zircon u pb geochronological and hf isotopic constraints on petrogenesis of late mesozoic intrusions in the southeast hubei province middle lower yangtze river belt mlyrb east china abstract during the late mesozoic extensive magmatism and associated ore deposits were developed in the southeast hubei province middle lower yangtze river metallogenic belt mlyrb east china to understand the petrogenesis of the intrusions in the area we performed in situ zircon u pb and hf isotopic analyses on 14 samples from the fengshangdong stock and from the echeng tieshan wangbaoshan jinshandian and yangxin batholiths three major suites of intrusive rocks are recognized in the southeast hubei province 1 141 146 ma granodiorite and granite porphyries associated with 143 144 ma porphyry skarn cu mo deposits have enriched radiogenic hf isotopic compositions ehf t 9 5 to 1 6 comparable to those of cretaceous pyroxene diorites trachyandesites and basalts ehf t 8 9 to 1 3 in the mlyrb which were derived from an enriched lithospheric mantle 2 voluminous 136 143 ma gabbros diorites and quartz diorites associated with 137 144 ma skarn cu fe fe cu and au cu deposits have variable hf isotopic compositions ehf t 19 1 to 5 4 indicating an origin via the hybridization of enriched mantle derived mafic magma and variable amounts of ancient lower crustal components 3 127 133 ma diorites quartz diorites and granites associated with 132 133 ma skarn fe deposits characterized by a wide range of ehf t values 28 2 to 6 4 suggest the assimilation of various ancient lower crustal materials by enriched mantle derived basaltic magma the intrusions of suites 1 and 2 are characterized by high sr contents 329 2087 ppm and high sr yb 36 1710 and la yb n ratios 17 6 172 but low yb contents 0 45 1 82 ppm and do not show negative eu anomalies eu 0 74 1 4 the intrusions have radiogenic sr nd isotopic compositions end t 10 0 to 3 4 and 87 sr 86 sr i 0 7054 0 7084 compared with the intrusions of suites 1 and 2 rocks of suite 3 have relatively low sr contents 60 5 327 ppm and low sr yb 33 0 315 and la yb n ratios 2 28 30 0 but relatively high yb contents 1 04 5 17 ppm and significant negative eu anomalies eu 0 22 0 73 the rocks of suite 3 are characterized by a wide range of radiogenic sr nd isotopes with end t values of 12 5 to 4 9 and 87 sr 86 sr i 0 7057 0 7085 the proposed magma sources combined with the geochemical and sr nd isotopic differences between these three suites of intrusive rocks indicate that late mesozoic magmatic activity in the southeast hubei province mlyrb was associated with lithospheric thinning induced by asthenospheric upwelling at that time

fifteen day observation of mesospheric and lower thermospheric motions with the aid of the arecibo uhf radar an attempt was made to have a continuous observation of the zonal wind component in the tropical mesosphere and lower thermosphere for 15 days of august 1 15 1980 with the aid of the uhf radar at arecibo 18 n by using the wind data together with additional data obtained from meteorological rockets meteor radar and tiros n satellite analyses were made of the time mean zonal wind profile tides long period waves and short period gravity type waves respectively there appears a remarkable day to day variation of the zonal wind throughout the region between 70 and 95 km with a characteristic time scale of about 5 days indicating the passage of traveling planetary scale waves in the summertime tropical middle atmosphere it was also found that the short period oscillation with a time scale of a few 10 min appears intermittently in association with the strong vertical shear of the background flow this oscillation is considered to be the manifestation of the kelvin helmholtz type instability in the lower thermosphere

the solubility of nb ta zr hf w in granitic melts with li and li f constraints for mineralization in rare metal granites and pegmatites tantalum mineralization is associated with granites and pegmatites that invariably are rich in lithium this in part is due to the extreme fractionation that is necessary for melts to reach saturation in either a ta or an li phase however there may also be chemical interactions in melts that explain this association experiments therefore were conducted to determine the effect of lithium on the solubility of tantalite mnta 2 o 6 in water saturated granitic melts other important elements in rare metal granites include nb zr hf and w consequently the effect of li on the solubilities of columbite mnnb 2 o 6 zircon zrsio 4 hafnon hfsio 4 and hbnerite mnwo 4 in granitic melts was also investigated the haplogranitic melt compositions used in these experiments have constant mole percent si and al and the al li na k ratio was 1 0 for all experiments i e the lithium content was the only compositional variable columbite and tantalite solubilities in the granitic liquids increase by a factor of approximately 2 to 3 with the addition of 2 wt percent li 2 o to haplogranite at 750 degrees to 1 035 degrees c 2 kbars and water saturated conditions the solubility data were extrapolated to a lower temperature more reasonable for columbite tantalite crystallization then compared to compositions representative of evolved liquids from which rare metal granites and pegmatites crystallize it is estimated that at 600 degrees c these melt compositions could be saturated in columbite but not tantalite however tantalite saturation is predicted if the melts contained less li and f therefore the genesis of tantalum mineralization may be explained by ta being retained in the melt because of high li f concentrations tantalite crystallization is delayed until an li or f or p mineral crystallizes which lowers tantalite solubility and results in a general association of ta with li in mineralized granitic rocks in contrast to columbite and tantalite the solubility of wolframite is not affected by the lithium content of the melt with up to 3 8 wt li 2 o in starting glasses and the solubilities of zircon and hafnon decrease with increasing li content of the melt one possible interpretation of the hbnerite solubility data is that the melt contains dominantly w super 6 which behaves as a network former the decrease in zircon hafnon solubility with li may reflect the lower field strength of zr super 4 and hf super 4 compared to nb super 5 and ta super 5 i e zr and hf are less able to compete with li for nonbridging oxygens whereas nb and ta are more able to compete it is also significant that the solubility of hafnon is greater than that of zircon similar to the higher solubility of tantalite compared to columbite this can explain why zr hf and nb ta ratios both decrease with fractionation

the role of hydrothermal processes in concentrating high field strength elements in the strange lake peralkaline complex northeastern canada abstract the middle proterozoic peralkaline pluton at strange lake quebec labrador comprises hypersolvus to subsolvus phases which are unusually enriched in zr y rees nb be and f as exotic alkali and alkaline earth silicate minerals the highest concentrations of these elements are in subsolvus granite which underwent intense low temperature 200 c hydrothermal alteration involving hematization and the replacement of alkali high field strength element hfse minerals by calcic equivalents this alteration is interpreted to have been caused by meteoric or formational waters high temperature 350 c alteration attributed to orthomagmatic fluids is evident in other parts of the subsolvus granite by the replacement of arfvedsonite by aegirine comparisons of the chemical compositions of fresh and altered rocks indicate that rocks subjected to high temperature alteration were chemically unaffected except for depletion in zr y and hrees these elements were appreciably enriched in rocks that underwent low temperature alteration other elements affected by low temperature alteration include ca and mg which were added and na which was removed available data on hfse speciation in aqueous fluids and the chemistry of the pluton suggest that the hfses were transported as fluoride complexes if this was the case the low temperature fluid could not have been responsible for hfse transport because the high concentration of ca and low solubility of fluorite would have buffered f activity to levels too low to permit significant complexation we propose that hfse mineralization and accompanying alteration were the result of mixing in the apical parts of the pluton of a f rich essentially ca free orthomagmatic fluid containing significant concentrations of hfses with an externally derived meteoric dominated fluid enriched in ca as a result of interaction with calc silicate gneisses and gabbros according to this interpretation the latter fluid was responsible for the exchange of ca for alkalis mainly na in hfse rich minerals and by sharply reducing f activity in the mixed fluid through fluorite precipitation and or increasing ph destabilised the hfse fluoride complexes causing deposition of hfse bearing minerals an important implication of this study is that major hfse enrichment may be restricted to those rare cases where f rich ca free metal leaching environments and ca rich depositional environments are juxtaposed

cretaceous ridge subduction along the lower yangtze river belt eastern china the lower yangtze river belt is one of the most important metallogenic belts in china the mechanisms responsible for ore genesis and the formation of related cretaceous igneous rocks such as adakite a type granitoid and nb enriched basalt remain controversial mesozoic granitoids in the lower yangtze river belt were mostly formed in the early cretaceous 140 125 ma and three granitoid belts the inner the south and the north have been defined according to petrological and geochemical characteristics previously based mainly on negative end and high initial sr isotope values the adakitic rocks were generally attributed to partial melting of thickened or delaminated lower crust both of which require crustal thickening mesozoic crustal thickening however is not supported by the development of extensional basins in the region from the late jurassic to cretaceous eastern china was closely associated with subduction of the pacific plate in the south and the izanagi plate in the north the midocean ridge mor between these two plates was drifting toward and likely subducting under the lower yangtze river belt a ridge subduction model can therefore explain the distribution of different magmatic rocks and ore deposits in the belt partial melting of subducting young hot oceanic slabs close to the ridge formed adakitic rocks the negative end values of adakitic rocks can be plausibly interpreted by mixing between adakitic magmas and enriched components in the lithospheric mantle and or crustal materials through afc process a slab window opened during ridge subduction as indicated by a type granitoids in the center of the inner belt nb enriched basalt found in the belt was likely formed by partial melting of a mantle wedge metasomatized by fluids released from the subducting slab at shallow depths

a review of the intracontinental porphyry deposits in the middle lower yangtze river valley metallogenic belt eastern china abstract the middle lower yangtze river valley metallogenic belt mlyb is one of the most important metallogenic belts in eastern china and contains many important porphyry deposits these deposits include the tongshankou cu mo jiguanzui cu au chengmengshan cu mo wushan cu mo fengshandong cu au dingjiashan cu yangjishan au shaxi cu au dongguashan cu au shujiadian cu and anjishan cu deposits etc in this review we summarize the geological characteristics including the stratigraphy structure ore bearing porphyry types vein characteristics and wall rock alteration metallogenic ages and petro geochemistry of representative porphyry deposits in the mlyb we conclude that porphyritic magmatism and metallogeny have occurred in three stages the early ca 149 135 ma and late ca 123 105 ma stages comprise mainly porphyry skarn mineralization whereas the middle ca 133 125 ma stage comprises porphyry mineralization ore bearing porphyries in the mlyb are the high k calc alkaline to calc alkaline series with the majority possess adakitic geochemical signature the ore bearing porphyries with adakitic signature may have originated from magma mixing produced by the delamination of enriched lithospheric mantle and partial melting of the thickened lower crust the enriched mantle derived mafic melts component are very important for generating fertile magma and the 34s and 18o values suggest that ore forming materials were magma derived compared with porphyry deposits in typical magmatic arc settings porphyry deposits in the mlyb do not contain advanced argillic lithocaps or high to intermediate sulfidation systems and the magmatic and ore forming material sources are also very different

texture and geochemistry of multi stage hydrothermal scheelite in the tongshankou porphyry skarn cu mo w deposit eastern china implications for ore forming process and fluid metasomatism

the role of hydrothermal processes in the granite hosted zr y ree deposit at strange lake quebec labrador evidence from fluid inclusions abstract the strange lake zr y ree nb and be deposit is hosted by a small high level late proterozoic peralkaline granite stock that intruded into high grade metamorphic gneisses on the quebec labrador border the stock is extensively altered early alteration is manifested by the replacement of arfvedsonite with aegirine later alteration involved ca na exchange zr ti y rees nb and be are concentrated in ca bearing minerals that together with quartz commonly pseudomorph na bearing minerals fluid inclusions in pseudomorphs comprise several distinct types high salinity 13 to 24 wt nacl eq ca rich aqueous inclusions that homogenize to liquid between 135 and 195 c mixed aqueousmethane inclusions methane inclusions and solid bearing inclusions aqueous methane inclusions represent heterogeneous entrapment of immiscible high salinity aqueous liquid and methane bastnasite tentatively identified by sem analysis occurs as a daughter mineral other daughter or trapped minerals include a y hree bearing mineral possibly gagarinite and hematite galena sphalerite fluorite pyrochlore kutnahorite and griceite the first three inclusion types also occur in quartz in pegmatites and veins together with lower temperature lower salinity na dominated aqueous inclusions the entrapment temperature inferred for the aqueous inclusions from microthermometry and the na k ca geothermometer range from 155 to 195 c for the higher salinity inclusions and 100 to 165 c for the low salinity inclusions a model is proposed in which the intrusion of a peralkaline granite to high crustal levels initiated a ground formational water dominated hydrothermal system in adjacent gabbroic calc silicate and graphitic gneisses reaction of the high salinity ca rich liquid with the graphitic gneisses led to the production of an immiscible methane gas subsequent interaction of this liquid with the granite led to extensive replacement of sodic minerals by calcium analogues at temperatures of less than 200 c some time after the onset of ca metasomatism the high salinity liquid mixed with a ca poor low salinity low temperature liquid that had leached f and rare metals from the granite yttrium and ree mineral deposition occurred as a result of the decreased ligand concentration that accompanied fluorite deposition during mixing of the ca rich and ca poor aqueous liquids

ore forming fluids and isotopic h o c s pb characteristics of the fujiashan longjiaoshan skarn w cu mo deposit in the edong district of hubei province china abstract the fujiashan longjiaoshan deposit is located in the southern area of the edong district of the middle lower yangtze river metallogenic belt w cu mo orebodies are found in the contact zone between the granodiorite porphyry and carboniferous to triassic carbonate strata four stages of ore formation are identified 1 the prograde skarn stage 2 retrograde skarn stage 3 quartz sulfide stage further subdivided into the early 3a and later 3b and 4 carbonate stage in this study we applied fluid inclusion microthermometry laser raman spectroscopy and h o c s pb isotopic compositions to constrain hydrothermal processes and ore precipitation mechanisms of the fujiashan longjiaoshan deposit early stage 1 and 2 ore forming fluids belong to a high temperature above 550 c high salinity 60 70 wt nacl equiv and 15 20 wt nacl equiv respectively high pressure above 700 bars and high oxygen fugacity nacl kcl h2o system and in the quartz sulfide stage 3 the system changes into a nacl kcl co2 h2o system homogenization temperatures and salinities of ore forming fluids gradually decrease throughout the evolutionary process fluid temperatures vary at 550 c in prograde skarn stage 1 from 350 to 400 c in retrograde skarn stage 2 from 250 to 300 c in quartz sulfide stage 3 and finally from 100 to 150 c in carbonate stage 4 salinity levels vary from 15 to 20 wt nacl equiv in prograde skarn stage 1 from 5 to 20 wt nacl equiv in retrograde skarn stage 2 from 10 to 15 wt nacl equiv in quartz sulfide stage 3a from 5 to 10 wt nacl equiv in quartz sulfide stage 3b and from 0 to 5 wt nacl equiv in carbonate stage 4 the h o c isotopic compositions indicate that the ore forming fluids were derived from magmatic water d of 123 to 83 18ov smow of 6 1 to 7 4 with the input of meteoric water and organic matter in the quartz sulfide stage d of 91 to 53 18ov smow of 2 4 to 4 6 and cv pdb of 14 7 to 6 4 sulfur and pb isotopic compositions show that the ore forming materials were mainly derived from granitic magma 34sv cdt values of granodiorite porphyry sulfides and skarns of 5 7 to 6 6 and in part from host sedimentary strata 34sv cdt values of sulfides of country rocks clustering at 20 and at 10 fluid boiling in the retrograde skarn stage gave rise to the first precipitation of scheelite the precipitation of scheelite chalcopyrite and molybdenite in the quartz sulfide stage was probably triggered by the input of meteoric water and organic carbon according to mineral assemblages and all available geological and geochemical data we conclude that the fujiashan longjiaoshan deposit is an oxidized skarn type w cu mo deposit

zr nb ree mineralization in peralkaline granites from the amis complex brandberg namibia evidence for magmatic pre enrichment from melt inclusions the amis complex is a late intrusive phase associated with the brandberg anorogenic granite intrusion it consists of peralkaline arfvedsonite bearing granitic and pegmatitic dikes and sills and is characterized by locally extreme enrichments in ree and rare metals with high charge ionic radius ratios such as zr and nb the highest concentrations e g 1 7 wt zr 0 3 wt nb 0 5 wt total ree are found in aegirine albite aplites that formed around arfvedsonite pegmatite cores quartz hosted melt inclusions in coarse grained arfvedsonite granite and pegmatite give unequivocal evidence that the peralkaline composition and rare metal enrichments are primary magmatic features electron microprobe and sims analyses of rehomogenized inclusion glasses reveal their peralkaline high si rhyolite compositions avg molar na k al 1 1 and very high contents of h2o max 10 6 wt and f 2 2 wt inclusion glasses also have high concentrations of incompatible trace elements including nb min 803 ppm zr min 3 187 ppm and ree y min 1 271 ppm the ree zr and nb compositions of the aegirine albite aplites plot along the same linear enrichment trends as the melt inclusion glasses and y ho ratios mostly display unfractionated near chondritic values the chemical and textural features of the aegirine albite aplites are compatible with an origin by rapid crystallization compositional quenching after volatile loss from a residual peralkaline granitic melt of a composition like that of the melt inclusions interaction of postmagmatic fluorine rich aqueous fluids with the arfvedsonite granites caused local remobilization of ree and secondary mineralization of fluorocarbonate phases such as bastnaesite and fractionation of y and ho

bokan mountain peralkaline granitic complex alexander terrane southeastern alaska evidence for early jurassic rifting prior to accretion with north america the circular bokan mountain complex bmc on southern prince of wales island southernmost alaska is a jurassic peralkaline granitic intrusion about 3 km in diameter that crosscuts igneous and metasedimentary rocks of the alexander terrane the bmc hosts significant rare metal rare earth elements y u th zr and nb mineralization related to the last stage of bmc emplacement u pb zircon and 40ar 39ar amphibole and whole rock geochronology indicates the following sequence of intrusive activity i a paleozoic basement composed mainly of 469 4 ma granitic rocks ii intrusion of the bmc at 177 1 ma followed by rapid cooling through ca 550 c at 176 1 ma that was synchronous with mineralization associated with vertical wnw trending pegmatites felsic dikes and aegirine fluorite veins and late stage sinistral shear deformation and iii intrusion of crosscutting lamprophyre dikes at 150 ma and again at ca 105 ma the peralkaline nature of the bmc and the wnw trend of associated dikes

testing for pb isotopic differences between minerals in the kiglapait layered intrusion by la icp ms abstract mineral scale pb isotopic variations in cumulates of the kiglapait intrusion the largest troctolitic intrusion of the proterozoic nain plutonic suite in labrador canada are evaluated directly in thin section by single spot la icp ms analysis of minerals with low pb concentrations e g plagioclase 0 31 3 3 ppm clinopyroxene 0 06 1 1 ppm at high spatial resolution

new evidence of magmatic fluid related phyllic alteration implications for the genesis of porphyry cu deposits the phyllic alteration in a number of circum pacific porphyry cu au deposits is related to high temperature saline magmatic fluids this contradicts the widely used genetic models wherein phyllic alteration formed as the result of mixing between magmatic and meteoric fluids at the endeavour 26 north porphyry deposit in eastern australia the transition from early potassic to the main stage phyllic alteration is associated with fluids that with time decline in total salinity nacl kcl and temperature from 600 to 550 degrees c calculated and measured delta 18 o and delta d compositions of fluids 5 1 8 5 parts per thousand 57 to 73 parts per thousand delta d confirm a primary magmatic origin for both the early potassic and main stage phyllic alteration these results are consistent with other recent studies e g el salvador chile far southeast philippines and panguna and porgera papua new guinea and suggest that rather than these results being unusual a major revision of porphyry cu genetic models is required

evidence from neodymium isotopes for mantle contributions to phanerozoic crustal genesis in the canadian cordillera sm nd and rb sr isotopic studies of several phanerozoic orogenic belts have shown that much of the crust in these belts is composed of reworked pre existing continental crust in contrast isotopic data collected from two of the largest terranes in the canadian cordilleran orogenic belt the alexander and stikine terranes show that these tectonic fragments are composed of mantle derived continental crust in many respects the style and rate of crustal accretion of these and related terranes appear similar to those of some proterozoic crustal regions

petrology and petrogenesis of the bokan granite complex southeastern alaska the bokan granite complex is a peralka line ring dike complex emplaced into marine shales volcanic flows and tuffs and plutonic rocks mineralogically and chemically the complex is composed of i type granites aegirine and riebeckite bearing granite aplites porphyries and pegmatites comprise twelve distinct intrusive episodes the aegirine bearing rocks occur in an outer annular zone formed during early crystallization subsequent rocks are riebeckite bearing due to devolatilization of the magma chamber during a collapse ring dike emplacement event early crystallization of alkali feldspar occurred during magma ascension from a lower crustal upper mantle source at shallow depths subsolvus crystallization allowed microcline and albite to dominate local bodies of aegirine syenite were formed during the early collapse ring dike emplacement in response to the magma devolatilization the riebeckite granites reflect lower po2 and possibly declining peralkalinity the granitic rocks at bokan all exhibit na2o contents greater than k2o lithophile elements are concentrated in all the rocks especially in zones where hydrothermal albite and chlorite formed rb sr ratios increase in progressively younger rocks in the complex agpaitic ratios vary from 0 92 to 2 08 for the granitic rocks

a new style of rare metal granite with nb rich mica the early cretaceous huangshan rare metal granite suite northeast jiangxi province southeast china

oxygen isotope alteration in the noranda mining district abitibi greenstone belt quebec a regional whole rock oxygen isotope survey carried out in the noranda district shows how oxygen isotope alteration can be used to guide exploration for massive sulfide deposits the survey is based on 588 outcrop whole rock oxygen isotope determinations from 478 sites in a approximately 35 by 50 km area between the destor porcupine and cadillac larder lake breaks from east of the horne mine to west of the magusi river mine the mean isotopic composition of all samples is 7 4 or 2 per mil smow nested analysis of variance of 478 isotopic determinations from 371 of these sites shows that 74 percent of the total variance in whole rock delta 18 o r r whole rock is associated with outcrop location 21 percent with outcrop sampling and 5 percent with sample analysis an analysis of 259 determinations indicates that rock type is statistically no more important than outcrop sampling the statistical analysis indicates that isotopic variations greater than or 1 per mil can be used to map the hydrothermal circulation responsible for massive sulfide mineralization specific traverses visually confirm the lack of 18 o dependence on rock type and the utility of a 2 per mil interpretive band the large scale pattern of isotopic alteration in the noranda district is dominated by a nearly continuous 2 to 3 km wide annulus at the margins of the flavrian pluton of delta 18 o r 18 o r 18 o r depletion is surrounded up section by a approximately 10 km wide band of patchy but intense 18 o enrichment 8 5 14ppm the combined pattern of concentric light and heavy alteration has a diameter of approximately 30 km the clericy intrusion shows a similar pattern of isotope alteration on a smaller 10 km diam scale the lake dufault pluton seems to have been isotopically altered by continuing convection driven by the flavrian hydrothermal system modeling suggests that the 18 o depletion is produced by water circulating toward and along the edges of an intrusion and that the surrounding heavy alteration is produced either by seawater recharge or limited hydrothermal discharge the large scale and coherency of the alteration pattern centered on the flavrian pluton is remarkable and indicates that this pluton drove a major long lived approximately 10 m y hydrothermal system in which convection penetrated to an 8 kin depth the intensity and coherency of the 18 o depletion correlates with the tonnage of associated massive sulfide mineralization oxygen isotope depletion may in general mark the margins of plutons that have driven sufficient hydrothermal circulation to produce economic massive sulfide deposits up section it may be possible to screen plutons for up section massive sulfide exploration potential by collecting and isotopically analyzing approximately 50 samples from five traverses across a pluton9s margins additional samples may provide details light fingers that guide exploration to particular deposits

mineralogic and stable isotope zonation at the surface over the el salvador porphyry copper deposit chile we examined in detail the mineralogic and stable isotope characteristics of alteration minerals exposed at the surface of the el salvador porphyry copper deposit a total of 276 samples was collected from 203 localities over an area of 5 km 2 at elevations between 2 900 and 3 300 m the alteration assemblages can be separated into two groups broadly corresponding to the stages previously identified from underground studies although the early stage k silicate alteration identified underground is not evident at the surface a transitional to late stage is characterized at the surface by assemblages of 1 muscovite andalusite with trace diaspore including some areas rich in andalusite and 2 muscovite with trace diaspore there is a sharp contact outward with a marginal propylitic assemblage chlorite calcite epidote pyrophyllite occurs as a retrograde overprint of muscovite in both of the transitional to late stage assemblages these assemblages are concentrically zoned and centered on a core of least altered granodiorite porphyry a late intramineral intrusion the muscovite andalusite assemblage occurs up to 500 m away from the granodiorite porphyry and andalusite rich zones are located near the brecciated margin of the porphyry further outward is the muscovite zone from 500 to 1 500 m wide the pyrophyllite overprint overlaps the contact of the muscovite andalusite and muscovite zones and occurs mainly above 3 000 m elevation such that its present distribution is controlled largely by topography very late alteration minerals occur in radial pebble dikes of hydrothermal breccia and their extensions and they are dominated by an advanced argillic assemblage of alunite aluminum phosphate sulfate minerals diaspore zunyite pyrophyllite dickite with residual muscovite in one case a breccia extends upward and appears to be the root of a 300 500 m outcrop 80 m thick of massive quartz alunite replacement of rhyolite pure mineral separates were prepared from these samples for o h and s isotope analysis including 48 samples of silicate minerals muscovite pyrophyllite dickite and supergene kaolinite and 20 samples of alunite some supergene in origin information on mineral assemblage was used to estimate temperatures of formation which then allowed calculation of the isotopic composition of associated hydrothermal fluids the fluid responsible for forming the muscovite had a relatively narrow range of isotopic composition 6 5 1 5 per mil 18 o and 40 10 per mil d the heaviest 18 o and d values about 8 and 35 per mil respectively were obtained from the samples with andalusite muscovite diaspore assemblage this composition is close to that expected for a magmatic fluid with 10 to 20 percent meteoric water component responsible for forming the other muscovite samples the fluid compositions calculated for the very late stage alunite range from 5 and 30 per mil to 1 and 40 per mil 18 o and d respectively this range in composition agrees with the trend predicted for magmatic vapor absorbed by local groundwater the latter similar in composition to that responsible for forming the supergene kaolinite there is no systematic spatial zonation of the alunite samples in terms of isotopic composition or paleotemperature the temperature estimates from s isotope geothermometry are higher than those based on mineral assemblage possibly caused by partial supergene replacement of some hypogene alunites there is no strong isotopic zonation of hydrothermal minerals from surface alteration assemblages at el salvador that can be applied to generate clear exploration guidelines by contrast mapping of alteration mineralogy in the field backed up by laboratory checking of mineralogy and examination of relict minerals and replacement textures in thin section clearly indicates the center of the late intramineral intrusion

mesospheric winds at low and mid latitudes in the southern hemisphere mesospheric wind measurements were made by using the partial reflection technique at a tropical location townsville 19 s and at a mid latitude location adelaide 35 s in june and november 1978 it is shown that the prevailing winds were typical of expected winter and summer type circulations in june and november respectively but there was a large difference in the amplitudes and structure of the diurnal tide between the two sets of observations in november the tide was stable with a large amplitude and it appeared to break at a height of 86 km the propagating s1 1 mode dominated in june however the tide was weak with large day to day variability and the evanescent s1 2 mode was dominant the semi diurnal tide amplitudes were relatively small but internal gravity wave amplitudes were significant spectral analyses showed that in the 2 to 8 hour period band the wave energy decreased as f k with k in the range 1 1 5 and it is also shown that the waves were losing energy as a function of height the inferred energy loss rates were 0 05 w kg 1 and a turbulent viscosity of about 500 m s 1 was estimated near the mesopause at both sites and in both seasons

molybdenite re os and albite 40ar 39ar dating of cu au mo and magnetite porphyry systems in the yangtze river valley and metallogenic implications abstract the area of the middle lower yangtze river valley eastern china extending from wuhan hubei province to western zhenjiang jiangsu province hosts an important belt of cu au mo and fe deposits there are two styles of mineralization i e skarn porphyry stratabound cu au mo fe deposits and magnetite porphyry deposits in several nne trending cretaceous fault bound volcanic basins the origin of both deposit systems is much debated we dated 11 molybdenite samples from five skarn porphyry cu au mo deposits and 5 molybdenite samples from the datuanshan stratabound cu au mo deposit by icp ms re os isotope analysis nine samples from the same set were additionally analyzed by ntims on re os results from the two methods are almost identical the re os model ages of 16 molybdenite samples range from 134 7 2 3 to 143 7 1 6 ma 2 the model ages of the five samples from the datuanshan stratabound deposit vary from 138 0 3 2 to 140 8 2 0 ma with a mean of 139 3 2 6 ma their isochron age is 139 1 2 7 ma with an initial os ratio of 0 7 8 1 mswd 0 29 these data indicate that the porphyry skarn systems and the stratabound deposits have the same age and suggest an origin within the same metallogenic system albite 40 ar 39 ar dating of the magnetite porphyry deposits indicates that they formed at 123 to 125 ma i e 10 20 ma later both mineralization styles characterize transitional geodynamic regimes i e the period around 140 ma when the main ns trending compressional regime changed to an ew trending lithospheric extensional regime and the period of 125 115 ma of dramatic ew trending lithospheric extension

geology and uranium thorium mineral deposits of the bokan mountain granite complex southeastern alaska abstract the bokan mountain kendrick bay uranium thorium deposits are associated with a late jurassic peralkaline granite ring dike complex the uranium thorium deposits form pipe like bodies along contacts or occur as pods in en echelon northwest striking shear zones the host intrusive is a multiphased body consisting mainly of riebeckite granite porphyry and subordinately of pegmatite aplite aegirine granite porphyry and eight other lesser rock types the ore is closely associated with an albitized aegirine syenite the ore consists of thorium and rare earth rich rock containing uranothorite uraninite and generally less than 2 of sulfide species about 100 000 tons 89 000 t of ore have been mined at an average grade of about 1 u3o8 and nearly 3 tho2 mainly from the ross adams pipe the pipe itself lies along the contact of aegirine syenite and aegirine granite porphyry it is as much as 24 m across and was mined along strike for over 300 m the ore in shear zones occurs in lenses as much as 3 m thick and 30 m in strike length wallrock alteration within and adjacent to orebodies consists of pervasive hydrothermal albite and lesser amounts of chlorite fluorite calcite quartz sericite and tourmaline hematite is present in the outer distal parts of the ore zones the minerals produced to date occur within the outer annular zone of the bokan granite complex in which aegirine is present as the major alkali ferro magnesian mineral ore emplacement occurred during the first subsidence event in association with devolatilization of the magma chamber the pod like ore zones appear to have formed during regional faulting synchronous with magma crystallization and subsequent hydrothermal events subsequent magma crystallization yielded riebeckite granites that were depleted in u and th filling temperatures in ore stage fluid inclusions within quartz range from 320 to 331 c with pressure corrections increasing the temperature of formation to 420 c or higher depending on dissolved gas content sulfur isotopic analyses on pyrite galena sphalerite and pyrrhotite indicate disequilibrium but 34sh2s is estimated at 7 6 carbon and oxygen isotopic analyses on ore stage calcite yield 18oh2o of 6 8 to 8 1 and 13c c of 4 3 to 7 0 the oxygen and carbon isotopic data support a magmatic origin for the calcite and associated thorium uranium deposits

on ferroan a type granitoids their compositional variability and modes of origin we recognize eight types of ferroan granitoid that can be distinguished on the basis of major element chemistry these include alkalic granitoids that may be metaluminous or peralkaline alkali calcic granitoids that may be metaluminous peraluminous or peralkaline calc alkalic granitoids that may be metaluminous or peraluminous and rare calcic ferroan granitoids these granitoids may form by two distinct end member processes extreme differentiation of basaltic melts results in ferroan granitoids that are either peralkaline alkalic and alkali calcic or metaluminous alkalic alkali calcic and calc alkalic with alkalinity increasing with increasing pressure of differentiation partial melting of tonalitic to granodioritic crust produces alkali calcic to calc alkalic granitoids that are metaluminous at low pressures and peraluminous at high pressures it is likely that a combination of these two processes plays some role in the formation of most ferroan granitoids most granitoids that are referred to as ferroan however the term has become more confusing than edifying because it has been applied to a broad spectrum of granitoid compositions with varying petrogenesis for this reason we recommend that the term be discontinued and ferroan used in its stead

modification of a rare earth element deposit by low temperature partial melting during metamorphic overprinting norra karr alkaline complex southern sweden abstract rare earth elements play a crucial role in modern technologies and are necessary for a transition to a green economy potentially economic deposits of these elements are typically hosted in minerals such as monazite bastnasite and eudialyte a complex na ca fe zr silicate mineral with cl making these prime targets for geological research globally rare earth mineral deposits commonly show evidence of polyphase development and mineralisation processes which need to be better understood to improve exploration strategies the norra karr alkaline complex sweden contains a globally significant deposit of rare earth elements hosted in the mineral eudialyte in this study we focussed on eudialyte crystals in undeformed cross cutting pegmatoid veins from norra karr in order to determine their age we refined an established micromilling method to enable sampling of minerals rich in rare earth elements for precise analysis of major and trace elements nd isotope ratios and sm nd geochronology down to a scale of

melt composition control of zr hf fractionation in magmatic processes zircon zrsio4 and hafnon hfsio4 solubilities in water saturated granitic melts have been determined as a function of melt composition at 800 and 1035 c at 200 mpa the solubilities of zircon and hafnon in metaluminous or peraluminous melts are orders of magnitude lower than in strongly peralkaline melt moreover the molar ratio of zircon and hafnon solubility is a function of melt composition although the solubilities are nearly identical in peralkaline melts zircon on a molar basis is up to five times more soluble than hafnon in peraluminous melts accordingly calculated partition coefficients of zr and hf between zircon and melt are nearly equal for the peralkaline melts whereas for metaluminous and peraluminous melts dhf dzr for zircon is 0 5 to 0 2 consequently zircon fractionation will strongly decrease zr hf in some granites whereas it has little effect on the zr hf ratio in alkaline melts or similar depolymerized melt compositions the ratio of the molar solubilities of zircon and hafnon for a given melt composition temperature and pressure is proportional to the hf zr activity coefficient ratio in the melt the data imply that this ratio is nearly constant and probably close to unity for a wide range of peralkaline and similar depolymerized melts however it changes by a factor of two to five over a relatively small interval of melt compositions when a nearly fully polymerized melt structure is approached for most ferromagnesian minerals in equilibrium with a depolymerized melt dhf dzr typical values of dhf dzr range from 1 5 to 2 5 for clinopyroxene amphibole and titanite because of the change in the hf zr activity ratio in the melt the relative fractionation of zr and hf by these minerals will disappear or even be reversed when the melt composition approaches that of a metaluminous or peraluminous granite it is thus not surprising that fractional crystallization of such granitic magmas leads to a decrease in zr hf whereas fractional crystallization of depolymerized melts tends to increase zr hf there is no need to invoke fluid metasomatism to explain these effects results demonstrate that for ions with identical charge and nearly identical radius crystal chemistry does not alone determine relative compatibilities rather the effect of changing activity coefficients in the melt may be comparable to or even larger than elastic strain effects in the crystal lattice

zircon geochemistry of edong granitoids in the middle lower yangtze metallogenic belt eastern china constraints on w cu fe skarn mineralization abstract it has long been established that skarn deposits of different metals are associated with intrusions of different compositions intermediate felsic granitoids in the edong district of the middle lower yangtze metallogenic belt host skarn deposits with varying w cu fe proportions yet previous whole rock geochemical studies could not distinguish between the magmatic suites that formed the different skarn deposits in this study la icp ms zircon geochemical data are presented for the ruanjiawan w skarn 60300 t wo3 tongshankou cu skarn 0 6 mt cu tonglushan cu fe skarn 1 1 mt cu and 56 8 mt fe and jinshandian fe skarn 200 mt fe deposits in the edong district zircons from the ore forming intrusions of these skarn deposits are all characterized by heavy rare earth element hree enrichments and light rare earth element lree depletions with positive ce anomalies and slightly negative eu anomalies tungsten contents in zircons from the w ore forming intrusion 0 02 3 16 ppm w avg 1 14 ppm are generally higher than in zircons from the cu ore forming intrusion 0 00 0 24 ppm w avg 0 03 ppm copper content in zircons from the cu ore forming intrusion is higher than in those from the w ore forming intrusion fertile intrusive rocks from the four skarn deposits contain zircons with high calculated ce4 ce3 ratios ruanjiawan 71 7 tongshankou 207 5 tonglushan 263 6 jinshandian 189 0 fluorine content of the ruanjiawan intrusion is higher than the tonglushan and jinshandian intrusions followed by the tongshankou intrusion chlorine contents show the opposite trend we propose that the different source regions for the ore fertile intrusions is the critical factor that controls the metal content oxygen fugacity and volatile components our studies suggest that zircon geochemistry is a good indicator to distinguish tungsten causative intrusions from copper and iron ore related intrusions i e w content 1 14 ppm and ce4 ce3 ratios 207 5

u mo and ree mineralization in late tectonic granitic pegmatites southwestern grenville province canada abstract late tectonic granitic pegmatites occur throughout most of the southwestern grenville province of ontario and quebec these vary from mineralogically simple 3 4 major phases to complex 4 major phases pegmatites the latter are variably enriched in u th mo and rare earth elements ree and zr and nb the mineralogical and whole rock geochemical data obtained from simple pegmatites suggest crystallization from low temperature h 2 o undersaturated partial melts generated in amphibolite to granulite grade felsic paragneisses and orthogneisses that have undergone an earlier stage of melting these magmas coalesced and fractionated during ascent to mid crustal levels the mineralogical complexity and increase in abundance of ferromagnesian silicates in individual pegmatites arises from interaction with the host rocks hybridization skarnification previous research has shown that there is an empirical relationship between ferromagnesian silicate content and u th and ree enrichment although this phenomena has not been investigated petrogenetically interaction with the host rocks hybridization produced compositional changes in the pegmatites through bimetasomatic two way exchange processes that modified normal fractional crystallization processes high concentrations of ca fe mg and possibly ti depending on the host rock are interpreted to indicate bimetasomatic exchange resulting in a mineralogical modification of the pegmatitic magma for instance the introduction of ca into the pegmatite magma may lead to local saturation of titanite and or allanite high concentrations of u th ree and nb in these titanites suggests that elemental distribution coefficients are affected within the pegmatite melts by the appearance of hybrid titanite the role of a fluid phase in the hybridization skarnification process is two fold 1 the fluid phase will enhance bimetasomatic diffusive exchange of constituents between the host rocks e g ca fe mg ti and the pegmatite si al k na fe u th ree nb zr h 2 o f cl over that of normal melt solid diffusivities and 2 the fluid may be enriched in certain constituents that become saturated during metasomatic interaction between the pegmatite and host rocks

columbite solubility in granitic melts consequences for the enrichment and fractionation of nb and ta in the earth s crust the behaviour of niobium and tantalum in magmatic processes has been investigated by conducting mnnb2o6 and mnta2o6 solubility experiments in nominally dry to water saturated peralkaline aluminium saturation index a s i 0 64 to peraluminous a s i 1 22 granitic melts at 800 to 1035 c and 800 to 5000 bars the attainment of equilibrium is demonstrated by the concurrence of the solubility products from dissolution crystallization mn doped and nb or ta doped experiments at the same pressure and temperature the solubility products of mnnb2o6 ksp nb and mnta2o6 ksp ta at 800 c and 2 kbar both increase dramatically with alkali contents in water saturated peralkaline melts they range from 1 2 10 4 and 2 6 10 4 mol2 kg2 respectively in subaluminous melt a s i 1 02 to 202 10 4 and 255 10 4 mol2 kg2 respectively in peralkaline melt a s i 0 64 this increase from the subaluminous composition can be explained by five non bridging oxygens being required for each excess atom of nb5 or ta5 that is dissolved into the melt the ksp nb and ksp ta also increase weakly with al content in peraluminous melts ranging up to 1 7 10 4 and 4 6 10 4 mol2 kg2 respectively in the a s i 1 22 composition columbite tantalite solubilities in subaluminous and peraluminous melts a s i 1 02 and 1 22 are strongly temperature dependent increasing by a factor of 10 to 20 from 800 to 1035 c by contrast columbite tantalite solubility in the peralkaline composition a s i 0 64 is only weakly temperature dependent increasing by a factor of less than 3 over the same temperature range similarly ksp nb and ksp ta increase by more than two orders of magnitude with the first 3 wt h2o added to the a s i 1 02 and 1 22 compositions whereas there is no detectable change in solubility for the a s i 0 64 composition over the same range of water contents solubilities are only slightly dependent on pressure over the range 800 to 5000 bars the data for water saturated sub and peraluminous granites have been extrapolated to 600 c conditions at which pegmatites and highly evolved granites may crystallize using a melt concentration of 0 05 wt mno 70 to 100 ppm nb or 500 to 1400 ppm ta are required for manganocolumbite and manganotantalite saturation respectively the solubility data are also used to model the fractionation of nb and ta between rutile and silicate melts predicted rutile melt partition coefficients increase by about two orders of magnitude from peralkaline to peraluminous granitic compositions it is demonstrated that the nb2o5 ta2o5 activity coefficient ratio in the melt phase depends on melt composition this ratio is estimated to decrease by a factor of 4 to 5 from andesitic to peraluminous granitic melt compositions accordingly all the relevant accessory phases in subaluminous to peraluminous granites are predicted to incorporate nb preferentially over ta this explains the enrichment of ta over nb observed in highly fractionated granitic rocks and in the continental crust in general

in situ analysis of trace elements and sr pb isotopes of k feldspars from tongshankou cu mo deposit se hubei province china insights into early potassic alteration of the porphyry mineralization system in the tongshankou porphyry deposit se hubei province south china three types of k feldspars are recognized i the phenocryst type in the porphyry that crystalized during the magmatic stage ii the megacryst type and iii the vein type in the altered porphyry and orebody that was produced by hydrothermal fluids a detailed in situ analysis of trace elements and sr pb isotopes was carried out on k feldspars in an attempt to unravel their formation processes and to trace the element sources during potassic alteration the type iii k feldspars show lower sr contents and sr isotope ratios but higher pb contents and pb isotope ratios than the type i and ii k feldspars possibly reflecting a contribution from the country carbonate rocks with less radiogenic sr but more radiogenic pb sources and indicate that the ore forming fluids and materials may have been partially derived from external sources such as the host sedimentary rocks during the early potassic alteration stage this article is protected by copyright all rights reserved

the early jurassic bokan mountain peralkaline granitic complex southeastern alaska geochemistry petrogenesis and rare metal mineralization abstract the early jurassic ca 177 ma bokan mountain granitic complex located on southern prince of wales island southernmost alaska cross cuts paleozoic igneous and metasedimentary rocks of the alexander terrane of the north american cordillera and was emplaced during a rifting event the complex is a circular body 3 km in diameter of peralkaline granitic composition that has a core of arfvedsonite granite surrounded by aegirine granite all the rock forming minerals typically record a two stage growth history and aegirine and arfvedsonite were the last major phases to crystallize from the magma the bokan granites and related dikes have sio2 from 72 to 78 wt high iron feo tot 3 4 5 wt and alkali 8 10 wt concentrations with high feo tot feo tot mgo ratios typically 0 95 and the molar al2o3 na2o k2o ratio

mean meridional winds in the mid and high latitude summer mesosphere we examine the mean meridional flow in the summer upper mesosphere using data from the poker flat mst radar and all other available stations the observed mean flow is equatorward at about 10 15 ms 1 near 60 n about an order of magnitude larger than expected from numerical model results the rayleigh friction coefficient required to balance the coriolis torque associated with this flow is about 4 days 1 about ten times larger than values currently used in numerical models

the lower changjiang yangzi yangtze river metallogenic belt east central china intrusion and wall rock hosted cu fe au mo zn pb ag deposits abstract the lower valley of changjiang from wuhan of the hubei province in the west to zhenjiang of the jiangsu province in the east contains more than 200 polymetallic cu fe au mo zn pb ag deposits and is one of the most important metallogenic belts in china this metallogenic belt situated at the northern margin of the yangzi craton and bordered by the dabieshan ultrahigh pressure metamorphic belt to the north consists mainly of cambrian triassic marine clastic sedimentary rocks and carbonate and evaporite rocks which overlay a precambrian basement and are intruded by yanshanian 205 to 64 ma granitoid intrusions and subvolcanic complexes repeated tectonism from late proterozoic to triassic resulted in extensively developed networks of faults and folds involving the cambrian triassic sedimentary strata and the precambrian basement the yanshanian granitoid intrusions and subvolcanic complexes in the lower changjiang metallogenic belt are characterized by whole rock 18 o of 8 to 10 initial 87 sr 86 sr of 0 704 to 0 708 and ndt from 10 to 17 and have been interpreted to have originated from mixing between juvenile mantle and old crustal materials also the yanshanian granitoids exhibit eastward younging and increase in alkalinity i e from older calc alkaline in the west to younger subalkaline alkaline in the east which are related to oblique collision between the yangzi and sino korean cratons and tectonic evolution from early compressional to late extensional or rifting regimes most polymetallic deposits in the lower changjiang metallogenic belt are clustered in seven districts where the yanshanian magmatism is particularly extensive from west to east edong jiurui anqing guichi luzhong tongling ningwu and ningzhen mineralization is characterized by the occurrence of three distinct types of orebodies in individual deposits orebodies in yanshanian granitoid intrusions skarn orebodies at the contact zones between the yanshanian intrusions and late paleozoic early mesozoic sedimentary rocks and stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata the most important host sedimentary strata are the middle carboniferous huanglong formation lower permian and lower middle triassic carbonate and evaporite rocks the intrusion hosted and skarn orebodies exhibit well developed zonation in alteration assemblages metal contents and isotopic compositions within individual deposits and apparently formed from hydrothermal activities related to the yanshanian magmatism the stratabound massive sulfide orebodies in the late paleozoic early mesozoic sedimentary strata have long been suggested to have formed from sedimentary or volcano sedimentary exhalative processes in shallow marine environments however extensive research over the last 40 years failed to produce unequivocal evidence for syngenetic mineralization on the basis of geological relationships and isotope geochemical characteristics we propose a carbonate hosted replacement deposit model for the genesis of these stratabound massive sulfide orebodies and associated skarn orebodies this model suggests that epigenetic mineralization resulted from interactions between magmatic fluids evolved from the yanshanian intrusions with carbonate and evaporite wall rocks mineralization was an integral but distal part of the larger hydrothermal systems that formed the proximal skarn orebodies at the contact zones and the intrusion hosted orebodies the stratabound massive sulfide deposits of the lower changjiang metallogenic belt share many features with the well studied high temperature carbonate hosted replacement deposits of northern mexico and western united states particularly with respect to association with small shallow granitoid complexes structural and stratigraphic controls on mineralization alteration assemblages geometry of orebodies metal association metal zonation and isotopic systematics

intracontinental porphyry and porphyry skarn mineral systems in eastern china scrutiny of a special case made in china in this contribution we discuss a series of porphyry and porphyry skarn mineral systems which constitute important metallogenic belts along major lithospheric breaks and or collision zones that form the margins of the north china craton and the yangtze craton we describe a selection of porphyry and porphyry skarn deposits in the great xing an range in northeast china the yanshan liaoning xilamulum belts along the northern margin of the north china craton the qinling orogen and the middle lower yangtze river valley along the bonudaries between the north china and the yangtze cratons the occurrence of platform carbonate successions may have played some role in the evolution of ore fluids that resulted in the formation of porphyry skarn deposits the porphyry deposits of eastern china although sharing some common features with classic porphyry systems that are related to convergent margins do exhibit unusual features particularly in terms of ore fluid compositions the common presence of fluorite hydrothermal alteration assemblages which tend to be less hydrous than the porphyry at convergent margins on the other hand the porphyry mineral systems of eastern china have some similarities with the climax type porphyry a major tectonothermal event yanshanian which took place in the jurassic cretaceous affected eastern china and most of the eastern margin of asia this yanshanian event was responsible for the magmatism and associated mineral systems in the region the granitoid intrusions and accompanying porphyry and porphyry skarn deposits were developed along orogenic belts and major structural discontinuities mostly along the tectonic boundaries between the north china and yangtze cratons and between the northern margin of the north china craton and the mongolia siberia plate the porphyry and porphyry skarn deposits herein described include chalukou in the great xing an range orogen jiguanshan in the xilamulun metallogenic belt xiaojiayingzi lanjiagou chehugou yuanbaoshan in the yanshan liaoning belt nanninhu yuchiling jinduicheng lemeingou in the east qinling orogen tongchakoou shaxi from the middle lower yangtze river valley the role of mantle lithosphere dynamics in eastern china which led to the formation of these porphyry and porphyry skarn mineral systems is discussed and reviewed

longevity of magmatic hydrothermal systems in the daye cu fe au district eastern china with implications for mineral exploration the daye district represents one of the largest concentrations of cu fe au skarn deposits in china with additional porphyry cu mo deposits these deposits are closely associated with late mesozoic intrusions of intermediate to felsic composition previous studies have yielded important age constraints for several deposits timing and history of metallogenesis for the entire district however remain not well understood in this paper we present twenty five new ages re os 40ar 39ar and u pb to better understand the temporal framework of the district wide polymetallic mineralization these ages when combined with existing data indicate a prolonged history of mineralization lasting 25 million years from late jurassic to early cretaceous 157 132 ma and that most ore deposits of the district are results of multistage hydrothermal activity discrete episodes of ore formation coincide well with emplacement ages of granitoid intrusions within the district as revealed by recent zircon u pb dating this age consistency substantiates a genetic relationship between ore formation and intrusive magmatism prolonged and episodic magmatic and hydrothermal activities must have played significant roles in the formation of polymetallic ore deposits in the district by repeatedly supplying heat fluids and metals previous studies have demonstrated that the daye district was dominated by lithospheric extension during late jurassic to early cretaceous when extensive magmatism and mineralization took place under the extensional setting the area could have experienced significant uplift or extensional exhumation that would have brought early stage intrusions and associated ore deposits to shallower levels with ore bodies formed by subsequent magmatic hydrothermal events tending to be localized at greater depth this in turn indicates potentials to find new ore bodies at depth of known deposits especially for those formed by episodic magmatic hydrothermal processes this view is partly confirmed by the recent success in deep exploration beneath the tieshan fe cu and tonglushan cu au fe deposits

geochemical constraints on cu fe and fe skarn deposits in the edong district middle lower yangtze river metallogenic belt china abstract copper and iron skarn deposits are economically important types of skarn deposits throughout the world especially in china but the differences between cu and fe skarn deposits are poorly constrained the edong ore district in southeastern hubei province middle lower yangtze river metallogenic belt china contains numerous fe and cu fe skarn deposits in this contribution variations in skarn mineralogy mineralization related intrusions and sulfur isotope values between these cu fe and fe skarn deposits are discussed the garnets and pyroxenes of the cu fe and fe skarn deposits in the edong ore district share similar compositions i e dominantly andradite ad 29 100 gr 0 68 and diopside di 54 100 hd 0 38 respectively this feature indicates that the mineral compositions of skarn silicate mineral assemblages were not the critical controlling factors for variations between the cu fe and fe skarn deposits intrusions associated with skarn fe deposits in the edong ore district differ from those cu fe skarn deposits in petrology geochemistry and sr nd isotope intrusions associated with fe deposits have large variations in their la yb n ratios 3 84 24 6 and eu anomalies eu 0 32 1 65 and have relatively low sr y ratios 4 2 44 0 and high yb contents 1 20 11 8 ppm as well as radiogenic sr nd isotopes end t 12 5 to 9 2 and 87 sr 86 sr i 0 7067 to 0 7086 in contrast intrusions associated with cu fe deposits are characterized by relatively high sr y 35 0 81 3 and la yb n 15 0 31 6 ratios low yb contents 1 00 1 62 ppm without obvious eu anomalies eu 0 67 0 97 as well as 87 sr 86 sr i 0 7055 to 0 7068 and end t 7 9 to 3 4 geochemical evidence indicates a greater contribution from the crust in intrusions associated with fe skarn deposits than in intrusions associated with cu fe skarn deposits in the edong ore district the sulfides and sulfates in the cu fe skarn deposits have sulfur isotope signatures that differ from those of fe skarn deposits the cu fe skarn deposits have a narrow range of 34 s values from 6 2 to 8 7 in sulfides and 13 2 to 15 2 in anhydrite while the fe skarn deposits have a wide range of 34 s values from 10 3 to 20 0 in pyrite and 18 9 to 30 8 in anhydrite sulfur isotope data for anhydrite and sedimentary country rocks suggest that the formation of skarns in the edong district involved the interaction between magmatic fluids and variable amounts of evaporites in host rocks

the peralkaline granite related khaldzan buregtey rare metal zr nb ree deposit western mongolia the khaldzan buregtey rare metal nb zr ree etc deposit in peralkaline granitoids is located in western mongolia 45 km northeast of the town of kobdo the deposit which was discovered by the authors is composed of dome shaped stocks of rare metal peralkaline granite covering 0 85 km and represents the late plutonic phases of the devonian 380 390 ma multiphase khaldzan buregtey peralkaline granite massif the formation of the massif took place during tectonic extension as shown by the development of a major dike complex synchronous with granite emplacement the massif consists of peralkaline granitoids as well as gabbro and basalt and is characterized by a radial circular shape eight intrusive phases are recognized and consist of 1 nordmarkite 2 peralkaline granite 3 dikes of fine grained peralkaline granite 4 dikes of pantellerite 5 rare metal peralkaline granite 6 gabbroids 7 miarolitic peralkaline rare metal granite and 8 syenite and leucite basalt field relationships of the rare metal peralkaline granite bodies indicate an intrusive igneous origin the rare metal peralkaline granites consist of k na feldspar quartz albite arfvedsonite aegirine fluorite and diverse rare metal minerals ranging up to 25 vol percent ore minerals are represented by elpidite gittinsite and zircon pyrochlore nb rare metal flurocarbonate and monazite ree and polylithionite li the zirconium minerals often occur in the endocontact and apical parts of rare metal granite bodies and are reflected in the negative correlation of zr and nb contents in the seventh phase granites the rare metal peralkaline granites of the deposit differ from those of other massifs by their high and variable ca and f contents the granites are rich in zr up to 5 3 wt nb up to 0 8 wt ree up to 0 4 wt y up to 0 3 wt be sn rb and sometimes li pb zn hf and ta they are depleted in sr and ba and have an almost flat ree distribution pattern with a small negative eu anomaly the initial 87 sr 86 sr ratio of fluorite from rare metal peralkaline granite is 0 70433 or 7 the end value for these rocks at 386 ma ranges from 4 3 to 5 7

a tectono genetic model for porphyry skarn stratabound cu au mo fe and magnetite apatite deposits along the middle lower yangtze river valley eastern china abstract the middle lower yangtze river valley metallogenic belt yrb situated along the northern margin of the yangtze craton is characterized by porphyry skarn stratabound cu au mo fe deposits in the areas of uplift and magnetite apatite deposits in cretaceous fault basins following detailed field investigations and a review of published data we recognize two episodes of magmatism and mineralization in the yrb 1 156 137 ma high k calc alkaline granitoids associated with 148 135 ma porphyry skarn stratabound cu au mo fe deposits and 2 135 123 ma shoshonitic series associated with 134 9 122 9 ma magnetite apatite deposits a type granitoids and associated alkaline volcanic have a small age range from 126 5 to 124 8 ma and are temporally spatially and genetically associated with the second episode the geodynamic history of the yrb did not experience the paleozoic to mesozoic lithospheric thickening that took place in the north china craton this process is inferred to be linked to partial melting of the delaminated lower crust at high pressures resulting in the development of c type adakitic rocks the petrochemical and sr nd isotopic data show that both the shoshonitic series and a type granitoids are quite different from adakites with only some of the k calc alkaline granitoids having adakitic signatures previous ore genesis models were established based on an assumed relationship with adakites and a continuous tectono thermal evolution from 150 to 100 ma all data obtained for the middle lower yangtze river region consistently show that the tan lu regional strike slip fault zone initiated at 233 6 to 225 6 ma from the collision between the north china and yangtze cratons and was reactivated at ca 160 ma the tan lu fault was caused by the oblique subduction of the izanagi plate which along the yrb the low angle subducted slab and the overlying crust was disrupted or broken due to the disharmonious movement of the two blocks the high k calc alkaline granitoids magmas were derived from melting of the subducted slab with some input of crustal material these magmas were emplaced at the intersections between ne and ew trending faults and formed porphyry skarn stratabound cu au mo fe deposits between 156 and 137 ma after 135 ma the subducted plate changed its direction of motion to northeast now running parallel to the eurasian continental margin and leading to large scale continental extension the shoshonitic series and subsequent a type granitoids magmatism and the development of magnetite apatite ores in the yrb took place in both fault basins and ne trending rifts between 135 and 124 ma

isotopic and elemental partitioning of boron between hydrous fluid and silicate melt the fractionation of b and its isotopes between aqueous fluid and silicate melt has been studied from 550 to 1100 c and 100 500 mpa fluid melt partition coefficients are 1 for rhyolite melt this shows that b is not always strongly extracted from melts into hydrous fluids boron isotopic fractionation is large compared with the carbon and oxygen stable isotopic systems especially at high t and is most simply explained by differences in coordination trigonal vs tetrahedral among coexisting phases combined with earlier measurements on illite water 300 350 c b isotopic fractionation defines a temperature dependent trend from 300 to 1100 c because of the large magnitude and apparent low sensitivity to bulk composition b isotopic fractionation can be readily applied to studies of diagenesis hydrothermal alteration of planetary bodies subduction zone processing and arc magma generation and magma chamber evolution

quartz trace element composition by la icp ms as proxy for granite differentiation hydrothermal episodes and related mineralization the beauvoir granite echassieres district france despite quartz being a ubiquitous mineral in the earth s crust only little is known about its trace chemical composition and whether and how this is influenced by the medium from which it precipitated using in situla icp ms analysis we investigated the trace element composition of several types of quartz from a magmatic hydrothermal system in the echassieres district of the french massif central this system consists of the colettes granite the beauvoir rare element granite a w bearing stockwork and dispersed mineralized veins all of the elements tested li be b na al ti ge rb sr nb sn sb ta w were detected in quartz from at least one sample a rigorous multivariate statistical approach permitted to assign a specific chemical signature to each of the quartz groups that were recognized by petrographic observations differences among these groups were interpreted to reflect different sources or genetic evolutionary trends within magmatic and hydrothermally derived quartz groups for example the evolution of al rb ge li and ti could be related to genetic processes such as the degree of magma differentiation and crystallization temperatures quartz from the w stockwork anterior to the beauvoir leucogranite clearly stands out from that related to the beauvoir mineralization system i e the greisen facies and proximal ta nb sn w mineralized veins it was also possible to demonstrate a similarity in composition notably the sb contents between quartz from the greisen and from distal stibnite bearing veins in addition elevated values of sb sn as well as li and rb in quartz correspond to similarly high values of these elements in the rock indicating that quartz trace chemistry can provide useful information for the mineralization potential of its host at least for these elements on the other hand nb ta and w are less reliable as they occur mostly at very low levels in quartz the highest values corresponding to samples that were not particularly enriched in these metals a comparison of our quartz data with those from a similar granitic complex at cinovec czech republic breiter et al 2017a shows a similar trend for the ge ti ratio reflecting magmatic differentiation conversely the al ti ratio values differ in the two complexes the al content of quartz from the various cinovec granites being systematically lower than in quartz from echassieres nevertheless caution must be taken when analyzing quartz for its trace element chemistry as processes occurring during i e trapping of fluid inclusions and formation of zoning and after crystal growth i e diffusion and alteration can introduce heterogeneities thus affecting the original chemistry

geochemistry and nd sr isotopic studies of late mesozoic granitoids in the southeastern hubei province middle lower yangtze river belt eastern china petrogenesis and tectonic setting abstract a geochemical and isotopic study was carried out for the mesozoic yangxin tieshan and echeng granitoid batholiths in the southeastern hubei province eastern china in order to constrain their petrogenesis and tectonic setting these granitoids dominantly consist of quartz diorite monzonite and granite they are characterized by sio 2 and na 2 o compositions of between 54 6 and 76 6 wt and 2 9 to 5 6 wt respectively enrichment in light rare earth elements lree and large ion lithophile elements lile and relative depletion in y concentrations ranging from 5 17 to 29 3 ppm and yb 0 34 2 83 ppm with the majority of the granitoids being geochemically similar to high sio 2 adakites hsa their initial nd e nd 12 5 to 6 1 and sr 87 sr 86 sr i 0 7054 0 7085 isotopic compositions however distinguish them from adakites produced by partial melting of subducted slab and those produced by partial melting of the lower crust of the yangtze craton in the late mesozoic the granitoid batholiths in the southeastern hubei province exhibit very low mgo ranging from 0 09 to 2 19 wt with an average of 0 96 wt and large variations in negative to positive eu anomalies eu eu 0 22 1 4 especially the tieshan granites and yangxin granite porphyry eu eu 0 22 0 73 geochemical and nd sr isotopic data demonstrate that these granitoids originated as partial melts of an enriched mantle source that experienced significant contamination of lower crust materials and fractional crystallization during magma ascent late mesozoic granitoids in the southeastern hubei province of the middle lower yangtze river belt were dominantly emplaced in an extensional tectonic regime in response to basaltic underplating which was followed by lithospheric thinning during the early cretaceous

petrogenesis of a type granites associated with sn nb zn mineralization in ririwai complex north central nigeria constraints from whole rock sm nd and zircon lu hf isotope systematics abstract we report a combined study of whole rock major and trace element geochemistry sm nd isotope composition zircon u pb dating and lu hf systematics of peralkaline and aluminous a type granites from the ririwai ring complex in north central nigeria the ririwai peralkaline and aluminous a type granites are strongly ferroan alkalic to alkali calcic and enriched in hf zr ga rb y and rees they were emplaced between 176 2 3 ma and 169 6 0 75 ma the peralkaline granites yield relatively higher nd t 2 3 to 1 2 and zircon hf t values 5 8 to 1 7 than the aluminous granites nd t 3 6 to 3 3 zircon hf t 7 8 to 2 4 in addition inherited zircons in the aluminous granites yield pan african 590 ma ages and low hf t values 14 0 taken together these data suggest that the granites formed from extensive fractional crystallization of a transitional basaltic melt derived from an enriched oib mantle source the depletions of mgo cao ti2o sr and ba in the granites indicate that mg rich olivine calcic pyroxene calcic amphibole feldspars and fe ti oxides were the major fractionated phases during magma evolution in addition several types of evidence e g moderately negative nd t and hf t values and the presence of inherited zircons imply that the parental melt was modified by assimilation of pan african upper crust into which the granites were emplaced a transtensional regime generated prior to late jurassic breakup of gondwana which led to reactivation of shear zones and opening of associated transcurrent faults paved the way for emplacement of the a type suite the sn nb zn mineralization of the ririwai a type suite was probably linked to complex magmatic evolutionary processes involving extensive fractional crystallization coupled with crustal assimilation and late stage hydrothermal fluid activity

ree fractionation during crystallization and alteration of fergusonite y from zr ree nb rich late to post magmatic products of the keivy alkali granite complex nw russia abstract the keivy alkali granite complex kola peninsula nw russia contains numerous zr ree y nb occurrences and deposits formed by a complex sequence of pegmatitic hydrothermal and metasomatic processes the rare metal rich lithologies have abundant fergusonite y mineralization 90 epma analyses of fergusonite y from different occurrences are used to document ree behavior during crystallization and alteration of the mineral variations in y hree ratio during growth of fergusonite y in a pegmatite are explained by a change of the fluorine content in the fluid loss of y and hree and addition of ce during alteration are governed by two major processes ce accumulation in late derivatives and high f contents in the crystallization environment the decreases of ce and other ree in some occurrences resulted from a low f content the extent of alteration possibly depends on the actinide content in fergusonite y and the resulting radiation damage positive eu eu anomalies in fergusonite y from a number of occurrences were due to external contributions of eu into the fluid from country rocks after the breakdown of plagioclase the specific ree distribution in fergusonite y indicates crystallization at low co2 h2o and changing f activity a f rich fluid is suggested during fergusonite y formation in alkali granite pegmatite and quartzolite and a low f fluid is characteristic of minerals from a metasomatite and amazonite pegmatite located in country rocks of alkali granite massifs

chlorite chemistry of tongshankou porphyry related cu mo w skarn deposit eastern china implications for hydrothermal fluid evolution and exploration vectoring to concealed orebodies abstract recent years the depletion of shallow mineral resources has drawn increasing attention to the exploration of hidden ore bodies in deep of skarn type deposits chemical composition of chlorite is an effective tool for tracing the hydrothermal fluid evolution and has been increasingly used for deep level exploration of porphyry cu au deposits pcds however the technique was rarely applied onto porphyry related skarn deposits the tongshankou cu mo w deposit 0 55 mt cu 0 86 0 01 mt mo 0 10 and 0 12 mt wo3 0 19 is one of the largest skarn porphyry deposits in the middle lower yangtze river metallogenic belt mlyrb in eastern china in this study new petrographic and trace element data of the hydrothermal chlorites from tongshankou were presented to constrain the ore fluid evolution and to explore the vectoring potential of the concealed orebodies at tongshankou four types of chlorite have been identified i e g type chlorite that replaced the original magmatic biotite or hornblende v type chlorite in chlorite quartz sulfides veins in the granodiorite porphyry alteration zones i and ii s type chlorite that replaced garnet in the intensive skarn alteration zone iii and m type chlorite quartz calcite sulfides veins that cut the dolomitic marble in the distal alteration zones iv and v all the four types of chlorites are typically trioctahedral chlorite the fe mg tschermark and di trioctahedral substitution mechanisms likely control the geochemical variations of the tongshankou chlorites empirical thermometer indicates that the tongshankou chlorites were crystallized at 169 322 compared with typical metamorphic chlorites the higher zn and sr contents but lower al content in the tongshankou chlorites can potentially distinguish the skarn type hydrothermal chlorites from typical metamorphic ones compared with the chlorites in the typical pcds the tongshankou g type chlorite has higher fe zn as and sn contents but lower al mg co and cu contents which likely reflect its protolithic and or fluid geochemical inheritance the tongshankou v m and s type chlorites have high contents of mobile elements such as sr ca sn and b and metals such as fe cu as zn and pb indicating that they were directly precipitated from the hydrothermal fluids from the granodiorite porphyry to the marble wallrocks the spatial chlorite geochemical variations at tongshankou indicate that the increasing zn mn ga ge and pb contents and decreasing v sc and ti contents are potential vectors toward concealed mineralized porphyries at tongshankou our study highlights that the chlorite geochemistry is a potential tool for ore fluid tracer and vectoring tool toward concealed skarn porphyry orebodies in the mlyrb

origin of topaz bearing and related peraluminous granites of the late devonian davis lake pluton nova scotia canada crystal versus fluid fractionation abstract the davis lake pluton in the late devonian south mountain batholith in southwestern nova scotia canada is composed of peraluminous leucomonzogranites and subordinate topaz bearing leucogranites that host greisens and a primary tin deposit the concentrations of incompatible trace elements e g rb li u f ta and sn and element e g k rb nb ta and la sm and isotopic ratios e g 206 pb 204 pb and 87 sr 86 sr display a spatial zonation the granitic rocks were generated by extensive fractional crystallization of major phases feldspars and biotite and accessory minerals monazite apatite and zircon in a compositionally zoned magma chamber fractional crystallization of the evolving f rich peraluminous granitic magma was accompanied particularly in later stages by fluid fractionation involving fluorine complexing fluid fractionation was a major differentiation process during the terminal stages of the pluton s evolution it played an important role in the genesis of the evolved rocks which are characterized by low k rb 24 150 nb ta 1 6 la sm 1 5 4 and eu eu 0 01 0 3 ratios these ratios as well as the enhanced concentrations of li rb u ta and sn in these rocks correlate with f fluorine rich fluids modified the rb sr and u pb ratios which produced the distinct variations of 87 sr 86 sr and 206 pb 204 pb isotopic ratios the parent magma was formed by dehydration melting of lower crustal metasedimentary rocks the melting was related to crustal thickening in association with terrane and collision along the eastern margin of the appalachians

petrologie du granite peralcalin du lac brisson labrador central nouveau quebec 1 mode de mise en place et evolution chimique the lake brisson peralkaline granite in labrador which by way of its age of 1189 ma is the most recent phase of the gardar magmatic stage was intruded in the middle proterozoic at the margin of a granulitic complex retrograded to an amphibolite facies during aphebian and of an elsonian adamellite pluton it shows a petrographie zonation feldspathic facies at the center quartzose facies including early quartz at the edge suggestive of a permissive multiphase intrusion and is characterized by deuteritic alteration via metalliferous fluids zr y nb be rare earths all facies are na peralkaline well evolved and represent end members of a differentiated magmatic suite of the designated a type the relative behavior of the major elements indicates that the facies differentiation was controlled by fractional crystallization and was also greatly influenced by alkaline feldspath and by increase of f o2 in the final stage of evolution the trace elements contents significantly higher than those

distribution of porphyry deposits in the eurasian continent and their corresponding tectonic settings in the eurasian continent there are three huge metallogenic belts of cu and mo porphyry deposits comprising the paleozoic central asian ore belt in the north the tethyan eurasian ore belt of jurassic to cenozoic age in the southwest and the east margin ore belt of the eurasian continent of jurassic to cretaceous age in the east the latter is considered to be part of the vast circum pacific ore belt some of the main features of the spatial temporal distribution of cu and mo porphyry systems and related geodynamic processes of the three metallogenic belts are described in particular the key role of postsubduction related porphyry ore systems is emphasized comprising collisional and post collisional cu mo porphyry deposits during the geological history of the eurasian continent the recurrent feature of these ore systems and related felsic rocks is their derivation from partial melting of stagnant or residual oceanic slabs and mixing with a variable amount of crustal material during magma ascent to shallower levels 2013 published by elsevier ltd

hydrothermal alteration and short wavelength infrared swir characteristics of the tongshankou porphyry skarn cu mo deposit yangtze craton eastern china abstract the early cretaceous tongshankou cu mo deposit is located in the eastern yangtze craton and comprises both porphyry and skarn mineralization the porphyry ore is hosted in a granodiorite porphyry with the skarn mineralization found along the contacts with the carbonate host rocks alteration in the porphyry mineralization can be divided into three stages potassic alteration phyllic alteration and a carbonate stage with phyllic alteration associated with the main porphyry mineralization no propylitic alteration is present at tongshankou the skarn type alteration comprises five stages early skarn stage late skarn stage oxide stage quartz sulfide stage and late vein stage short wave length infrared swir analysis identified 15 hydrothermal minerals in the tongshankou deposit including illite dickite halloysite phengite talc muscovite saponite gypsum chlorite prehnite montmorillonite serpentine phlogopite actinolite kaolinite with montmorillonite illite and chlorite being the most common swir parameters and the electron microprobe results of chlorites show that chlorites close to the mineralization center tend to be iron rich and have high feoh absorption position pos 2250 2251 nm consequently chlorite may be a useful indicator mineral for mineralization in the tongshankou deposit pos 2250 is not correlated to temperature as calculated using a chlorite geothermometer but does correlate with the iron contents of the chlorites our results show that the ore forming fluids are fe rich in the proximity to the mineralization but mg rich towards the distal area unlike in other porphyry deposits the white mica show no consistent variation in the tongshankou deposit and cannot be used as vectors towards mineralization the fe mg al poor carbonate host rocks of the tongshankou deposit restrict the development of a propylitic alteration zone the fe mg al host rocks also prevent tschermak exchange in white mica siiv mg fe vi alivalvi making white mica pos 2200 and illite crystallinity ic randomly distributed our results show that swir spectroscopy of chlorite may be an applicable exploration tool in skarn related hydrothermal systems