the stone source of predynastic basalt vessels mineralogical evidence for quarries in northern egypt abstract about 22 of all predynastic stone vessels are basaltic in composition as a result of their nondescript petrography the raw material source of these common artefacts is challenging to determine electron microprobe analyses of pyroxene and plagioclase in 0 0001 g samples from nine predynastic basalt vessels indicate compositions consistent with an origin from haddadin basalt outcrops west of cairo the raw material or finished vessels were transported 600 km up the nile to abydos and qena bypassing closer basalt sources in middle egypt these results and stylistic considerations indicate that a major vessel manufacturing industry existed in northern egypt but the location of the workshops has yet to be found quarrying of haddadin basalt for vessels spanned at least 900 years accessibility and breakage characteristics of the basalt help account for its prolonged and widespread use but basalts in middle egypt may have similar properties suggesting that either tradition or some unidentified physical quality was also important this study underscores the utility of the electron microprobe for fingerprinting basalt flows the factor equations and discrimination diagrams allow the stone source for egyptian basaltic artefacts to be determined on a more routine basis it is not necessary to re sample the quarries and obtain hundreds of mineral analyses to determine a source miniscule amounts of material are required making the method applicable even to extremely valuable antiquities

chert from the munsungun lake formation maine in palaeoamerican archaeological sites in northeastern north america recognition of its occurrence and distribution abstract numerous fluted point palaeoamerican sites in the northeast contain significant numbers of chert artefacts whose origin is from the munsungun lake formation in northern maine these sites include adkins bull brook dam hedden lamareau michaud morss munsungun lake three sites neponset plenge point sebago searsmont spiller farm vail vail kill two sites wheeler dam two sites and whipple lithic materials in order of decreasing importance at these sites include 1 chert whose physical characteristics are wholly consistent with chert outcrops and quarries near munsungun lake 2 a variety of cherts whose physical characteristics are inconsistent with outcrops and quarries near munsungun lake 3 a spherulitic flow banded rhyolite 4 miscellaneous fine grained igneous rocks 5 clear or milky quartz 6 miscellaneous very fine grained or fine grained metamorphic rocks portions of all collections contain artefacts which are completely weathered and which are not assignable to any specific rock type and cannot be classified as to specific rock type we developed a hierarchy to classify munsungun lake chert ranging from hand specimen characteristics to polarized light microscopy and x ray diffraction to chemical analysis we conclude that hand specimen characteristics combined with polarized light microscopy are viable techniques for assigning munsungun lake formation provenance three distinctive hand specimen features are sedimentary lamination organic burrow structures and colour variation using these chert quarries and outcrops in the geographic vicinity of munsungun lake may be assigned to one of the following categories a structureless grayish red dusky red blackish red or dark reddish brown b laminated grayish red dusky red blackish red or dark reddish brown chert with varve like laminations c mottled or colour laminated red and dark grey or mottled red and greenish grey chert d colour laminated and burrow mottled chert e greyish to blackish laminated chert f dark grey to black structureless or weakly and thinly laminated g olive grey to olive black laminated chert which is locally pyrite rich the nature of weathered surfaces may be a diagnostic tool for assistance in recognizing munsungun chert chemical weathering tends to produce much lighter colourations and enhances the visibility of sedimentary structures munsungun cherts tend to weather to a very light tan very light grey or greyish white radiolarians are uncommon chert palaeoquarries are numerous in the munsungun lake area they are of two types one type occurs on topographically flat areas here the quarries are small 1 5 m to large 5 30 m size depressions within and along outcrops in plan view these range in shape from roughly circular to broad ovals along the margins of these depressions are piles of poorly sorted worked and discarded debitage these tailing piles are generally less than 1 m in height but exhibit wide variations in areal extent and shape larger tailing piles overlap one another suggesting that they have experienced more than one episode of growth due to repeated quarry activity the second quarry type occurs on steeper slopes these are near vertical quarried faces which range from 1 to nearly 3 m in height excavation here has occurred both inwards to the slope and downwards small cavern or adit like mines have not been recognized

comment on neutron activation analysis of stone from thechadron formation and a clovis site on the great plains by hoard et al 1992 abstract comments are made on the previously published paper by hoard et al neutron activation analysis of stone from thechadron formation and a clovis site on the great plains journal of archaeological science 19 655 665 1992 a number of questions and their implications are discussed

chemical characterization of obsidians from different mediterranean sources by non destructive sem eds analytical method the aim of our research is to check the sem eds non destructive analytical method for discriminating and locating the possible sources of obsidian artefacts moreover in order to obtain a significant discrimination of mediterranean obsidians we analysed samples collected from outcrops of the major sources monte arci sardinia and palmarola lipari pantelleria gyali and melos islands all samples were analysed by both xrf whole rock and sem eds glass and microliths microphenocrysts the xrf analysis reveals that major elements discriminate obsidian the discrimination using major elements is very useful because the amount of trace elements is lower than the detection limit of a si li ed detector the major elements particularly sio2 al2o3 cao na2o and k2o of obsidian glass discriminate the six main mediterranean sources our work demonstrates therefore the possibility of discriminating different provenance of obsidian artefacts using sem eds by means of a relatively rapid effective and above all non destructive method

hydration during uplift is recorded by reset rb sr whole rock ages the garn fadryn sub volcanic intrusion of n wales gives a u pb zircon age of 4533 2 2 ma this is the first reliable emplacement age from the welsh caradoc volcanic province proving that the rb sr whole rock age of 392 32 ma does not date intrusion but reflects resetting during early devonian low grade metamorphism resetting in this setting is chemically controlled and is a function of disturbance during water rock interaction it is not analogous to the predominantly thermally controlled resetting of k ar systems post volcanism rb sr whole rock secondary ages in this region have a mean age of 399 9 ma and record a specific event which is the time of hydration it is proposed that this event was triggered by uplift which opened fractures increased permeability facilitated formation of secondary hydrated minerals and reset the rb sr system this model for resetting should have widespread applicability to other volcanic provinces affected by low grade metamorphism

the transformation of amphibolite facies gneiss to charnockite in southern karnataka and northern tamil nadu india amphibolite facies metamorphic grade gives way southward to the granulite grade in southern karnataka as acid gneisses develop charnockite patches and streaks and basic enclaves develop pyroxenes petrologic investigations in the transitional zone south of mysore have established the following points 1 the transition is prograde amphibole bearing gneisses intimately associated with charnockite at kabbal and several similar localities are not retrogressive after charnockite as proved by patchy obliteration of their foliation by transgressive very coarse grained charnockite high fluorine content of biotite and amphibole in gneisses and high large ion lithophile element contents in gneisses and charnockites these features are in contrast to very low fluorine in retrogressive amphiboles and biotites very low large ion lithophile element contents and zonal bleaching of charnockite in clearly retrogressive areas as at bhavani sagar tamil nadu 2 metamorphic temperatures in the transitional areas were 700 800 c pressures were 5 7 kbar and h2o pressures were 0 1 0 3 times total pressures based on thermodynamic calculations using mineral analyses dense co2 rich fluid inclusions in the kabbal rocks confirm the low h2o pressures at the first appearance of orthopyroxene farther to the south in the nilgiri hills and adjacent granulite massif areas peak metamorphic temperatures were 800 900 c pressures were 7 9 kbar and water pressures were very low so that primary biotites and amphiboles those with high f contents are rare 3 the incipient granulite grade metamorphism of the transitional areas was introduced by a wave of anatexis and k metasomatism this process was arrested by drying out under heavy co2 influx charnockites so formed are hybrids of anatectic granite and metabasite of metabasite and immediately adjacent gneiss or are virtually isochemical with pre existing gneiss despite gross recrystallization to granulite mineralogy these features show that partial melting and metasomatism are attendant rather than causative in charnockite development copious co2 from a deep crustal or mantle source pushed ahead of it a wave of more aqueous solutions which promoted anatexis granulite metamorphism of both neosome and paleosome followed the process is very similar to that deduced for the madras granulites by weaver 1980 the massif charnockites for the most part extremely depleted in lithophile minor elements show many evidences of having gone through the same process

isotopic datings of reddish granitoids in southern varmland southwestern sweden three reddish granites from the gneiss complex of south western sweden have been dated with the u pb and one of them also with the rb sr method the gneiss complex consists of two mega units separated by a tectonic discontinuity the two granites from the western mega unit the western gneiss segment yield zircon upper intercept ages of 1552 36 38 and 1499 36 36 ma 2 these ages are minimum estimates of the intrusion ages but the difference between the obtained and the true age is probably small this assumption is based on studies of the morphology and internal structures of the zircons and also on air abrasion experiments the third granite is located in the eastern mega unit the eastern gneiss segment and forms a number of small massifs 50 m in diameter the u pb and rb sr ages agree within the limits of the errors 1140 52 54 ma upper intercept and 1104 100 ma respectively but the obtained age is nevertheless dubious thin section studies reveal that the zircons are heterogeneous with different types of material making up the inner and outer parts electron microscopic studies as well as air abrasion and leaching experiments were performed to establish possible differences in age and chemistry between the inner and outer parts the central parts are made up of almost pure zrsio4 whereas the outer parts are layered with alternating pure zrsio4 layers and layers rich in trace elements the leaching and air abrasion data do not indicate any age difference between the inner and outer parts this supports the validity of the upper intercept age as an intrusion age the rb sr age is questionable since the obtained initial87sr 86sr ratio is as low as 0 7027 this cannot possibly be true for a felsic late proterozoic granite a plausible explanation could be a rotation of the isochron due to migration of rb and sr during a low grade event this event is also responsible for the alteration of the biotites and plagioclases these data provide additional evidence for extensive ensialic magmatism in the period succeeding the lithosphere forming event

age relationships in the proterozoic high grade gneiss regions of southern norway reply to discussion and comment by weis and demaiffe

resetting of rb sr whole rock isochrons during sveconorwegian low grade events in the gjerstad augen gneiss telemark southern norway abstract the gjerstad augen gneiss comprises a single igneous body that shows intrusive relationships to the surrounding older telemark gneisses the formation of the gneissic structure and augen texture was due to mylonitic deformation along a major shear zone the porsgrunn kristiansand fault zone the augen gneiss can be divided petro graphically into green grey both pyroxene bearing and pink types samples from three locations were analysed isotopically two distinct at 2 level groups of ages were obtained which are interpreted as a 1250 ma cooling after high temperature deformation and formation of retrogressive corona structures b 1080 ma resetting of whole rock systems during low grade mineral alteration by hydrous fluids at 900 ma there was further isotopic disturbance during low grade alteration related to the intrusion of pegmatite veins the significant age differences are not related to colour grade of samples and significantly different ages have been found in the same rock body within a single locality as the gjerstad augen gneiss was intruded before 1250 ma into a previously existing gneissic terrain the gneiss forming event and associated upper amphibolite facies metamorphism in the gjerstad region is constrained to be pre 1250 ma i e pre sveco norwegian

archean mantle heterogeneity and the origin of diamondiferous eclogites siberia evidence from stable isotopes and hydroxyl in garnet data are presented for the o isotopic composition of clinopyroxene and garnet the c isotopic composition of diamond and the oh content of garnet from eclogite xenoliths brought to the surface by the udachnaya kimberlite pipe yakutia siberia radiogenic isotopic data suggest that the eclogites could have been derived from an ultradepleted mantle at approximately 2 9 ga pearson et al 1995 snyder et al in preparation o isotopic compositions generally show equilibration between the eclogitic minerals cpx grt 0 11 0 41 and have 18 o smow for both garnet and clinopyroxene that lie near the range of accepted mantle values of 5 7 0 7 however several eclogites indicate significant deviations from this range at higher values of 6 8 7 0 also two eclogites lie at the lower end of the mantle range at values of 4 8 and 5 0 all in clinopyroxene c isotopic compositions of diamonds all have 13 c pdb in the range of 1 to 7 and are centered at approximately 5 also within the range of accepted mantle values the oh contents of the garnet are generally between 0 and 22 ppm as h 2 0 although two samples exceed 70 ppm this range of oh is similar to eclogitic garnet from the kaapvaal craton of southern africa the mantle c isotopic values of associated diamonds the majority of o isotopic data and the low oh content of the minerals although suggesting a general lack of crustal participation in the formation of the udachnaya eclogites do not rule out the participation of some ancient crustal material that these eclogites include both 18 o enriched and 18 o depleted types suggests that the protoliths may have been overprinted by both low and high temperature hydrothermal events cf jacob et ai 1994 a positive correlation between 18 o and 87 sr 86 sr allows the interpretation of these eclogites as representing a cross section of an archean ophiolite however the lack of a single coherent grouping on a plot of 18 o vs 87 sr 86 sr suggests that if the udachnaya eclogites were derived from oceanic crust they cannot be cogenetic and must represent at least two separate ophiolite sequences conversely if the eclogites are found to be cogenetic then a totally different process affected their formation and a probable metasomatic mechanism was operative because of the total lack of correlation of 18 o with other geochemical parameters we find no compelling evidence that all eclogites are derived ultimately from oceanic crust

obsidian from pulo di molfetta bari southern italy provenance from lipari and first recognition of a neolithic sample from monte arci sardinia twenty four obsidian artefacts of the neolithic age were found at the large karstic doline of molfetta near bari along the southern italian adriatic coast non destructive chemical analyses of the glass by sem eds allowed their source rock regions to be determined twenty three of the studied artefacts had been traded from the island of lipari only one sample had a glass composition and microphenocrysts biotite pyroxene and feldspar that indicate provenance from the monte arci area of sardinia in particular from the perdas urias sc outcrops the attribution of this artefact to sardinia enlarges the geographical pattern of monte arci obsidian exploitation and distribution from island to southern italy during the middle to late neolithic

crystal structure refinement of na bearing clinopyroxenes from mantle derived eclogite xenoliths nine omphacitic clinopyroxenes with a jadeitic content between 25 and 57 from the udachnaya and zagadochnaya diamond bearing kimberlites were investigated using single crystal x ray diffraction electron microprobe analysis and mossbauer and infrared spectroscopy crystal structure refinements incorporating constraints from chemical analyses and mossbauer data show a significant concentration of vacancies at the m2 site in three of the samples the cell volumes of the non stoichiometric samples plot below the linear trend defined by stoichiometric diopside jadeite compositions where the deviation from the linear trend is positively correlated with the concentration of vacancies charge balance appears to be achieved primarily through substitution of al3 for mg2 on the m1 site which causes a contraction of the m1 site volume compared to stoichiometric clinopyroxenes with the same composition vacancies are not associated with oh incorporation as the sample with the highest concentration of vacancies contains only 89 ppm wt h2o significant hydrogen loss through iron oxidation during ascent is ruled out based on the low fe3 concentrations h content in omphacite samples from kimberlites could provide a sensitive tool for determining f h2o during diamond formation

chipped stone artefacts source areas and provenance studies of the northern belize chert bearing zone previous studies of the northern belize chert bearing zone which was widely exploited by the ancient maya for the production of chipped stone artefacts have suggested that chert from different parts of this zone might be chemically distinct this hypothesis is tested with an expanded data base of neutron activation analyses of raw chert and chalcedony from throughout northern belize these data together with data from previous studies indicate that the chert bearing zone is one chemically homogenous source and that meaningful distinctions cannot be made between different areas of the zone a more specific lithic source hypothesis is that the black chipped chert and chalcedony artefacts found at coastal maya sites in northern belize may come from a localized source area exhibiting this unique visual characteristic however the analysis conclusively demonstrates that these artefacts fall within the range of chemical variation of other chert and chalcedony from northern belize further the study yields convincing evidence that the colouration of these black lithic artefacts is caused by a weathering phenomenon and hence is not indicative of a particular source location

charge contrast imaging of fine scale microstructure and compositional variation in garnet using the environmental scanning electron microscope gaseous secondary electron gse imaging of eclogite garnets under the environmental scanning electron microscope esem at low chamber gas pressures reveals detailed image contrast patterns charge contrast images cci that are not present in back scattered or secondary electron images image intensity is a function of the amount of surface charge accumulation successful acquisition of cci depends on frame size and beam scan rate at a given chamber gas pressure and beam current images are obtained in a few seconds and are stable and reproducible cci patterns do not correlate with cracks or grain boundaries but do correspond closely to variations in major element composition both in the form of concentric growth zoning and branching linear features interpreted as cracks that have been healed by new garnet growth causes of cci are not yet well understood but may be related to variations in lattice defect density and their influence on charge trapping and dissipation these in turn influence the rate of charge build up at or very close to the specimen surface one interesting possibility is that cci images detect vacancies related to non homovalent coupled substitutions involving for example ree and hydroxyl so the method offers a way of imaging the distribution of these trace species in garnets the cci images are rich in microstructural detail and offer the potential for rapid high resolution low noise reconnaissance mapping of intragranular microstructure and compositional variation in both natural and synthetic garnets

quantitative analysis of trace oh in garnet and pyroxenes to calibrate infrared ir spectroscopy for quantitative analysis of trace structural oh in specific minerals we have determined concentrations of h in pure separates of mantle derived pyrope garnet 56 6 ppm h 2o by weight augite 268 8 ppm h 2o and enstatite 217 11 ppm h 2o by manometry after heating the samples and extracting h 2 gas under vacuum ir spectroscopy confirmed the presence of intrinsic oh in these samples prior to extraction and indicated between 86 and 100 removal of h during the extraction procedure the integral specific absorption coefficients of 1 39 0 14 l 7 09 0 32 and 15 6 0 94 ppm h 2o cm 2 for pyrope augite and enstatite respectively allow precise spectroscopic determination of the oh content of upper mantle garnets and pyroxenes to concentration levels of a few parts per million uncertainties in accuracy depend on mineral composition and characteristics of the oh absorption spectrum and are estimated to range between 10 and 50

sodic amphibole exsolutions in garnet from garnet peridotite north qaidam uhpm belt nw china implications for ultradeep origin and hydroxyl defects in mantle garnets two types of amphibole exsolution lamellae were discovered in garnet from a few garnet peridotites from the north qaidam ultrahigh pressure metamorphic belt northern tibet nw china the amphibole lamellae are strictly oriented in four directions corresponding to the isometric form 111 i e octahedron planes of garnet observations by transmission electron microscopy tem show that amphibole lamellae are topotaxtially concordant with the host garnet and possess 9 8 to 10 a lattice c spacing electron microprobe analysis reveals that these exsolved amphibole lamellae are high in na and ti the tem observations and recalculated compositions indicate that the oriented amphibole lamellae exsolved from original supersilicic majorites with high concentrations of na2o 0 3 wt and hydroxyl up to 1000 ppm by weight these results imply that the host garnet peridotites were formed at depths greater than 200 km and that garnet can be an important reservoir of water at such depths in the mantle

hydroxyl contents of accessory minerals in mantle eclogites and related rocks infrared spectra in the region 3000 to 3800 cm 1 have been measured on coesite kyanite sanidine and rutile occurring in inclusions of eclogite and on garnet and spinel in an inclusion of alkremite from south african kimberites coesite and sanidine contain virtually no h 2o or oh although one sanidine crystal was observed to contain abundant h2o apparently as fluid inclusions of molecular h2o kyanite contains significant oh consistent with previous results for similar samples corundum gives no indication of the presence of h 2o or oh rutile containing significant amounts of fe cr al and nb also contains significant amounts of structural oh garnet in alkremite contains small amounts of molecular h 2o whereas the spinel coexisting with this garnet gives no indication of h 2o or oh indicating that the spinel structure is not able to accommodate significant amounts of oh ammonium contents of all samples were less than the detection limit about 10 ppm

hydroxyl defects in garnets from mantle xenoliths in kimberlites of the siberian platform a suite of more than 200 garnet single crystals extracted from 150 xenoliths covering the whole range of types of garnet parageneses in mantle xenoliths so far known from kimberlites of the siberian platform and collected from nearly all the kimberlite pipes known in that tectonic unit as well as some garnets found as inclusions in diamonds and olivine megacrysts from such kimberlites were studied by means of electron microprobe analysis and single crystal ir absorption spectroscopy in the voh vibrational range in search of the occurrence energy and intensity of the voh bands of hydroxyl defects in such garnets and its potential use in an elucidation of the nature of the fluid phase in the mantle beneath the siberian platform the voh single crystal spectra show either one or a combination of two or more of the following major voh bands i 3645 3662 cm 1 ii 3561 3583 cm 1 iii 3515 3527 cm 1 and minor bands ia 3623 3631 cm 1 iia 3593 3607 cm 1 the type of combination of such bands in the spectrum of a specific garnet depends on the type of the rock series of the host xenolith mg mg ca ca mg fe or alkremite on the xenolith type as well as on the chemical composition of the respective garnet nearly all garnets contain band systems i and ii band system iii occurs in ti rich garnets with wt tio2 ca 0 4 from xenoliths of the mg ca and mg fe series only the voh spectra do not correspond to those of oh defects in synthetic pyropes or natural ultra high pressure garnets from diamondiferous metamorphics there were no indications of voh from inclusions of other minerals within the selected 60 60 m measuring areas in the garnets the voh spectra of pyrope knorringite and pyrope knorringite uvarovite rich garnets included in diamonds do not show band systems i to iii instead they exhibit one weak broad band voh 200 460 cm 1 near 3570 cm 1 a result that was also obtained on pyrope knorringite rich garnets extracted from two olivine megacrysts the quantitative evaluation on the basis of relevant existing calibrational data bell et al 1995 of the sum of integral intensities of all voh bonds of the garnets studied yielded a wide range of water concentrations within the set of the different garnets between values below the detection limit of our single crystal ir method near 2 10 4 wt up to 163 10 4 wt the water contents vary in a complex manner in garnets from different xenolith types obviously depending on a large number of constraints inherent in the crystal chemistry as well as the formation conditions of the garnets during the crystallization of their mantle host rocks secondary alteration effects during uplift of the kimberlite play if any only a minor role despite the very complex pattern of the water contents of the garnets preventing an evaluation of a straightforward correlation between water contents of the garnets and the composition of the mantle s fluid phase during garnet formation at least two general conclusions could be drawn 1 the wide variation of water contents in garnets is not indicative of regional or local differences in the composition of the mantle s fluid phase 2 garnets formed in the high pressure high temperature diamond pyrope facies invariably contain significantly lower amounts of water than garnets formed under the conditions of the graphite pyrope facies this latter result 2 may point to significantly lower fh2o and fo2 in the former as compared to the latter facies

application of non destructive xrf method to the study of the provenance for archaeological obsidians from italian central european and south american sites abstract this paper presents the results of the attribution of approximately 1700 artifacts from italian central european and south american sites to the geological obsidian sources the provenance was determined using the non destructive x ray fluorescence xrf analytical method based on the secondary x ray intensity proposed by crisci et al 1994 and optimized by de francesco et al 2008 in the first phase of the research to test the non destructive xrf method the analysis on entire obsidian fragments similar to archaeological waste was initially carried out on 60 samples representative of all the geological outcrops in the mediterranean region the secondary x ray intensities obtained by non destructive xrf on whole pieces were compared with the results using the xrf method on powders carried out on the same samples major elements and selected trace elements such as nb y zr rb and sr as exhaustively described in de francesco et al 2008 these five trace elements were sufficient to characterize by both methods the different places of obsidian origin because they are particularly indicative of the genetic processes that produced obsidian the provenance of the obsidian artifacts was determined by comparing the x rays intensity ratios of the selected elements with those obtained on the entire fragments of the obsidian sources in the mediterranean the purpose of this paper is to show the results obtained in almost two decades of the application of the non destructive xrf method about 1700 archaeological obsidian fragments from numerous italian corsican central european romanian and south american central western argentina and central chile archaeological sites have been analyzed by non destructive xrf and assigned to obsidian sources the provenance of 97 of the obsidian artifacts was successfully determined the results demonstrate that the non destructive xrf method thanks to its sensitivity low cost and high speed is an extremely valuable tool for the attribution of the provenance of archaeological obsidian in the areas under consideration

cation deficient phlogopitic mica exsolution in diopside from garnet peridotite in sulu china article i nfo deep subduction and return to the surface of sediments and other continental rocks is now well known forming terranes of ultrahigh pressure metamorphism uhpm a common constituent of these terranes is garnet peridotite mantle rock that has been brought to the surface along with the returning subducted material microstructures of these peridotites especially precipitates within their constituent minerals offer promise of providing information not only about their depth of origin but also about the subduction environment here we report exsolution lamellae of cation deficient phlogopitic mica within diopside of a drill core from the uhpm terrane of sulu china detailed analysis by transmission electron microscopy tem shows these precipitates to be phlogopitic mica that is highly complex both structurally and compositionally with a significant component of the 10 a phase a talc like phase stable only at quite high pressures several mica polytypes are present the simplest one 1m being the most cation deficient the presence of a significant 30 10 a phase component in the mica suggests a means of expanding the 10 a phase bridge for subduction of h2o to deep mantle depths published by elsevier b v

neutron activation analysis of stone from the chadron formation and a clovis site on the great plains abstract cryptocrystalline silicates from the chadron formation were widely used by prehistoric human groups in the great plains of north america there are two documented quarry areas flattop butte in colorado and the white river badlands of south dakota cryptocrystalline silicates from these sources are visually indistinguishable making it difficult to determine the sources of artefacts found at archaeological sites in this investigation neutron activation analysis is used to distinguish the two sources this technique also identifies lithic material from the clovis age eckles site in kansas as being from flattop butte

decrease of hydrogen incorporation in forsterite from co2 h2o rich kimberlitic liquid to test if hydrogen incorporation by ionic diffusion can occur between a volatile rich kimberlitic liquid and forsterite results of high pressure and high temperature experiments using a piston cylinder apparatus at 1200 1300 c and 1 gpa for durations of 1 min 5 h and 23 h are reported here kimberlitic liquid in the system cao mgo al2o3 sio2 co2 h2o and synthetic forsterite single crystals were chosen as a first simplification of the complex natural kimberlite composition unpolarized fourier transform infrared spectroscopy was used to quantify the concentrations of oh in the crystallographically oriented forsterite scanning electron microscopy electron backscattered diffraction electron microprobe analyses and transmission electron microscopy were performed to identify the run products after 5 and 23 h a forsterite overgrowth crystallized with the same orientation as the initial forsterite single crystal the kimberlitic liquid has crystallized as micrometer scale euhedral forsterite neocrystals with random crystallographic orientations as well as a nanoscale aluminous phase and a calcic phase despite theoretical water saturation of the system and long duration none of the initial forsterite single crystals display signs of hydration such as hydrogen diffusion profile from the border toward the center of the crystal most likely the presence of co2 in the system has lowered the h2o fugacity to such an extent that there is no significant hydration of the starting forsterite single crystal or its overgrowth also the presence of co2 enhances rapid forsterite crystal growth forsterite growth rate is around 2 108 m3 h at 1250 c these experimental results suggest a deep mantle origin of the high oh content found in natural mantle derived xenoliths transported in kimberlites as reported from the kaapvaal craton in agreement with previous studies it also points out to the fact that significant hydration must take place in a co2 poor environment

hydroxyl in olivines from mantle xenoliths in kimberlites of the siberian platform from a total of 335 olivine crystal grains crystallographically orientated platelets and where possible parallelepipeds were prepared chemically analysed by electron microprobe examined under the polarisation microscope and studied by polarised ftir microscope absorption spectrometry in the oh vibrational range 3 000 3 800 cm 1 the 335 crystal grains were extracted from 174 different specimens of yakutian upper mantle material including 97 xenoliths that represent all the rock types occurring in all the kimberlites of the siberian shield the other specimens were mega and macrocrysts or inclusions in diamonds and garnets analysis of the polarised oh spectra allowed distinction between hydroxyl in non intrinsic separate inclusions nsi and in isolated local or condensed extended defects intrinsic to the olivines ild or ced respectively as the two latter types cannot be distinguished by vibrational spectroscopy and as they are presumably interconnected by intracrystalline condensation reactions of the type n ild ced n we propose to symbolise them as ild ced of the total of 70 polarised oh bands that were found in the whole set 17 are caused by nsi 53 by ild ced total mean integrated oh band intensities int total with int a b c int 3 were determined from the spectra they yielded the contents of structurally unallocated water using the recent calibration of the ir method bell et al 2003 the range is 0 a b at 3 327 3 328 cm 1 an energy typical of oh in hydrous wadsleyite we assume this phase to be present as nis in the respective olivines possibly as relic phase 4 weak bands between 3 175 and 3 260 cm 1 polarised along c are tentatively assigned to molecular water nsi with relatively strong hydrogen bonds to the matrix we did not find larger clusters of molecular water i e liquid like water with its characteristic broad band centred at ca 3 400 cm 1 we did also not find any humite minerals as an nsi of the 53 oh bands intrinsic to olivine the 29 most abundant and strong ones were subject to further analysis in terms of oh bearing structural defects ild ced nearly all these bands are strongly polarised along a two bands at 3 672 and 3 535 cm 1 are assigned to boron related defects ild ced b five bands at 3 573 3 563 3 541 3 524 and 3 512 cm 1 are intensity correlated and are assigned to si depleted titan clinohumite like defects ild ced thl the other so far unidentified oh of ild ced are suggested to originate from oh in different types of mg fe depleted defects recently predicted and discovered by tem these are called ild ced kwk eight mostly strong bands of them occur at energies higher than 3 573 cm 1 ild ced kwk h 13 strong to medium strong bands occur below 3 500 cm 1 ild ced kwk l such intrinsic defects may occur alone ild ced thl and ild ced kwk h or in different combinations with each other ild ced kwk h ild ced thl ild ced kwk h ild ced kwk l and ild ced kwk h ild ced thl ild ced kwk l though there are indications that the occurrences of such types and combinations of the intrinsic oh bearing defects in the olivines are related to the types and genetic peculiarities of their host rocks straightforward and simple correlations do not exist the reasons for this and also for the great number of varieties of intrinsic ild ced are discussed

micro and nano size hydrogrossular like clusters in pyrope crystals from ultra high pressure rocks of the dora maira massif western alps the supracrustal metamorphic rocks of the dora maira massif western alps have been intensively studied certain ultra high pressure lithologies contain coesite and nearly end member composition pyrope mg3al2si3o12 making this locality petrologically and mineralogically unique structural oh loosely termed water in pyrope crystals of different composition has been investigated numerous times using different experimental techniques by various researchers however it is not clear where the minor oh is located in them ir single crystal spectra of two pyropes of composition mg2 79 fe2 0 15 ca0 04 2 98 al 2 02 si 2 99o12 and mg2 90 fe2 0 04 ca0 02 2 96 al 2 03 si 3o12 were recorded at room temperature rt and 80 k the spectra show five distinct oh bands located above 3600 cm 1 at rt and seven narrow bands at 80 k and additional fine structure the spectra were curve fit and the oh stretching modes analyzed and assigned it is argued that oh is located in microscopic and nano size ca3al2h12o12 like clusters the basic substitution mechanism is the hydrogarnet one where h4o4 4 sio4 4 and various local configurations containing different numbers of h4o4 4 groups define the cluster type the amounts of h2o range between 5 and 100 ppm by weight depending on the ir calibration adopted and are variable among crystals hydrogrossular like clusters are also present in a synthetic pyrope with a minor ca content grown hydrothermally at 900 c and 20 kbar as based on its ir spectra at rt and 80 k experiment and nature are in agreement and oh groups are partitioned into various barely nano size hydrogrossular like clusters this proposal is new and significant mineralogical petrological and geochemical implications result ca and proton ordering occur hypothetical defect and or coupled substitution mechanisms to account for structural oh are not needed to interpret experimental results oh incorporation in pyrope of different generations at dora maira is discussed and oh could potentially be used as an indicator of changing p text h text 2 text o text a text h text 2 text o text t conditions in a metamorphic cycle published experimental hydration dehydroxylation and hydrogen diffusion results on dora maira pyropes can now be interpreted atomistically

h2o contents and d h ratios of nominally anhydrous minerals from ultrahigh pressure eclogites of the dabie orogen eastern china abstract garnet and omphacite from ultrahigh pressure eclogites from the dabie orogen eastern china were investigated by micro ftir the results show that all garnet and omphacite grains contain structural water occurring as hydroxyl oh with h2o contents varying from 14 to 1915 ppm h2o wt and from 105 to 695 ppm respectively within the same sample the water contents are either homogeneous at the grain scale or vary systematically from higher in the core to lower in the rim low water contents at crystal rims possibly result from hydroxyl exsolution after pressure decrease upon rock exhumation the d values of omphacites are between 108 4 and 114 2 and independent of water contents heterogeneous water contents of garnet occur at the centimeter scale and fluid mobility during uhp metamorphism was very limited the estimated whole rock water content based on mineral h2o contents is between 260 and 750 ppm thereby implying that eclogitic rocks formed during continental subduction have the potential to recycle at least several hundreds ppm water to mantle depths the preserved chemical differences likely indicate that the eclogitic rocks resided at mantle conditions for a limited time span and imply that they were exhumed shortly after subduction the water released during decompression might represent the early stage retrograde fluid

water in the lower crustal granulite xenoliths from nushan eastern china 1 nominally anhydrous clinopyroxene cpx orthopyroxene opx and plagioclase pl from 10 lower crustal granulite two pyroxene granulite and hypersthene granulite xenoliths in cenozoic basalts from the nushan volcano eastern china have been analyzed for their hydrogen content by microscopic fourier transform infrared spectroscopy micro ftir the results demonstrate that hydrogen was incorporated in all these minerals in the manner of oh and that the content h2o weight is up to 2360 ppm for cpx 1170 ppm for opx and 880 ppm for pl on the basis of the water content of constitutive minerals and their proportions whole rock water contents of the nushan granulites were estimated to be 150 950 ppm estimated equilibrium temperatures of the nushan granulites are in the range of 810 892 c corresponding to the lowermost crust at nushan about 25 30 km therefore this study provides direct evidence that the lower continental crust even the lowermost part devoid of hydrous minerals can contain a certain amount of water in nominally anhydrous minerals

low water contents in diamond mineral inclusions proto genetic origin in a dry cratonic lithosphere the mantle is the major reservoir of earth s water hosted within nominally anhydrous minerals nams e g bell and rossman 1992 peslier et al 2010 peslier 2010 nestola and smyth 2015 in the form of hydrogen bonded to the silicate s structural oxygen from whence cometh this water is the water in these minerals representative of the earth s primitive upper mantle or did it come from melting events linked to crustal formation or to more recent metasomatic re fertilization events during diamond formation nams are encapsulated at hundreds of kilometers depth within the mantle thereby possibly shielding and preserving their pristine water contents from re equilibrating with fluids and melts percolating through the lithospheric mantle here we show that the nams included in diamonds from six locales on the siberian craton contain measurable and variable h 2o concentrations from 2 to 34 parts per million by weight ppmw in olivine 7 to 276 ppmw in clinopyroxene and 11 17 ppmw in garnets our results suggest that if the inclusions were in equilibrium with the diamond forming fluid the water fugacity would have been unrealistically low instead we consider the h 2o contents of the inclusions shielded by diamonds as pristine representatives of the residual mantle prior to encapsulation and indicative of a protogenetic origin for the inclusions hydrogen diffusion in the diamond does not appear to have modified these values significantly the h 2o contents of nams in mantle xenoliths may represent some later metasomatic event s and are not always representative of most of the continental lithospheric mantle results from the present study also support the conclusions of peslier et al 2010 and novella et al 2015 that the dry nature of the sclm of a craton may provide stabilization of its thickened continental roots

isotopic and structural responses of granite to successive deformation and metamorphism within the sybella granite west of mount isa in northern australia differential response of u pb and rb sr isotopic systems to deformation metamorphism enables ages of emplacement and three discrete deformation metamorphic events to be determined based on zircon u pb systems two of the plutons were emplaced at 1671 pm 8 ma and 1668 pm 26 21 ma and the third at 1610 pm 10 ma a separate microgranite body gives aberrantly old u pb ages of up to 1780 ma due to partial inheritance of older zircon the three discrete deformation metamorphic events d 1 d 2 and d 3 occurred at 1610 pm 13 ma 1544 pm 12 ma and 1510 pm 13 ma respectively based on whole rock rb sr isotopic systems the youngest body was emplaced syntectonically and has possible significance to the origin of the mount isa ag pb zn orebodies homogenization of rb and sr isotopes via extensive syntectonic fluid migration associated with deformation partitioning and resultant solution transfer appears to have been

coupled substitution of h and minor elements in rutile and the implications of high oh contents in nb and cr rich rutile from the upper mantle infrared absorption spectra of rutile crystals from a variety of geological environments carbonatite hydrothermal vein kyanite rutile lazulite association xenoliths that are kimberlite hosted and dominated by nb and cr rich rutile exhibit strong absorption in the 3300 cm 1 region due to interstitial protons bonded to structure o in general the proton is located at sites slightly displaced from 1 21 20 of the unit cell although some samples show evidence of additional protons at tetrahedral interstitial sites h contents of rutile range up to 0 8 wt h 2o the highest concentrations occurring in mantle derived nb and cr rich rutile of metasomatic origin the role of h in rutile was examined particularly with respect to its relations to other impurities protons are present in the rutile structure to compensate for trivalent substitutional cations cr fe v ai which are only partly compensated by pentavalent ions nb ta the possibility of using the h content of rutile as a geohygrometer is illustrated for the case of coexisting hematite and rutile

green grey and black a comparative study of sierra de las navajas mexico and lipari italy obsidians abstract sierra de las navajas state of hidalgo mexico and lipari aeolian islands italy were among the most important sources for obsidian trade in mesoamerica and in the mediterranean during the stone age in this paper obsidians from these two localities were compared in terms of their aspect chemical composition microcrystallinity and microvesiculation in sierra de las navajas the typical deep green obsidian with a golden hue has been analyzed together with a less common dark grey porphyritic variety lipari obsidian is commonly black but a light grey variety also occurs obsidian of both varieties was analyzed for this paper microvesicularity was investigated through scanning electron microscope sem observation microporosimetry and for sierra de las navajas green obsidian through a preliminary x ray computed microtomographic study crystallinity and micro or nano crystallinity were investigated through x ray powder diffraction and eds energy dispersion system microanalyses finally the chemical composition in terms of major and trace elements including rare earth elements was determined using x ray fluorescence xrf and inductively coupled plasma mass spectrometry icp ms the comparison of samples of different colors suggests that the characteristic green color of sierra de las navajas obsidians could be related to their relatively high iron content and to the occurrence of many elongated and iso oriented vesicles which may also be responsible for the obsidian s golden hue low iron and an absence of vesicles give lipari obsidian its normal black color the light grey obsidian from lipari probably owes its color and imperfect conchoidal fracture to numerous bubbles of less than 1 m in size and to nano crystallinity sierra de las navajas obsidians show a significant chemical variability in terms of trace elements that can be explained by common evolutionary processes in the magma chamber however this variability is also internal to a single volcanic complex and this makes the trace element contents unsuitable to differentiating between the different sub sources of the same area on lipari our data do not allow us to distinguish between the two sub sources of vallone del gabellotto and canneto dentro on the basis of major and trace elements on the whole our study suggests that caution should be used for both lipari and sierra de las navajas when identifying obsidian sub sources on the basis of trace element contents

uvarovite from chromite bearing ultramafic intrusives orissa india a crystal chemical characterization using 57fe mossbauer spectroscopy epma analyses of uvarovite from the chromite bearing ultramafic intrusive of sukinda india show that uvarovite containing 9 83 to 17 68 wt cr 2 o 3 represents a solid solution of the binary uvarovite andradite series with uva 34 58 and 42 58 associated chromite grains with 57 59 wt cr 2 o 3 do not show any compositional variation from core to rim 57 fe mossbauer spectroscopic studies on the uvarovite samples undertaken both at room temperature 298 k and low temperature 110 k indicate the presence of fe 3 only in octahedral coordination uvarovite grew from chromite cr source and pyroxenes al fe and ca source of the ultramafic host rocks

hydrogarnet substitution in pyrope a possible location for water in the mantle abstract single crystal spectra of pyropes synthesized on the 3 1 3 composition of the system mgo al2o3 sio2 atph2o ptotal 25kbar and 1000 c show a broad band centered at around 3400 cm 1 due to h2o of h2o n aggregates in fluid inclusions and a sharp intense band near 3600 cm 1 due to oh of ho 44 clusters introduced by the hydrogarnet substitutionsi4 4h the water contents in the synthetic pyrope due to ho 44 clusters are estimated near 0 05 wt h2o from spectroscopic data si deficits in microprobe analyses of the pyropes studied support the hydrogarnet substitution these results show that the hydrogarnet substitution in pyrope may contribute to water contents in the mantle

mineral oxygen isotope and hydroxyl content changes in ultrahigh pressure eclogite gneiss contacts from chinese continental scientific drilling project cores a combined study of mineral o isotopes and hydroxyl contents was carried out for the contacts between ultrahigh pressure eclogite and gneiss from main hole of the chinese continental scientific drilling project in the sulu orogen while there is a large d 18 o variation from 8 3 to 7 3 for all minerals different styles of mineral pair fractionation occur at the boundaries of different lithologies both equilibrium and disequilibrium o isotope fractionations are observed between quartz and the other minerals with reversed fractionations between omphacite and garnet in some samples of eclogite this suggests that both eclogite and gneiss acquired their negative d 18 o values by meteoric hydrothermal alteration of their protoliths at high temperatures before subduction and that fluid assisted o isotope exchange did take place across the boundary of different lithologies at local scales during amphibolite facies retrogression fourier transform infrared spectroscopy analysis yielded h2o concentrations of 50 to 1144 p p m by weight for garnet and 139 to 751 p p m for omphacite the state of equilibrium or disequilibrium o isotope fractionations between omphacite and garnet are correlated with variations in their water content at local scales indicating that the internally derived fluid plays a critical role in retrograde metamorphism during exhumation the retrograde metamorphism results in mineral reactions and o isotope disequilibria between some of the minerals but the fluid for retrogression was derived from the decompression exsolution of structural hydroxyl and thus internally buffered in the o isotope composition a quantitative estimate suggests that a hand specimen 3 6 9 cm of eclogite composed of 70 garnet and 30 omphacite can release 0 316 g water by the decompression exsolution of structural hydroxyl which can form 14 4 g amphibole during exhumation this provides sufficient amounts of water for the amphibolite facies retrogression

solubility of water in pyrope rich garnet at high pressures and temperature 1 the water solubility in pyrope rich garnet was determined between pressures of 5 9 gpa and temperatures of 1373 1473 k under silica activity and oxygen fugacity similar to those expected in the earth s upper mantle we found that pyrope rich garnet has substantial water solubility up to 0 1 wt under these conditions in addition the water content in garnet varied as a function of chemical conditions in particular the variation in water fugacity and mg caused a variation in water partitioning with olivine the substantial water solubility in pyrope rich garnet under deep upper mantle conditions might have significant influence on physical and transport properties

new u pb and rb sr constraints on pre acadian tectonism in north wales a new u pb date of 615 2 1 3 2 ma for the twt hill granite north wales contrasts with an rb sr isochron age of 491 12 2 ma from the same body the latter age is thought to result from isotope resetting during regional low grade metamorphism or fault reactivation the rb sr age also coincides with the onset of latest cambrian to early tremadoc regression and is taken to reflect tectonic uplift prior to the arenig overstep at around 478 ma it is proposed that this in turn reflects plate scale processes along the contemporary peri gondwanan continental margin

middle proterozoic uplift events in the dunbar dome of northeastern wisconsin usa isotopic ages of granitic and metamorphic rocks exposed in the dunbar structural dome of northeastern wisconsin identify a protracted series of tectonic and hydrothermal events that culminated in major regional uplift during middle proterozoic keweenawan ca 1 100 ma continental rifting and volcanism the major rock forming events and the structural development of the dome occurred during the interval 1 862 4 ma to 1 836 6 ma whole rock rb sr ages are partly reset in response to a widely recognized but cryptic event in wisconsin and michigan at about 1 630 ma the scale and systematic character of the whole rock resetting strongly suggests the presence of a fluid phase derived in situ from water dissolved in the silicates or externally from a subthrust plate of low grade metamorphic rocks the regional nature of the 1 630 ma disturbance possibly indicates that it is related to a major tectonic event such as an active plate margin far to the south rb sr biotite ages for the dunbar dome this study the southern complex of the marquette district van schmus and woolsey 1975 and the felch trough area aldrich and others 1965 provide a remarkably coherent pattern that reflects multiple episodes of differential uplift younger events superimposed on a regional 1 630 ma imprint are recorded at 1 330 ma and 1 140 ma the 1 330 ma disturbance could reflect stabilization following intrusion of the wolf river batholith at 1 485 ma the 1 140 ma uplift event occurred during keweenawan rifting and volcanism as a result of stresses imposed on a mosaic of fault bounded blocks with possible subcrustal influence the remarkably small variance in the 1 140 ma biotite age peak argues for rapid uplift and cooling and hence rapid erosion detritus from the uplift probably was being shed into nearby tectonic basins most of which did not survive subsequent uplift and erosion

metagabbros in the modum complex southern norway an important heat source for sveconorwegian metamorphism abstract the precambrian modum complex in southern norway is characterized by supracrustal rocks penetrated by numerous gabbro intrusions occurring as elongated bodies subparallel with the regional foliation these gabbroic bodies show a partial alteration to amphibolites the best preserved parts of the metagabbros show a subophitic texture with olivine and plagioclase as the major cumulus phases and clinopyroxene orthopyroxene and ilmenite as the major intercumulus phases subsequent alteration of these igneous phases has led to formation of coronas around olivine in contact with plagioclase and recrystallization of clinopyroxene the igneous phases indicate intrusion temperatures in the range of 1100 1000 c and pressures below 5 8 kbar formation of coronas and recrystallization of clinopyroxene occurred in the pressure temperature range of 7 10 kbar and 800 600 c a 1224 15 ma sm nd mineral isochron obtained from igneous phases indicates emplacement at the start of the sveconorwegian metamorphism a complex evolution is suggested for the sveconorwegian metamorphic event involving both magmatism and high grade metamorphism

water transport by subduction clues from garnet of erzgebirge uhp eclogite a key question concerning the water budget of earth s mantle is how much water is actually recycled into the mantle by the subduction of eclogitized oceanic crust hydrous phases are stable only in quartz eclogite not coesite eclogite so that water transport to greater depths is mainly governed by structural water in omphacite and garnet here we explore if garnet can be used as a proxy to assess the amount of this water available data on the water contents of garnet in coesite eclogite vary over orders of magnitude from a few up to ca 2000 ppm by implication the maximum bulk rock water contents are unrealistically high wt level new data from the erzgebirge indicate moderate amounts of structural h 2 o stored in garnet 43 84 ppm omphacite 400 820 ppm and in the bulk coesite eclogite ca 280 460 ppm higher garnet water contents occur but these are not primary features they are related to molecular water in fluid inclusions that can be attributed to eclogite facies fluid influx postdating the metamorphic peak fluid influx also caused the uptake of additional structural water in garnet domains close to fluid inclusions such secondary h 2 o incorporation is only possible in the case of primary water deficiency indicating that garnet hosted less water than it was able to store this is insofar astonishing as comparably high h 2 o amounts are liberated by the breakdown of prograde eclogite facies hydrous minerals as a result of ultrahigh pressure uhp metamorphism judging from erzgebirge quartz eclogite dehydration of 5 10 hydrous minerals equal portions of zoisite calcic amphibole produces 1500 3000 ppm water we infer that the largest part of the liberated water escaped probably due to kinetic reasons and hydrated exhuming uhp slices in the hanging wall depending on the physical conditions water influx in eclogite during exhumation 1 produces fluid inclusions and simultaneously enhances the structural water content of nominally anhydrous minerals as in the erzgebirge and or 2 it may give rise to retrograde hydrous minerals we conclude that eclogite transports moderate quantities of water several hundred parts per million to mantle depths beyond 100 km an amount equivalent to that in ca 1 calcic amphibole

reassessment of wd xrf method for obsidian provenance shareable databases abstract the x ray fluorescence technique using peak intensity ratios of trace elements is one of the faster less expensive and less invasive methods for obsidian sourcing moreover xrf peak intensity ratios are particularly useful when the artifact is slightly altered particularly affecting the alkali cations or when its surfaces are covered with a fine film of carbonate deposits formed while the sample was buried the limitation of this technique results from the dimensions of the obsidian samples very small obsidian samples nowadays about 1 cm in size are difficult to measure given the very few x rays emitted by their surface an aluminium holder closed with a very thin mylar polyester film was prepared and the specimen positioned at the centre of the surface of the mylar film was placed in the xrf spectrometer the use of recent technology xrf apparatus equipped with a 4 kw rh anode x ray tube coupled with an accurate measurement of refined x ray characteristic lines that exclude the x ray background contribution of five trace elements rb sr y zr nb made it possible to determine the source geological outcrop of archaeological obsidian samples as little as 7 mm and as light as 40 mg a database of peak intensity ratios background and interference free of five trace elements was produced for obsidian samples from monte arci palmarola lipari pantelleria gyali and melos this database may be used by other laboratories provided the x ray intensity of the trace elements rb sr y zr nb are measured as net intensities that is purified from the contribution of the background and from interelemental interferences a comparison between data obtained with two spectrometers of different generation and differently calibrated confirmed the possibility of obtaining a database that can be shared with other laboratories the proposed xrf method was tested on neolithic obsidians from four apulian sites ripa tetta at lucera palestra ex g i l at foggia pulo di molfetta and grotta di santa barbara at polignano a mare whose source outcrops had been also determined by sem eds

extreme differentiation in the proterozoic gjerstad morkeheia complex of south norway the gjerstad morkeheia complex contains a series of highly differentiated iron and alkali enriched intrusions the rocks range from basic to acid compositions and were variably mylonitised under anhydrous conditions before being metamorphosed and hydrated at upper amphibolite facies grade they now form a series of ironenriched metagabbros metadiorites and granodioritic gneisses together with granitic and charnockitic augen gneisses the augen formed by shearing of original megacrysts in the igneous rocks a major mylonite zone formed at the same time

uplift and cooling magnetisation record in the bamble and telemark terranes sveconorwegian orogenic belt se norway and the grenville sveconorwegian loop article i nfo the 1100 ma sveconorwegian orogenic belt comprises allochthonous terranes juxtaposed by major fault zones and emplaced against and onto the south western margin of the fennoscandian shield to resolve the magnetic signature acquired during post orogenic uplift and cooling and evaluate wider correlations with the contemporaneous grenville belt of north america this study reports a regional palaeomagnetic study on a range of rock types from sectors of the medium high metamorphic grade bamble terrane 48 sites and 390 cores and the adjoining medium low grade telemark terrane 33 and 240 cores juxtaposed by an orogen parallel porsgrunn kristiansand fault zone with major vertical displacement magnetite and ilmeno hematites are magnetic carriers with the latter more significant in the higher metamorphic grades magnetic intensities are stronger in the higher grade terrane presumably due to the growth of metamorphic ferromagnets but are an order lower than values predicted for the lower continental crust and indicate that an additional mechanism is responsible for high magnetisations in deep crust anisotropy of magnetic susceptibility ams largely reflects the ne sw tectonic grain of the last stage of sveconorwegian ductile deformation the magnetisation record is filtered by excluding magnetisations possibly acquired during regional mesozoic dyke emplacement development of the permo carboniferous oslo rift and late proterozoic magmatism the remaining record is a dual polarity signature summarised by mean poles at 31 9 n 50 9 e n 191 components in the bamble terrane and at 34 2 n 58 9 e n 151 components in the telemark terrane however these means are non fisherian and embrace arcuate distributions of magnetic components acquired during protracted exhumation cooling of the orogen with the best defined parts

the effects of penetrative sveconorwegian deformations on rbsr isotope systems in the romskog aurskog holand area se norway abstract the area investigated consists of five granitoid complexes which range over more than 900 ma 1850 925 ma rb sr whole rock in age as well as an old series of layered para and orthogneiss the relative ages of the old gneiss series and the oldest granitoid complex which is a series of augen gneisses 1850 1710 ma are uncertain the layered para and orthogneisses were however definitely gneissified before the intrusion of a 1631 ma old grey orthogneiss deformational activity took place several times during the geological evolution the major structures developed mainly after the intrusion of both a 1277 20 ma old red granitic orthogneiss and the mafic dykes that transsect it the post 1277 ma structures resulted from the following a foliation forming event with migmatization a fold phase giving e w directed folds a fold phase giving n s directed folds which affect the southern part of the area only and finally a large scale overthrusting towards the east along the western limit of the area the upper age limit of the folding activity is established by a 925 ma old undeformed granite the post 1277 ma structures are regarded as constituting the infrastructure of the sveconorwegian orogeny in the area possible correlation with the suprastructure of this orogeny in the dalsland area further south is discussed although the dated rocks have suffered from high grade metamorphism we argue that the rb sr whole rock ages mark the ages of intrusion crystallization of the plutonic complexes

heterogeneity of water in garnets from uhp eclogites eastern dabieshan china abstract garnets in uhp eclogites from bixiling in dabieshan were investigated by fourier transform infrared spectroscopy ftir the results indicate that all garnets contain structural water that occurs as hydroxyl oh and non structural molecular water h 2 o possibly in the form of sub microscopic fluid inclusions the structural hydroxyl contents range from 92 to 1735 ppm h 2 o wt and most are between 200 and 1000 ppm therefore garnet in eclogite can recycle surface water into the mantle various water contents were observed among different samples of the same outcrop 150 m and in different domains of the same sample 1 cm this variability in structural h 2 o contents suggests that the mobility of fluids during uhp metamorphism was very limited and that both subduction and exhumation processes of uhp rocks occurred in a short time interval

water content of mantle garnets garnet megacrysts from colorado plateau diatremes green knobs garnet ridge and the wesselton kimberlite south africa commonly contain a structural hydrous component the colorado plateau samples range from 0 0 to 0 26 wt h 2 o and the wesselton samples contain from 0 01 to 0 07 concentrations were measured using p 2 o 5 cell coulometry h 2 gas manometry and thermogravimetry these were used to calibrate infrared integrated absorbance in the 3 m region which is a more sensitive measure of total o h content than the other analytical methods infrared absorbance patterns were also used to differentiate structural hydrous component from water contained in alteration and included phases the structure of the hydrous component in these garnets appears to be the classic h 4 o 4 4 sio 4 4 profiles at 100 m intervals across these samples show flat concentration profiles or slightly increasing concentration toward the center a large range of water content among samples appears to represent real differences in water fugacity at the point where the garnets equilibrated garnets in eclogite nodules from south africa and the solomon islands were also studied but were either anhydrous or too badly altered to determine the content of structurally bound water the high concentration of hydrous component in the colorado plateau samples is consistent with other indicators of high volatile content in that region of the mantle the water content of mantle garnets may prove to be an accurate indicator of mantle water fugacities

rb sr systematics of a gardar age layered alkaline monzonite suite in southern norway the morkheia monzonite suite mms is part of a layered alkaline complex of anorogenic affinity which intruded discordantly into high grade gneisses of the telemark sector in the mms one complete outcrop and low rb sr samples from other outcrops preserve a rb sr whole rock date of ca 1250 ma interpreted as approximating an intrusive age the mms is thus contemporaneous with similar alkaline complexes of early to mid gardar age in southern greenland and labrador during this period felsic alkaline magmatism was apparently a widespread expression of the anorogenic tensional regime that obtained in the north atlantic provinces mms whole rock samples from three outcrops fall below the ca 1250 ma primary isochron and define secondary ages of ca 1060 ma at this time these outcrop scale rb sr systems approached sr isotope equilibration and rb sr ratios were augmented mainly by rb addition these isotopic effects relate to minor low grade hydrous alteration of the primary minerals this low grade gree

sampling for provenance tailings from prehistoric stone quarries in the south pacific stone is a principal component in archaeological assemblages across the pacific it provided a major element in architecture used as trade goods and was fashioned into implements and ornaments monolithic monuments statues money and emblematic symbols of victory status and ethnicity in short stone is a pervasive element in the economic social and political fabric of pacific cultural traditions however provenance of rock quarries the source of this raw material has received limited attention in oceania provenance studies have been sidestepped or short changed in the rush to analyse artifactual materials here we establish a foundation for more robust provenance studies and field sampling strategies through a discussion of 1 quarry identification and 2 sampling within prospective sources a model of quarry identification sampling and characterization is drawn from work on rapa nui easter island and the fundamental precepts are outlined for future sampling experiments and provenance work in stone quarries generally

the distribution of hydroxyl in garnets from the subcontinental mantle of southern africa 166 garnets of dominantly mantle origin were analyzed for oh content by infrared ir spectroscopy ir spectra in the 3400 3700 cm 1 region display consistent absorption patterns attributable to oh structurally bound within the garnet crystal occasionally contaminated by low intensity oh absorptions from microscopic inclusions the principal structural oh absorption occurs near 3570 cm 1 with the appearance of additional absorptions near 3512 cm 1 and 3650 cm 1 dependent on garnet composition or paragenesis samples derive from a wide variety of rock types occurring as xenoliths in kimberlites of southern africa oh abundances using the best currently available calibration range from less than 1 up to 135 ppm h 2o and increase in the general order as follows on craton eclogites group 1 basaltic kimberlite alnoite alkali basalt the oh contents of common lithospheric granets from coarse peridotites including several phlogopite bearing samples are typically less than 20 ppm h 2o for tectonic settings of kimberlites both on and off the archaean kaapvaal craton ti rich garnets from deformed peridotites are richer in oh supporting previous suggestions of association of these xenoliths with putative megacryst magmas subcalcic cr rich xenocrysts diamond inclusion garnets and garnets from diamondiferous eclogites have very low oh contents similar to eclogites and depleted peridotites without macroscopic diamonds the oh content of southern african peridotite and eclogite garnets are significantly lower on average than those previously examined from the colorado plateau diatremes while details of emplacement related h mobility in garnets remain to be established our results suggest that garnets record useful information on the role of water or other hydrous volatile species in petrological processes at their source regions in the mantle although garnets do not appear to constitute a large reservoir of mantle hydrogen the large stability range of oh bearing garnet in the crust and mantle implies wide applicability as a qualitative hydrobarometer

origin of retrograde fluid in ultrahigh pressure metamorphic rocks constraints from mineral hydrogen isotope and water content changes in eclogite gneiss transitions in the sulu orogen abstract by taking advantage of having depth profiles between contrasting lithologies from core samples of the chinese continental scientific drilling ccsd project a combined study was carried out to examine changes in mineral h isotope total water and hydroxyl contents in garnet and omphacite across the contacts between ultrahigh pressure uhp eclogite and gneiss in the sulu orogen east central china the samples of interest were from two continuous core segments from the ccsd main hole at depths of 734 21 737 16 and 929 67 932 86 m respectively the results show d values of 116 to 64 for garnet and 104 to 82 for omphacite consistent with incorporation of meteoric water into protoliths of uhp metamorphic rocks by high t alteration both equilibrium and disequilibrium h isotope fractionations were observed between garnet and omphacite suggesting fluid assisted h isotope exchange at local scales during amphibolite facies retrogression while bulk water analysis gave total h2o concentrations of 522 1584 ppm for garnet and 1170 20745 ppm for omphacite structural hydroxyl analysis yielded h2o contents of 80 413 ppm for garnet and 228 412 ppm for omphacite it appears that significant amounts of molecular h2o are present in the minerals pointing to enhanced capacity of water storage in the uhp eclogite minerals hydrogen isotope variations in the transition between eclogite and gneiss show correlations with variations in their water contents petrographically the degree of retrograde metamorphism generally increases with decreasing distance from the eclogite gneiss boundary thus retrograde metamorphism results in mineral reactions and h isotope variation because hydroxyl solubility in nominally anhydrous minerals decreases with dropping pressure significant amounts of water are expected to be released from the minerals during decompression exhumation decompression exsolution of structural hydroxyl from 1 m3 volume of eclogite composed of only garnet and omphacite results in release of a quantitative estimate of 3 07 3 44 kg water that can form 140 156 kg amphibole during exhumation therefore it is concluded that fluid for retrogression of the eclogites away from the eclogite gneiss boundary was derived from the decompression exsolution of structural hydroxyl and molecular h2o in nominally anhydrous minerals for the eclogites adjacent to gneiss in contrast the retrograde metamorphism was principally caused by aqueous fluid from the gneiss which is relatively rich in water consequently both the origin and availability of metamorphic fluid during exhumation of deeply subducted continental crust are deciphered by this combined study focusing on the transitions and the retrograde processes between the felsic and mafic uhp rocks

age relationships in the proterozoic high grade gneiss regions of southern norway abstract the proterozoic high grade gneiss regions of southern norway bamble kongsberg rogaland and ostfold historically belong to the so called sveconorwegian 1 2 0 9 ga zone this has long been correlated with the grenville province of north america and features prominently in proterozoic reconstructions across the north atlantic several recent radiometric studies have provided compelling evidence for an earlier high grade gneiss forming event at 1 6 1 5 ga ago in parts of southern norway it has also been shown that at least a section of the bamble sector suffered only a relatively low grade thermal deformational event during the sveconorwegian cycle in this paper new rb sr age determinations for metasediments and an anatectic granite from the same area confirm a pre grenvillian age for the high p t event and preclude the possibility of later high grade reworking previously published age determinations for all sectors are compared with the available radiometric data from the adjoining gneissic terrane of southwest sweden and reviewed in the light of the new data from bamble and recent evidence that relatively low grade events are capable of disturbing and possibly resetting both rb sr total rock and u th pb zircon isotope systems the conclusions are that the main high grade gneiss forming event may have been pre grenvillian in all sectors and that there may have been no regional high grade reworking during the period 1 2 0 9 ga ago

sem eds characterization of western mediterranean obsidians and the neolithic site of a fuata corsica during the neolithic obsidians of the monte arci sardinia volcanic complex were by far more used in the northern tyrrhenian area than those of the three other source islands lipari palmarola pantelleria in the western mediterranean it is shown that merely determinations of content for six major elements with a scanning electron microscope by energy dispersion spectrometry sem eds are sufficient to distinguish the four types of monte arci obsidians because of the compositional similarities between these obsidian types a multivariate analysis is recommended in provenance studies although sem eds electron microprobe wavelength dispersion spectrometry emp wds and particle induced x ray emission pixe give essentially concordant results in the determination of these six element contents subtle technique related biases prevent the combination of sem eds emp wds and pixe data on source samples for provenance purposes an sem eds test study reveals the first occurrence of obsidians of lipari for the a fuata middle to late neolithic site of nw corsica north of sardinia in addition to the usual monte arci obsidians similar to emp wds the sem eds technique requires only millimeter sized fragments

deep penetration of sedimentary fluids in basement rocks from southern norway evidence from hydrocarbon and brine inclusions in quartz veins abstract this paper presents evidence for fluid flow and fluid rock interaction at upper crustal levels within the crystalline basement of southern norway in the high grade modum complex postmetamorphic veins of quartz occur in association with albitisation of metagabbros and metasediments pressure temperature conditions for the formation of these veins are in the range 250 300 c and ca 1 2 kbar primary and pseudosecondary fluid inclusions in the quartz veins show two fluids 1 hydrocarbon c0 2 inclusions and 2 aqueous inclusions with variable salinities dark carbonaceous solid inclusions are also present the hydrocarbon inclusions are methane dominated ca 80 100 mot and the presence of higher complex hydrocarbons is demonstrated the aqueous inclusions in the metagabbro hosted veins show more saline compositions than the metasediment hosted veins a salinity range of ca 23 0 wt nacl eq is found some of the aqueous inclusions may contain nahco 3 crush leach analyses of inclusion fluids show na ca k ci dominated compositions with na ca k hydrocarbon poor concentrates yield br cl ratios close to seawater while hydrocarbon rich concentrates show higher values the types and chemistry of the hydrocarbons in these veins indicate a biogenic origin of the hydrocarbon fluids the inclusion fluids are interpreted as derived from an overlying sedimentary basin in late precambrian or permian times the veining is interpreted as the deep expression of the percolation of basinal fluids into the metamorphic basement during crustal extension

the oh content of pyrope at high pressure the oh contents of pyrope garnets synthesised at 1000 c and pressures between 2 and 13 gpa have been measured by infrared spectroscopy we find that under the same conditions of pressure temperature ah2o and asio2 the oh content of pyrope is similar to that of grossular this shows that observed differences in nature between water contents of pyrope and grossular are related to paragenesis rather than reflecting higher intrinsic solubility in grossular in the presence of excess sio2 the h2o content increases with pressure to 5 gpa 1000 ppm then decreases to below the detection limit at pressures above 7 gpa thus garnet becomes more hydrous with pressure to some critical value beyond which dehydration occurs even under h2o saturated conditions this observation is consistent with the measured partial molar volume of water in hydrogarnet which becomes greater than that in fluid water within the pressure range of this study when corrected to upper mantle conditions we find that pyrope should dehydrate with increasing depth below about 250 km pyrope is unlikely therefore to be a major site of water storage in the transition zone and upper mantle