isotope geochemistry sr nd pb and petrogenesis of leucite bearing volcanic rocks from colli albani volcano roman magmatic province central italy inferences on volcano evolution and magma genesis the colli albani composite volcano is made up of strongly silica undersaturated leucite bearing rocks magmas were erupted during three main periods but a complex plumbing system dominated by regional tectonics channelled magmas into different reservoirs the most alkali rich magmas restricted to the caldera forming period pre caldera are extremely enriched in incompatible trace elements and display more radiogenic sr 87sr 86sr 0 71057 0 71067 with slightly less radiogenic pb with respect to those of the post caldera period post caldera volcanic activity was concentrated in three different volcanic environments external to the caldera along the caldera edge and within the caldera the post caldera magmas produced melilite to leucitite bearing plagioclase free leucitites in contrast to the pre caldera lavas they are characterised by lower incompatible trace element abundances and less radiogenic sr 87sr 86sr 0 71006 0 71039 magmas evolved through crystal fractionation plus minor crustal assimilation in a large magma chamber during the pre caldera period the multiple caldera collapses dissected and partially obliterated the early magma chamber during the post caldera stage magmas were channelled through several pathways and multiple shallow level magma reservoirs were established a lithospheric mantle wedge previously depleted in the basaltic component and subsequently enriched by metasomatic slab derived component is suggested as the mantle source of colli albani parental magmas two different parental magmas are recognised for the pre and post caldera stages the differences may be related to the interplay between smaller degrees of melting for the pre caldera magmas and more carbonate rich recycled subducted lithologies in the post caldera magmas

isotope and trace element evidence for late stage intra crustal melting in the high andes abstract purico chascon is an acid igneous complex less than 1 5 ma old rising to 5800 m in the north chilean andes and consisting of andesite dacite cones and dacite domes on an ignimbrite shield the rocks are subdivided into two groups those from chascon appear to exhibit evidence for magma mixing with more basic material now preserved as xenoliths whereas among those at purico no xenoliths have been found 87sr 86sr 0 7095 0 7081 at purico 0 7079 0 7069 at chascon and 0 7061 0 7057 in the xenoliths from the chascon lavas 143nd 144nd 0 51222 0 51236 overall the purico lavas are characterised by higher sio2 rb sr 87sr 86sr and ree abundances and lower sr nd sr ba and143nd 144nd than most andean igneous suites there is no indication ofselective crustal contamination of sr or any systematic change in isotope ratios during differentiation nonetheless the trend of for example high sr nd and sr contents in rocks with low87sr 86sr 0 704 ecuador to low sr nd and sr and high sio2 in rocks with87sr 86sr 0 7081 0 7095 at purico is interpreted as a shift from subduction zone related magmatism to one with greater crustal affinity the formation of the least evolved purico lavas 60 sio2 is discussed in terms of bulk assimilation of crustal material mixing between crustal and mantle derived magmas and partial melting of pre existing crust although such models are still extremely primitive the simplest explanation of the observed chemical variations is that the purico rocks evolved from parental magmas derived by crustal anatexies thermal considerations suggest that such late stage crustal anatexis is a predictable response to crustal thickening which in the andes is thought to have taken place during the cenozoic

a predictive methodology for multi seam mining induced subsidence abstract multi seam longwall mining induced subsidence profiles are often different from those of single seam mining as a result conventional subsidence prediction methods are less reliable for multi seam subsidence predictions in this study significant differences between the single and multi seam subsidence parameters are studied in a multi seam case study in australia results from this case study are employed to establish a characterisation of the multi seam subsidence which is applicable for every multi seam mining configuration the proposed characterisation is then utilised for modification of a conventional influence function method ifm in the modified method namely discrete ifm a mine section is divided into discrete segments with certain subsidence parameters the resultant subsidence of each segment is calculated and then superimposed to achieve the final subsidence profile application of the discrete ifm is demonstrated in an example case study where reliable subsidence predictions are achieved it is illustrated that the discrete ifm offers a flexible approach for consideration of multiple subsidence parameters for different segments which enables this method to predict irregular subsidence profiles

petrology and geochemistry of potassic and ultrapotassic volcanism in central italy petrogenesis and inferences on the evolution of the mantle sources major trace element sr isotopic and mineral chemical data are reported for mafic volcanic rocks mg value 65 from the northern central sector of the potassic volcanic belt of central italy the rocks investigated range from potassic series ks and high k series hks to lamproitic lmp and kamafugitic kam through a transitional series trans thus covering the entire compositional spectrum of potassic and ultrapotassic magmas kam rocks are strongly silica undersaturated and compared with the other rock series have low sio2 al2o3 na2o sc and v and high cao k na na k al ks and hks have high al2o3 cao and variable enrichment in k2o and incompatible elements lmp rocks are saturated in silica and have high sio2 k2o k2o na2 mgo ni and cr and low al2o3 cao na2o sc and v trans rocks display intermediate compositional characteristics between lmp and ks all the rocks under study have fractionated hygromagmaphile element patterns with high lil hfs element values and negative anomalies of ti ta nb and ba negative sr anomalies are observed in the lmp and trans rocks lil elements show overall positive correlations with k2o whereas different trends of sr and hfse vs k2o are defined by lmp trans and ks hks kam 87sr 86sr range from about 0 710 to 0 716 ks hks and kam rocks have similar 87sr 86sr values clustering around 0 710 lmp and trans rocks have the highest 87sr 86sr values geochemical and isotopic data reported for the most primitive italian potassic and ultrapotassic rocks support the hypothesis that the interaction between crustal and mantle reservoirs was a main process in the genesis of italian potassic magmatism simple mass balance calculations exclude however an important role of crustal assimilation during ascent of subcrustal magmas to the surface and indicate that the sources of central italy volcanics underwent contamination with fluids and or melts released by upper crustal material previously brought into the mantle by subduction processes different trends of incompatible elements vs k2o observed in the studied rocks suggest distinct metasomatic processes for the sources of the investigated magmas liquids derived by bulk melting of pelitic sediments are believed to be the most likely contaminants of the source of lmp rocks fluids or melts rich in ca sr and with high lile hfse value and sr isotopic composition around 0 710 are the most likely contaminant of the source region of ks hks and kam volcanics variations in cao na2o and ferromagnesian element abundances and ratios suggest that in some zones the mantle source of potassic magmas experienced partial melting with extraction of basaltic liquids prior to metasomatism

the cryptotephra record of the marine isotope stage 12 to 10 interval 460 335 ka at tenaghi philippon greece exploring chronological markers for the middle pleistocene of the mediterranean region abstract precise chronologies that allow direct correlation of paleoclimate archives are a prerequisite for deciphering the spatiotemporal characteristics of short term climate variability such chronologies can be established through the analysis of tephra layers that are preserved in the respective sedimentary archives here we explore the yet untapped tephrochronological potential of the eastern mediterranean region for the middle pleistocene specifically for the interval spanning marine isotope stages mis 12 10 460 335 ka high resolution cryptotephra analysis was carried out on peat cores spanning the mis 12 10 interval that have been recovered from the iconic climate archive of tenaghi philippon ne greece eighteen primary cryptotephras were identified and major and trace element analyses of single glass shards from all cryptotephras were performed in order to correlate them with their eruptive sources the results suggest origins from both italian and aegean arc volcanoes specifically one cryptotephra layer could be firmly correlated with the cape therma 1 eruption from santorini which makes it the first distal tephra finding for this eruptive event while eight further cryptotephras could be tentatively correlated with their volcanic or even eruptive sources the provenance of another nine cryptotephras as yet remains unknown the relatively large number of cryptotephras that could not be assigned to specific volcanic sources and eruptive events reflects the still considerable knowledge gap regarding the geochronology and geochemistry of proximal tephra deposits from the middle pleistocene of the central and eastern mediterranean regions due to the lack of well dated middle pleistocene eruptions we provide age estimates for all cryptotephra layers identified in the mis 12 10 interval at tenaghi philippon based on high resolution pollen data from the same cores while eight of the identified cryptotephras were deposited within mis 12 438 427 ka one cryptotephra was deposited at the onset of mis 11 419 ka five cryptotephras during the younger part of mis 11 391 367 ka and four cryptotephras during mis 10 359 336 ka the high number of cryptotephras from multiple sources as recorded in the mis 12 10 interval at tenaghi philippon highlights the key role of this archive for linking tephrostratigraphic lattices for the middle pleistocene of the central and eastern mediterranean regions

petrogenesis of the tertiary anorogenic volcanic series of southern queensland australia in the light of trace element geochemistry and o sr and pb isotopes the magmas of the tertiary volcanic province of s queensland are chemically bimodal and occur in numerous volcanic centres at least three representing original shield volcanoes the mafic lavas are dominantly hawaiites and tholeiitic andesites whereas the silicic magmas comprise mainly trachytes rhyolites and comendites the silicic rocks exhibit variable trace element abundance patterns there is a progressive depletion of sr ba v mg ni cr mn and p through the trachytes to the rhyolites and comendites while the behaviour of zr nb lree y and zn is very variable rb th and to a lesser extent pb exhibit a more regular behaviour becoming most generally concentrated in the comendites and rhyolites these trace element patterns are modelled by application of the rayleigh distillation model using partition coefficients based on analysed phenocrysts from the s queensland silicic lavas trace mineral phases namely zircon chevkinite and allanite are shown to be important in the probable control of lree zr and th abundances while nb and zn are probably controlled during fractionation by magnetite trace element data for the hawaiites and tholeiitic andesites also indicate extensive although variable levels of fractional crystallization of these magmas the sr and o isotopic compositions of the mafic lavas trachytes comendites and rhyolites are as follows initial 87sr 86sr ratios 0 70357 0 70456 0 70432 0 70589 0 70495 0 70917 and 0 70708 0 70863 respectively 18o range between 5 6 7 0 mafic lavas 4 9 8 7 trachytes 5 0 7 6 comendites and 8 1 10 4 per mil rhyolites pb isotopic compositions are variable showing a variation of 6 7 per cent for 206pb 204pb ratios through the range of volcanic compositions the rhyolites exhibit a much greater divergence in their o sr and pb isotopic compositions compared with those of associated mafic lavas than is found in the trachytes and comendites within the silicic volcanics positive correlations exist between 18o and initial sr ratios and between pb isotopic compositions and initial sr ratios with one group of trachytes providing a noteworthy exception these correlations are not so clearly defined for the mafic lavas although these do exhibit positive correlations between differentiation index 18o and initial sr isotope ratios the development of the silicic magmas excepting two groups is interpreted in terms of a model in which assimilation and fractional crystallization occur concurrently involving a basalt or hawaiite magma component and a crustal component modelled on the analysed carboniferous basement greywackes outeropping in the region the data indicate however that differentiation continued in isotopically closed systems i e isolated from the wallrocks the highly depleted sr and ba abundances of the rhyolites and comendites suggest that contamination did not occur after differentiation had ceased the rhyolites have the highest isotopic input of the crustal components and are interpreted as crustal anatectic melts produced locally within the crust in response to basalt hawaiite magma intrusion whereas most of the trachytes and comendites are interpreted as primarily the differentiated products from original mafic parental magmas with variable assimilation of crustal wallrock components the isotopic data suggest that only the minerva hills trachytic lavas and a glass house comendite have not been significantly modified by wallrock assimilation processes the erpted mafic magmas were also evidently modified by isotopic crustal wallrock interactions which independent petrological data suggest has occurred at intermediate to lower crustal depths

petrology and isotope geochemistry of san vincenzo rhyolites tuscany italy two groups of rhyolites have been recognized at san vincenzo tuscany italy group a rhyolites are characterized by plagioclase quartz biotite sanidine and cordierite mineral assemblages they show constant mgo and variable cao and na2o contents initial87sr 86sr ratios in group a samples range between 0 71950 and 0 72535 whereas the nd isotopic compositions are relatively constant 0 51215 0 51222 group b rhyolites are characterized by orthopyroxene and clinopyroxene as additional minerals and show textural mineralogical and chemical evidence of interaction with more mafic magmas the sr and nd isotopic ratios range between 0 71283 0 71542 and 0 51224 0 51227 respectively magmatic inclusions of variable size 1 mm to 10 cm were found in groups b rhyolites these inclusions consist mainly of diopsidic clinopyroxene and minor olivine and biotite they are latitic in composition and represent blobs of hybrid intermediate magmas entrained in the rhyolitic melts these magmatic inclusions have relatively high sr contents 996 1529 ppm and sr and nd isotope ratios of 0 70807 0 70830 and 0 51245 0 51252 respectively 87sr 87sr data on minerals separated from both group a and b rhyolites and magmatic inclusions reveal strong isotopic disequilibria due to the presence of both restitic and newly crystallized phases in group a rhyolites and due to interaction of rhyolites with a mantle de rived magma in group b rhyolites isotopic data on whole rocks and minerals allow us to interpret the group a rhyolites as representative of different degrees of melting of an isotopically fairly homogeneous pelitic source conversely group b rhyolites underwent interactions with a mantle derived magma the crustal source as inferred from isotopic systematics would be characterized by87sr 86sr and143nd 144nd ratios close to 0 7194 and 0 51216 respectively the sub crustal magma would have sr isotopic composition close to 0 7077 and a143nd 144nd ratio greater than or equal to 0 51252 these isotopic features are different from those reported for the parental magmas postulated for vulsini and alban hills in the nearby roman magmatic province and are similar to those of the vesuvius and ischia magmas

crystal chemistry and site configuration of the clinopyroxene from leucite bearing rocks and related genetic significance the sabatini lavas roman region italy

re os age of non mineralized black shale from the kupferschiefer poland and implications for metal enrichment six samples of non mineralized black shale from a kupferschiefer section in the northern part of the polish zechstein basin zdrada ig 8 drill hole 1026 16 1026 90 m were studied for re os isotopes and selected major and trace elements these black shales averaging 5 82 wt corg and 1 69 wt stot display very low base metal values up to 106 ppb cu 792 ppb pb and 144 ppb zn and have abundances of 64 1376 ppb re and 0 37 1 25 ppb os with a 187os 188os ratio of 6 95 22 5 the regression of all re os data yields an age of 247 20 ma which is within the range of uncertainties of previous rb sr and k ar geochronological studies the scatter in the re os data can be explained in terms of fluctuations in sedimentary conditions i e restricted basin with terrestrial influence

fluid geochemistry and geothermometry in the unexploited geothermal field of the vicano cimino volcanic district central italy abstract the vicano cimino volcanic district vcvd is related to the post orogenic magmatic activity of the peri tyrrhenian sector of central italy the chemical and isotopic compositions of 333 water discharges and 25 gas emissions indicate the occurrence of two main sources 1 cold ca hco 3 to ca na k hco 3 type waters from relatively shallow aquifers hosted in volcanic and sedimentary formations and 2 thermal ca so 4 hco 3 type waters located in a deep co 2 pressurized reservoir hosted in carbonate evaporite rocks and separated from the shallow aquifers by thick sequences of low permeability formations carbon dioxide is mainly produced by thermal metamorphic decarbonation within the deepest and hottest parts of the carbonate evaporite reservoir 13 c co 2 from 3 1 to 2 2 vs vpdb likely affected by a mantle rooted co 2 release of co 2 rich gases from the deep aquifer into the overlying shallow aquifers produces high co 2 springs and bubbling pools the spatial distribution of thermal waters and co 2 rich cold discharges is strongly controlled by fractures and faults located in correspondence with buried structural highs stable isotopes d and 18 o suggest that meteoric water feeds both the shallow and deep reservoirs the relatively low r r a values 0 27 1 19 indicate that he is mainly deriving from a crustal source with minor component from the mantle affected by crustal contamination related to the subduction of the adriatic plate consistently relatively high n 2 ar and n 2 3 he ratios and positive 15 n n 2 values from 0 91 to 5 7 vs air characterize the vcvd gas discharges suggesting the occurrence of a significant excess nitrogen isotopic compositions of ch 4 13 c ch 4 and d ch 4 values from 28 9 to 22 1 vs vpdb and from 176 to 138 vs vsmow respectively and composition of light alkanes are indicative of prevalent thermogenic ch 4 although the occurrence of abiogenic ch 4 production cannot be excluded the 34 s h 2 s values from 9 3 to 11 4 vs vcdt are consistent with the hypothesis of h 2 s production from thermogenic reduction of triassic anhydrites gas geothermometry in the h 2 o h 2 ar h 2 s system suggests that the vcvd gases equilibrated in a liquid phase at redox conditions controlled by interactions of fluids with the local mineral assemblage at temperatures lower 2000 m geothermal wells this confirms that secondary processes i e steam condensation gas dissolution in shallow aquifers re equilibration at lower temperature and microbial activity significantly affect the chemistry of the uprising fluids thermal water chemistry supports the occurrence in this area of an anomalous heat flow that coupled with the recent demographic growth makes this site suitable for direct and indirect exploitation of the geothermal resource in agreement with the preliminary surveys carried out in the 1970 s 1990 s for geothermal exploration purposes

crystal chemistry of clinopyroxenes from potassic and ultrapotassic rocks in central italy implications on their genesis the clinopyroxenes mentioned have been investigated by single crystal x ray diffraction combined with electron microprobe analysis the aim of this study was to characterize the crystal chemical variations of clinopyroxenes in order to delineate the intracrystalline constraints which are characteristic of specific magmatic environments clinopyroxenes cpx crystallized from peralkaline ultrapotassic melt with kamafugitic and lamproitic affinities are characterized by high si contents which are insensitive to variations in silica abundance and silica saturation of the melt the high si occupancy in clinopyroxenes from kamafugitic magma is coupled to large m1 i e mg and fe2 and m2 high ca occupancy sites whereas in clinopyroxenes from magmas with lamproitic affinity high si content is combined with large m1 but small m2 sites clinopyroxenes from romantype alkaline potassic and ultrapostassic rocks are characterized by an expanded tetrahedron high iva1 content and small m1 site which is combined with small m2 polyhedron in clinopyroxenes from the potassic rocks and large m2 site in those from the ultrapotassic rocks

crystallization paths of leucite bearing lavas examples from italy the salic phases found in leucite basanites trachytes and phonolites may be used to portray crystallization in the system naalsio 4 kalsio 4 caal 2si 2o 8 sio 2 the phonolite pentahedron only two lavas have been found that contain the assemblage leucite nepheline plagioclase sanidine and liquid a natural pseudo invariant assemblage at 900 c 100 equivalent to the isobaric invariant point of the four component system the diversity of phases in this group of lavas illustrates the role of halogens in controlling their crystallization paths thus the presence of f in the leucite basanites has stabilized magnesian biotite and suppressed sanidine as has been found in other basanitic lavas brown and carmichael 1969 the presence of cl in these same lavas has induced the crystallization of sodalite which takes the place of nepheline in the groundmass however in the leucite trachytes biotite has suppressed olivine and coexists with sanidine and leucite the presence of s may produce hauyne at the expense of nepheline and in general sulphate minerals which include apatite have the role in lavas of low silica activity that pyrrhotite plays in liquids of high silica activity both pyroxenes and titaniferous magnetites in this suite of lavas are very aluminous groundmass crystals of pyroxene may have one fifth of si replaced by al other phases which occur occasionally are melanite garnet and a potassium rich hastingsite but neither ilmenite nor a sulphide mineral has been found phenocryst equilibration temperatures derived from olivine and sr rich plagioclase are generally in the range from 1 050 c to 1 150 c the high content of incompatible elements e g k ba rb f sr p in these lavas suggests that they represent a small liquid fraction from a mantle source which possibly contains phlogopite

origin of the acidic volcanics of the tolfa district tuscan province central italy an elemental and sr isotopic study volcanic rocks from the southern part of the tuscan province the tolfa district range in composition from dacites to rhyolites they have relatively high contents of many incompatible elements and their 87sr 86sr ratios vary between 0 7129 and 0 7148 28 analyses with one analysis of 0 7112 the four major eruption centres of the district can be distinguished geochemically it is shown that the variation of major and trace elements within each area can be explained by fractional crystallization without significant crustal assimilation the geochemical patterns of the incompatible elements of the investigated volcanics have a close similarity to the alkaline undersaturated volcanics from the nearby roman province the geochemical and isotopic similarity between the tolfa volcanics and those of the roman province suggests a common origin for these components of the magmas it is suggested that while the origin of the lil element enrichment of the roman province magmas is a mantle which was metasomatised by fluids or melts derived from upper crustal material of sedimentary origin recycled into the mantle by subduction the tolfa volcanics were derived directly from the subducted material by melting

an integrated approach for the prediction of subsidence for coal mining basins abstract in this study land subsidence caused by underground mining activities was investigated by means of a new subsidence prediction approach isp tech which takes into account the most important parameters contributing subsidence development such as coal production methods depth mining sequence and other geomechanical characteristics of underground rock strata etc isp tech can be applied to operating mines to keep land subsidence under control as well as virgin coal sites to predict surface subsidence prior to mining activities in the method geological information gathered from the geographic information system gis and the mining information system mis are utilised to obtain geological cross sections which are used in finite element models for mesh building then a number of two dimensional finite element modelling analyses are carried out to determine land subsidence occurring due to mining operations finally land subsidence predicted from modelling studies is compared to the gps and or differential interferometry synthetic aperture radar din sar measurements if incompatibility of the results is detected finite element meshes should be optimised and then reanalysed to obtain more compatible results in the study two different case studies were given as examples of the application of isp tech results of the case studies showed that isp tech can successfully be applied to complex mine subsidence problems the proposed approach gives more accurate results than those obtained from other classical subsidence prediction methods

the role of the kupferschiefer in the formation of hydrothermal base metal mineralization in the spessart ore district germany insight from detailed sulfur isotope studies the spessart district sw germany located at the southwestern margin of the permian kupferschiefer basin in central europe hosts abundant stratabound and structurally controlled base metal mineralization the mineralization styles identified are 1 stratabound cu pb zn ag ores in zechstein sedimentary rocks 2 structurally controlled cu as ag ores in zechstein sedimentary rocks 3 crosscutting co ni bi as and cu fe as veins 4 stratabound metasomatic fe mn carbonate ores in zechstein dolomite 5 barren barite veins and 6 fe mn as veins in permian rhyolites building on previous work that involved mineralogical textural and chemical characterization of the major mineralization types we have performed a comprehensive sulfur isotope study that applied both conventional and novel laser ablation multi collector inductively coupled plasma mass spectrometry techniques the 34s values of sulfide minerals from the different ore types are consistently negative and highly variable in the range between 44 5 and 3 9 whereas the 34s values of barite are all positive in the range between 4 7 and 18 9 remarkably stratabound and structurally controlled mineralization in zechstein sedimentary rocks has the least negative 34s values whereas vein type deposits have consistently more negative 34s values the observed pattern of sulfide 34s values can be best interpreted in terms of fluid mixing at the basement cover interface hydrothermal fluids originating from the crystalline basement migrated upward along subvertical fault zones and were periodically injected into groundwaters that were flowing in the post variscan sedimentary cover these groundwaters had interacted with the zechstein sedimentary rocks resulting in fluids characterized by elevated concentrations of reduced sulfur with negative 34s values and alkaline ph repeated mixing between both chemically contrasting fluids caused rapid and efficient precipitation of sulfide ore minerals in hydrothermal veins with highly variable but distinctly negative 34s values

the geochemistry of potassic lavas from vulsini central italy and implications for mantle enrichment processes beneath the roman region major and trace element and 143nd 144nd 0 51209 0 51216 and 87sr 86sr 0 70879 0 71105 isotope analyses are presented on a representative group of lavas from the vulsini district of the roman magmatic province three distinct series are identified the high k and low k series are similar to those described from other italian volcanoes while the third is represented by a group of relative ly undifferentiated leucite basanites which are thought to be near primary mantle melts major and trace element variations within the high k series are consistent with fractional crystallisation from a parental magma similar to the most magnesian leucitites crustal contamination resulted in an increase in 87sr 86sr with increasing fractionation but it was superimposed on magmas which had already inherited a range of incompatible element and isotope ratios from enrichment processes in the sub continental mantle these are reviewed using the available results from vulsini roccamonfina and ernici transition element abundances and ta yb ratios indicate that the pre enrichment mantle was similar to that of e type morb and that these elements were not mobilised by the enrichment process mixing calculations suggest that three components were involved in the enrichment process mantle comparable with the source of morb and two other components rich in trace elements one the low k component had high sr nd th ta and ba nb and no europium anomaly while the second had lower sr nd a negative europium anomaly and very high th ta it was also characterised by low nb ba and high rb ba ratios similar to those reported from phlogopite rich peridotite xenoliths the trace element enrichment processes are therefore thought to have occurred in the mantle wedge above a subduction zone with the trace element characteristics of the high k end member reflecting the subduction of sediments and the stabilisation of mantle phlogopite

geochemistry of tuscan archipelago granitoids central italy the role of hybridization processes in their genesis this paper reports major trace and rare earth element data for selected samples from the elba giglio and monte cristo plutons which lie in the tuscan archipelago italy on the basis of field and petrologic constraints all the rocks can be divided into five facies and range in composition from granodioritic to alkali granitic with a strong predominance of monzogranites tuscan archipelago granitoids are clearly collision related rocks and they straddle the i and s types of chappell and white however mineralogical and chemical characteristics indicate that the more basic rocks are broadly i type while the high silica rocks are s type genetic models that relate these magmas through the segregation of their major and accessory mineral phases are inconsistent with major trace and ree element abundant data geological petrographical and geochemical constraints show that the microgranular mafic enclaves found within the rocks are blobs of mafic high temperature magma chilled within a cooler m

eocene melting of precambrian lithospheric mantle analcime bearing volcanic rocks from the challis kamloops belt of south central british columbia abstract potassic silica undersaturated mafic volcanic rocks form a minor portion of the predominantly calc alkaline eocene challis kamloops volcanic belt which extends from the northwestern united states into central british columbia canada their major occurrence is in the penticton group in south central british columbia where they reach a thickness of up to 500 m and form the northwestern edge of the montana alkaline province these analcime bearing rocks 53 52 ma old are typically rhomb porphyries of ternary feldspar an28ab52or20 additional phenocryst phases include clinopyroxene analcime phlogopite and rare olivine the rocks are characterized by high total alkalis particularly k2o 4 5 wt as well as by a distinct enrichment of large ion lithophile elements versus heavy rare earth elements and high field strength elements they have unusual isotopic compositions compared to most other rocks of the challis kamloops belt particularly high negative nd values and elevated but relatively uniform initial 87sr 86sr ratios 0 7065 the potassic silica undersaturated rocks overlie precambrian crust and lithosphere and were at least in part derived from ancient metasomatized subcontinental mantle lithosphere which was modified in a precambrian subduction setting the alkaline rocks of the challis kamloops belt are related to a slab window environment in particular they were formed above the southern edge of the kula plate adjacent to the kula farallon slab window whereas the montana alkaline province situated well to the southeast was formed directly above the kula farallon slab window upwelling of the hotter asthenospheric mantle may have been the thermal trigger necessary to induce melting of fertile and metasomatized lithospheric mantle

common trace element characteristics of crustal and mantle derived k rich magmas at mt amiata central italy rare earth and other trace element data are reported for k rich mafic inclusions and siliceous lavas from mt amiata southern tuscany italy which form an almost complete mixing series as a result of magmachamber replenishment despite a wide range of sio2 contents 48 67 wt most of the rocks are equally enriched in light ree 200 300 and heavy ree 10 15 relative to chondritic values whereas intermediate ree are slightly less abundant in the lavas compared with the inclusions eu shows negative anomalies eueu 0 49 0 70 that are most pronounced in the lavas the compatible elements cr v sc and co are found to behave like sr ba and most major elements as they show a distinct inverse correlation with sio2 while cs follows na and li and markedly increases with sio2 however k and a number of other predominantly incompatible elements viz rb zr la ce yb lu nb y hf th and u display surprisingly little or no variation and all of the rocks have unusually high concentrations of many of these elements based on arguments that mixing in the magma chamber was not accompanied by significant selective enrichment of certain elements these chemical characteristics are attributed to the end members which can be identified as a silica saturated tuscan type magma and a primitive silica undersaturated roman type magma of the high k series it is tentatively suggested that the different sources in the lower crust and upper mantle from which the end member magmas are thought to originate were metasomatized by the same fluids prior to melting

dissolved potassium in the shallow groundwaters circulating in the volcanic rocks of central southern italy abstract the water rock interaction processes occurring in the low temperature shallow volcanic aquifers of central southern italy were simulated by means of the eq3 6 software package in reaction progress mode in the investigation both the roman magmatic province and monte amiata which belongs to the tuscan magmatic province were included the average k2o content of the volcanic rocks from the two areas is similar but the main k bearing phases are leucite in the roman magmatic province and sanidine at monte amiata computed concentrations of major dissolved components and sio2 are consistent with analytical data suggesting that the results of the eq3 6 runs are reliable simulations of the natural water rock interaction processes hence eq3 6 results can be used to investigate the transfer of k from rocks to water it turns out that the attainment of saturation with sanidine during early stages of rock dissolution limits k concentration in the monte amiata groundwaters to around an average of 2 9 1 3 mg l 1 1sd in the silica undersaturated roman magmatic province saturation with leucite is not attained during the evolution of groundwaters and consequently k concentration reaches comparatively high levels with an average of 24 6 27 1 mg l 1 1sd most of these unusually high k concentrations are due to natural weathering of silicates without any anthropogenic influence

contrasting radon background levels in volcanic settings clues from 220rn activity concentrations measured during long term deformation experiments to better understand the mechanisms leading to different radon background levels in volcanic settings we have performed two long term deformation experiments of 16 days using a real time setup that enables us to monitor any variation of radon activity concentration during rock compression our measurements demonstrate that in the case of highly porous volcanic rocks the emanating power of the substrate changes as a function of the volcanic stress conditions constant magmatic pressures such as those observed during dike intrusions and hydrothermal fluid injections can result in pervasive pore collapse that is mirrored by a significant radon decrease until a constant emanation is achieved conversely repeated cycles of stress due to for example volcano inflation deflation cycles cause a progressive radon increase a few days but even weeks and months before rupture after rock failure however the formation of new emanation surfaces leads to a substantial increase of the radon signal our results suggest that surface deformation in tectonic and volcanic settings such as inflation deflation or constant magmatic pressures have important repercussions on the emanating power of volcanic substrates

structural evolution of the pleistocene cimini trachytic volcanic complex central italy structural geomorphological geophysical and volcanological data have been processed for the implementation of a dedicated gis through which the structural evolution of the pleistocene trachytic cimini volcano central italy has been reconstructed the evolution of the cimini complex includes three main close in time phases 1 intrusion of a shallow laccolith rising along nw and ne trending faults and stagnating at the contact between the mesozoic cenozoic and the pliocene pleistocene sedimentary units constituting the bedrock of the volcano 2 emplacement of lava domes along radial and tangential fractures formed by the swelling induced by the laccolith growth 3 ignimbrite eruptions and final effusion of olivine latitic lavas domes are both of pelean and low lava dome type and their morphology was controlled by the location on the inclined surface of the swelled area some domes show to have uplifted upper pliocene thermally metamorphosed clay sediments suggesting a cryptodome like growth comparison of the top of the mesozoic cenozoic units with the top of the upper pliocene pleistocene sedimentary complex suggests that the laccolith emplaced in a graben of the mesozoic cenozoic sedimentary complex filled by the pliocene pleistocene sediments uplifted by the shallow intrusion stress patterns acting on the cimini area have been deduced analysing the drainage network and the morphotectonic lineaments rose diagrams show a large dispersion of the lineaments reflecting the local presence of radial and tangential fractures the most frequent extensional nw and ne trending lineaments have regional significance and controlled the magma uprise leading to the laccolith emplacement

an experimental and numerical investigation on the deformation of overlying coal seams above double seam extraction for controlling coal mine methane emissions abstract this study investigates the deformation and the resultant pressure relief of highly gassy coal seams where a double seam mining operation takes place at lower depths at the wulan coal mine china in order to predict the depressurization effect in the overlying coal seams we simulate the extraction process by constructing a scaled model in the laboratory using similar rock materials analyses of experimental results concluded that due to the mining induced stress redistribution the pressure within target coal seams which were 109 m above the mined seams could be fully relieved to attain the statutory approval for gas drainage in addition to scaled model studies computational modeling studies were conducted using udec universal distinct element code which showed that the features of deformation resulting from the double seam extraction were different from that of in the case of single seam extraction the results of the numerical studies revealed that in addition to the panel margin on the air return side areas near the intake entry could also be considered as borehole drilling positions besides it was found that the gob of the extracted seams below the gassy one provided a buffering effect for the would mined protective coal seam and that the depressurization effect was largely weakened the laboratorial findings are instructive to the field practice of methane drainage during the mining operation a displacement comparison method was adopted to measure the dilated amount of protected coal seams and as expected the maximum dilation percentage was much more than 0 2 the critical value upon which the target coal seam is appropriately depressurized to allow gas drainage to be safely and effectively implemented

phase relationships in the system kalsio 4 mg 2 sio 4 sio 2 h 2 o as a model for hybridization between hydrous siliceous melts and peridotite the system kalsio4 mg2sio4 sio2 h2o includes model representatives of 1 hydrous siliceous magma from subducted oceanic crust the eutectic liquid in kalsi3o8 sio2 h2o and 2 the overlying mantle peridotite the assemblage forsterite enstatite fo en in a series of partly schematic isobaric isothermal sections the products of hybridization between the model materials at pressures between 20 and 30 kbar have been determined the liquid dissolves peridotite components with little change in composition hybridization is not a simple mixing process because of the incongruent melting of peridotitic assemblages with phlogopite ph hybridization causes solidification of the liquid with products a sequence of three mineral assemblages ph ph quartz qz and ph en the products represent an absolute geochemical separation and local concentration of all potassium from the liquid hybridization is accompanied by h2o saturation of melts and evolution of aqueous fluid although there are significant differences between the melt composition and that of the magma rising from subducted oceanic slab and between fo en and the mantle rock extrapolation of the results suggests that the conclusions can probably be extended to mantle conditions with sodium in the melt and jadeitic clinopyroxene included in the hybrid products

physical model test and numerical simulation for the stability analysis of deep gas storage cavern group located in bedded rock salt formation abstract the stability of gas storage cavern complex constructed in bedded salt rock formation might be influenced by multiple factors during the operation process in order to assess these effects three dimensional rheological model tests were conducted in this study physical model with four ellipsoid caverns were constructed with scaled in situ stresses applied through independent sets of hydraulic jacks and internal pressure applied by digital controlled latex balloons influences of different factors on the deformation properties of surrounding rock were systematically evaluated including the gas recovery and injection rate the loss of pressure the extremely low and high gas pressure and the pillar width and pressure difference between adjacent caverns test results revealed that the deformation of the cavern wall was accelerated when the gas extraction injection rate exceeds 0 65 mpa d loss of internal pressure dramatically promoted the deformation tertiary creep stage arose when the internal pressure was too low 3 mpa or too high 22 mpa internal pressure difference and pillar width worked together to affect the deformation properties tests results obtained in this study provided physical evidence for the safety analysis of cavern group as well as the optimization of design and operation scheme these results can also serve as benchmark for the validation of numerical models

the magma mixing origin of mantled feldspars the key to mantled feldspar genesis is epitaxial nucleation of plagioclase on k feldspar or k feldspar on plagioclase once this nucleation takes place there is a relatively straightforward process of crystal growth yielding rapakivi and antirapikivi textures the most common mantling is plagioclase on k feldspar which occurs in both volcanic and plutonic environments in the volcanic environment the morphology of the plagioclase overgrowth typically is dendritic though in subvolcanic and shallow plutonic environments dendritic growth is followed by a more or less continuous non cellular shell of plagioclase in the plutonic environment early stages of plagioclase overgrowth also tend to be dendritic although with coarser grained characteristics dendritic morphology is thus a common denominator in rapakivi genesis since growth of dendritic plagioclase is clearly related to marked undercooling in silicate melt systems its occurrence in many volcanic rocks is to be expected equivalent quenching in the plutonic environment requires a cooling mechanism independent of conductive heat transfer to wallrock and also independent of effective cooling related to sudden loss of volatile phases that could only occur late in the crystallization of most magmas and therefore after much dendritic plagioclase had already formed internal quenching of portions of magma systems must occur if mafic magma is abruptly mixed with felsic magma such magma mixing yields a heterogeneous system at first one that is in a drastic state of disequilibrium and tending to force nucleation of one feldspar type on the surface of another resulting in epitaxial crystallization of dendritic plagioclase on k feldspar mantling of one feldspar type by another during magma mixing is paralleled by dendritic growth zones in coexisting plagioclase crystals

syn depositional substrate deformation produced by the shear force of a pyroclastic density current an example from the pleistocene ignimbrite at monte cimino northern lazio italy substrate deformation by pyroclastic density currents is very sparsely described in the literature the rare occurrence of syn depositional substrate deformation suggests that special circumstances are required to transmit shear from the base of a pyroclastic density current into the deposited ignimbrite and the substrate one example of a substrate deformed by a pyroclastic density current is found at the base of the pleistocene ignimbrite at monte cimino central italy a series of reverse faults that offsets the basal contact were produced by the shear force of the pyroclastic current during deposition of the ignimbrite the faults formed on the vent facing side of a palaeo slope that strikes sub parallel to the flow direction of the pyroclastic current fault offsets suggest motion was parallel to the flow direction of the pyroclastic current rather than down slope we propose that these faults resulted from fluctuations in the shear force of the pyroclastic density current as it was channelled down a palaeovalley the lower flow boundary which separated the deposited ignimbrite and the substrate from the moving pyroclastic density current momentarily stepped down into the substrate so that the upper 0 5 m of the substrate and about 1 5 m of the deposited ignimbrite became incorporated into the current this momentary coupling of the current and the substrate induced reverse faulting in the substrate and the deposited portion of the ignimbrite deposition appears to have been ongoing during the formation of these faults as well as afterward following the formation of the faults the lower flow boundary seems to have been quickly re established above the faults approximately 1 5 m above the base of the ignimbrite allowing deposition to continue without further deformation of the substrate

local acceleration monitoring and its application in physical modelling of underground mining abstract a micro electro mechanical systems mems inertial sensor was introduced to perform local acceleration monitoring lam in a physical model to showcase mining induced strata movements to prove the feasibility of lam a physical model experiment was performed using four sensors mounted on the roof strata acquired acceleration signals were processed by a moving average and median filter analysed with respective trend variation and fluctuation along with excavation sequence to identify the movement of roof strata a key reference was the mid span section that characterized by adjacent sensors with opposite acceleration change direction to assess the stability of strata a clear evidence is the synchronicity loss of two adjacent sensors in terms of acceleration change in the presented experiment the first weighting and the fracture position can be predicted 1 5 h prior to final failure this study represents a novel attempt to apply lam in a physical modelling experiment and tentatively interpret signals in accordance with strata movement the proposed lam based approach succeeded in identifying the movement and assessing the stability of the strata results presented in this paper verify the validity of lam in terms of noise analysis sensibility and rationality this lam technique is capable of serving as an easy to implement high precision and low cost method in mining and geotechnical related physical modelling research

application of proton microprobe data to trace element partitioning in volcanic rocks abstract in situ proton microprobe analyses are used to calculate partition coefficients d for mn fe cu zr ga rb sr y zr ba and pb and more restricted data for ni ge nb and as in pyroxenes olivines biotites hornblendes feldspars and fe ti oxides from 32 volcanic rocks all with glassy matrices these range from leucitite and picritic basalt to high silica and peralkaline rhyolites data for pigeonite aenigmatite allanite and leucite are included where these occur as additional phases coefficients have also been rayleigh fractionation corrected this correction being significant for those elements with high coefficients in specific mineral phases and where pronounced crystallisation has occurred partition coefficients are presented as plots vs nbo t ratios of coexisting glasses melts negative correlations are observed based on log transformed data for mn zn fe and y pyroxenes mn zn and fe olivines mn and zn fe ti oxides nb y sr and zr hornblendes sr plagioclase and ba cu zn and fe feldspars these element partition coefficients are not correlated with bulk mineral compositions zr and ga are not correlated with either glass or mineral compositions except zr in hornblende the correlations support the role of melt polymerisation in controlling element partitioning at least for those elements listed although possible effects of temperature cannot be uniquely isolated in the present data set the coefficients presented here are generally consistent with published values for equivalent rock compositions one difference being that some of the higher published coefficients e g sr in plagioclase are not matched in the present data set from a practical viewpoint the relative regularity of the coefficient data presented does facilitate choice of relevant coefficient values that are required for petrogenetic modelling procedures

physical modelling of subsidence from sequential extraction of partially overlapping longwall panels and study of substrata movement characteristics field examples of subsidence from sequential extraction of overlapping coal longwall panels have shown that complex and unexpected subsidence effects can occur physical models comprising sand and plaster obeying relevant similarity rules were used to investigate the subsidence mechanisms displacements within the models were measured using a combination of optical transducers photogrammetry and laser scanning the observed results were compared with finite element models the models demonstrate that the incremental subsidence and substrata movement profiles after lower seam extraction can be separated into three different zones these zones undergo different horizontal and vertical movement characteristics the zone of overlap of the two longwall panels undergoes greater total subsidence compared to a single seam of equivalent thickness the limit angle of the subsidence also differs at the two ends of the lower extraction as a result of the effects of the previously mined out area above

model experimental research on deformation and subsidence characteristics of ground and wall rock due to mining under thick overlying terrane abstract based on the prototype of a mine a physical simulation test is conducted the characteristics of the deformation and failure of the ground surface and the wall rock around a goaf as well as the creep behavior of the wall rock deformation and the failure mechanism are analyzed the simulation test has greatly improved our understanding on the wall rock s deformation and failure characteristics for the first time digital close range photogrammetry was used to measure the displacements in a sectional model test the measurements by this technique agreed very well with those obtained by other methods such as using dial gauges

a proposal for the kinematic modelling of w dipping subductions possible applications to the tyrrhenian apennines system in w dipping subduction zones there is a general eastward progression of the back arc basin accretionary wedge foredeep complex with the forward progression early stages of the complex are revealed by slices of upper crust and sedimentary cover abandoned to the west left floating above a new section of mantle a major shear zone should form at the new moho separating upper crust slices of earlier accretionary stages and the eastward flowing mantle the mantle wedging at the top of the subduction plane could be responsible for the uplift of the central parts of the belt the retreating of the subduction hinge is interpreted as due to the push generated by the eastward mantle flow detected in the hot spot reference frame the foredeep depth is mainly a function of the radius of curvature of the subduction hinge the frontal wedge is constructed from the stacking of the upper layers of the subducting plate and the syntectonic clastics that fill the foredeep which are progressively involved in thrusting and later by extension in order to preserve volume balance the lithosphere of the eastern plate before subduction has to be the same size as that which has been subducted due to the longer length of the arc with respect to the original length of the linear margin between the two converging plates laterally stretched subducted lithosphere is predicted at depth w dipping subductions usually have a short life probably due to their inherent capability to produce new lateral heterogeneities of the lithosphere the thin back arc which are a key factor in controlling and generating new subductions both e and w dipping this model is applied to the apennines tyrrhenian sea system

partition coefficients of hf zr and ree between zircon apatite and liquid concentration ratios of hf zr and ree between zircon apatite and liquid were determined for three igneous compositions two andesites and a diorite the concentration ratios of these elements between zircon and corresponding liquid can approximate the partition coefficient although the concentration ratios between apatite and andesite groundmass can be considered as partition coefficients those for the apatite in the diorite may deviate from the partition coefficients the hree partition coefficients between zircon and liquid are very large 100 for er to 500 for lu and the hf partition coefficient is even larger the ree partition coefficients between apatite and liquid are convex upward and large d 10 100 whereas the hf and zr partition coefficients are less than 1 the large differences between partition coefficients of lu and hf for zircon liquid and for apatite liquid are confirmed these partition coefficients are useful for petrogenetic models involving zircon and apatite

limestone assimilation and the origin of co2 emissions at the alban hills central italy constraints from experimental petrology abstract the alban hills volcanic region 20 km south of rome in the roman province emitted a large volume of potassic magmas 280 km 3 during the quaternary chemical interactions between ascending magmas and the 7000 8000 m thick sedimentary carbonate basement are documented by abundant high temperature skarn xenoliths in the eruptive products and have been frequently corroborated by geochemical surveys in this paper we characterize the effect of carbonate assimilation on phase relationships at 200 mpa and 1150 1050 c by experimental petrology calcite and dolomite addition promotes the crystallization of ca rich pyroxene and mg rich olivine respectively and addition of both carbonates results in the desilication of the melt furthermore carbonate assimilation liberates a large quantity of co 2 rich fluid a comparison of experimental versus natural mineral glass and bulk rock compositions suggests large variations in the degree of carbonate assimilation for the different alban hills eruptions a maximum of 15 wt assimilation is suggested by some melt inclusion and clinopyroxene compositions however most of the natural data indicate assimilation of between 3 and 12 wt carbonate current high co 2 emissions in this area most likely indicate that such an assimilation process still occurs at depth we calculate that a magma intruding into the carbonate basement with a rate of 1 2 10 6 m 3 year estimated by geophysical studies and assimilating 3 12 wt of host rocks would release an amount of co 2 matching the current yearly emissions at the alban hills our results strongly suggest that current co 2 emissions in this region are the shallow manifestation of hot mafic magma intrusion in the carbonate hosted reservoir at 5 6 km depth with important consequences for the present day volcanic hazard evaluation in this densely populated and historical area

characterising the multi seam subsidence due to varying mining configuration insights from physical modelling abstract multi seam mining induced subsidence profile is observed to be different from that of single seam mining understanding the characteristics of multi seam subsidence is the first step in achieving reliable subsidence predictions characteristics of multi seam subsidence are investigated by means of several sand plaster physical models geological and site specific parameters are kept constant in all the models in order to compare the multi seam subsidence parameters for different mining configurations based on observations from the physical models it is concluded that the panel configurations of the two seams have significant impact on the multi seam subsidence development based on the relative location of the panels the multi seam mine area can be divided into different zones to which suitable subsidence characteristics can be assigned dividing the mine area into different zones enables characterisation of the strata movement and multi seam subsidence for various multi seam configurations the proposed characterisation of the multi seam subsidence can also be utilised in subsidence prediction methods in order to achieve reliable prediction results

the origin of k feldspar megacrysts hosted in alkaline potassic rocks from central italy a track for low pressure processes in mafic magmas abstract in situ sr isotope and microchemical studies were used to determine the provenance of k feldspar megacrysts hosted in mafic alkaline potassic ultrapotassic rocks and in differentiated rocks from two nearby volcanic apparatus in central italy at monte cimino volcanic complex mafic leucite free ultrapotassic megacryst bearing rocks of olivine latitic composition are associated with evolved latite and trachyte here latites and trachytes straddle the sub alkaline field age corrected 87sr 86sr values sri of the analysed cimino olivine latites vary from 0 71330 and 0 71578 and strongly increase at constant mg value latite and trachyte have lower sri than olivine latites ranging between 0 71331 and 0 71361 sri of k feldspar megacrysts from olivine latites are between 0 71352 and 0 71397 but core and rim 87sr 86sr ratios within individual megacryst are indistinguishable in all the mafic rocks the megacrysts are not in isotopic equilibrium with the hosts k feldspar megacrysts from both the latite and trachyte have similar sr isotope compositions sri 0 71357 0 71401 to those in the olivine latites however sri of megacryst in the trachyte vary significantly from core to rim sri from 0 71401 to 0 71383 as with the olivine latites the k feldspar megacrysts are not in isotopic equilibrium with bulk rock compositions of the latite or trachyte at vico volcano megacryst bearing rocks are mafic leucite free potassic rocks mafic leucite bearing ultrapotassic rocks and old trachytic rocks the mafic leucite bearing and leucite free rocks are a tephri phonolite and an olivine latite respectively a megacryst in vico trachyte is isotopically homogeneous sri core 0 71129 rim 0 71128 and in equilibrium with the host rock sri bulk rock 0 71125 sri of megacryst from tephri phonolite is clearly not in isotopic equilibrium with its host sri bulk rock 0 71158 and it increases from core sri 0 71063 to rim sri 0 71077 a megacryst in vico olivine latite is isotopically homogeneous sri core 0 71066 rim 0 71065 but not in equilibrium with the host rock sri bulk rock 0 71013 the sr isotope microdrilling technique reveals that cimino megacrysts were crystallised in a cimino trachytic magma and were subsequently incorporated by mixing mingling processes in the latitic and olivine latitic melts a model invoking the presence of a mafic sub alkaline magma which was mixed with the olivine latite is proposed to justify the lack of simple geochemical mixing relation between cimino trachytes and olivine latites this magmatological model is able to explain the geochemical characteristics of cimino olivine latites otherwise ascribed to mantle heterogeneity the similarity of core sri of megacrysts hosted in vico tephri phonolite and olivine latite suggests that the k feldspar megacrysts are co genetic isotopic equilibrium between megacryst and vico host trachyte indicates that the trachyte is the parent of this megacryst on the contrary the megacrysts hosted in tephri phonolite and olivine latite do not derive from the old trachytic magma because no diffusion process may explain the core to rim sr isotope increase of the xenocryst hosted in the tephri phonolite the megacrysts hosted in the vico mafic rocks might derive from a trachytic melt similar in composition to the old vico trachytes

influences of secondary oxidation and sulfide formation on several maturity parameters in kupferschiefer vitrinite reflectance and methylphenanthrene indices are important maturity parameters for coal and other sedimentary organic matter they have been widely used for determining the maturity of organic matter in kupferschiefer however during the study of organic matter in kupferschiefer it has been found that vitrinite reflectance and methylphenanthrene indices were influenced by oxidizing fluids and sulfide formation in order to study the influence degree on maturity parameters three kupferschiefer profiles from the konrad polkowice and sangerhausen mines were analysed by microscopic and geochemical methods the results indicate that the kupferschiefer in the studied areas was deposited in normal marine and euxinic environment according to organic facies parameters the kerogen belongs to type ii under the influence of secondary oxidation organic matter was altered from type ii to type iii in the oxidized samples the values of vitrinite reflectance are clearly higher and the values of methylphenanthrene indices are lower than those of non oxidized samples because of the depletion of alkylated phenanthrenes the actual maturity can be calculated by revision of measured vitrinite reflectance and calculated vitrinite reflectance in the oxidized kupferschiefer samples in high mineralized samples hydrogen donation for thermochemical sulfate reduction occurred in alkylated phenanthrenes and resulted in a decrease of methylphenanthrene index values during kupferschiefer mineralization the methylphenanthrene index values in these samples can be calculated empirically

the composition of brines in the early diagenetic mineralization of the permian kupferschiefer in germany the kupferschiefer is an approximately 0 5 m thick black marly shale of lower zechstein age in germany if one includes some of its footwall and hanging wall it contains 300 mt cu 800 mt zn and 300 mt pb the regional pattern of metal distribution demonstrates its relationship to variscan and permian tectonic structures faults and the topographic relief of the basement apparently controlled the uprise and lateral migration of reducing and slightly acid hot brines from deeper crustal levels to supply the metals for the mineralization of the proto kupferschiefer deep fluids are mainly richer in zn than pb and richer in pb than cu mixing of such slightly acid fluids with slightly alkaline formation waters seawater caused a gradient in ph from about three to eight and in sulfide concentration most of the sulfide came from dissolved pyrite which was very light in sulfur isotopes this gradient controlled the sequential precipitation of bornite chalcopyrite chalcocite galena and sphalerite which is observed in a lateral and vertical zoning of these sulfides the fluids experienced a fractionation of the metals during migration over meter to kilometer distances from the tectonically controlled vents within the unconsolidated proto kupferschiefer close to the vents the sulfide deposits attained concentrations up to 2 zn pb cu the migration of the metals over large distances took place in unconsolidated sediment thus the major mineralization of the kupferschiefer has to be classed as an early diagenetic process

subsurface ground strain and fracture development associated with longwall mining abstract experiments employing physical modelling to study ground behaviour above longwall faces in different geological conditions are reported the development of subsurface fractures from longwall mining extractions and the resulting principal strain patterns are described the significance of the strain patterns in relation to the mining dimensions and the geological setting in terms of rock strength is discussed the effect of faulting on subsidence behaviour is also considered

numerical analysis and prediction of ground surface movement induced by coal mining and subsequent groundwater flooding abstract ground surface movement shows different features during mining and post mining period if the mine goaf is dry surface subsidence is observed in both periods if the mine goaf is flooded by groundwater however ground surface uplift can be observed although much smaller in amplitude compared to the preceding subsidence a numerical modeling strategy is proposed to predict uplift during the flooding process of an excavated coal mining area under complex geological conditions the modeling approach considers three phases virgin state before mining stage immediately after mine closure flooding phase the model considers elasto plastic material behavior including faults represented by interfaces in situ measurements are used for calibration of the model the oelsnitz abandoned coal mine is used for model validation and prediction the measured subsidences up to 17 m were reproduced as well as the uplift within the last 10 years with values between 0 5 2 0 mm year spatial distribution of uplift areas is well reproduced predictions up to the year 2051 show an increase in uplift velocity between 0 5 3 0 mm year and additional total uplift of up to 300 mm

apatite liquid partition coefficients for the rare earth elements and strontium abstract sixteen sets of apatite liquid partition coefficients dap liq for the rare earth elements ree la sm dy lu and six values for sr were experimentally determined in natural systems ranging from basanite to granite the apatite melt glass assemblages were obtained from starting glasses artificially enriched in ree sr and fluorapatite components these were run under dry and hydrous conditions of 7 5 20 kbar and 950 1120 c in a solid media piston cylinder apparatus an sem equipped electron microprobe was used for subsequent measurement of ree and sr concentrations in coexisting apatites and quenched glasses the resulting partition coefficient patterns resemble previously determined apatite phenocryst groundmass concentration ratios in the following respects 1 the rare earth patterns are uniformly concave downward i e the middle ree are more compatible in apatite than the light and heavy ree 2 dreeap liq is much higher for silicic melts than for basic ones and 3 strontium and therefore eu2 is less concentrated by apatite than are the trivalent ree the effects of both temperature and melt composition on dreeap liq are systematic and pronounced at 950 c for example a change in melt sio2 content from 50 to 68 wt causes the average ree partition coefficient to increase from 7 to 30 a 130 c increase in temperature on the other hand results in a two fold decrease in dreeap liq partitioning of sr is insenstitive to changes in melt composition and temperature and neither the sr nor the ree partition coefficients appear to be affected by variations in pressure or h2o content of the melt the experimentally determined partition coefficients can be used not only in trace element modelling but also to distinguish apatite phenocrysts from xenocrysts in rocks reported apatite megacryst host basalt ree concentration ratios 12 for example are considerably higher than the equilibrium partition coefficients which suggest that in this particular case the apatite is actually xenocrystic a reversal experiment incorporated in our study yielded diffusion profiles of ree in apatite from which we extracted a ree ca interdiffusion coefficient of 2 4 10 14 cm2 s at 1120 c extrapolated downward to crustal temperatures this low value suggests that complete ree equilibrium between felsic partial melts and residual apatite is rarely established

effects of arch structure in unconsolidated layers on fracture and failure of overlying strata abstract the conventional model for bearing structures was established based on the assumption that the effect of unconsolidated layers can be assumed to be similar to uniformly distributed loading while ignoring the variations in the loading stress imposed on the strata owing to an arch structure in the unconsolidated layers asul in order to make up for this deficiency in this study a mechanical model of the arch structure in the unconsolidated layers was established and the conditions for the formation of the arch structure in the unconsolidated layers were derived the evolution of the arch structure in the unconsolidated layers during excavation was simulated using two dimensional physical simulations mechanical models of the fractural characteristics of the key stratum ks and the voussoir beam structure vbs based on the arch structure in the unconsolidated layers were also developed the simulation results showed that when the thickness of the unconsolidated layers is larger than the critical thickness corresponding to the formation conditions an arch structure in the unconsolidated layers can form the critical thickness is affected by the mining width and the thickness of the bedrock strata in the absence of the arch structure in the unconsolidated layers the loading stress applied on the underlying strata can be assumed to correspond to uniformly distributed loading as is the case in the traditional model when affected by the arch structure in the unconsolidated layers the loading stress of the overlying strata is transferred to the abutment of the arch structure in the unconsolidated layers there is a stress decreased zone under the arch structure in the unconsolidated layers which can decrease the loading stress on the underlying strata in longwall face lw 7130 of the qidong coal mine in an area affected by an arch structure in the unconsolidated layers the fractural interval of the key stratum will increase and the key strata will be fractured successively upward however the sliding and rotational failures of the voussoir beam structure will not occur under the arch structure in the unconsolidated layers in the absence of the arch structure in the unconsolidated layers the fractural interval of the primary key stratum will decrease resulting in the complete breakage of the overlying strata and the sliding of the voussoir beam structure the results of the theoretical calculations were verified through field observations performed in longwall face 7130

geochemical and isotopic sr pb evidence of crust mantle interaction in acidic melts the tolfa cerveteri manziana volcanic complex central italy a case history abstract the tolfa cerveteri manziana volcanic complex tvc 3 5 ma located about 100 km north of rome represents the southernmost outcrop of the tuscan magmatic province the overlapping of tuscan acidic and roman alkaline volcanic rocks in the area makes it suitable for the study of the interaction between crustal and mantle derived melts major trace element rb sr ba y nb zr pb u and th rare earth element and sr and pb isotopic data on lavas quartz latites rhyolites and high silica rhyolites magmatic enclaves and metasediments from the basement allow the following conclusions to be drawn 1 a the tvc volcanic rocks are derived from the anatexis of a metasedimentary source having a composition similar to that of the metasediments present in the basement beneath the m amiata geothermal region at depths ranging from 1 4 to 3 2 km 2 b the anatectic magma during its differentiation by fractional crystallization interacted with two mafic magmas with differing sr and pb isotopic compositions and variable degrees of enrichment in incompatible elements the most differentiated rocks high silica rhyolites are the most highly contaminated 3 c the inferred mafic contaminants appear to be derived from a heterogeneous metasomatized mantle with isotopic and geochemical characteristics similar to those of the mantle which presently underlies the roman and campanian regions

horizontal stress under supercritical longwall panels abstract this study identifies the relative magnitude of horizontal stress change below a series of parallel longwall panels as a consequence of multi seam mining the investigation method yields an upper bound to the horizontal stress change by assuming that the fractured and caved overburden above the supercritical longwall panels is not able to support any lateral load finite element modelling was conducted to consider the effects of the following variables on the horizontal stress redistribution the ratio of the equivalent width of the extracted area to the overburden depth the ratio of the original horizontal to vertical in situ stress components and anisotropy in the rock mass behaviour the key findings of this research are that the maximum horizontal stress induced as a consequence of extracting multiple supercritical longwall panels will be within approximately 10 of the original in situ horizontal stress for the case of isotropic rock strata the magnitude of this horizontal stress may be larger in a stiff stratum if the overall sequence of strata consists predominantly of softer rocks anisotropy in the strata underlying the extracted longwall panels also causes an increase in the maximum horizontal stress induced into the immediate floor of the first extracted seam and an increase in the rate of dissipation of horizontal stress change with depth these findings indicate that a significant increase in horizontal stress relative to the original in situ horizontal stress should not be expected in multi seam mining situations the results from this study need to be considered in conjunction with predicted vertical stress distributions in order to accurately predict the overall stress environment likely to be encountered when conducting multi seam mining

determination of the rare earth element abundances in 29 international rock standards by instrumental neutron activation analysis a critical appraisal of calibration errors abstract a standard additions method has been used to calibrate an in house multi element rock standard for the analysis of the rare earth elements ree and th ta hf and co by instrumental neutron activation analysis this preliminary calibration with a precision of typically better than 7 1 has been refined by comparing our analyses of the four u s g s standard rocks agv 1 bcr 1 g 2 and gsp 1 with compiled analyses obtained by a critical survey of over 70 published references our standard calibration was adjusted by the average discrepancy between our analyses and published analyses for each element for all four u s g s standards the accuracy of this final calibration is estimated to be better than 5 absolute and it has been used to determine the above elemental abundances in 29 international rock standards five of the ree have been determined by interpolation from chondrite normalised plots

hybrid character and pre eruptive events of mt amiata volcano italy inferred from geochronological petro geochemical and isotopic data abstract a new geochronological and geochemical study was carried out to better constrain the petrogenesis and eruptive history of monte amiata a large pleistocene trachydacitic volcano of southern tuscany previous studies suggested a magma mixing origin between calc alkaline silicic melts from the tuscan magmatic province tmp and potassic mafic melts like those found in the roman magmatic province rmp two eruptive episodes the first at ca 300 kyr the second at ca 200 kyr were distinguished from the few available ages however both the involvement of a rmp like melt as mafic end member and the timing of volcanic activity remained to be ascertained the k ar ages obtained on plagioclase sanidine and glass separated from mt amiata volcanic rocks demonstrate the sanidine is the most suitable phase for k ar dating sanidine yields ages of 304 293 kyr for the basal trachydacitic unit btc 298 280 kyr in the domes unit dlc and unexpected older ages of 312 308 kyr for the more mafic summit lava unit oll a careful re examination of the literature ages together with those obtained in this study shows that they tend to a common age of ca 300 kyr whatever the volcanic unit we interpret this as a reset of the k ar chronometer in response to a consequent recharge of the silicic magma reservoir by hot mafic melts this recharge most probably triggered the first volcanic eruption of mt amiata magmas in our model we suppose an initially chemically stratified magma chamber the input of deep hot mafic melts reset the crystals clock and probably allowed the eruption of the huge amount of trachydacitic crystal mush we propose that the controversial btc unit could have emplaced during a non explosive eruption if we consider either pre eruption passive degassing or extrusion of the trachydacites as magmatic foam first pb isotopic data of mafic enclaves from the trachydacitic units together with major and trace elements and new sr and nd data support the magma mixing as the dominant process at the origin of the mt amiata volcanic rocks the similar lile hfse ratios evidenced in this contribution between the magmatic enclaves of mt amiata and rmp volcanic rocks together with their comparable sr nd and pb isotopic compositions definitively argue for the involvement of a rmp like melt in the mixing the mt amiata is thus indisputably a hybrid volcano between tmp and rmp in terms of petrogenesis and ages

surface collapse control under thick unconsolidated layers by backfilling strip mining in coal mines abstract surface subsidence induced by mineral extraction from underground mines can significantly affect the ecological environment and human life surface collapse is extremely hazardous and typically occurs without warning in china numerous surface collapses have occurred during mining operations in coal mines located under thick unconsolidated layers via analysis of the stability of the bearing structure arch structure in unconsolidated layers and key strata in rock strata based on their effects on strata movement our study reveals the formation mechanism of surface collapses and the roles played by two critical parameters mining length and mining height it is speculated that the bearing structure cannot be self stable and will collapse during longwall mining with increasing mining length and mining height as a result the ground surface will collapse on the longwall face gob accompanied by the failure of the bearing structure with these risks in mind this study proposes a backfilling strip mining method via determination of the appropriate longwall face length and mining height to guard against bearing structure failure and thus avoid surface collapse a field trial of the technique was conducted at a suitable chinese coal mine located under thick unconsolidated layers the maximum surface subsidence observed was only 0 369 m which is 92 less than the subsidence in longwall face lw 3a04 no surface collapse occurred during the mining process thus our results indicate that the proposed technique can successfully prevent surface collapse during longwall mining under thick unconsolidated layers

behaviour of trace elements during magmatic processes in the crust application to acidic volcanic rocks of tuscany italy abstract plio quaternary acidic rock suites from three volcanic centres of tuscany italy san vincenzo roccastrada and monte amiata are composed predominantly of rhyolitic and rhyodacitic ignimbrites the rocks are characterized by distinct enrichments particularly of k and rb and display considerable compositional differences among the various volcanic centres the volcanic rocks of roccastrada and most of s vincenzo were probably generated by partial melting of metapelitic rocks from the paleozoic basement of tuscany leaving a residue composed of biotite cordierite and quartz and sometimes plagioclase or garnet the enrichment of k and related elements can be attributed to selective contamination by fluids the other volcanic rocks including trachytes of mt amiata have also been affected by interaction with an upper mantle component probably k rich basaltic rocks a similar petrogenetic model can be applied to the granodiorite pluton of mt capanne elba which belongs to the same magmatic cycle since the variation trends observed in the tuscany volcanic rocks are similar to those reported from many acidic plutons it appears that crustal anatexis accompanied by interaction with upper mantle components has frequently played an important role in the genesis of the granitic rocks

palaeoenvironmental and palaeoclimatic implications of the late quaternary sediment record of vico volcanic lake central italy a 15 m long sediment core recovered from the lago di vico caldera lake in central italy has been the subject of macrofacies description and sedimentological organic carbon content grain size and mineralogy investigation the results have been integrated with the pollen data from the same core in order to provide a regional climatic and environmental history with inferences on past lake levels and on moisture and temperature regimes radiometric 14c and 40ar 39ar dating biostratigraphical considerations and tephra analyses provide a chronological framework and indicate that the sequence spans the last 90 000 yr several moist periods have been identified that were characterised by enhanced weathering by hydrolysis of the catchment rocks these alternated with relatively dry phases associated with lowering of lake levels the lowest hydrolysis efficiency of the whole record accompanied by notable aeolian deposition was attained during the last glacial phase but moisture conditions were such that the lake level did not decrease probably owing to reduced temperatures evidence for cool climate also emerges for the early pleniglacial the highest available moisture was achieved within the holocene at 5 kyr bp the late holocene does not show either increase of aridity or degradation of the vegetation cover until at least roman times copyright 2001 john wiley sons ltd

adakites without a slab remelting of hydrous basalt in the crust and shallow mantle of borneo to produce the miocene sintang suite and bau suite magmatism of west sarawak abstract we present new geochronological and geochemical data for neogene magmatism from west sarawak zircon u pb geochronology divides neogene magmatic rocks of west sarawak into a lower miocene west sarawak sintang suite with ages of c 19 to 21 ma and a middle miocene bau suite with ages of c 12 to 14 ma magmatism occurred in multiple short lived pulses from approximately 24 ma and was coeval with magmatic activity in nw kalimantan and east kalimantan the majority of but not all bau suite samples display adakitic chemistry while the west sarawak sintang suite is predominantly non adakitic there was no active subduction zone or subducted slab associated with this adakitic magmatism instead the geochemical diversity is consistent with the bau and west sarawak sintang suites representing mixtures of mafic mantle derived magma with felsic magma derived from remelting of hydrous mafic rock that had been emplaced into the lithosphere of borneo as arc basalt tens or hundreds of millions of years previously this origin is most evident in the main sintang suite of central borneo kalimantan which has preserved less contaminated examples of the mafic endmember this endmember resembles basaltic rocks from several locations across borneo suggesting that intraplate mantle derived magmatism was responsible for remelting older hydrated basaltic rocks in the crust

a process based approach to estimating the copper derived from red beds in the sediment hosted stratiform copper deposit model most estimates of the total tonnage of copper metal leached from footwall red beds to form sediment hosted stratiform copper deposits are based on the amounts of copper at ppm levels that might have been derived from the volume of red beds underlying given sediment hosted stratiform copper deposits that static calculation is replaced here with a process based approach in which the release of copper results from the progressive diagenetic alteration of the footwall aquifers by oxygen rich meteoric water driven by topographic recharge in highlands adjacent to the intracontinental rift basins hosting these deposits the total amount of liberated copper depends on the volume of meteoric water its oxygen content and the duration of the diagenetic leaching of copper estimates suggest that adequate amounts of copper may be derived from footwall red beds within reasonable periods of early and possibly more advanced diagenesis

trace element partitioning in pantellerites and trachytes abstract in order to investigate the effect of increasing melt peralkalinity on partitioning partition coefficients have been determined using neutron activation analyses of coexisting phenocrysts and glass of five samples from pantelleria spanning the range trachyte to pantellerite alkali feldspar partition coefficients for fe rb ba sr and eu vary with melt peralkalinity due to changes in melt polymerization and to the systematic increase in xor and decrease in xan of the feldspar in going from trachyte to pantellerite fe partition coefficients increase from 0 04 to 0 10 presumably because fe 3 increasingly substitutes in the feldspar tetrahedral site as melt activity of al declines and fe concentrations increase partition coefficients for trivalent light rees decrease and the partitioning pattern becomes flatter the most evolved samples having some of the lowest published values for feldspar the hundredfold decline in eu partition coefficients 2 5 to 0 024 and the decrease in the size of the positive partitioning anomaly are attributed to increasing eu3 eu2 in the melt as it becomes more peralkaline as well as to concomitant decrease in the ca content of feldspar as a result the behavior of eu during fractional crystallization of peralkaline suites is fundamentally different from that in metaluminous suites absolute abundances rise and the size of the negative eu anomaly changes little with fractionation beyond pantelleritic trachyte barium and strontium do not decline to extremely low concentrations in pantellerites as they do in highly evolved metaluminous rhyolites because the feldspar partition coefficients drop precipitously with peralkalinity similarly rb contents do not get large because the partition coefficient increases slightly 0 11 to 0 25 with peralkalinity and is sufficient to make rb only weakly incompatible in the feldspar dominated assemblage partition coefficients calculated for sr and ba from natural phenocryst matrix pairs can be gross over estimates in these feldspar rich felsic rocks if phenocrysts are zoned this effect is severe for assemblages with bulk distribution coefficients d greater than 4 even at very small crystal contents and for 4 d 2 it is significant if crystal contents exceed about 25 some of the very high values and much of the variability reported in the literature for ba and sr feldspar partition coefficients may be a result of this effect in contrast to feldspar partition coefficients for apatite and mafic phases change little with peralkalinity partition coefficients for rees and the compatible elements sc co and cr are all less than half those in fe rich clinopyroxene and olivine of similar composition in high silica rhyolite although absolute levels of partition coefficients are a function of melt polymerization the shapes of the ree partitioning patterns appear to be related to the composition of the clinopyroxene scandium is most strongly concentrated in clinopyroxene partition coefficient 27 60 having larger values in more fe rich compositions apatite shows a wide range in composition within the suite the concentrations of si fe rees and y increasing and mg ca and p decreasing in more evolved samples these trends however parallel those in coexisting glasses so that partition coefficients are essentially constant in peralkaline suites cs is the most incompatible of commonly analyzed elements but its great mobility during alteration and weathering limits its use as a differentiation index next in order of incompatibility are th u hf zr and ta which have small but finite values of d due to the partitioning of th and u into apatite 2 the accommodation of zr and hf by clinopyroxene 0 4 and titanomagnetite 0 2 and relatively high concentrations of ta in cossyrite and fe ti oxides the next most incompatible are the lightest and the heaviest rees and finally the middle trivalent rees and rb plots of pairs of relatively incompatible elements form straight line trends over large compositional ranges in peralkaline suites because the replacement of olivine titanomagnetite by cossyrite as the melt becomes more peralkaline causes little change in d the ree patterns of titanomagnetite and cossyrite are both approximately flat at values less than 0 1 and the relatively high titanomagnetite partition coefficients for ta 2 zr and hf when combined with the very low partition coefficients for these elements for olivine approximate the moderate partition coefficients for cossyrite

the geochemistry and petrogenesis of the lavas of the vulsinian district roman province central italy the vulsinian lavas are dominated by a suite of undersaturated leucite bearing basic to intermediate compositions the remaining lavas are mainly oversaturated and have shoshonitic affinities one hundred and thirty five samples have been analysed for major elements and most for 20 trace elements twenty seven lavas have been analysed for ree they are all perpotassic for the undersaturated lavas k2o na2o 2 8 and have very high lil element concentrations e g rb 400 800 ppm th 25 150 ppm ree reecho c 200 lree hree cho c 20 even in the most basic rocks

geologic volcanologic and tectonic setting of the vico cimino area italy abstract although the cimino and vico volcanic complexes are located close to each other in a structural low they belong to two different provinces cimino is connected to the tuscan roman anatectic magmatic province and vico to the roman campanian potassic alkaline province barberi et al 1971 marinelli 1975 the two volcanic centers lie on a basement formed by clays and sands of a miocene pliocene aged sedimentary cycle the mount cimino complex forms a central volcano composed of a series of rhyodacitic domes it was emplaced along a nw se trending fracture zone which can be followed for about 16 km cimino volcano was active from 1 4 m y to 0 95 m y ago eruption of rhyodacitic ignimbrites were preceded and followed by the emplacement of domes of the same composition fluid lavas of latitic and olivine latitic composition were emitted from the central volcano during the final phase of activity vico is a central volcano mainly composed of lava with a composite summit caldera it was emplaced along a ne sw trending fracture system the vico stratovolcano is formed by lavas of various compositions including phonolitic tephrites tephritic phonolites and slightly undersaturated trachytes the construction of the stratovolcano the most ancient exposed products of which have an age of 0 4 m y was followed by the eruption of four pyroclastic flows totalling several cubic kilometers which are dated at 0 3 0 15 m y the collapse of the caldera is most likely connected to the eruption of these pyroclastic flows the ring fractures of the caldera are associated with the emplacement of a pyroclastic unit most of which erupted along the inner northeast and north rim of the caldera post caldera activity is characterized by the emission of tephritic phonolitic and tephritic products that form the intra caldera stratovolcano named mount venere the vico cimino area northern latium located between the apennine chain and the tyrrhenian sea lies along the circum tyrrhenian belt that extends from northern tuscany to campania this zone has experienced post orogenic tensional movements since the middle miocene the teconic evolution of the tyrrhenian basin is closely associated with acid anatectic and potassic alkaline volcanism along the tyrrhenian margin of the apennines the age composition and geographic position of the volcanoes are controlled by different magnitudes of tensional tectonics and crustal thinning processes of the western margin of the apennine chain

the relationship between potassic and calc alkaline post orogenic magmatism at vico volcano central italy abstract post orogenic magmatism in italy took place during the plio pleistocene alkaline ultrapotassic magmas and sub alkaline magmas were erupted from closely spaced volcanoes throughout the central part of italy therefore central italy is one of the best site to study the relationship between calc alkaline and alkaline magmatism in complex tectonic regimes activity at vico volcano developed in three periods between 0 419 ma and 0 095 ma vico products overlie leucite free volcanic rocks of monte cimino volcano that have a variable affinity from high potassium calc alkaline to ultrapotassic most of the vico rocks are leucite bearing roman type ultrapotassic however during the first period leucite free silicic rocks are interbedded with leucite bearing products the early erupted vico magmas are isotopically distinct from the youngest magmas age corrected sr sr i 0 71110 0 71149 and nd nd i 0 51210 0 51211 isotope ratios fall within the gap between roman type including younger vico and monte cimino rocks some leucite free vico rocks contain orthopyroxene crystals and al contents in clinopyroxenes are lower than those in clinopyroxenes from roman type rocks these characteristics are however also found in monte cimino rocks at the beginning of the first period leucite free latites to trachytes and rhyolites with high sr i 0 71127 0 71149 were erupted trachytes and leucite bearing latites with lower sr i 0 71110 0 71138 were erupted later the younger trachytes have higher rb and lre element contents than older leucite free rocks with similar sio 2 contents furthermore the onset of leucite crystallization is marked by a change in 87 sr 86 sr and sio 2 sr isotope ratios and their time related variations as well as the presence of two different trends in some trace element variation diagrams define two distinct modes of magma differentiation magmas evolved along a stratigraphically lower trend at the beginning of the activity whereas they evolved differently along a stratigraphically upper trend later in the volcanic history modelling of geochemical and sr isotope variations indicates that along the lower trend fractional crystallisation was the main evolutionary process whereas along the upper trend mixing between a leucite free magma and a leucite bearing magma occurred during crystallisation the sr isotope compositions of rocks from the early stage of activity at vico suggest mixing between magmas having different petrological affinities a leucite bearing roman type magma and a high potassium calc alkaline magma

uth fractionation by fluids in k rich magma genesis the vico volcano central italy abstract the 230th 238u disequilibrium method has been applied to the potassic volcanic series of vico latium central italy the 3 main events of the recent volcanic activity have been dated using whole rock isochrons the lava flows of the main cone were erupted between 260 and 180 ky pyroclastic flows are dated around 90 ky and the final effusive activity mte venere around 60 ky these results are in good agreement with previous k ar ages the intense th u fractionation th u varying from 3 2 to 11 is apparently not related to processes of partial melting and crystal fractionation the th u fractionation is the most intense in basic terms of the first episode and is due to the percolation of a deep hydrothermal fluid which impoverishes u in different batches of primary magmas more limited th u fractionations in highly differentiated magma are due to u accompanied by sb and alkalies enrichments in the shallow magma chambers a time integrated model is proposed for the evolution of the 230th 232th ratio in the mantle source of vico it shows that th u and th ta fractionations are probably related to the bulk k u and th enrichment of the mantle of the roman province around 300 ky ago a metasomatic enrichment by a silicate melt is proposed to explain the anomalously high th u and th ta fractionations

fluid rock interactions in a geothermal rotliegend permo carboniferous reservoir north german basin abstract comprehensive data on the chemical composition of reservoir rocks and geothermal brines from the geothermal well doublet gro schonebeck north german basin drilled into a rotliegend sedimentary and permo carboniferous volcanic rock reservoir were sampled over the past years they were characterized with respect to their major and minor elemental composition including various isotope ratios the study considered the impact of drilling and reservoir operations on fluid composition and aimed at determining fluid rock interactions to gain information on fluid origin and hydraulic pathways the highly saline fluids up to 265 g l tds show 18 o and d of water 2 7 5 6 and 3 1 15 respectively as well as 34 s of sulfate 3 6 5 and 87 sr 86 sr ratios 0 715 0 716 that resemble rotliegend brines from an area located around 200 km in the west the altmark halogen ratios indicated that brines developed predominantly by evaporation of meteoric water primary brine together with halite dissolution brine secondary brine indication for mixing with zechstein brine or with younger meteoric water was not found no geochemical distinction was possible between fluids deriving from different rock formations dacites or sedimentary rocks respectively this is due to the evolution of the sediments from the effusive rocks resulting in a similar mineralogical and chemical composition and due to a hydraulic connectivity between the two types of rock this connection existed probably already before reservoir stimulation as indicated by a set of faults identified in the area that could connect the rotliegend formation with both the volcanic rocks and the lower units of the zechstein additional geochemical indication for a hydraulic connectivity is given by 1 the very high heavy metal contents mainly cu and pb in fluids and scaling that derive from the volcanic rocks and were that were also found in increased amounts up at the zechstein border kupferschiefer formation 2 the 87 sr 86 sr isotope ratios of fluid samples correspond to the ratios determined for the sedimentary rocks indicating that initially the fluids developed in the sedimentary rocks and circulated later when faults structures were created by tectonic events into the volcanic rocks

a multistage origin for kupferschiefer mineralization new re os age determinations on mineralized material from the polish kupferschiefer elucidate the timing of mineralization and thus the likely mechanisms of ore deposition three mineralization parageneses were analysed a chalcocite as pore space filling in sandstone b disseminated cu mo mineralization in shale and c massive bedded copper sulphides the resulting ages fall into two ranges 245 2 1 6 264 7 1 8 ma and 162 3 0 8 184 3 2 2 ma these results substantiate previous age determinations although no upper triassic ages were found in this study some of the younger ages for the mineralization could represent alteration and recrystallization of existing sulphides the results confirm that mineralization took place in several stages from soon after kupferschiefer sediment deposition in the upper permian and for at least 100 m y after until at least the cretaceous the genesis of the mineralization can be explained by the episodic release of hydrothermal fluids from the subsiding adjacent southern permian sedimentary basin although the relative importance of each successive mineralizing event for introducing additional metals is as yet unknown

isotope and chemical microsampling constraints on the history of an s type rhyolite san vincenzo tuscany italy fine scale heterogeneities in strontium isotope ratios 40ar 39ar ages and chemical com sition have been determined for individual mineral grains and enclaves in the rhyolites of san vincenzo italy the rhyolites are peraluminous with phenocrysts of alkali feldspar piagioclase biotite and cordierite and have previously been divided into two groups on the basis of whole rock major element chemistry group b lavas are distinguished from group a in having higher mgo and cao contents as well as containing two pyroxenes and chilled latite enclaves the group b lavas show textural evidence for d sequilib um such as resorption and sieve zones in feldspars laser fusion 40ar 39ar dating of individual alkali feldspar crystals suggests that the eruption of these rhyolites took place 4 38 0 04 ma though small amounts of excess argon are present in subhedral and cloudy crystals the groundmass in the group a sample has a higher initial r7sr 86sr 0 725 than that of the group b 0 7 13 the sr isotope compositions of chemically and texturally characterized individual grains reveal marked disequilibrium between minerals and the host glass as well as within grain zonation the feldspars and coarse grained biotites have initial 87sr 8 sr that are intermediate between those of the group a and b glasses with alkali feldspar generally having higher initial 87sr 86sr ratios than plagioclase chilled latite enclaves which are present in only the group b lavas have relatively low initial 8 sr 86sr ratios in the range 0 7082 0 7088 the mineral chemistry and isotope data indicate that restite does not form a significant portion of the crystalline assemblage and therefore cannot be the source of the strontium isotope dis equilibrium xenocrysts mixed into the rhyolite from a mafic magma were identified as clinopyroxene megacrysts clinopyroxene orthopyroxene clots orthopyroxene plagioclase clots and plagioclase with extensive sieve textures these grains all have relatively low initial 87sr 86sr ratios other grains that may be xenocrysts are cordierites with cores containing inclusions of biotite spinel and sillimanite and alkali feldspars with excess 4 ar the strontium isotope di quilib um in phenocrysts of plagioclase alkali feldspar and biotite is attributed to a changing melt chemistry that was too rapid for strontium diffusive equilibration a mode1 for the san vincenzo magma chamber is proposed in which the sr isotope evolution of the group b rhyolites is due to magma mixing of a crustal melt with latite magma containing unra diogenic strontium the variable initial strontium isotope compositions of group a phenocrysts may be due to assimilation or crystallization along the interface between mingled group a and b magmas

k richterite olivine phlogopite diopside sanidine lamproites from the afyon volcanic province turkey middle miocene volcanic activity in the afyon volcanic province eastern part of western anatolia is characterized by multistage potassic and ultrapotassic alkaline volcanic successions the volcanism is generally related to the northward subduction of the african plate beneath the eurasian plate in afyon the middle miocene volcanic products consist of melilite leucitite tephriphonolite trachyte basaltic trachyandesite phonolite phonotephrite tephriphonolite and lamproite rocks near surface emplacement and relatively quiescent subaerial eruptions of lamproitic magma produced different emplacement forms such as dome plug shaped bodies and lava flows showing variation in volume and texture the mineralogical constituents of the lamproites are sanidine olivine 77 mg no 81 phlogopite 74 mg no 78 k richterite clinopyroxene 74 mg no 78 with accessory apatite calcite and opaque minerals afyon lamproites resemble mediterranean type si rich lamproites their compositional range is 50 52 wt sio2 4 8 wt mgo and they display a typical lamproitic affinity chondrite normalized ree patterns exhibit enrichment in lree relative to hree la yb cn 15 3 17 0 they show extreme enrichment in lile relative to primitive mantle values and troughs of nb and ti the lamproites give a range of high initial 87sr 86sr ratios and low 143nd 144nd ratios the geochemical and isotopic characteristics suggest that lamproitic magma is derived from highly metasomatized mantle the enrichment history may include metasomatic events related to subduction as in other active orogenic areas of the mediterranean

red bed and basement sourced fluids recorded in hydrothermal mn fe as veins sailauf germany a la icpms fluid inclusion study the hydrothermal mn fe as vein mineralization at sailauf germany hosts a complex sequence of oxide and carbonate minerals that record a protracted fluid history the mineralization is related to a major unconformity that separates permian zechstein sedimentary rocks from underlying variscan crystalline basement the hydrothermal veins contain two principal mineralization stages which are mn oxides associated with calcite and hematite associated with mn calcite the fluid evolution of the hydrothermal system has been reconstructed from fluid inclusion petrography microthermometry and la icpms microanalysis coupled with stable isotope geochemistry of carbonate and oxide minerals the fluid inclusions are high salinity sodic calcic brines and the bulk fluid properties show no major differences between the mn oxide and the hematite stage la icpms analysis of major and trace elements demonstrates that the mineralization formed from chemically distinct fluid pulses characterized by variations in their k li b pb and zn concentrations the fluid that precipitated the mn oxide stage has anomalous pb zn and li b ratios which closely resemble fluids found in fracture fillings in red beds of the permian rotliegend basin by contrast the fluids associated with the hematite stage have pb zn and li b ratios typical of crustal fluids that were derived from interaction with crystalline basement both fluids possess characteristic element ratios including cl br but variable absolute concentrations of most metals this suggests that both fluids were modified by mixing with a common metal depleted brine that had a similar cl br ratio most likely a formation water from the overlying zechstein sedimentary rocks the sailauf mineralization provides insight into the protracted post variscan fluid evolution at the basement cover interface the compositionally anomalous fluid that precipitated the mn oxides is comparable to brines derived from interaction with red beds and likely represents the ore fluid of kupferschiefer type sediment hosted cu deposits conversely the fluid that deposited the hematite mineralization resembles fluids that typically form basement and sediment hosted pb zn deposits

study on the structural characteristics of the overburden under thick loose layer and thin bed rock for safety of mining coal seam the geological conditions of the first working face at the baodian coal mine of the yanzhou mining district in china are examined to determine the feasibility of modifying coal pillars that prevent water seepage to those that prevent sand flow the coal pillars are under a thick loose layer of sediment and thin layer of bedrock after analyzing the structure of the rock and soil mass above the coal seam the thickness of the bedrock bottom clay layer and bottom aquifer of two detecting roadways are discussed at the center of the xingxing anticline the thinnest of the bedrock is only about 30 m however the thickness of the bottom clay layer is at least 10 m and more and the jurassic rock sandstone is the thinnest with low levels of water and a layer of weathered material the bottom aquifer has low water yield with no pressure the similarity theory is used to construct a prototype with 30 m high bedrock the conclusion is that the height of the caved zone height is about 21 3 m after the complete extraction of no 3 coal seam and the results are in agreement with the experimental data the results show that it is feasible for the first working face to use a coal pillar to prevent sand flow moreover the findings in this study can act as an important reference source for predicting the height of the overburden that would cause damage and reasonable advancement of mining that is considered to be safe under similar geomining conditions

geochemical characteristics of the south tuscany italy volcanic province constraints on lava petrogenesis abstract three suites of volcanic rocks from radicofani mts cimini and mt amiata south tuscany italy were analyzed for major and trace element contents and sr isotopic composition all samples are silica saturated hypersthene normative and some are peraluminous samples from radicofani and the less evolved mts cimini samples have high mg numbers 74 5 66 3 consistent with the fosteritic rich nature of their olivine phenocrysts and high bulk rock abundances of ferromagnesian trace elements all samples are highly enriched in light ree 150 315 chondrites compared to heavy ree 9 15 chondrites and have negative eu anomalies eu eu 0 92 0 44 87 sr 86 sr ratios are high and variable radicofani 0 7137 0 7150 mts cimini 0 7128 0 7138 mt amiata 0 7119 0 7131 a distinctive feature of the radicofani samples is that with decreasing age the rocks increase in k2o content but decrease in la ce these south tuscany rocks have geochemical characteristics of the calc alkaline and alkaline series namely in addition to the high k rb cs ba and lree contents they have high ratios of incompatible elements relative to the high field strength ions such as ti zr hf nb and hree when compared to an estimated primitive mantle composition in general the geochemical characteristics of south tuscany volcanics are consistent with mixing between crustal derived material and mantle derived magma the mantle derived component was unusually rich in radiogenic sr and incompatible elements and had geochemical features similar to basic lavas of the high k series in the roman province

evolution and effect of the stress concentration and rock failure in the deep multi seam coal mining supports crushing accident occasionally occurs in the protected seam exploitation of deep multi seam coal mining structure and results in adverse effect to the production to prevent its recurrence in a newly developed working field a 3d numerical extraction model was built based on the geologic and mining conditions of jining coal mine to evolve the changes state and characteristics of the reconstructed vertical and lateral stress in rock interlayer after protective seam exploitation stress release and increase zones of this mining structure were separated mining induced localized stress concentration and the interlayer rock failure behavior were explored the action of concentrated stress on the hydraulic supports in protected seam was discussed upon the major stress redistribution using the infinitesimal strain method a mechanical model was created to further explore from the vertical and lateral directions the cause and mechanism of localized stress concentration and rock failure behavior in rock interlayer the field investigation was finally performed to verify the numerical and mechanical results and the essential control measures were proposed to prevent this accident key findings of this study bring some new insights into the deep multi seam coal extraction and help to promote a more reliable underground mining

application of 3d laser scanner optical transducers and digital image processing techniques in physical modelling of mining related strata movement a physical testing protocol for modelling mining related problems has been presented a new method for monitoring fracture propagation pattern has been introduced laser based and optical devices have been used for physical modelling of subsidence multiple seam subsidence has been measured by photogrammetry dic analysis optoncdt and 3d tls

evidence for mantle metasomatism an oxygen and strontium isotope study of the vulsinian district central italy this paper presents new o and sr isotope data for lavas from the northern part of the roman perpotassic province the samples comprise the tephritic leucititic to leucite phonolitic lavas and the saturated lavas from the vulsinian district the olivine leucite melilitite of san venanzo and the kalsilite diopside melilitite of cupaello previous oxygen isotope work on the lavas of the vulsinian district suggested crustal contamination of normal mantle derived magmas the new data cover the ranges previously found o and sr isotope ratios of evolved lavas of the undersaturated suite indicate assimilation in variable amounts of up to ca 10 of continental crustal material the saturated lavas probably assimilated large amounts up to ca 50 of crust lavas chemically identified as corresponding to little modified mantle derived liquids are high in both87sr 86sr and 18o 0 7103 0 7107 7 8 to 9 4 vulsini 0 7104 12 3 san venanzo and 0 7112 14 4 cupaello these high values are interpreted to have been inherited from a metasomatized parental mantle hydrous fluids enriched in large ion lithophile elements and high in 18o and87sr 86sr are thought to have mixed with mantle of normal 18o and87sr 86sr the fluids probably origi dehydration of continent derived sediments which were subducted beneath a mantle wedge in the continent continent collision of the corsica sardinia block and the adriatic italian plate this hypothesis is supported by pb and nd isotopic evidence and is probably valid for the entire roman province

mass balance evaluation of the late diagenetic hypothesis for kupferschiefer cu mineralization in the lubin basin of southwestern poland ments of the early permian rotliegende sequence fig lb and c the kupferschiefer shale hosts base and precious metal mines that have been important in the development of mining technology and the european mining industry whether the kupferschiefer and adjacent strata were mineralized uring their deposition syngenetic early diagenetic hypothesis or later by brines expelled from the red bed filled basins late diagenetic hypothesis has been a matter of continuing debate see jowett 1991 a data set derived from over 400 cored drill holes