rb sr systematics of permian volcanites in the schwarzwald sw germany from the quartz porphyry occurrences of haigerach and geisberg central schwarzwald which were dated by minerals and whole rock samples the whole rock samples generally yielded lower ages than the minerals this result agrees with other studies on apparently rejuvinated whole rock ages of acid volcanic rocks compare mckerrow et al 1980 petrographic and geochemical observations show that two processes disturbed the rb sr relations 1 fast alterations immediately after extrusion such as sericitization during autohydrothermal bleaching in the pipe area of the volcanoes gain of rb addition of common sr 2 loss of radiogenic 87sr due to long lasting exchange processes with groundwaters

limited availability of sulfur promotes copper rich mineralization in hydrothermal pb zn veins a case study from the schwarzwald sw germany abstract mixing of compositionally contrasting fluids is widely accepted as the major ore forming process in unconformity related hydrothermal pb zn fluorite barite veins although the general process is relatively well understood the temporal evolution of such fluid systems which may result in distinct mineralogical changes of the ore and gangue minerals precipitating are insufficiently constrained one specific example is the occurrence of late stage siderite chalcopyrite gersdorffite mineralization in 28 hydrothermal veins of the schwarzwald sw germany post dating the major fluorite barite galena sphalerite phase which is very common in the whole area to investigate the underlying process for this late stage cu ni stage published fluid inclusion data have been complemented by detailed confocal raman micro spectroscopy of fluid inclusions petrographic observations and electron microprobe analyses petrography as well as mineral compositions of sphalerite gersdorffite pyrite arsenopyrite fahlore and galena record a gradual but significant influx of cu and ni into a prevailing pb zn hydrothermal system this influx caused a distinct shift towards lower fo2 and pb zn sb ag s in the hydrothermal system at the transition from the pb zn to the cu ni mineralization stage this transition in mineralogy and the related gradual change of the hydrothermal fluid can be explained by changes in the relative proportion of involved fluid components however the transition to the cu ni mineralization stage by fluid influx is significantly different compared to the common rapid fluid mixing from below which is thought to be responsible for the typical pb zn veins and probably records the gradual transition from long term stable deep fluid reservoirs with constant chemical compositions towards more shallow and perturbed fluid reservoirs during rifting and exhumation

b rich melt immiscibility in late cretaceous nattaung granite myanmar implication by composition and b isotope in tourmaline abstract there is a strong controversy about the petrogenesis of tourmaline nodules and their relationship with coeval tourmaline bearing granites which are commonly associated with magmatic hydrothermal rare metal deposits e g sn nb and ta in this study tourmaline is extensively distributed in tourmaline bearing nodules nt type pegmatite pt type and fine grained granitic dyke gt type which are hosted by the late cretaceous nattaung biotite granite myanmar zircon u pb dating results 71 ma indicate that pt and gt types tourmaline bearing magmatic rocks formed synchronously with biotite granite all tourmalines have alkali group and schorl composition with mg mg fe ratios of 0 03 0 45 and na na ca ratios of 0 73 to 1 00 nt type tourmaline shows high nb ta ratios and v and sr contents indicating that they were likely crystallized from b rich melts early immiscible with less evolved granitic magmas pt and gt type tourmalines probably formed in aggregated b rich melts that continuously separated from more evolved granitic magma supported by their low nb ta ratios and v and sr contents in addition the studied tourmaline displays a slight variation of b isotopic compositions 11b values ranging from 12 2 0 7 to 14 9 0 4 likely resulted by rayleigh fractionation of tourmaline their light b isotopic values are consistent with those of average continental crust also revealing that the nattaung granite was mainly derived from partial melting of the ancient sibumasu crust importantly late stage pt and gt type tourmalines have higher sn zn nb and ta contents than early stage nt type tourmaline suggesting that the evolved b rich magma could be one precursor to produce sn nb ta zn deposits associated with extensive tourmaline in the world

trace element behaviour during migmatization evidence for a complex melt residuum fluid interaction in the st malo migmatitic dome france the st malo migmatitic dome represents an interesting example wherein migmatites arise from the anatexis of the surrounding gneisses petrographical and chemical data suggest that leucosome compositions are compatible with partial melting of the quartzo feldsphathic fraction of the parent gneiss the contribution of the incongruent melting of biotite to the melt does not exceed 5 of the parent rock

trace and rare earth element geochemistry in tourmaline and cassiterite from the yunlong tin deposit yunnan china implication for migmatitic hydrothermal fluid evolution and ore genesis abstract yunlong tin deposit is a medial sized hydrothermal deposit in western yunnan province of china this deposit is unusual because the tin mineralization occurs exclusively within the migmatite bodies the genesis of the ore deposit has been hotly debated and various models have been proposed including granite related magmatic hydrothermal and migmatitic hydrothermal origins this paper reports a systematic trace and rare earth elements ree geochemical study in tourmaline and cassiterite from the orebodies and associated migmatites from the yunlong tin deposit tourmaline and cassiterite from this deposit show light ree lree enriched patterns with variable eu and ce anomalies consistent with hydrothermal fluids being derived from local high grade metamorphism and migmatization the data suggest that tourmaline and cassiterite were likely precipitated from migmatitic hydrothermal fluids and indicate that the yunlong tin deposit was probably formed during migmatitic hydrothermal process the high concentrations of transition metals e g sc ti v cr mn and zn in tourmalines are also consistent with this model the high concentrations of sn sr and especially sc v and cr in tourmalines can be used to discriminate tourmaline from barren deposits relative to those associated with economic tin mineralization

unloading scheme of angooran mine slope by discrete element modeling abstract angooran mine is located in the northwest of iran and has experienced a large scale slope failure in northern wall sliding mass volume occurred in angooran mine was about 12 10 6 m 3 i e 25 10 6 t the sliding mass moved about 45 m vertically and 100 m horizontally for managing this sliding and keeping mine alive simultaneously it was necessary to monitor sliding mass and modeling its behavior because of velocity value and volume of sliding mass should not be exceeded a certain limit and also opportunities for mining have to be surveyed velocity and displacement have been monitored during the unloading stages of sliding mass velocities cannot be zero but with prediction of velocity and displacement of sliding mass the scheme of unloading can be evaluated in this paper modeling of the sliding mass in angooran mine and then unloading it in five stages have been done during the five stages of unloading maximum velocity and maximum displacement among the particles are obtained the modeling results indicate that the maximum velocity occurred in the second stage of unloading mass in the crushed zone and maximum displacement occurred in the third stage of unloading mass in the sliding zone 0 39 m day and 40 14 m respectively

chemical and boron isotope compositions of tourmaline in the hadamiao porphyry gold deposit inner mongolia china abstract the hadamiao porphyry gold deposit in inner mongolia china is located in the northern margin of the north china craton ncc tourmaline is a common mineral in hydrothermal veins and granitic rocks contemporaneous with the mineralized granite porphyry in this deposit the tourmaline can be divided into six types including magmatic tourmaline tur m1 in granite porphyry dikes magmatic hydrothermal transitional tourmaline tur m2 in nodular granitic rocks and hydrothermal tourmalines in early tourmaline veins tur v1 gold bearing quartz tourmaline chalcopyrite veins tur v2 breccia cements tur v3 and late carbonate quartz veins tur v4 the gold mineralization is closely related to the occurrence of tur v2 almost all the tourmalines from the hadamiao deposit belong to the alkali group and show a schorlitic dravitic composition except for some tur m1 belonging to uvite the concentrations of most elements in different tourmaline types overlap tur m1 has higher ca w th u pb mn and zr contents than other types and the hydrothermal tourmalines v1 v4 show slightly higher ba cu and y contents than tur m1 and tur m2 the concentration of au in tur m1 and tur m2 can reach up to 80 ppb and is higher than that in tur v1 the au content in tur v2 is an order of magnitude higher than that in other stages of tourmaline systematic contrasts in major and trace element compositions between magmatic and hydrothermal tourmalines are attributed to the assimilation of the country rock by the magmatic hydrothermal system the six types of tourmaline exhibit variable 11b values ranging from 8 7 to 21 2 tur m1 shows the highest 11b values of 15 1 to 21 2 and tur v2 yields the lowest values ranging from 8 7 to 5 4 the boron probably came from two sources with different isotopic compositions one with high positive 11b values and the other with negative 11b values magmatic hydrothermal fluids could have provided isotopically light boron for hydrothermal tourmalines whereas the heavy boron in magmatic tourmaline was probably derived from marine carbonates that are widespread in the study area the magma related to the mineralization and the one containing magmatic tourmaline may have experienced different degrees of interaction with wall rocks resulting in the diversity of 11b values in hadamiao tourmaline

an empirical oxygen and hydrogen isotope geothermometer for quartz tourmaline and tourmaline water abstract oxygen isotope equilibration temperatures of coexisting quartz muscovite illite chlorite and biotite from a variety of geologic environments have been used in conjunction with the 18o and d values of associated tourmaline to formulate empirical quartz tourmaline and tourmaline water isotope fractionation factors over temperatures from 200 to 600 c the fractionation factors determined using this method are as follows 1 1 1000 in quartz tourmaline 1 0 0 17 10 6 t 2 0 39 0 44 oxygen 2 2 1000 in tourmaline water 27 2 4 4 10 6 t 2 28 1 9 8 hydrogen 350 600 c the isotopic properties of tourmaline are nearly identical to those of muscovite and illite despite the significant differences in their crystal structures similarities in the oxygen and hydrogen isotope systematics of tourmalines and micas imply that the dominant controls on the isotopic properties of these minerals are the vibrational energies of the al si o and si o bonds however the bo3 groups in the tourmalines may have some effect on oxygen isotopic properties as there are minor differences between the 18o values of coexisting tourmalines and micas d values of coexisting tourmalines and micas are generally concordant to within 10 chemical compositions indicate that varying fe mg ratios in the tourmalines appear to have only a minor control on their d values there is a discontinuity in the 1000 in tourmaline water values for hydrogen at temperatures between 200 c and 300 c suggesting that the hydroxl groups in tourmaline are affected by hydrogen bonding and changes in the properties of water near its critical point as are some other hydrous minerals

boron isotope variations in tourmaline from hydrothermal ore deposits a review of controlling factors and insights for mineralizing systems abstract tourmaline group minerals are typically the predominant host of boron in hydrothermal mineral deposits boron is a fluid mobile element whose isotopic composition reflects many factors that are relevant to understanding mineralizing processes including fluid source s fluid rock interaction and formational temperature a new compilation of 2622 published 11b values for tourmaline from diverse types of hydrothermal ore deposits is presented here with the focus 2215 analyses on seven main types porphyry cu mo au deposits granite related sn w deposits iocg deposits orogenic au deposits stratabound vms and sedex deposits and sediment hosted u deposits the total range of 11b values for the seven types is 26 8 to 35 0 four granite sn w orogenic au stratabound vms and sedex have median 11b values close to the continental crustal average of about 10 the median values for iocg and porphyry cu mo au deposits are higher 3 9 and 2 1 respectively whereas sediment hosted u deposits have distinctly high 11b median 25 3 importantly a considerable range of 11b values exists for tourmaline within each deposit type the smallest 17 8 for granite sn w deposits and the largest 48 0 for iocg deposits the boron isotope variations in tourmaline from different deposits are suggested reflect three levels of controlling factors and how these factors operated is illustrated with selected number of case studies the primary factor is the composition of the boron source secondary effects relate to fluid tourmaline fractionation equilibrium or rayleigh there are commonly also tertiary factors that depend on evolution of the specific deposit these include fluid mixing changing water rock ratio and or depositional temperature influences of other boron bearing minerals and where relevant post ore metamorphism separating the effects of these factors is rarely possible from boron isotopes alone however the growth of multi isotope studies of tourmaline and coexisting phases such as mica as well as developments in modelling experimentation of boron isotopes and element partitioning suggest that this limitation will be overcome

stable isotope b h o and mineral chemistry constraints on the magmatic to hydrothermal evolution of the varutrask rare element pegmatite northern sweden abstract the internal evolution of the varutrask rare element pegmatite skellefte district northern sweden has been investigated using stable isotope b h o geochemistry of tourmaline and coexisting micas feldspar and quartz varutrask is a classic and typical example of highly fractionated lct type pegmatites with a pronounced concentric zoning pattern composed of well developed border wall and intermediate zones and a quartz core the pegmatite displays considerable rare element enrichment culminating in the formation of albite lepidolite and pollucite units in the innermost zones major and trace element variations in tourmaline from the main pegmatite zones correlate well with the internal zoning pattern mineral compositions record an abrupt change in fractionation trends between the barren outer and intermediate zones and the inner late stage assemblages that carry rare element mineralization this change is also shown by the b isotope variations of tourmaline early and mid stage tourmalines record a systematic increase in 11 b from 14 6 to 6 2 which can be explained by closed system melt mineral isotope fractionation whereby crystallization of large amounts of muscovite preferentially removes 10 b from the residual melt in contrast tourmaline from late stage assemblages in the inner zones and cross cutting veinlets shows a reversal in the b isotope trend with a decrease in 11 b from 8 to 14 1 this reversal cannot be explained by mineral melt isotope fractionation but requires fluid melt partitioning and partial fluid loss hydrogen isotope variations in mica support this model the systematic increase in d from 75 in the outer zones muscovite to 63 and 53 in the inner zones li micas cannot be explained by closed system variations in temperature or melt mica fractionation but it is consistent with late fluid exsolution oxygen isotope compositions of tourmaline 18 o from 9 7 to 11 6 quartz 13 3 to 14 and mica 10 3 to 11 3 show good agreement with equilibrium partitioning and yield temperatures in the range 450 c to 600 c combining this with the stability fields of li aluminosilicates petalite and spodumene indicates crystallization pressures of 2 3 kbar taken together the stable isotope and mineral chemistry data demonstrate that rare element enrichment in the innermost fractionated assemblages in the varutrask pegmatite was associated with the transition from purely magmatic crystallization to conditions where a separate aqueous fluid phase became important

major and trace element geochemistry of tourmalines from archean orogenic gold deposits proxies for the origin of gold mineralizing fluids abstract orogenic style gold mineralizations in the archean hattu schist belt e finland are present in all major host rock lithologies including epiclastic sedimentary and volcanogenic rocks as well as felsic intrusives the gold mineralizations occur as dissemination in altered wall rocks and within hydrothermal quartz veins hydrothermal tourmalines are often associated with the gold mineralizations occurring in the quartz veins as alteration minerals in contacts of the metasedimentary host rocks and quartz veins but also within mineral assemblages of the metasedimentary and magmatic rocks we characterize and compare the major trace and rare earth element chemistry of these tourmalines in order to evaluate their suitability as a petrogenetic tool for tracing the fluid sources of the hydrothermal system by comparing the chemistry of tourmalines from gold mineralization with those from metamorphic and magmatic host rocks we test whether tourmaline composition can be used to identify the source rocks of the gold transporting hydrothermal fluids all analyzed tourmalines belong to the alkali super group and plot along the schorl dravite join the hydrothermal tourmalines have li sr and v concentrations comparable to metamorphic tourmalines and clearly distinct from magmatic tourmalines because the concentrations of ni pb cr mn ga zn and sn show a wide overlap between magmatic metamorphic and hydrothermal tourmalines these elements do not permit to discriminate between different source rocks the co variations of many elements in hydrothermal tourmalines when plotted against li show more similarity to metamorphic tourmalines and the whole rock compositions of metasedimentary and metavolcanic host rocks than to their magmatic counterparts this indicates that the major and trace element composition of hydrothermal tourmalines in the hattu schist belt is predominantly controlled by the host rocks and local fluid rock interactions and does not reflect the distal fluid sources the effect of local fluid rock interaction is also manifested by the ree patterns of tourmalines the magmatic tourmalines have distinct lree enriched patterns resembling the whole rock ree patterns of granitic intrusives while the metamorphic and hydrothermal tourmalines have flat or weakly fractionated patterns similar to metavolcanic and metasedimentary host rocks taken together the tourmaline data suggest that hydrothermal tourmalines associated to gold mineralizing fluids are most likely genetically related to metamorphic rock sources without important contributions of magmatic fluids and that local fluid rock interaction exerted a major control on tourmaline chemistry

episodic tourmaline growth and re equilibration in mica pegmatite from the bihar mica belt india major and trace element variations under pegmatitic and hydrothermal conditions mica pegmatites from the bihar mica belt contain three distinct generations of tourmaline the major element composition substitution vectors and trajectories within each group are different which indicates that the three types of tourmalines are not a part of one evolutionary series rather the differences in their chemistries as well their mutual microtextural relations can be best explained by growth of tourmaline from pegmatitic melts followed by episodic re equilibration during discrete geological events the euhedral coarse grained brown type i tourmaline cores have relatively high ca mg x mg c 0 37 and al with correlated variation in sr sc ti zr y cr pb and rare earth elements rees they are inferred to have crystallized from pegmatitic melts monazites included within these tourmalines give chemical ages of 1290 1242 ma interpreted to date the crystallization of the pegmatitic tourmaline the bluish type ii and greyish type iii tourmalines with low ca and mg contents x mg 0 16 0 27 and high zn sn nb ta and na formed by pseudomorphic partial replacement of the pegmatitic tourmaline via fluid mediated coupled dissolution reprecipitation are ascribed to a hydrothermal origin the ages obtained from monazites included in these tourmalines indicate two alteration events at c 1100 ma and c 950 ma the correlated variation of ca mg and fe and the trace elements sr sn sc zn and ree within the tourmalines indicates that the trace element concentrations of tourmaline are controlled not only by the fluid chemistry but also by coupled substitutions with major element ions

trace elements in tourmalines from massive sulfides deposits and tourmalinites geochemical controls and exploration applications trace element contents of tourmalines from massive sulfide deposits and tourmalinites have been determined in situ by proton microprobe 390 analyses were acquired from 32 polished thin sections concentrations of trace elements in the tourmalines vary widely from 40 to 3 770 ppm mn 4 to 1 800 ppm ni 2 to 1 430 ppm cu 9 to 4 160 ppm zn 3 to 305 ppm ga 6 to 1 345 ppm sr 10 to 745 ppm sn 49 to 510 ppm ba and 3 to 4 115 ppm pb individual grains and growth zones are relatively homogeneous suggesting that these trace elements are contained within the crystal structure of the tourmaline and are not present in inclusions the highest base metal contents are in ore related tourmaline samples from kidd creek ontario broken hill australia and sazare japan tourmaline data from these and many other massive sulfide deposits cluster by sample and display broadly linear trends on zn vs fe plots suggesting chemical control by temperature and hydrothermal and or metamorphic fluid mineral equilibria significant ni occurs only in samples from the kidd creek cu zn pb ag deposit which is associated with a large footwall ultramafic body an overall antithetic relationship between zn and ni probably reflects fluid source controls mn is correlated with fe in tourmalines from barren associations and possibly in some tourmalines associated with sulfide vein deposits sn increases systematically with fe content irrespective of association the highest values are found in schorls from granites other trace elements are generally uncorrelated with major element concentrations e g sr ca base metal proportions in the tourmalines show systematic patterns on ternary cu pb zn diagrams that correlate well with the major commodity metals in the associated massive sulfide deposits for example data for tourmalines from cu zn deposits e g ming mine newfoundland fall mainly on the cu zn join whereas those from pb zn deposits e g broken hill australia plot on the pb zn join no data fall on the cu pb join consistent with the lack of this metal association in massive sulfide deposits the systematic relationship between base metal proportions in the tourmalines and the metallogeny of the host massive sulfide deposits indicates that the analyzed tourmalines retain a strong chemical signature of their original hydrothermal formation in spite of variable metamorphic recrystallization such trace element patterns in massive sulfide tourmalines may be useful in mineral exploration specifically for the evaluation of tourmaline concentrations in rocks soils and stream sediments

origin of the atypical puy les vignes w breccia pipe massif central france constrained by trace element and boron isotopic composition of tourmaline abstract the puy les vignes w deposit is an atypical wolframite bearing hydrothermal breccia pipe hosted in migmatitic biotite sillimanite gneisses in the northwestern french massif central the deposit is characterized by volumetrically important tourmaline alteration allowing to investigate the fluid evolution of the ore forming hydrothermal system four generations of hydrothermal tourmaline tur 1 tur 4 formed during pre syn and post mineralization stages were identified based on detailed petrographic observations and were analyzed in situ for their chemical and boron isotopic compositions at the grain scale tourmaline commonly shows oscillatory zoning and dissolution textures resulting from a multi stage crystallization in a fluid dominated system the different generations of hydrothermal tourmaline have dravite schorl compositions and show similar major and trace element contents falling into the field of metamorphic rocks high concentrations of v cr sr and low concentrations of li sn in tourmaline suggest a metamorphic dominated origin of these elements the boron isotopic compositions of tourmaline range between 13 3 and 7 8 and cannot unambiguously distinguish between a magmatic and a metamorphic fluid origin our data indicate that the chemical and boron isotopic composition of tourmaline was dominantly controlled by high temperature fluid rock interactions between the metamorphic basement and boron rich reduced and low salinity hydrothermal fluids based on these results we propose a fluid evolution scenario for the puy les vignes ore forming hydrothermal system release of magmatic hydrothermal fluids from an unexposed peraluminous leucogranite at ca 324 ma is proposed as the main mechanism responsible for early greisenization and formation of disseminated tur 1 this episode was followed by massive tourmalinization and hydraulic brecciation of the overlying gneisses producing a tourmaline rich tur 2 crackle breccia by interactions with boron rich hydrothermal fluids fluid assisted reopening and collapse of the former tourmalinite at ca 318 ma yielded a matrix supported quartz tourmaline breccia pipe and formation of wolframite bearing quartz veins accompanied by deposition of tur 3 finally post ore hydraulic fracturing at ca 300 ma led to formation of tourmaline rich microbreccias tur 4 possibly from metamorphic fluids

boron isotopes in tourmaline as a tracer of metasomatic processes in the bamble sector of southern norway the bamble sector of southern norway comprises metagabbros and metasediments that were metasomatically altered to various extents during a late stage of the sveconorwegian orogeny 1 06 ga the infiltration of highly saline brines along veins led to penetrative scapolitization and albitization on a regional scale and the local deposition of fe ti oxides typical secondary mineral assemblages include either scapolite apatite amphibole phlogopite tourmaline or albite epidote calcite chlorite white mica indicating that the fluids introduced large amounts of na cl mg ca k p and b to the system metasomatic tourmalines associated with different alteration stages as identified by variations in major element composition and initial 87sr 86sr were analyzed for b isotopic compositions to constrain possible sources and the evolution of the hydrothermal fluid s measured 11b values range from 5 to 27 relative to srm 951 suggesting marine evaporites interlayered with various amounts of continental detritus and pelagic clay as a possible b source reservoir the influence of a seawater derived component is clearly indicated by the heavy b isotope signature of tourmaline related to al mg rich metapelites in contrast negative 11b values can be explained by the influence of pneumatolytic fluids associated with granitic pegmatites on a regional scale i e several km 11b values in tourmaline vary widely whereas variations within a single outcrop tens of m are typically small and can be ascribed to different generations of tourmaline related to several fluid pulses

stable isotope compositions of tourmalines from granites and related hydrothermal rocks of the karagwe ankolean belt northwest tanzania abstract tourmaline is a ubiquitous mineral in the mid proterozoic peraluminous syn to post tectonic granites and aplites and the related hydrothermal rocks of the karagwe ankolean belt in northwest tanzania electron microprobe analysis indicates that tourmalines from all of the intrusive and hydrothermal lithologies 1 belong to the schorl dravite solid solution series and 2 plot within the field occupied by tourmaline from li poor granitoids on the fe al mg classification diagram oxygen isotope compositions range from 12 2 to 11 6 smow for magmatic tourmalines and from 10 8 to 9 8 for those of hydrothermal origin hydrogen isotope compositions vary from 79 to 65 smow for magmatic tourmalines and from 99 to 84 for hydrothermal tourmalines water contents measured by manometry are constant at 3 0 3 2 wt within the broad grouping there arc systematic variations in both chemical particularly fe tot fe tot mg ratio and isotopic composition that relate to evolving magmatic and hydrothermal conditions igneous differentiation increasing fe tot fe tot mg ratio in magmatic tourmaline has produced trends with higher 18o in quartz lower 18o in tourmaline and larger qtz tour values that reflect a combination of a reduction of crystallization temperature and an increase of fe tot fe tot mg ratio in the residual melt subsequent cooling and interaction of an exsolved b rich magmatic fluid with the pelitic country rocks resulted in the deposition of hydrothermal tourmaline with increasing fe tot fe tot mg ratio ratios and progressively lower 18o and d values

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

tourmaline occurrences within the penamacor monsanto granitic pluton and host rocks central portugal genetic implications of crystal chemical and isotopic features tourmalinization associated with peraluminous granitic intrusions in metapelitic host rocks has been widely recorded in the iberian peninsula given the importance of tourmaline as a tracer of granite magma evolution and potential indicator of sn w mineralizations in the penamacor monsanto granite pluton central eastern portugal central iberian zone tourmaline occurs 1 as accessory phase in two mica granitic rocks muscovite granites and aplites 2 in quartz mica tourmaline rocks tourmalinites in several exocontact locations and 3 as a rare detrital phase in contact zone hornfels and metapelitic host rocks electron microprobe and stable isotope 18o d 11b data provide clear distinctions between tourmaline populations from these different settings a schorl oxyschorl tourmalines from granitic rocks have variable foititic component x 17 57 and mg mg fe ratios 0 19 0 50 in two mica granitic rocks and 0 05 0 19 in the more differentiated muscovite granite and aplites granitic tourmalines have constant 18o values 12 1 0 1 with wider ranging d 78 2 4 7 and 11b 10 7 to 9 0 values b vein breccia oxyschorl mg mg fe 0 31 0 44 results from late b and fe enriched magma derived fluids and is characterized by 18o 12 4 d 29 5 and 11b 9 3 while replacement tourmalines have more dravitic compositions mg mg fe 0 26 0 64 close to that of detrital tourmaline in the surrounding metapelitic rocks and yield relatively constant 18o values 13 1 13 3 though wider ranging d 58 5 to 36 5 and 11b 10 2 to 8 8 values and c detrital tourmaline in contact rocks and regional host metasediments is mainly dravite mg mg fe 0 35 0 78 and oxydravite mg mg fe 0 51 0 58 respectively boron contents of the granitic rocks are low 650 ppm compared to the minimum b contents normally required for tourmaline saturation in granitic melts implying loss of b and other volatiles to the surrounding host rocks during the late magmatic stages this process was responsible for tourmalinization at the exocontact of the penamacor monsanto pluton either as direct tourmaline precipitation in cavities and fractures crossing the pluton margin vein breccia tourmalinites or as replacement of mafic minerals chlorite or biotite in the host rocks replacement tourmalinites along the exocontact of the granite thermometry based on 18o equilibrium fractionation between tourmaline and fluid indicates that a late b enriched magmatic aqueous fluid av 18o 12 1 at 600 c precipitated the vein breccia tourmaline 18o 12 4 at 500 550 c and later interacted with the cooler surrounding host rocks to produce tourmaline at lower temperatures 400 450 c and an average 18o 13 2 closer to the values for the host rock although b metasomatism associated with some granitic plutons in the iberian peninsula seems to be relatively confined in space extending integrated studies such as this to a larger number of granitic plutons may afford us a better understanding of variscan magmatism and related mineralizations

tectonothermal history of the schwarzwald ore district germany an apatite triple dating approach abstract exceptionally large u rich apatite from the schwarzwald ore district germany was triple dated using id tims u pb fission track ft and u th he dating methods the aim of adopting the multi dating approach on a single sample was to i further constrain thermo tectonic evolution of the schwarzwald from the formation of crystalline basement through to cooling and exhumation and ii test potential and limitations of in situ ft u th he double dating the apatite u pb age of 289 5 4 5 ma records the cooling of the basement through the 550 c during the early permian and brackets the age of the apatite hosting rhyolite between 289 5 4 5 ma and 314 6 ma which is the age of rhyolite hosting granite this is in excellent agreement with radiometric ages of related rhyolites and fits with the magmatic evolution of the schwarzwald during variscan orogeny in the eocene between 50 and 40 ma the basement resided at 100 c and then cooled to surface temperatures as revealed by the ft age 37 6 1 3 ma and thermal modelling results based on track lengths during the cooling event the basement was likely exhumed as a rift shoulder of newly formed upper rhine graben rift nine apatite grains yielded u th he ages from 30 7 1 5 to 65 0 2 6 ma mean age 45 7 1 3 ma three possible reasons for the lack of reproducibility are i non homogeneous distribution of parent isotopes evidenced by strong u zoning ii bad neighbourhood causing implantation of extraneous he and iii radiation damage leading to increased he retentivity implied by the high 250 ppm u concentration these problems could not be circumvented by mechanical abrasion of outermost rim of dated crystals which yielded u th he ages from 26 0 1 0 to 56 2 2 2 ma mean age 37 2 1 4 ma in situ ft and traditional u th he double dating of single apatite crystals revealed that the vast majority of u th he ages were younger than indistinguishable from or overlap within error with corresponding ft ages proving the robustness of this approach the results also show that apparent discrepancies between ft and u th he ages reported in the literature may arise simply as a result of statistical misconceptions and conventional data treatment considering the range of single grain ft ages and the oldest single grain ft age in addition to the central ft age may provide an effective basis on which to evaluate the viability of u th he data

effects of meteoric water interaction on hercynian granites from the sudschwarzwald southwest germany abstract hercynian granites from the sudschwarzwald plutons of klemmbach st blasien schluchsee barhalde show a wide range of whole rock 18 o values from 2 5 to 10 9 smow detailed 18 o analysis of separated minerals indicates strong isotopic disequilibrium a feature which can be explained by large scale post magmatic hydrothermal interaction of the granites with isotopically light meteoric water at temperatures below 500 c microthermometric investigation of homogenization and melting temperatures from two phase vapour liquid secondary fluid inclusions in quartz indicates a temperature range between 200 and 400 c for the alteration the aqueous fluid inclusions typically have low salinities but reach values up to 9 eq wt nacl in samples with evidence for secondary mineral development i e chloritization sericitization etc trace element variations in k feldspar rb sr ba tl pb bi provide a guide to elemental mobilization with increasing water rock ratios a gain of rb tl and bi and a loss of sr ba and pb is observed during alteration combining all data a three stage reaction scheme for the hydrothermal alteration of the granites is proposed 1 t 400 c granite prim fluid 1 granite alter fluid 2 2 t 200 300 c fluid 2 granite alter secondary mineralization fluid 3 3 t 200 c fluid 3 gangue mineralization

the rand granite in the southern schwarzwald and its geodynamic significance in the variscan belt of sw germany the rand granite is a heterogeneous metamorphosed granitoid rock complex with numerous wallrock inclusions situated in the moldanubian zone at the southern margin of the central schwarzwald gneiss complex it is a largely mylonitized elongated body and is thrust over the badenweiler lenzkirch zone forming a nappe with shear zones along its northern and southern boundaries it comprises meta granites meta trondhjemites and biotite augen gneisses derived from monzogranites to granodiorites mineral behaviour indicates that the magmatic body has been deformed under upper greenschist facies conditions nappe thrusting which also affected the south schwarzwald gneiss complex occurred in visean time during high temperature low pressure metamorphism kinematic indicators in the mylonites document e to ese directed nappe transport highly transpressive relative to the trend of the nappe boundaries and the foliation the trondhjemites formed at 351 5 4 ma predating the variscan ht metamorphism they have initial end values of 6 6 to 6 7 and relatively low initial 87sr 86sr ratios 0 7042 to 0 7063 indicating a predominant mantle origin the granites and protoliths of the biotite augen gneisses probably crystallised between 436 and 377 ma suggested by u pb zircon model ages they are different from the trondhjemites with low initial end values 4 7 to 3 3 and higher initial 87sr 86sr ratios 0 7068 0 7077 indicating that large part of the rand granite originated from anatexis of continental crust internal structure of zircons from the rand granite reveals mixing of magmas derived from both mantle and crust sources these new data support an interpretation that the rand granite developed along an active continental margin and therefore represents a possible root of a variscan magmatic arc

tourmaline boron and strontium isotope systematics reveal magmatic fluid pulses and external fluid influx in a giant iron oxide apatite ioa deposit abstract tourmaline is a common boron bearing mineral in hydrothermal system and has been widely used as a mineral probe to reconstruct geological processes because of its broad range in composition and resistance to metasomatic alteration the origin of kiruna type iron oxide apatite ioa deposits commonly linked to andesitic subvolcanic or volcanic rocks is highly controversial constraints on the evolution of these mineralizing systems are needed to advance understanding of the ore forming process in this study we apply in situ elemental and combined b sr isotopic analyses of tourmaline to elucidate the nature and evolution of the subsurface hydrothermal system associated with ioa mineralization in the giant taocun deposit eastern china taocun is hosted at the top of a diorite intrusion and exhibits three stages of hydrothermal alteration that contain tourmaline pre ore na alteration tur i syn ore magnetite formation and associated ca fe alteration tur ii and post ore ca mg alteration with sulfide veins tur iii compositional data for each stage of tourmaline plot along the oxy dravite povondraite join which is indicative of precipitation from relatively oxidizing fluids ranges of sr isotopic compositions in tur i 0 7065 0 7078 and tur ii 0 7068 0 7076 are identical to those of the igneous host rocks indicating precipitation from magmatic hydrothermal fluids the range of b isotopic compositions in tur i 11b values of 6 3 to 1 2 is also consistent with a magmatic source higher 11b values 2 4 to 5 4 obtained from tur ii are mainly ascribed to rayleigh fractionation in the magmatic hydrothermal system as tourmaline precipitated post ore tur iii has a wide range of mostly lower b isotopic compositions 8 5 to 0 8 that record another pulse of magmatic fluid input this interpretation is supported by the enrichment of na li be w sn v and ti in tur iii relative to tur i and ii however the higher sr isotope composition 0 7076 0 7086 of tur iii and available o isotope composition 7 to 3 5 of fluids of this stage record the infiltration of meteoric ground water from adjacent sedimentary country rocks the results suggest that the taocun ioa deposit formed in a magmatic hydrothermal system characterized by two or more pulses of magmatic fluid discharge from subvolcanic diorite intrusions followed by the influx of external ground water as the system waned this study highlights the utility of tourmaline as a robust geochemical and isotopic monitor of ore forming processes in such systems

in situ elemental and boron isotopic variations of tourmaline from the maogongdong deposit in the dahutang w cu ore field of northern jiangxi province south china insights into magmatic hydrothermal evolution abstract in this paper we present a systematic investigation of in situ major trace elements and boron isotopic variations of tourmaline from the maogongdong deposit in the dahutang w cu ore field of northern jiangxi province south china which demonstrates both the magmatic and hydrothermal origin for the formation of the tourmalines the tourmaline occurs mainly in granites pegmatites and quartz veins five types of tourmaline are identified 1 disseminated tourmaline in the pegmatites tur p type 2 isolated and disseminated tourmaline clots in the granites tur r1 type 3 typical anhedral quartz tourmaline nodulars in the granites tur r2 type 4 tourmaline clots in quartz tungsten sulfide veins tur q1 type 5 euhedral needle columnar tourmaline crystals in quartz or quartz sulfide veins tur q2 type these tourmalines mostly fall into the alkali group representing schorl dravite solid solution series petrography and chemical discrimination diagrams suggest that the tur p tur r1 and tur r2 are of magmatic origin and the tur q1 and tur q2 are of hydrothermal origin hydrothermal tourmalines have higher mg mg fe ratios higher li be sn rb co sr v pb zn ni contents and lower na na ca ratios lower nb ta contents than the magmatic tourmalines the tur p show negative eu anomalies and their ree patterns are equivalent to the muscovite granite the eu anomalies in tur r1 and tur r2 change from negative to positive compared with magmatic tourmalines tur q1 and tur q2 exhibit more pronounced positive eu anomalies and a majority of the tur q1 and tur q2 have higher ree contents tourmalines from the maogongdong deposit have a b isotopic composition range from 17 9 to 12 3 the average 11b values of the tur p tur r1 and tur r2 are 13 8 14 8 and 14 5 respectively tourmalines in early hydrothermal veins have similar 11b values average 14 6 while the tourmalines in later hydrothermal veins have slightly lower 11b values average 16 5 boron isotopic variations of tourmaline are controlled by temperature rayleigh fractionation and external fluid

tourmaline as a recorder of magmatic hydrothermal evolution an in situ major and trace element analysis of tourmaline from the qitianling batholith south china four types of tourmaline in the qitianling granitic batholith south china were identified in this study euhedral disseminated tourmaline dt type in the early stage of granite consolidation typical interstitial nodular tourmaline nt type formed late in the crystallization history radial tourmaline veinlet rt type and vein tourmaline vt type of hydrothermal origin we performed major and trace element analysis by in situ electron microprobe and laser ablation inductively coupled plasma mass spectrometry on these four tourmaline types compositionally these tourmalines fall into the alkali group and schorl dravite solid solution series there is clear correlation between trace and major elements in vt type tourmalines likely related to co variations of these elements in the hydrothermal fluid from which the tourmaline precipitated tourmaline from granites displays low ree abundances and negative lree trends positive eu anomalies and hree below or close to their detection limits the dt type tourmalines show a positive eu anomaly which is probably due to a preferential incorporation of eu2 over eu3 ree depletion in nt type tourmalines may reflect co crystallization of ree rich minerals the positive eu anomaly in nt type tourmalines is due to late stage release of eu2 caused by tourmaline replacement of early feldspar vein tourmalines rt and vt type display similar slopes from la to nd without an eu anomaly the chondrite normalized ree patterns in tourmalines from veins display a concave upward shaped mree depleted pattern with minimum values at ho increasing steadily to lu and may reflect the ree characteristics of the precipitated medium hree enrichment in hydrothermal fluid can be attributed to the formation of ree fluoride complexes during the internal fluid evolution

the geochemical differentiation of s type pegmatites constraints from major trace element and li b isotopic composition of muscovite and tourmaline pegmatites often exhibit regional as well as internal zonation in this study we use major and trace element and li b isotopic composition of muscovite and tourmaline from internally zoned and un zoned s type pegmatites and their host granites to characterize the geochemical and isotopic fractionation associated with their formation the internally zoned pegmatites comprise three distinct textural zones namely wall intermediate and core muscovite and tourmaline occur in all the zones of these pegmatites the trace element concentrations ratios of muscovite from the three zones form well defined differentiation trends marked by enrichment of incompatible elements such as rb cs sr b zn nb ta p and the depletion of ni co v sc ti ba from the wall zone through the intermediate zone to the core zone this is suggestive of a strong role of fractional crystallization in producing the compositional diversity in the internally zoned pegmatites alkali element ratios such k rb and k cs in muscovite exhibit near exponential decline from the wall to the core zone which is suggestive of rayleigh type fractional crystallization fractional crystallization modelling reveals that the formation of the wall zone requires 69 crystallization the intermediate zone 85 95 and the core zone ca 99 crystallization leading to extreme enrichment of rb and cs and other incompatible elements muscovites and tourmaline from the un zoned pegmatites display similar compositional trends as the internally zoned ones but with a significant compositional gap between the host granite and the pegmatite lithium isotopic composition of muscovites and b isotopic composition of tourmalines become progressively lighter from wall to core zone of the internally zoned pegmatite and from the granite to the pegmatite for the un zoned pegmatites this is suggestive of an important role of vapour exsolution in the formation of the pegmatites taken together the geochemical and isotopic trends in the pegmatites can be explained by rayleigh fractional crystallization operating in tandem with vapour exsolution

trace element systematics of tourmaline in pegmatitic and hydrothermal systems from the variscan schwarzwald germany the importance of major element composition sector zoning and fluid or melt composition article an extensive data set on the compositional variation of tourmaline from granitic pegmatites from migmatitic gneisses and from various types of hydrothermal veins from the schwarzwald germany is provided the investigated tourmalines are members of the alkali and x vacant groups representing mostly dravite schorl solid solutions with some analyses belonging to the foitite mg foitite series oxygen isotope data on quartz tourmaline pairs indicate formation temperatures between 550 and 350 c for most of the quartz tourmaline veins most of the tourmalines show strong sector zonation fractionating certain major e g na mg minor e g ti ca and trace elements e g sr pb ree among the different crystallographic sectors of the crystals we conclude that comparison of tourmaline compositions for petrogenetic interpretations must be based on the concentrations in the neutral a sector in order to eliminate the effects of intra crystalline fractionation most trace element contents vary over several orders of magnitude with median concentrations generally be tween 0 1 and 10 g g the highest concentrations are found for zn v sr sc sn and li median concentrations of several tens to hundreds of g g whereas very low median concentrations b0 1 g g were found for u th bi tl and cs the concentration of several trace elements e g sr ree co correlates with the major element composition of the tourmaline which implies potential crystal chemical effects on their incorporation conse quently the general assumption that tourmaline is a passive monitor for the chemical compositions of the melts or fluids from which it crystallizes has to be questioned nevertheless our study demonstrates that the trace element composition of tourmaline allows to distinguish between geochemically distinct fluid sources and the trace element composition of tourmaline may therefore be used to unravel the chemical complexity of granite related hydrothermal systems

tourmaline geochemistry and δ11b variations as a guide to fluid rock interaction in the habachtal emerald deposit tauern window austria tourmalines from the habachtal emerald deposit in the eastern alps formed together with emerald in a ductile shear zone during blackwall metasomatism between pelitic country rocks and a serpentinite body electron microprobe and secondary ion mass spectrometric sims analyses provide a record of chemical and b isotope variations in tourmalines which represent an idealized profile from metapelites into the blackwall sequence of biotite and chlorite schists tourmaline is intermediate schorl dravite in the country rock and become increasingly dravitic in the blackwall zones while f and cr contents increase and al drops metasomatic tourmaline from blackwall zones is typically zoned optically and chemically with rim compositions rich in mg ti ca and f compared with the cores the total range in 11b values is 13 8 to 5 1 and the within sample variations are typically 3 5 both of these ranges are beyond the reach of closed system fractionation at the estimated 500 550 c conditions of formation and at least two boron components with contrasting isotopic composition are indicated a key observation from tourmaline core analyses is a systematic shift in 11b from the country rock 14 to 10 to the inner blackwall zones 9 to 5 we suggest that two separate fluids were channeled and partially mixed in the habachtal shear zone during blackwall alteration and tourmaline emerald mineralization a regional metamorphic fluid carried isotopically light boron as observed in the metapelite country rocks the other fluid is derived from the serpentinite association and has isotopically heavier boron typical for morb or altered oceanic crust

in situ elemental and boron isotopic variations of tourmaline from the sanfang granite south china insights into magmatic hydrothermal evolution abstract tourmaline often occurs in boron rich granites and its genesis is still in dispute either formed from residual boron rich silicate melt or from magmatic hydrothermal fluids with or without external fluid involvement here we present a systematic investigation of in situ major trace elemental and boron isotopic variations of tourmaline from the sanfang granite in guangxi province of south china which demonstrate both the magmatic and hydrothermal origin for the formation of the tourmalines the tourmaline occurs mainly in quartz tourmaline nodules and tourmaline pegmatitic segregations within the sanfang granite four types of tourmaline are identified 1 isolated and disseminated tourmaline tur d type distributed in granite 2 euhedral and subhedral tourmaline in quartz tourmaline nodules tur n type 3 the earlier stage tourmaline tur pe type in pegmatitic segregations and 4 the later stage tourmaline tur pl type which replaced the tur pe type tourmaline in pegmatitic segregations all the tourmalines belong to the alkali group representing dravite schorl solid solution series with the former three types being schorl and the tur pl type being dravite petrography chemical discrimination diagrams and al occupations in the y site suggest that the tur d tur n and tur pe type tourmalines are of magmatic origin and the tur pl type tourmalines are of hydrothermal fluid origin elemental and boron isotopic composition variations of tourmalines reflect the compositional and environmental evolution from late boron rich magma to exsolved hydrothermal fluids chemical variations from the tur d to the tur n tourmalines are controlled by magma differentiation the increase of mg mg fe and ca ca na ratios from the tur n to the tur pe tourmalines suggests the contamination of surrounding strata e g the sibao group hydrothermal tourmalines have higher mg mg fe and lower na na ca ratios than the magmatic tourmalines there is clear correlation at least in some trace elements e g sr pb with major elements for all tourmalines indicating the potential crystal chemical effects on their incorporation other trace element incorporation in tourmaline is largely controlled by melt and fluid composition hydrothermal tourmalines have high and stable v co and ni contents indicating relatively constant partition coefficient between hydrothermal tourmalines and the fluid hydrothermal tourmalines exhibit lower total ree contents but more pronounced positive eu anomalies than the magmatic tourmalines the 11b values of all tourmalines from the sanfang granite vary from 14 4 to 9 3 which indicate the boron in the sanfang granite was mainly derived from partial melting of the metasedimentary source rocks boron isotopic variations of tourmaline are controlled by fractionation between melt fluid and rayleigh fractionation

diverse tourmaline compositions from orogenic gold deposits in the hutti maski greenstone belt india implications for sources of ore forming fluids the late archean hutti maski greenstone belt hosts the largest operational gold mine in india at hutti as well as two satellite mines at hira buddini and uti tourmaline is a common accessory mineral in the auriferous altered wall rocks proximal to the gold bearing veins of these orogenic gold deposits we report here major rare earth element ree and selected trace element compositions of tourmalines from these alteration zones at hutti and hira buddini and from spatially associated volcaniclastic rocks at uti in order to compare and evaluate possible fluid sources related to tourmaline precipitation and gold mineralization tourmalines at hutti occur as tourmaline calcite microveins within proximal alteration zones and as disseminated grains along the biotite chlorite defined mylonitic foliation these tourmalines belong to the dravite oxydravite group with an evolutionary trend towards magnesio foitite and commonly are mg rich up to 2 06 apfu with low na 0 61 apfu and up to 53 x site vacancies characteristics are low abundances of total ree 0 25 0 67 chondrite and a flat trend with minor hree enrichment accompanied by strong positive eu anomalies at hira buddini tourmalines of the oxydravite povondraite series replace amphiboles and hydrothermal biotite based on textural and chemical characteristics three generations of tourmalines are present at hira buddini earliest type i tourmaline has moderate fe content up to 1 46 apfu high na average 0 80 apfu and moderate x site vacancies up to 22 type ii tends to be relatively enriched in fe up to 2 08 apfu have similar na contents average 0 79 apfu and low x site vacancies up to 8 these tourmalines contain higher total ree 0 93 2 23 chondrite and display a flat trend with slight middle rare earth element mree depletion accompanied by a small positive eu anomaly the latest tourmalines type iii are fe poor up to 1 52 apfu and na poor average 0 67 apfu with relatively high x site vacancies up to 21 this tourmaline type has relatively low total rees 0 21 1 05 chondrite and similar abundance patterns to those of hutti tourmalines accompanied by large positive eu anomalies similarity in tourmaline compositions with evolutionary trends in compositional space from different textural associations suggests that a single low salinity and reduced metamorphogenic fluid with inherently low ree was responsible for proximal alteration and gold mineralization at hutti the type i and type ii tourmalines from hira buddini display oxydravite povondraite trends with compositional overlap that suggests fluid mixing at a paragenetically early stage the early hydrothermal fluid was more saline oxidizing and likely had a granite derived component with high ree contents a later evolved relatively low salinity and reduced fluid is recorded by the last generation type iii tourmalines at hira buddini the tourmalines from uti metapelites are characterized by dravitic composition low na contents high x site vacancies 31 47 and an evolutionary trend toward magnesio foitite these tourmalines have higher ree contents 1 16 2 08 chondrite lree enriched patterns together with large positive eu anomalies and low concentrations of most trace elements all features that suggest a metamorphic origin

magmatic hydrothermal fluids and volatile metals in the spirit lake pluton and margaret cu mo porphyry system sw washington usa the halogen bearing minerals tourmaline amphibole and biotite formed during magmatic hydrothermal processes associated with the late stage cooling of the spirit lake granitoid pluton mt st helens wa and with the younger sulphide mineralised rocks of the margaret cu mo porphyry deposit located entirely within the pluton major and trace element discrimination suggests that one tourmaline population crystallised from fractionated late stage melt pockets in granodiorite monzogranitic dykes of the pluton these coarse euhedral oscillatory and complexly sector zoned uvite tourmalines span a limited range in mg mg fe mg space 0 4 0 7 apfu and show the highest ti ca f nb and ta contents and low x site vacancies 0 6 apfu lower ca and f contents and the highest li as and hree contents 80 ppm li 1200 ppm as this population appears to record direct rapid crystallisation from magmatic meteoric fluid s bearing the signature of the breakdown of primary feldspars and pyroxenes with fluid exsolution from fractionated melt patches likely triggered by the formation of the previous generation of tourmaline mineralised porphyry deposit tourmaline compositions from the stockwork span a much larger range in mg space 0 05 0 9 apfu and are almost entirely ca free x sites of these schorl tourmalines are dominated by na or vacancies and the y sites are strongly fe enriched the highest mn and zn concentrations 4000 and 1000 ppm respectively potentially reflect the composition of mineralising fluids during ore deposition a number of boron isotopic analyses yield predominantly heavy boron but 11b values range from 5 2 to 6 2 and average 1 4 whilst most plutonic tourmalines conform to reported a and c sector element partitioning models those from the mineralised porphyry show large and variable sector fractionation differences suggesting that external controls may also be important wider evidence for late stage pervasive metasomatism by halogen bearing exsolved fluid s is provided by the high mg 70 secondary amphiboles and biotites from within the spirit lake pluton where the amphiboles are clear replacement products of primary pyroxenes fluid halogen fugacity ratios calculated from the biotite compositions overlap with other global mineralised porphyry systems despite not being immediately associated with sulphide ores the evidence suggests complex fluid processes and the coincidental development of the mineralised porphyry system within the pluton heat fluids and metals were therefore likely supplied by a later phase of magmatism unrelated to the consolidation of the main spirit lake granitoid these new constraints on magmatic hydrothermal fluid signatures have wider applicability to potentially tracing proximal barren and mineralised processes and for distinguishing between formation mechanisms for primary and secondary halogen bearing minerals

hourglass sector zoning in metamorphic tourmaline and resultant major and trace element fractionation a new type of sector zoning with an hourglass shape has been identified in metamorphic tourmalines that formed under a wide variety of physical and chemical conditions the two sectors in the c direction are not equivalent due to asymmetry in the crystal structure of tourmaline along the c axis the c sector is characterized by low concentrations of ti ca mg and na although al is high and has a pale commonly blue or pale green color conversely the c sector is low in mg and al and high in ca fe and ti the latter two causing the dark brown color of this sector the a sector has intermediate characteristics and probably approximates a sector free tourmaline thin sectioning of these sector zoned tourmalines perpendicular to the c axis can produce three types of apparent radial zoning patterns blue green cores dark brown cores or no distinct cores these apparent cores will further vary in relative diameter depending on the sectioning level furthermore core boundaries can be straight or ragged depending on whether the relative growth speeds for the different faces was constant or variable these textures have been used to argue for a prograde or detrital origin of tourmaline cores however sector zoning is a more appealing explanation for most of these textures and can further explain the textural resemblance among metamorphic tourmalines from highly variable bulk rock composition metamorphic history and mineral paragenesis the sector zoning that is described here develops by preferential uptake of elements on the r growth plane resulting from a combined effect of differences in surface charge and morphology of this plane in the c and c directions this leads to the preferential incorporation of more positively charged elements in the c direction and a preference for a vacant x site in the c direction because the compositional differences among the sectors are pronounced in both major and trace elements and in the same order of magnitude as growth zoning variability the presence of sector zoning must be established and taken into account when making inferences from tourmaline chemistry

chemical and boron isotopic compositions of tourmaline from the archean big bell and mount gibson gold deposits murchison province yilgarn craton western australia abstract tourmaline is a commonly found gangue mineral in archean greenstone belt lode gold deposits worldwide in this paper we report major trace and rare earth element ree and boron isotopic compositions of tourmaline from two major amphibolite grade archean gold deposits big bell and mount gibson murchison province yilgarn craton western australia in an attempt to better understand the hydrothermal gold formation processes that were also responsible for tourmalinization tourmalines in these two major deposits all belong to the dravite schorl series and tend to be mg rich where closely associated with gold and sulfide ores the ore related tourmalines also contain high concentrations of ore metals such as au ag pb and cu in the big bell deposit tourmalines occur along the foliation in lode schists and show low fe fe mg ratios of 0 11 0 30 tio 2 contents of 0 15 0 73 wt and negligible mno 11 b values of 17 7 to 15 0 in the mount gibson deposit the tourmalines closely associated with the sulfide ores are the most mg rich with low fe fe mg ratios of 0 19 0 22 while tourmalines from garnet bearing biotite muscovite schists that overly the lode gold orebody are more fe rich fe fe mg 0 30 0 63 tourmalines from an amphibolite schist are mg rich with fe fe mg ratios 0 27 0 34 that lie between the above two groups of tourmalines the compositional trend from fe rich tourmalines in the sulfide poor schists to mg rich in the sulfide ores at mount gibson is similar to that observed in massive sulfide ore deposits worldwide alternatively the mg rich nature of the sulfide related tourmalines may be due to metamorphic reactions that are accompanied by fe incorporation into sulfides leaving coexisting silicates more mg rich the ree geochemistry of the tourmalines from the mount gibson ore zone schists displays strong hree enrichments and positive eu anomalies with eu eu ratios up to 2 4 which are similar to tourmalines associated with massive sulfide deposits the ore related tourmalines disseminated in the host schists show 11 b values of 18 6 to 17 0 whereas one coarse grained tourmaline vein has a lower 11 b value of 21 9 to 21 4 these data support hypotheses which suggest that the schists that host the gold mineralization are the metamorphosed equivalents of a base metal rich hydrothermally altered seafloor horizon that is typical of vms style mineralization with the boron possibly derived from leaching of footwall sedimentary and volcanic rocks during hydrothermal circulation

boron metasomatism and behaviour of rare earth elements during formation of tourmaline rocks in the eastern arunta inlier central australia tourmaline rocks of previously unclear genesis and spatially associated with w cu bearing calc silicate rocks occur in palaeoproterozoic supracrustal and felsic intrusive rocks in the bonya hills in the eastern arunta inlier central australia tourmalinisation of metapelitic host rocks postdates the peak of regional low pressure metamorphism m1 d1 500 c 0 2 gpa and occurred synkinematically between the two main deformation events d1 and d2 coeval with emplacement of late strangways 1 73 ga tourmaline bearing leucogranites and pegmatites tourmaline is classified as schorl to dravite in tourmaline quartz rocks and surrounding tourmaline rich alteration zones and as fe rich schorl to foitite in the leucogranites boron metasomatism resulted in systematic depletion of k li rb cs mn and enrichment of b and in some samples of na and ca in the tourmaline rocks compared to unaltered metasedimentary host rocks whole rock ree concentrations and patterns of unaltered schist tourmalinised schist and tourmaline quartz veins the latter were the zones of influx of the boron rich hydrothermal fluid are comparable to those of post archaean shales thus the whole rock ree patterns of these rocks are mostly controlled by the metapelitic precursor in contrast ree concentrations of leucogranitic rocks are low 10 times chondritic and their flat ree patterns with pronounced negative eu anomalies are typical for fractionated granitic melts coexisting with a fluid phase ree patterns for tourmalines separated from metapelite hosted tourmaline quartz veins and tourmaline bearing granites are very different from one another but each tourmaline pattern mirrors the ree distribution of its immediate host rock tourmalines occurring in tourmaline quartz veins within tourmalinised metasediments have lree enriched lan ybn 6 3 55 shale like patterns with higher ree 54 108 ppm in contrast those formed in evolved leucogranites exhibit flat ree patterns lan ybn 1 0 5 6 with pronounced negative eu anomalies and are lower in ree 5 6 30 ppm we therefore conclude that ree concentrations and patterns of tourmaline from the different tourmaline rocks studied are controlled by the host rock and not by the hydrothermal fluid causing boron metasomatism from the similarity of the ree pattern of separated tourmaline with the host rock we further conclude that incorporation of rees in tourmaline is not intrinsically controlled i e by crystal chemical factors tourmaline does not preferentially fractionate specific rees or groups of rees during crystallisation from evolved boron and fluid rich granitic melts or during alteration of clastic metasediments by boron rich magmatic hydrothermal fluids

quartz veins with associated sb pb ag au mineralization in the schwarzwald sw germany a record of metamorphic cooling tectonic rifting and element remobilization processes in the variscan belt a combination of textural observations from 38 permian sb pb ag au bearing quartz veins in the schwarzwald sw germany with isotopic fluid inclusion and geochemical data allows to refine genetic models for this common type of mineralization to understand the origin of mineralogical diversity and the correlation with large scale tectonic events textures record four main mineralization stages i fe as sb au ii pb zn cu iii pb sb and iv ag sb stage i sulfides dominated by pyrite and arsenopyrite formed due to cooling of low salinity metamorphic fluids during the permian with maximum homogenization temperatures of 400 c invisible gold in arsenopyrite pyrite marcasite and stibnite was remobilized and locally precipitated as electrum at the end of stage i minerals of stages ii and iii comprise a rich diversity of sb bearing sulfosalts including e g bournonite zinkenite and jamesonite this assemblage formed during jurassic times due to mixing of high salinity mid and upper crustal fluids up to 27 wt nacl cacl2 with homogenization temperatures between 50 and 250 c stage iii is marked by a rich variety of pb sb sulfosalts its local abundance is directly related to the presence of stage i mineralization and its extent of remobilization during a significant influx of pb in the jurassic cretaceous the formation of the upper rhine graben during the tertiary reactivated especially ne sw oriented veins percolating ag rich fluids reacted with earlier stage iii pb sb sulfosalts forming ag rich minerals stage iv such as miargyrite pyrargyrite and stephanite the transition from metamorphic fluids to basinal saline e g pb bearing brines over hundreds of millions of years as is shown in this study and present in other variscan occurrences indicates a possibly typical poly stage characteristic of sb deposits worldwide which has however not been investigated in detail so far

deformation controlled cation diffusion in tourmaline a microanalytical study on trace elements and boron isotopes abs tract plastic deformation of variable intensity has modified primary textures composition and element distribution in tourmaline from a mylonitic pegmatite from the nw argentinean sierras pampeanas the primary concentric tourmaline zonation has been overprinted and partly destroyed by synkinematic cation diffusion that occurred under amphibolite facies p t conditions textural changes include bending of crystals formation of subgrains and subgrain rotation leading locally to recrystallization of tourmaline some parts of deformed crystals were less affected or unaffected by plastic deformation and secondary cation diffusion two principal processes intracrystal trace element diffusion and matrix exchange of trace elements caused the compositional variations in deformed tourmaline domains intracrystal diffusion partly or completely destroyed the primary trace element zonation by cation diffusion from zones of high to low concentration small cations occupying the y position are readily mobilized even by weak deformation whereas large cations on the x site require higher deformation intensity to be mobilized and show less pronounced or no homogenization of the primary zonation matrix exchange between tourmaline and co existing solid or fluid phases generally leads to trace element loss from deformed tourmaline domains the extent of the matrix exchange is primarily controlled by the compatibility of mobilized cation species with matrix phases during mylonitization in contrast the b isotopic compositions in deformed and undeformed crystal domains are uniform indicating absence of significant b diffusion and isotope fractionation during crystal growth and plastic deformation i e the activation energy to move b in tourmaline must be too high even for intense plastic deformation to overcome

calculation of oxygen isotope fractionation in hydroxyl bearing silicates abstract the modified increment method has been applied to the calculation of oxygen isotope fractionation factors for hydroxyl bearing silicate minerals the order of 18o enrichment obtained in common rock forming minerals is pyrophyllite kaolinite tourmaline talc prehnite topaz illite phengite lepidolite muscovite staurolite epidote glaucophane serpentine chlorite tremolite hornblende phlogopite biotite humite norbergite ilvaite hydroxyl bearing silicates are enriched in 18o relative to hydroxyl groups but depleted in 18o relative to anhydrous counterparts three sets of self consistent fractionation factors between quartz and the hydroxyl bearing silicate minerals between calcite and the silicate minerals and between the silicate minerals and water have been calculated for a temperature range of 0 1200 c the fractionation factors calculated for mineral pairs are applicable to isotopic geothermometry in igneous metamorphic and sedimentary petrology they can be used as a test of isotopic equilibrium or disequilibrium in natural mineral assemblages over all temperature ranges of geological interest the difference in oxygen isotope composition between the hydroxyl bearing mineral and the oh group is quantitatively demonstrated to be temperature dependent and therefore can be used as a single mineral geothermometer

from granite to highly evolved pegmatite a case study of the pinilla de fermoselle granite pegmatite system zamora spain abstract the pinilla de fermoselle pegmatite is a cap like body with an asymmetrical vertical zoning from a granitic facies at the bottom to the upper contact with the metamorphic country rocks the granite grades imperceptibly into the pegmatite which includes three main zones with different degrees of enrichment in li f b p rb cs be sn the essential minerals are quartz feldspar al micas from the muscovite lepidolite series fe micas biotite and zinnwaldite tourmaline schorl elbaite rossmanite and fe mn phosphates apatite beryl cassiterite and cookeite are the most significant accessory minerals the trace elements li be and sr show similar trends in feldspar micas and tourmaline with an increase in the li and be contents and a decrease in sr from the granite to the most evolved pegmatitic zone similar trends are shown by rb cs and ba for micas and k feldspar rb and cs increasing gradually from the granite to most evolved pegmatitic zones simultaneously to the decrease of ba in tourmaline nb and ta contents increase upwards whereas zn contents decrease in the same way the mn contents increase until intermediate degrees of evolution and decrease again in the pinkish elbaite combined field petrographic and geochemical data are consistent with a fractional crystallization model from a granitic melt with a clear petrogenetic relationship between the underlying peraluminous granite and the pegmatite body k feldspar and particularly micas and tourmaline appear as good geochemical monitors using trace elements such as li rb be sr and ba which offer intriguing insights into the petrogenesis of pegmatites

p t evolution of a variscan lower crustal segment a study of granulites from the schwarzwald germany pressure temperature time p t t paths of orogenic granulites introduction provide important information on the thermal and chemical structure general background of the lower continental crust through time and constraints on tectonic granulites are typical rocks of the earth s middle to processes we present the first detailed petrological investigation of lower crust under high temperature conditions they are granulites from the variscan schwarzwald pelitic granulites from the found as xenoliths in basaltic volcanic rocks mainly central schwarzwald gneiss complex csgc are characterized by within continental rifts but most granulites occur as the peak assemblage garnet rutile kyanite antiperthite complexes or terranes in orogenic settings orogenic quartz felsic to intermediate granulites from the southern granulites display a wide compositional range harley schwarzwald gneiss complex ssgc exhibit different peak as1989 1998 and are known from a variety of collisional semblages with clinopyroxene orthopyroxene ternary feldspar garnet belts that formed during different episodes since the quartz and sillimanite and manifold retrograde reaction textures archaean e g harley 1998 clarke et al 2000 moller peak p t conditions were calculated by two feldspar thermometry et al 2000 determination of bulk rock and mineral garnet orthopyroxene thermometry and various geobarometers minicompositions calculation of peak equilibration conmum estimates for peak conditions are 950 1010 c and 1 4 1 8 ditions and dating of orogenic granulites thus provide us gpa for the granulites of the csgc which followed a clockwise with important constraints on the thermal and chemical p t path the retrograde path is characterized by initial isothermal structure of the earth s continental crust at different decompression associated with partial melting followed by isobaric geological times cooling peak conditions for the ssgc are 1015 c and 1 5 gpa harley 1989 showed that equilibration conditions minimum temperature maximum pressure no prograde relics are deduced from natural orogenic granulites cover a wide preserved and isothermal decompression was less pronounced than range in particular pressures are highly variable and in the csgc other variscan hp ht granulites from central the granulite field may be divided into a low pressure europe show similar lithologies equilibration temperatures and lp a medium pressure mp and a high pressure hp ages 340 335 ma the heat for widespread high temperature facies according to green ringwood 1967 peak metamorphism in the variscan lower crust could have been supplied temperatures of many granulite terranes scatter around by repeated intrusion of subduction related basic magmas rapid 800 c bohlen 1987 but an increasing number of near isothermal decompression of the granulites may have been ultra high temperature uht granulite complexes facilitated by considerable volumes of partial melt and by orogenic extension 900 1100 c and 0 7 1 3 gpa harley 1998 are being recognized e g harley hensen 1990 dasgupta et al 1995 klemd brocker 1999 hokada 2001 regarding retrograde p t paths harley 1989 distinguished two

elemental and b o h isotopic compositions of tourmaline and associated minerals in biotite muscovite granite of mashhad ne iran constraints on tourmaline genesis and element partitioning abstract abundant tourmaline occurs in late triassic biotite muscovite granites of mashhad ne iran with several distinct morphologies including tourmaline nodules in granite pegmatitic tourmalines aplitic tourmalines and vein related tourmalines quartz tourmaline vein tourmaline rich vein and radial tourmalines pegmatitic and aplitic tourmalines are compositionally fe rich schorl and the nodule radial and vein tourmalines are mg rich schorl the tourmalines have generally low abundances for most trace elements except for sr ga li be sn pb and some transition elements tourmalines have low ree abundances and are enriched in lree and depleted in hree mostly below detection limits with positive eu anomalies the concentration of several trace elements e g pb be sn ga sr pb and ree correlates well with the major element composition of the tourmalines e g mg mg mg fe vacancy x site vacancy na and na na ca trace element data of coexisting minerals with tourmaline indicate that the oligoclase and albite show the most preference in sr pb and eu and lrees biotite readily incorporates rb ba zn li cs and nb k feldspar has high contents of rb ba sr and pb and garnet incorporates hrees and y during magma differentiation the b o h isotopic compositions for all tourmalines are consistent with an s type granite source that was derived from partial melting of the continental crust the pegmatitic and aplitic tourmalines with fe rich schorl composition indicate magmatic conditions and the radial vein and nodule tourmalines with mg rich schorl composition formed during the transition from magmatic to hydrothermal conditions due to the internal evolution of the granitic magma

assessment of tourmaline compositions as an indicator of emerald mineralization at the tsa da glisza prospect yukon territory canada tourmaline is ubiquitous at the tsa da glisza emerald prospect yukon territory occurring as porphyroblasts in greenschistfacies metavolcanic and ultramafic rocks and as crystals in granites aplites and quartz tourmaline veins the principal occurrence of emerald is along contacts between the quartz tourmaline veins and mafic country rocks but it also occurs in the aplites we assess the potential of using tourmaline compositions as a guide to emerald mineralization at tsa da glisza based on major element trace element li be sc cr v mn ni co cu zn as rb sr y zr nb cd mo sn sb cs ba ta w bi pb th and u ree la ce pr nd sm eu yb lu and boron isotope data the tourmaline compositions encompass na fe schorl na mg dravite and ca mg uvite and show a strong dependence on host rock chemistry tourmalines closely associated with emeralds intergrown in same hand specimen are slightly more iron rich dravites compared with those from schists and alteration zones lacking emerald binary and ternary plots of major and trace element concentrations show that emerald associated tourmalines occupy restricted ranges of composition albeit considerably overlapping those not associated with emerald trace element concentrations in tourmaline associated with emerald mineralization include 20 to 40 ppm co 50 ppm ni 0 5 ppm la 0 5 ppm y 100 to 200 ppm li and 300 to 600 ppm zn boron isotope 11b values range from 15 6 to 4 2 per mil for all tourmalines n 80 low values are most common and are consistent with a dominantly granitic source of boron higher isotope ratios 8 are confined to tourmalines from country rocks and quartz veins suggesting a contribution of isotopically heavy b from the maficultramafic series the three emerald related samples have a restricted intermediate range of 10 3 to 7 9 per mil multivariate cluster analysis defines two populations of tourmalines corresponding to host rock type one cluster includes tourmaline from country rocks and quartz tourmaline veins and the other is dominated by samples from granites and aplites the latter cluster also includes all tourmalines associated with emeralds with trace element concentrations and boron isotope values as input variables one stepwise discriminant function analysis model produces a 91 percent correct classification matrix and an 88 percent correct jackknifed classification matrix this result suggests that tourmaline has potential as an indicator mineral at the tsa da glisza prospect and possibly also in the exploration for emeralds elsewhere

crustal scale thrusting and extension in the hercynian schwarzwald and vosges central europe the hercynian outcrop areas in the schwarzwald of sw germany and vosges of easternmost france consist from north to south of three major lithotectonic complexes very low to medium grade metamorphics of the saxothuringian belt the polymetamorphic central gneiss complex and the tectonic melange of the southern complex juxtaposition of these three complexes occurred by oblique convergent motions in early carboniferous time the saxothuringian belt is part of a major se dipping accretionary wedge that consists of lower paleozoic meta sedimentary and metaigneous rocks and superimposed upper devonian to lower carboniferous synorogenic volcanics and elastics the central gneiss complex consists of polymetamorphic paragneisses orthogneisses metabasites and meta ultramafics dipping to the nw the southern complex consists of an imbricated melange of north to nw dipping synorogenic elastics volcanics and blocks of ultramafics and gneissic basement the central gneiss complex cgc experienced pervasive hercynian low pressure high temperature metamorphisrn before it was emplaced against and thrust over the sedimentary and volcanic fill of the adjacent synorogenic basins this convergence 340 330 ma produced mylonitic cataclastic shear zones in the cgc the most significant shear zones are the se verging todtnau fault zone between the cgc and the southern complex and the nw verging lubine fault zone between the central gneiss complex and the rocks of the saxothuringian belt these two fault zones enclose a bivergent pop up of the polymetamorphic basement the todtnau fault zone probably extends for more than 100 km along strike and can be traced to a depth of 10 km by deep seismic reflection studies detachment probably occurred along a mid crustal zone of anatexis expressed by a domain of low seismic reflectivity between about 10 and 15 km crustal thickening during early carboniferous convergence led to an extensional phase of crustal reordering between about 330 and 280 ma that was accompanied by the massive rise of posttectonic granitic plutons from middle to high crustal levels simultaneous creation of a structural lamination in the refractory lower crust neglected the main convergent tectonic boundaries it produced a basin and range type lower crust and mantle crust transition in early permian time and involved a major advective input of heat

chemical and boron isotopic composition of tourmaline from the conadong leucogranite pegmatite system in south tibet abstract tourmalines occur widely within leucogranites and pegmatites that intrude the leucogranites in the south tibetan plateau morphological and geochemical elemental and boron isotopic studies on these tourmalines are very limited furthermore the tourmaline genetic correlation between the leucogranite and the pegmatite is also unknown in this contribution two types of tourmaline occurrences have been identified in the conadong area south tibet including randomly disseminated tourmaline in leucogranite gt type and radial dendritic or massive tourmaline aggregates in pegmatite dikes that intrude the leucogranite pt type we performed major element and boron isotopic analyses of tourmaline using electron microprobe empa and laser ablation multi collector inductively coupled plasma mass spectrometry respectively the two types of tourmalines are enriched in fe na and al but relatively depleted in ca and mg elements with compositions close to alkali group tourmaline and schorl all the tourmalines are likely the products of equilibrium crystallization and their dominance of na was controlled by the magmatic compositions of their host rocks the gt type tourmalines show a narrow range of 11b values between 9 78 0 81 and 8 53 0 68 with a mean of 8 91 0 18 whereas the pt type tourmalines have significantly lower 11b values than the gt type ranging from 14 02 0 85 to 11 83 0 57 with a mean of 13 31 0 49 these data together with their morphology and petrography indicate that the conadong granitic tourmalines were derived by the melts at the early magmatic stage whereas the pegmatitic tourmalines precipitated from magmatic hydrothermal fluids at the late magmatic stage the variation in boron isotopic compositions 11b 4 4 between the pt and the gt type tourmalines is most likely correlated with their different melt fluid source regions that had distinct sr nd b isotopic compositions

boron isotope and light element sector zoning in tourmaline implications for the formation of b isotopic signatures hourglass sector zoning in metamorphic tourmaline is known to effectively fractionate the major and trace elements between different sectors producing three distinct compositions at the growth surface here we show that the light elements li be h and b as well as the 11 b signature are also affected by sector zoning the sector enrichment in elements is controlled by a dual process of initial preference due to growth surface charge and morphology followed by consecutive charge balance controlled enrichment the light elements especially b and h appear to act as charge balance cations in this mechanism with a preferred b 3 for si 4 and o 2 for oh substitution in the c sector a lighter 11 b signature d c c 1 8f0 6x accompanies this increase in b iv in the c sector in line with the lighter signatures for b iv compared to b iii in minerals however it exceeds this theoretical fractionation by a factor of 10 although we have not identified a definite process that is responsible for this fractionation it may be related to local variations in host medium along the growth surface resulting from preferred uptake of elements these observations show that 11 b signatures in tourmaline are not an independent measure of its host environment but also a function of mineral composition and the 3 dimensional zoning variations herein 2007 elsevier b v all rights reserved

tourmaline rich features in the heemskirk and pieman heads granites from western tasmania australia characteristics origins and implications for tin mineralization distinctive magmatic hydrothermal tourmaline rich features have developed in the heemskirk and pieman heads granites from western tasmania australia they are categorized as tourmaline rich patches orbicules cavities and veins based on their distinctive morphologies sizes mineral assemblages and contact relationships with host granites these textural features occur in discrete layers in the roof zone of granitic sills within the heemskirk and pieman heads granites tourmaline patches commonly occur below a tourmaline orbicule rich granitic sill tourmaline filled cavities have typically developed above the tourmaline quartz orbicules in the upper layer of the white phase of the heemskirk granite tourmaline quartz veins penetrate all exposed levels of the granites locally cutting tourmaline orbicules and cavities the tourmalines are mostly schorl fe rich and foitite with an average end member component of schorl 45 dravite 6 tsilaisite 1 uvite 0 fe uvite 3 foitite 31 mg foitite 4 olenite 10 element substitutions of the tourmalines are controlled by femg 1 al y x square r2 na 1 and minor alo al y r2 oh 1 where r2 fe2 mg2 mn2 exchange vectors several trace elements in tourmaline have consistent chemical evolutions grouped from tourmaline patches through orbicules and cavities to veins there is a progressive decrease of most transition and large ion lithophile elements and a gradual increase of most high field strength elements these compositional variations in the different tourmaline rich features probably relate to element partitioning occurring in these phases due to volatile exsolution and fluxing of aqueous boron rich fluids that separated from the granitic melts during the emplacement of s type magmas into the shallow crust 4 to 5 5 km tourmalines from the heemskirk granite are enriched in fe na li be sn ta nb zr hf th and rare earth elements relative to the tourmalines from the pieman heads granite but depleted in mg mn sc v co ni pb sr and most transition elements these results imply that bulk compositions of the host granites exert a major control on the chemical variations of tourmalines the trace element compositions of tourmalines from the sn mineralized heemskirk granite are different from those of the barren pieman heads granite trace element ratios e g zn nb co nb sr ta and co la and sn concentrations in tourmaline can distinguish the productive heemskirk granite from the barren pieman heads granite

ion microprobe determinations of trace element concentrations in garnets from anatectic assemblages abstract trace element data for garnet cordierite plagioclase alkali feldspar and tourmaline have been obtained by ion microprobe analysis of assemblages from a pelite derived leucogranite a sillimanite grade anatectic gneiss and a kyanite grade sub solidus schist from the high himalaya results confirm that for equilibrium melting residual plagioclase will cause depletion in sr and eu in the melt and residual garnet will result in strong depletion of y and hree consistent with their published partition coefficients all trace elements of interest are strongly incompatible in cordierite implying that for equilibrium fractional melting of pelites at shallow depths hree concentrations in garnets from metasediments are independent of metamorphic grade but the metamorphic garnets are significantly less enriched in hree than is the leucogranite garnet this suggests either that the leucogranite is derived from a source with lower modal abundances of garnet than the analysed metasediments or that garnet from the anatectic gneiss has not reached chemical equilibrium with a granitic melt the latter possibility is consistent with sluggish self diffusion rates in garnets for ree at temperatures of 5 kbar

tourmaline as a recorder of contrasting boron source and potential tin mineralization in the mopanshan pluton from inner mongolia northeastern china abstract abundant tourmaline occurs in the mopanshan pluton in inner mongolia of ne china and can be classified by its occurrence into four types nodular tourmalines nd type pegmatite pocket tourmalines pp type stockwork tourmalines sw type and vein tourmalines vt type all these tourmalines belong to the alkali group and are dravite schorl petrography and major elements data suggest that the nd and pp type tourmalines crystallized during the transition from late magmatic to early hydrothermal evolution of granite with all the components derived from the magma petrography and trace elements especially sr v cr ni ti data suggest that the sw and vt type tourmalines may form by the mixing of magmatic and country rocks components in the post magmatic hydrothermal environment due to the similar 11b of the sw type with the nd and pp type tourmalines variation

deciphering fluid flow at the magmatic hydrothermal transition a case study from the world class panasqueira w sn cu ore deposit portugal abstract deciphering the behavior of fluid flow at the magmatic hydrothermal transition is crucial to understanding the physical processes leading to the formation of intrusion related ore deposits and hence to predicting the locations of mineralized bodies however the hydrodynamics direction and velocity of the hydrothermal fluid flows related to this transitional stage remains poorly constrained here we present a coupled textural and chemical study performed on tourmaline growth bands to constrain fluid flow during the initiation of the hydrothermal system of the panasqueira w sn cu deposit this exceptional deposit consists of a dense network of flat wolframite and cassiterite bearing quartz veins intensely developed above a well known but hidden greisen cupola the w sn mineralization is preceded by a tourmalinization stage occurring as metasomatic halos around veins and as selvages developed along the vein wall rocks contacts results emphasize the key role of the greisen cupola in fluid focusing and the role of fluid overpressure during vein opening velocity values highlight an efficient transport of metals in veins largely dominated by advective processes 10 4 to 10 3 m s 1 whereas fluid flow in the altered wall rocks is slow and pervasive 10 6 to 10 5 m s 1 suggesting that element transport through the metasedimentary host rock was low and limited to the alteration haloes la icp ms analyses of tourmaline growth bands reveal that fluids coming from the cupola are enriched in na k li sr and sn emphasizing the contribution of magmatic fluids during vein formation and the metasomatic alteration of the wall rocks more generally this study demonstrates that the apical portions of granite bodies act as emanative centers of mineralizing fluids and highlights the usefulness of mineral growth band analysis in the search for intrusion related mineralization

late magmatic immiscibility during batholith formation assessment of b isotopes and trace elements in tourmaline from the land s end granite sw england quartz tourmaline orbicules are unevenly distributed in the roof segment of the land s end granite sw england this study shows that the orbicules formed from an immiscible hydrous borosilicate melt produced during the late stages of crystallization and differentiates tourmaline formed by dominantly magmatic and dominantly hydrothermal processes trace elements and boron isotope fractionation can be tracked in tourmaline and create a timeline for crystallization tourmaline from the granite matrix has higher v cr and mg content and is isotopically heavier than the later crystallizing inner orbicule tourmaline overgrowths of blue tourmaline occurring together with quartz showing hydrothermal cathodoluminescence textures crystallized from an aqueous fluid during the very last crystallization and are significantly higher in sr and sn and isotopically heavier tourmaline associated with sn mineralization is also high in sr and sn but has boron isotopic compositions close to that of the magmatic tourmaline and is not formed by the same fluids responsible for the blue overgrowths the ore forming fluids precipitating tourmaline and cassiterite are likely derived from the same magma source as the granite but exsolved deeper in the magma chamber and at a later stage than orbicule formation tourmaline from massive quartz tourmaline rocks is concentrically zoned with major and trace element compositions indicating crystallization from a similar melt as for the orbicules but shows a more evolved signature