carried out to investigate and verify the mechanism of stress relief and permeability increase the results show that after adopting the hydraulic flushing gas drainage technology more tectonic coal in the thick coal seam was flushed out and the big hole in the tectonic coal sub layer enlarged the range of stress relief and permeability increase and the gas drainage efficiency increased significantly

ice core evidence for antarctic sea ice decline since the 1950s the instrumental record of antarctic sea ice in recent decades does not reveal a clear signature of warming despite observational evidence from coastal antarctica here we report a significant correlation p

temporal evolution of mechanisms controlling ocean carbon uptake during the last glacial cycle many mechanisms have been proposed to explain the 85 90 ppm decrease in atmospheric carbon dioxide co2 during the last glacial cycle between 127 000 and 18 000 yrs ago when taken together these mechanisms can in some models account for the full glacial interglacial co2 drawdown most proxy based evaluations focus on the peak of the last glacial maximum 24 000 18 000 yrs ago and little has been done to determine the sequential timing of processes affecting co2 during the last glacial cycle here we use a new compilation of sea surface temperature records together with time sequenced records of carbon and nd isotopes and other proxies to determine when the most commonly proposed mechanisms could have been important for co2 drawdown we find that the initial major drawdown of 35 ppm 115 000 yrs ago was most likely a result of antarctic sea ice expansion importantly changes in deep ocean circulation and mixing did not play a major role until at least 30 000 yrs after the first co2 drawdown the second phase of co2 drawdown occurred 70 000 yrs ago and was also coincident with the first significant influences of enhanced ocean productivity due to dust finally minimum concentrations of atmospheric co2 during the last glacial maximum resulted from the combination of physical and biological factors including the barrier effect of expanded southern ocean sea ice slower ventilation of the deep sea and ocean biological feedbacks

quaternary surface water temperature estimations new diatom transfer functions for the southern ocean abstract here we present an improvement of paleotemperature reconstructions for the southern ocean by combining new diatom data from the pacific sector with published atlantic and indian sector reference data the statistical analysis of 336 surface sediment samples recovered from a wide area of southern ocean environments defines a supra regional reference data set for quantitative summer sea surface temperature ssst estimations in situ temperature measurements covering the time span from approx 1900 to 1991 were used as reference instead of more recent time series of satellite derived data possibly biased by ocean warming different transfer function tf models for the imbrie and kipp method ikm the modern analog technique mat weighted averaging wa and weighted averaging partial least squares wapls were tested best performance for ikm was obtained using the d336 set with 29 diatom taxa and three factors resulting in root mean square error of prediction rmsep of 0 833 c for ssst mat estimates were best with six analogs resulting in the lowest rmsep of 0 812 c wapls applied to d336 resulted in a rmsep of 0 782 c wa performed less well expressed by a rmsep of 0 974 c furthermore two subsets for the atlantic d151 and the pacific sectors d107 were applied with ikm to test for the advantages of localized tfs ikm d151 and ikm d107 performed comparably good as ikm d336 with rmsep of 0 71 c and 0 68 c respectively application of the augmented reference data sets on two pleistocene sediment records from the atlantic ps1768 8 and pacific ps58 271 1 sectors led to the best performance of ikm with d336 expressed by high overall communalities 0 75 and fewer ps1768 8 to no ps58 271 1 no analogs compared to the regional data sets proving ikm d336 to deal better with higher assemblage variability ssst estimates for both cores exhibit similar glacial interglacial patterns for all four applied d336 based tf methods with the best concordance between ikm and wapls

distribution of diatoms in surface sediments of prydz bay antarctica abstract four diatom assemblages are identified from the surface sediments of prydz bay and the mac robertson shelf using multivariate analysis a coastal assemblage is characterised by the sea ice diatoms fragilariopsis curta f angulata f cylindrus and pseudonitzschia turgiduloides a continental shelf assemblage is characterised by sea ice and ice edge diatoms and an oceanic assemblage is characterised by the open water diatoms fragilariopsis kerguelensis thalassiosira lentiginosa t gracilis var expecta and trichotoxin reinboldii the cape darnley assemblage contains both sea ice and open water diatoms but all are characteristically large and heavily silicified multiple regression has been used to identify the relationships between the diatom assemblages and known environmental variables there are strong correlations between the coastal shelf and oceanic assemblages and ecological conditions including latitude sea ice distribution and ocean currents the cape darnley assemblage is thought to represent an assemblage from which the smaller and more lightly silicified species have been removed by current winnowing

the spatial structure of the 128 ka antarctic sea ice minimum we compare multi ice core data with 18o model output for the early last interglacial antarctic sea ice minimum the spatial pattern of 18o across antarctica is sensitive to the spatial pattern of sea ice retreat local sea ice retreat increases the proportion of winter precipitation depleting 18o at ice core sites however retreat also enriches 18o because of the reduced source to site distance for atmospheric vapor the joint overall effect is for 18o to increase as sea ice is reduced our data model comparison indicates a winter sea ice retreat of 67 59 and 43 relative to preindustrial in the atlantic indian and pacific sectors of the southern ocean a compilation of southern ocean sea ice proxy data provides weak support for this reconstruction however most published marine core sites are located too far north of the 128 000 years b p sea ice edge preventing independent corroboration for this sea ice reconstruction plain language summary the antarctic isotope and temperature maximum which occurred approximately 128 000 years before present b p during the warmer than present last interglacial period is associated with a major retreat of antarctic sea ice understanding the details of this major sea ice retreat is crucial in order to understand the sensitivity of the southern hemisphere sea ice system and to evaluate the performance of climate model simulations in response to future warming this work uses a multi ice and ocean core data model evaluation to assess the magnitude and spatial pattern of this sea ice retreat our results suggest that sea ice retreat was greatest in the atlantic and indian sectors of the southern ocean and less in the pacific sector these results may have had serious implications for the stability of marine terminating glaciers around the antarctic ice sheet and their contribution to the last interglacial sea level rise these results also support a hypothesized slowdown in northward ocean heat transport during the early last interglacial

last glacial holocene climate variability in the atlantic sector of the southern ocean abstract the southern ocean plays a major role in the glacial interglacial global carbon cycle however there is a substantial lack of information from its antarctic zone south of the polar front pf to understand key climate processes e g sea ice variability productivity changes co2 source region shifts of the southern westerly wind active in this region during the glacial interglacial transition due to the limited high resolution sediment records from this area to close this gap we investigated high resolution diatom records from a series of sediment cores from the atlantic and western indian sectors of the southern ocean between the modern pf and the winter sea ice wsi edge summer sea surface temperature ssst and sea ice information spanning the past 30 thousand years were derived from diatom transfer functions and indicators which augment comprehensive information on past surface ocean conditions and related ocean and atmospheric circulation as well as opal deposition these complementary lines of evidences also provide important environmental boundary conditions for climate simulations understanding the past climate development in the high latitudes southern ocean our reconstructions show that the last glacial lg sssts south of the modern pf are 1 3 c colder than modern conditions wsi expanded to the modern pf our data suggests effective carbon export in the antarctic zone during the lg deglacial two steps of warming support the bipolar seesaw mechanism antarctic zone is an important source region for the co2 deglacial increase the warming was more suppressed towards south due to continuous ice discharge from antarctica the sssts exceeded modern values during the early holocene optimum when wsi extent probably retreated south of its modern position the southern boundary of maximum opal deposition zone may have shifted to south of 55 s in the bouvet island area at this time the mid late holocene cooling with wsi re expanding to the bouvet island area probably related to enhanced cold water export by the weddell gyre from the developing cavity under the west antarctic ice shelf the cooling also suggests a northward shift of the southern westerly wind at least its southern boundary

phase relations of tourmaline leucogranites and the significance of tourmaline in silicic magmas by means of melting and recrystallization tourmaline seeded experiments phase relations of two natural tourmaline bearing fe rich members of the schorl dravite series leucogranites have been determined between 1 and 3 kbar under h2o saturation with fo2 close to ni nio the presence of tourmaline slightly lowers the solidus temperatures of both samples from 5 to 20 c compared to the corresponding tourmaline free solidus quartz k feldspar and plagioclase phase relations are not significantly dependent on the presence of tourmaline tourmaline is the last major phase to disappear for both samples and a demonstrated liquidus phase exists for one in the recrystallization experiments the compositions of the tourmalines growing from the melt change from more mg rich at high temperatures to more fe rich at lower temperatures the tourmalines are always richer in mg than the melt is but fe and mg are not especially partitioned between crystallizing tourmaline and melt melt compositions do not depart

boron in metapelites controlled by the breakdown of tourmaline and retrograde formation of borosilicates in the yanai area ryoke metamorphic belt sw japan tourmaline out isograd formed by the breakdown of tourmaline is defined in the upper amphibolite facies metapelites in the yanai area ryoke metamorphic belt sw japan the rim composition of tourmaline progressively becomes aluminous with ascending metamorphic grade and the chemical zoning of tourmaline is controlled by x alna 1mg 1 and mgtiyal 2 vectors in low to medium grade zones where muscovite is stable whereas it is controlled by mg oh yal 1o 1 camgox 1 yal 1 oh 1 and mgtiyal 2 vectors in further higher grade muscovite unstable zones the size of tourmaline increases drastically where breakdown of muscovite quartz takes place probably due to the growth of tourmaline during breakdown of muscovite on the high temperature side of the tourmaline out isograd depletion of whole rock boron is observed escape of boron bearing melt or the fluid evolved from the melt during its crystallization probably caused this depletion although locally trapped boron bearing melt or fluid formed irregularly shaped tourmaline and dumortierite during retrograde metamorphism

boron in graphite content speciation and significance abstract the mean boron content of syngenetic graphite in metasedimentary rocks is significantly higher than that of epigenetic vein graphite or igneous graphite the boron commonly found in chemical analyses of natural graphites does not occur in solid solution with the carbon but rather is contained in a mechanically included borosilicate phase

minimal antarctic sea ice during the pliocene antarctic sea ice concentration at ocean drilling program sites 1165 64 380 s 67 219 e and 1166 67 696 s 74 787 e was lower than today through much of the pliocene the low sea ice concentration is evident from the proportion of the diatom eucampia antarctica with intercalary valves eucampia index this sea ice proxy was calibrated by using modern diatom data obtained from core top samples and winter sea ice concentration data september average through 1979 1987 the modern relationship is expressed as a binomial generalized linear model modern sea ice model this model was applied to the pliocene eucampia index within a 95 tolerance interval obtained from bootstrap estimates the results indicate that reduced winter sea ice concentrations persisted through much of the pliocene and at times were 78 and 61 relatively less concentrated than today at sites 1165 and 1166 respectively 2005 geological society of america

tourmaline breakdown in the migmatite zone of the ryoke metamorphic belt sw japan a sharp line delimitating the distribution of tourmaline termed as a tourmaline out isograd is defined in the migmatite zone of the ryoke metamorphic belt japan the trend of the tourmaline out isograd closely matches that of the isograds formed through the regional metamorphism suggesting that it represents the breakdown front of tourmaline during regional metamorphism this is confirmed by the presence of the reaction textures of tourmaline to sillimanite and cordierite near the tourmaline out isograd the breakdown of tourmaline would release boron into associated melts or fluids and be an important factor in controlling the behaviour of boron in tourmaline bearing high temperature metamorphic rocks near the tourmaline out isograd large tourmaline crystals occur in the centre of interboudin partitions containing leucosome in the melanosome of the intervening matrix reaction textures involving tourmaline are locally observed these observations imply that tourmaline breakdown is related to a melting reaction and that the boron in the leucosome is derived from the breakdown of tourmaline in the melanosome during prograde metamorphism boron released by tourmaline breakdown lowers both the solidus temperature of the rock and the viscosity of any associated melt considering that the tourmaline out isograd lies close to the schist migmatite boundary these effects might have enhanced melt generation and segregation in the migmatite zone of the ryoke belt the evidence for the breakdown of tourmaline and the almost complete absence of any borosilicates throughout the migmatite zone suggest that boron was effectively removed from this region by the movement of melt and or fluid this implies that the tourmaline out isograd can reflect a significant amount of mass transfer in the anatectic zones

ree distribution in some layered migmatites constraints on their petrogenesis abstract the ree distributions in mesosomes neosomes leucosomes and melanosomes of four layered migmatites have been investigated in one example arvika migmatites the ree patterns in adjacent paragneisses the presumed parent rock of the migmatites were also determined ree patterns of neosomes and mesosomes of arvika migmatites are similar to the finegrained layers and coarse grained layers respectively observed in the adjacent paragneiss this is in agreement with the layer by layer paragneiss migmatite transformation model the ree patterns of mesosomes and neosomes indicate that these lithologies may have been closed systems for ree during the formation of the migmatites no indication of metasomatic reactions melt segregation or injection could be detected within the neosomes leucosomes are depleted and melanosomes enriched in ree contents this is interpreted to be due to separation and concentration of accessory minerals monazite epidote allanite zircon sphene apatite garnet into the melanosomes the behaviour of accessory minerals during migmatite formation is closely allied to that of biotite which is also concentrated in the melanosomes

application of modern analog technique to marine antarctic diatoms reconstruction of maximum sea ice extent at the last glacial maximum modern analog technique mat applied to antarctic diatoms is a new approach for quantitative sea ice paleoreconstructions in the southern ocean in a first step we show that mat is a better approach than the imbrie and kipp method to reconstruct the modern sea ice pattern we then use this approach to reconstruct sea ice presence in number of months per year during the last glacial maximum lgm at this time sea ice presence was greater than today leading to a shorter diatom growing season the maximum sea ice extent inferred from quantitative values of sea ice presence was located 5 8 north of its actual position leading to double the surface of modern winter sea ice this greater sea ice extent may have played a significant role on atmospheric and surface oceanic circulations and therefore on southern mid latitude and high latitude climates it may also have reduced the amount of heat moisture and co2 from the ocean to the atmosphere thus participating in the lowering of atmospheric co2 during the lgm

microdistribution of boron particle track images from samples of a caledonian igneous complex 7li recoil tracks in lexanr formed as a product of irradiation with thermal neutrons give an image of in sifu microdistribution of boron in dioritic to granitic rocks of the caledonian ballachulish zoned complex and in a carbonate rock from its contact aureole the images exhibit a polyphase incorporation of boron into primary and secondary minerals the boron microdistribution is inhomogeneous isomorphous incorporation of boron into pyroxene and plagioclase during the main stage of crystallization cannot be established because the boron distribution is blurred by secondary alteration in contrast to the intracrystalline feature the crystal interfaces are enriched in boron increased concentrations are also disclosed by overgrowths of primary crystals exsolution lamellae in alkali feldspar and alteration rims of clinopyroxene the highest amounts of boron in a siliceous dolomite marble of the contact aureole are found in the alteration products of olivine

deformation metamorphism of bituminous and anthracite coals from china abstract tectonic displacement of coal seams in china has resulted in faulting parallel to coal bedding displacement along these faults caused significant comminution of the coal on the footwall contributing to various mining problems the worst of which is catastrophic failure or outbursting of the working face during mining the granular texture and mostly unconsolidated nature of the coal suggests that faulting occurred relatively late in the coalification sequence at a time of maximum tectonic stress coal samples taken on either side of the fault plane normal and deformed coal layers were obtained in an effort to establish what influence these tectonic stresses might have had on coal properties as well as what they might reveal about the influence of tectonic pressure on organic maturity sample sets were collected within coal beds from undisturbed and adjacent deformed layers including 21 bituminous samples from the pingdingshan coal field and nine anthracite samples from the jiaozuo coal field the tieshenggou coal mine of the yuxi coal field in henan province the beijing xishan coal field the baijiao mine of the furong coal field in sichuang province and the baisha coal field in hunan province china results from vitrinite reflectance proximate and ultimate analyses show some differences in reflectance hydrogen content and nitrogen content of anthracite coal no significant difference was found between volatile matter yields of normal and deformed coal specimens gc measurements of the saturated hydrocarbon fraction of chloroform extracts from bituminous coals showed that lower molecular weight carbon fragments were concentrated in the deformed samples therefore although changes in the gross chemical properties of the deformed coal were insignificant some modification of the chemical structure is seen to have occurred as a result of exposure to tectonic pressure

behaviour of boron in the generation of an anatectic complex the pen a negra complex central spain abstract the pe na negra anatectic complex central spain was formed from a pelitic protolith low in boron 3 80 ppm by dehydration reactions melting and fluid loss which expelled much of the boron residual b is present in sillimanite and muscovite migmatite melanosomes and restites sillimanite biotite ilmenite are relatively richer in b mean 29 ppm while the leucosomes are poorer 13 ppm late shears fractures and zones of retrograde alteration have permitted some reintroduction of b experiments demonstrated that b cannot be removed from these rocks by heating or by leaching indicating that very little is present in superficial adsorption and that the element occurs in mineral structures

experimental study on ultrasonic velocity and anisotropy of tectonically deformed coal abstract tectonically deformed coal tdc is defined as coal formed by various tectonic stresses as one of the key concerns in the formation and recovery of coal bed methane cbm from the tectonic deformation coal seams the texture and fractures of tdc present various features in different deformation environments and as a result the physical properties change therefore the identification of tdc is significant and can be obtained from the physical properties in this study fourteen representative tdc and two undeformed coal samples from the suzhou mining area in the east of north china plate were collected to investigate the geophysical recognition parameters of tdc by elastic properties such as the velocities p and s waves elastic parameters v p v s and poisson s ratio and velocity anisotropies the results show that the elastic properties of undeformed coal and tdc samples from different deformation environments exhibit significant difference normally the velocities and elastic parameters of undeformed coal have the highest values while the velocity anisotropy has the lowest value in brittle deformation environment the velocity and elastic parameters decrease while the velocity anisotropy ascends with increased deformation extent for the tdc samples from shear deformation environment the velocity anisotropies present the significant high values among the selected tdc samples in plastic deformation environment the elastic parameters gradually decrease with the deformation extent ascending while the velocity anisotropies are relatively high among the elastic properties the v p v s poisson s ratio and velocity anisotropy are sensitive to deformation type and extent of coal samples furthermore the development characteristics of coal structural fractures have a significant impact on the elastic properties of measured coal samples from different deformation environments in summary the results may provide reference parameters for future studies in cbm rock physics from the tectonic deformation coal seams

quaternary surface water temperature estimations calibration of a diatom transfer function for the southern ocean the quantitative diatom analysis of 218 surface sediment samples recovered in the atlantic and western indian sector of the southern ocean is used to define a base of reference data for paleotemperature estimations from diatom assemblages using the imbrie and kipp transfer function method the criteria which justify the exclusion of samples and species out of the raw data set in order to define a reference database are outlined and discussed sensitivity tests with eight data sets were achieved evaluating the effects of overall dominance of single species different methods of species abundance ranking and no analog conditions e g eucampia antarctica on the estimated paleotemperatures the defined transfer functions were applied on a sediment core from the northern antarctic zone overall dominance of fragilariopsis kerguelensis in the diatom assemblages resulted in a close affinity between paleotemperature curve and relative abundance pattern of this species downcore logarithmic conversion of counting data applied with other ranking methods in order to compensate the dominance of f kerguelensis revealed the best statistical results a reliable diatom transfer function for future paleotemperature estimations is presented

the biogeography of major diatom taxa in southern ocean surface sediments 3 tropical subtropical species abstract this paper gives a modern circumscription of tropical subtropical diatoms regarding their relationship with sea surface temperatures sst and sea ice cover diatoms from 228 core top sediment samples collected from the southern ocean were studied to determine the geographic distribution of eight major diatom species taxa preserved in surface sediments generally located north of the subantarctic front the comparison of the relative contribution of diatom species with modern february sst and sea ice cover reveals species specific sedimentary distributions regulated both by water temperatures and sea ice conditions although selective preservation might have played some role their presence in surface and downcore sediments from the southern ocean are reliable indicators of high sst and poleward transport of waters from the tropical subtropical atlantic our work supports the use of diatom remains to reconstruct past variations of these environmental parameters via qualitative and transfer function approaches

distribution of boron in the tip top pegmatite black hills south dakota experimental evidence has shown the importance of boron on the crystallization behavior of granitic systems however the intercrystalline and intracrystalline distribution of boron in mineral phases crystallizing from granitic systems is not well documented the distribution of boron between coexisting phases in the tip top pegmatite south dakota is as follows beryl ca quartz ca triphylite ca montebrasite ca potassium feldspar biotite albite muscovite spodumene tourmaline the bulk boron content of the tip top pegmatite decreases significantly with the termination of tourmaline crystallization the significant decrease in boron in the inner zones of the pegmatite is consistent with the depletion of boron in the granite melt by either the crystallization of tourmaline from the granitic melt or the partitioning of boron into an exsolved aqueous solutions 35 references

reconstruction of sea surface temperatures from assemblages of planktonic foraminifera multi technique approach based on geographically constrained calibration data sets and its application to glacial atlantic and pacific oceans abstract we present a conceptual framework for a new approach to environmental calibration of planktonic foraminifer census counts this approach is based on simultaneous application of a variety of transfer function techniques which are trained on geographically constrained calibration data sets it serves to minimise bias associated with the presence of cryptic species of planktonic foraminifera and provides an objective tool for assessing reliability of environmental estimates in fossil samples allowing identification of adverse effects of no analog faunas and technique specific bias we have compiled new calibration data sets for the north n 862 and south n 321 atlantic and the pacific ocean n 1111 we show evidence that these data sets offer adequate coverage of the sea surface temperature sst and faunal variation range and that they are not affected by the presence of pre holocene samples and or calcite dissolution we have applied four transfer function techniques including artificial neural networks revised analog method and simmax with and without distance weighting on faunal counts in a last glacial maximum lgm data set for the atlantic ocean 748 samples in 167 cores based on the glamap 2000 compilation and a new data set for the pacific ocean 265 samples in 82 cores and show that three of these techniques provide adequate degree of independence for the advantage of a multi technique approach to be realised the application of our new approach to the glacial pacific lends support to the contraction and perhaps even a cooling of the western pacific warm pool and a substantial 3 c cooling of the eastern equatorial pacific and the eastern boundary currents our results do not provide conclusive evidence for lgm warming anywhere in the pacific the atlantic reconstruction shows a number of robust patterns including substantial cooling of eastern boundary currents with considerable advection of subpolar waters into the benguela current a cooling of the equatorial atlantic by 5 c and steep sst gradients in the mid latitude north atlantic the transfer function techniques generally agree that subtropical gyre areas in both hemispheres did not change significantly since the lgm although the ann technique produced glacial sst in the southern gyre 1 2 c warmer than today we have revisited the issue of sea ice occurrence in the nordic seas and using the distribution of subpolar species of planktonic foraminifera in glacial samples we conclude that the norwegian sea must have been ice free during the summer

distributions of highly branched isoprenoid alkenes and other algal lipids in surface waters from east antarctica further insights for biomarker based paleo sea ice reconstruction the occurrence and variable abundance of certain di and tri unsaturated c25 highly branched isoprenoid hbi biomarkers in antarctic marine sediments has previously been proposed as a possible proxy measure of paleo sea ice extent in the southern ocean in the current study we obtained 47 near surface ca 0 10 m water samples taken from locations in east antarctica with different sea ice settings and analysed them for their hbi sterol and fatty acid content sampling locations ranged from the permanently open ocean zone pooz with no seasonal sea ice cover the near shore summer sea ice zone siz where sea ice remains long into the summer melt season and the marginal ice zone miz located between the pooz and the siz and with a highly variable latitudinal sea ice edge throughout the season a di unsaturated c25 hbi diene ii was only identified in surface waters from the miz and the siz consistent with a sea ice diatom origin for this biomarker in contrast a tri unsaturated c25 hbi triene iii was detected in all samples from the pooz the miz and the siz and with a stable isotopic composition 13c 35 1 5 consistent with a phytoplankton source the highest concentrations of diene ii and triene iii were in samples from the siz and the miz respectively thus providing further insights into the sea ice conditions likely favourable for their production and how their relative abundances the ii iii ratio in underlying sediments might be better interpreted for paleo sea ice reconstruction in this respect relatively high ii iii might be a good indicator of extended into summer seasonal sea ice cover while lower ii iii may provide a better indicator of the miz however the observation of highly variable ii iii within the polynya setting of the siz may also have significant impacts on sedimentary values distributions of diatom sterols and fatty acids were also variable between the three sampling zones but these were not as distinctive as those observed for the hbis

application of seismic curvature attributes in the delineation of coal texture and deformation in zhengzhuang field southern qinshui basin coal texture refers to the in situ particle size morphological characteristics and structural components of coal beds and it determines the permeability and producibility of a coalbed methane cbm reservoir coal texture is commonly classified into undeformed coal with primary coal texture and deformed coal with increasing degree of deformation including cataclastic coal granulated coal and mylonitized coal geophysical logging has recently been proven effective for detecting coal texture in boreholes but it is inefficient for establishing a regional distribution where there have been only limited amounts of drilling in contrast seismic attributes have high lateral extent and an advantage in terms of characterizing fine structures even minor faults with throws of 2 3 m and other strata deformations by comparing seismic curvature data to the results of 221 core samples from the zhengzhuang field in the southern qinshui basin we provide a seismic curvature attribute based coal texture evaluation method evaluation of the results shows that the coal texture types of the no 3 coal seam include undeformed coal cataclastic coal and some granulated coal the undeformed coal is mainly located in the western and northwestern parts of the study area the cataclastic and granulated coals are mainly distributed in the southern and eastern parts of the study areas the permeability of no 3 coal seam is weakly correlated with undeformed coal and it has a high negative correlation with deformed coal permeability has a strong negative correlation with the maximum curvature attribute of the no 3 coal seam it is suggested that the in situ stress distribution combined with the curvature controlled the local development of the coal texture types and thus resulted in regional differences in permeability finally the distribution characteristics of coal textures of no 3 coal seam in the study area are divided into four types in which the undeformed cataclastic coal dominated area located in the midwestern part of the study area is the most favorable area for cbm production

ecology and paleoecology of the marine diatomeucampia antarctica castr mangin abstract the distribution of eucampia antarctica both in the water column and in the sediments of the southern ocean is discussed on the basis of these data it is concluded that although this species is widely distributed in the southern ocean it is most abundant in a near shore and or neritic environment however a pseudoneritic environment provided by floating ice may also provide a suitable substrate for the proliferation of this species

quantifying the opal belt in the atlantic and southeast pacific sector of the southern ocean by means of 230th normalization 1 a set of 114 samples from the sediment surface of the atlantic eastern pacific and western indian sectors of the southern ocean has been analyzed for 230th and biogenic silica maps of opal content th normalized mass flux and th normalized biogenic opal flux into the sediment have been derived significant differences in sedimentation patterns between the regions can be detected the mean bulk vertical fluxes integrated into the sediment in the open southern ocean are found in a narrow range from 2 9 g m 2 yr 1 eastern weddell gyre to 15 8 g m 2 yr 1 indian sector setting upper and lower limits to the vertically received fraction of open ocean sediments the silica flux to sediments of the atlantic sector of the southern ocean is found to be 4 2 1 4 1011 mol yr 1 just one half of the last estimate this adjustment represents 6 of the output term in the global marine silica budget

important role for ocean warming and increased ice shelf melt in antarctic sea ice expansion changes in sea ice significantly modulate climate change because of its high reflective and strong insulating nature in contrast to arctic sea ice sea ice surrounding antarctica has expanded1 with record extent2 in 2010 this ice expansion has previously been attributed to dynamical atmospheric changes that induce atmospheric cooling3 here we show that accelerated basal melting of antarctic ice shelves is likely to have contributed significantly to sea ice expansion specifically we present observations indicating that melt water from antarctica s ice shelves accumulates in a cool and fresh surface layer that shields the surface ocean from the warmer deeper waters that are melting the ice shelves simulating these processes in a coupled climate model we find that cool and fresh surface water from ice shelf melt indeed leads to expanding sea ice in austral autumn and winter this powerful negative feedback counteracts southern hemispheric atmospheric warming although changes in atmospheric dynamics most likely govern regional sea ice trends4 our analyses indicate that the overall sea ice trend is dominated by increased ice shelf melt we suggest that cool sea surface temperatures around antarctica could offset projected snowfall increases in antarctica with implications for estimates of future sea level rise

abundance and distribution of boron in the hauzenberg bavaria granite complex abstract hercynian s type granites from the hauzenberg igneous complex show a range of boron concentration from 1 to 12 ppm the whole rock boron data are not significantly correlated with concentrations of other trace elements zr rb ba sr ni v co cu zn f neither is boron correlated with the major elements except with sodium or with the differentiation index di the boron budget in the rock forming minerals plagioclase alkali feldspar quartz biotite muscovite of the tourmaline free granites reveals that the highest concentrations of boron occur in muscovite whereas the greatest amount of boron is incorporated in plagioclase 57 69 due to its high modal amount boron in plagioclase increases with the extent of serialization obtained by x ray diffractometry muscovite in a pegmatite contains more than 50 of the total boron the areal distribution of boron within the complex is neither uniform nor random an increase of boron concentrations from granodioritic to granitic rocks is indicated whereas the late differentiates are depleted in boron

numerical modelling and analysis of the influence of local variation in the thickness of a coal seam on surrounding stresses application to a practical case abstract one of the factors with the most influence in the carrying out of underground coal mining work is the stress state especially when such work is carried out at great depths one of the mining methods in which the influence of stresses becomes most patent is that of sublevel caving for that reason a variety of authors have studied many of the causes which condition the stress state of mining work of this kind at a general level however diverse types of conditioning factors exist at a local level that may substantially vary recorded pressures in the surroundings of the workings using numerical models this paper analyses the specific case of a coal seam mined by the sublevel caving method at a depth of 1000 m which suffers significant increases in stress and major deformations in certain advance headings as a result of variations in the geometry and dimensions of the load itself in particular thinning the results of the research carried out were validated by measuring the stresses in the area under study furthermore on the basis of a retrospective analysis of what was observed in the mine another series of predictive models were analyzed to establish the existing relation between the increase in stress due to thinning of the seam and the depth at which such thinning is situated

identification of coal structures using geophysical logging data in qinshui basin china investigation by kernel fisher discriminant analysis abstract coal structure is closely related to the porosity and permeability of coal reservoirs which not only affects the enrichment of coalbed methane cbm but also influences the hydraulic fracturing and efficient development of cbm the accurate identification of the coal structure would be a critical issue in cbm exploration and development and is always a challenge compared with traditional methods for identifying coal structure base on borehole cores or mining seam observation geophysical logging has become the most economic and efficient technique several linear correlations have been established to describe the relationships between the coal structures and well logs however those correlations cannot accurately reflect nonlinear relations between them therefore a reliable and efficient method to identify coal structure is needed as a powerful nonlinear classifier the kernel fisher discriminant analysis kfd method has been widely used due to its strong generalization ability in this paper a new quantitative coal structure identification model was developed based on the kfd method by using geophysical logging data the model was trained tested and optimized using 178 logging data sets from 15 cbm wells in qinshui basin china the approach accounted for all the available well logging attributes and the training data sizes and kernel parameters were analyzed to get the most appropriate model in practice in addition the built model was validated individually by employing logging data of a new cbm well the results indicate that the kfd based identification model has high prediction accuracy which can be used as a reliable method for coal structure identification the kfd method exhibits strong capability during the modeling and generalization in the determination of nonlinear relationships which provides an efficient way for the coal structure prediction in basic research of coal reservoirs

palaeotemperature estimation methods sensitivity test on two western equatorial pacific cores abstract this study examines three methods of estimating past sea surface temperature sst imbrie and kipp s transfer function method ikm the modern analogue technique mat and the weighted averaging method wam by testing a number of experimental transfer functions on two western equatorial pacific cores rc17 177 and erdc 93p it is shown that sst estimation is sensitive to the number of factors and to the selection of core top samples in the calibration the most plausible result was given by an equation which is calibrated from a restricted region which is sufficiently large to fully cover the potential range of down core sst estimates the mat gave spurious sst estimates probably due to the failure of the dissimilarity coefficient the wam persistently gave lower sst estimates than the ikm because of the averaging effect of the method but the sst time series estimated by the two methods show almost identical fluctuation patterns the tolerance weighting approach in the wam may be inappropriate because tolerances of different species may have different implications all the above methods are affected by the distribution of calibration samples

observations on the relationship between the antarctic coastal diatoms thalassiosira antarctica comber and porosira glacialis grunow jorgensen and sea ice concentrations during the late quaternary the available ecological and palaeoecological information for two sea ice related marine diatoms bacillariophyceae thalassiosira antarctica comber and porosira glacialis grunow jorgensen suggests that these two species have similar sea surface temperature sst sea surface salinity sss and sea ice proximity preferences from phytoplankton observations both are described as summer or autumn bloom species commonly found in low sst waters associated with sea ice although rarely within the ice both species form resting spores rs as irradiance decreases sst falls and sss increases in response to freezing ice in autumn recent work analysing late quaternary seasonally laminated diatom ooze from coastal antarctic sites has revealed that sub laminae dominated either by t antarctica rs or by p glacialis rs are nearly always deposited as the last sediment increment of the year interpreted as representing autumn flux in this study we focus on sites from the east antarctic margin and show that there is a spatial and temporal separation in whether t antarctica rs or p glacialis rs form the autumnal sub laminae for instance in deglacial sediments from the mertz ninnis trough george v coast p glacialis rs form the sub laminae whereas in similar age sediments from iceberg alley mac robertson shelf t antarctica rs dominate the autumn sub lamina in the dumont d urville trough adelie land mid holocene hypsithermal warm period autumnal sub laminae are dominated by t antarctica rs whereas late holocene neoglacial cool period sub laminae are dominated by p glacialis rs these observations from late quaternary seasonally laminated sediments would appear to indicate that p glacialis prefers slightly cooler ocean climate conditions than t antarctica we test this relationship against two down core holocene quantitative diatom abundance records from dumont d urville trough and svenner channel princess elizabeth land and compare the results with sst and sea ice concentration results of an antarctic and southern ocean holocene climate simulation that used a coupled atmosphere sea ice vegation model forced with orbital parameters and greenhouse gas concentrations we find that abundance of p glacialis rs is favoured by higher winter and spring sea ice concentrations and that a climatically sensitive threshold exists between the abundance of p glacialis rs and t antarctica rs in the sediments an increase to 0 1 for the ratio of p glacialis rs t antarctica rs indicates a change to increased winter sea ice concentration to 80 concentration cooler spring seasons with increased sea ice slightly warmer autumn seasons with less sea ice and a change from 7 5 months annual sea ice cover at a site to much greater than 7 5 months in the east antarctic sediment record an increase in the ratio from 0 1 to above 0 1 occurs at the transition from the warmer hypsithermal climate into the cooler neoglacial climate 4 cal kyr indicating that the ratio between these two diatoms has the potential to be used as a semi quantitative climate proxy

an occurrence of grandidierite kornerupine and tourmaline in southeastern ontario canada grandidierite kornerupine and tourmaline occur in high grade pelitic gneisses from southeastern ontario canada the kornerupine occurs in quartz bearing layers associated with biotite cordierite garnet ilmenite k feldspar magnetite quartz and less commonly sillimanite grandidierite is found in quartz poor cordierite sillimanite segregations in contact with biotite cordierite ilmenite k feldspar magnetite sillimanite and more rarely garnet tourmaline is sporadically distributed in all compositional layers but is not in contact with the other borosilicates there is no textural evidence for a reactive relationship among the three borosilicates neither chemical or textural equilibrium has been achieved on the scale of a thin section

the reconstruction of late quaternary antarctic sea ice distribution the use of diatoms as a proxy for sea ice the study of annual diatom transfer from the southern ocean surface to the sea floor using time series sediment traps combined with the mapping of diatom assemblages from surface sediments results in the definition of a proxy for past variations of sea ice extent the application and robustness of the proposed proxy are demonstrated by the study of late pleistocene sediment cores recovered from different environmental regimes in the southern ocean relative amounts of the sea ice indicator diatoms fragilariopsis cylindrus and fragilariopsis curta of 3 in diatom assemblages preserved in sediments are representative of the presence of seasonal winter sea ice summer sea ice occurrence is signalled by a distinct drop in biogenic sedimentation rate as a result of strongly reduced biogenic export in the presence 3 of diatom assemblage of the deep temperature diatom fragilariopsis obliquecostata the spatial and temporal distribution pattern of the sea ice proxy indicates significant sea ice variations during marine isotope stages 1 and 5 in the present antarctic zone of the southern ocean during glacial maxima the antarctic winter sea ice was extended into the present polar front zone while the antarctic summer sea ice was most probably expanded into the area of the present winter sea ice edge during the short climatic optima at the onset of interglacial periods the winter sea ice extent was distinctly reduced

effects of structural deformation on formation of coalbed methane reservoirs in huaibei coalfield china tectonically deformed coal is defined as coal formed by superimposed reformations from tectonic stress the huaibei coalfield is typically composed of various tectonically deformed coals containing rich coalbed methane resources however the occurrence of coal seam in this area is complicated largely by the structural deformation which has not yet been evaluated systematically for exploration and exploitation of coalbed methane in this study tectonism in huaibei coalfield is discussed by combining systematic analyses on the occurrence of coal seams and the formation of coalbed methane reservoirs the study shows that with structural deformation in the study area the coal seams in huaibei coalfield are distributed in north south tectonic blocks and east west tectonic zones north tectonic block of huaibei coalfield is not favourable for exploitation of coalbed methane because of low gas content or disadvantageous structural conditions within the south tectonic block the east suzhou syncline contains high gas content but coal permeability is very low this area is generally not suitable for exploitation of coalbed methane and is a dangerous mining area due to gas outburst because of the widely developed mylonitic coals south suzhou and nanping synclines in the middle part of the south tectonic block are exposed to relatively weak structural deformations these synclines contain coals with high gas content and moderate permeability which are beneficial for exploration and exploitation of coalbed methane linhuan mining area in the south tectonic block is generally not suitable for exploitation of coalbed methane mainly because of well developed normal faults and interlayer slip structure and presence of mylonitic coal resulting in low gas content and poor structural conditions for mining coalbed methane in contrast guoyang mining area in the west part of the south tectonic block where tectonically deformed coal was generally underdeveloped is a potential area for exploration and exploitation of coalbed methane because of moderate gas content and possibly higher permeability of its coal

boron geochemistry of the lower crust evidence from granulite terranes and deep crustal xenoliths abstract boron contents are uniformly low in more than 100 granulites from exposed terranes in india norway and scotland and from xenolith suites in the western usa averages for the terranes 2 5 ppm and for xenoliths 1 2 ppm suggest maximum b contents of about 2 1 ppm for the lower crust abundance distributions from exposed terranes are skewed to higher values as b has been added to some samples via retrograde fluids during decompression the samples studied include mafic to felsic lithologies of both igneous and sedimentary origin there is no correlation of b content with bulk composition or with protolith type in any of the suites studied boron is apparently depleted in all granulite protoliths during prograde metamorphism and dehydration similar depletions of b and other fluid mobile elements e g u cs with respect to rare earth elements ree zr ba rb and k 2 o are seemingly inconsistent with origin of granulites primarily via extraction of silicate melts these distinctive geochemical features are attributed to selective element transport in fluids released by devolatilization reactions anatexis is not necessarily precluded but dehydration of the subsolidus protolith normally would precede melting and lead to depletion of the fluid mobile elements compositions of any melts and restites eventually formed would reflect the effects of this antecedent process the systematic depletion of b and cs in granulites contrasts with the highly variable contents of most other incompatible elements determined for this reason the estimated lower crust abundance for b is relatively well constrained whereas abundance estimates for many other elements are model dependent have large uncertainties and are unlikely to be globally representative