u pb dating of prograde and retrograde titanite growth during the scandian orogeny u pb ages of metamorphic titanite from high grade gneisses of the nasafjallet window in the north central scandinavian caledonides record growth over an 20 m y interval during the late silurian to early devonian biotite amphibolite gneisses located near the basement cover boundary contain metamorphic titanite in two microtextural settings one as lenticular grains distributed throughout a recrystallized matrix of metamorphic phases and one as plate like grains enclosed within biotite grains these distinct morphological populations exhibit core overgrowth relationships with compositionally similar cores and overgrowths but the plate like titanite grains have a much higher proportion of overgrowth and give slightly younger ages cores and overgrowths in both types are inferred to have formed along the prograde ca 413 ma and retrograde ca 395 ma paths respectively of a single metamorphic cycle associated with the burial and exhumation of a slice of baltic basement during the caledonide orogeny baltica laurentia collision the existence of polygenic u pb systematics in metamorphic titanite demonstrates the potential usefulness of titanite to reveal multiple metamorphic and deformational episodes and to constrain the duration of metamorphic events

igneous and tectonic evolution of the batchawana greenstone belt superior province a u pb zircon and titanite study u pb isotopic dating of zircon and titanite from all the major litho tectonic units of the batchawana belt an archean greenstone belt of the abitibi subprovince of the superior province in canada shows that the belt evolved during a period of about 60 ma between about 2730 and 2670 ma ago the earliest date of 2729 3 2 ma was found in a predominantly tholeiitic metavolcanic sequence the base of which is intruded by a tonalite dated at 2716 2 ma younger ages of 2720 10 ma 2709 2ma 2711 2ma 2701 2ma and 2698 2 ma date rocks at increasingly higher stratigraphic levels of a mixed tholeiitic calc alkalic metavolcanic sequence which is itself overlain by a thick succession of clastic metasedimentary rocks subsequent deformation of the supracrustal sequences produced isoclinal folding and culminated in metamorphism ranging from lower greenschist to amphibolite facies and anatexis related to the intrusion of syn to late tectonic plutons four phases of which have ages of 2678 4 2ma 2677

formation of au polymetallic ore deposits in alkaline porphyries at beiya yunnan southwest china abstract the beiya gold deposit is located in the central part of the jinshajiang honghe strike slip belt at the junction zone of the tethys himalaya orogenic belt and the yangtze plate in sw china this large scale 125 6 million metric tonnes with a mean grade of 2 42 g t au rich polymetallic deposit is related to alkaline porphyry intrusions previous studies show that the beiya alkaline porphyry intrusions are the fractionation product of a mantle derived magma emplaced in an extension environment at the post collision stage of the india eurasian plate collision the beiya deposit is considered to be skarn related based on detailed field studies and previous work we propose that the beiya porphyry and associated au rich polymetallic ores were formed by the emplacement of magmas within the jinshajiang honghe strike slip fault during the late stage of the india eurasian plate collision at 45 25 ma at beiya the mineralized zones in the cu au rich porphyries are surrounded by au cu fe skarns and au cu veins pb zn ag rich mineralization was derived from the inner porphyry and is widely developed outside the central alkaline rich porphyry the sulfur isotope signature of the sulfide mineralization in the beiya and qinhe deposits is 2 40 4 50 and 1 25 2 75 respectively these values are close to 0 indicating that the sulfur may be mantle derived the 18 o compositions of the ore forming fluids responsible for the formation of calcites at qinhe are 8 10 9 61 which is lower than that of beiya 18 o 10 5 where the ores contain a larger contribution of oxygen from the mantle the beiya porphyry magmas provided fluids and the heat that drove the transport of the metals to the site of deposition alkaline porphyries are widely distributed throughout the jinshajiang honghe strike slip fault belt and they are potential hosts to future discoveries of beiya style mineralization

u pb geochronology of zircon and polygenetic titanite from the glastonbury complex connecticut usa an integrated sem empa tims and shrimp study abstract u pb ages for zircon and titanite from a granodioritic gneiss in the glastonbury complex connecticut have been determined using both isotope dilution thermal ionization mass spectrometry tims and the sensitive high resolution ion microprobe shrimp zircons occur in three morphologic populations 1 equant to stubby multifaceted colorless 2 prismatic dark brown with numerous cracks and 3 elongate prismatic light tan to colorless cathodoluminescence cl imaging of the three populations shows simple concentric oscillatory zoning the zircon tims age weighted average of 207pb 206pb ages from group 3 grains 450 5 1 6 ma mswd 1 11 and shrimp age composite of 206pb 238 u age data from all three groups 448 2 2 7 ma mswd 1 3 are interpreted to suggest a relatively simple crystallization history titanite from the granodioritic gneiss occurs as both brown and colorless varieties scanning electron microscope backscatter bse images of brown grains show multiple cross cutting oscillatory zones of variable brightness and dark overgrowths colorless grains are unzoned or contain subtle wispy or very faint oscillatory zoning electron microprobe analysis empa clearly distinguishes the two populations brown grains contain relatively high concentrations of fe2o3 ce2o3 up to 1 5 wt nb2o5 and zr cerium concentration is positively correlated with total ree y concentration which together can exceed 3 5 wt oscillatory zoning in brown titanite is correlated with variations in ree concentrations in contrast colorless titanite both as discrete grains and overgrowths on brown titanite contains lower concentrations of y ree fe2o3 and zr but somewhat higher al2o3 and nb2o5 uranium concentrations and th u discriminate between brown grains typically 200 400 ppm u all analyses but one have th u between about 0 8 and 2 and colorless grains 10 60 ppm u th u of 0 0 17 in contrast to the zircon u pb age results shrimp u pb data from titanite indicate multiple growth episodes in brown grains oscillatory zoned cores formed at 443 6 ma whereas white in bse cross cutting zones are 425 9 ma colorless grains and overgrowths on brown grains yield an age of 265 8 ma using the total pb method or 265 5 ma using the weighted average of the 206pb 238u ages however empa chemical data identify zoning that suggests that this colorless titanite may preserve three growth events oscillatory zoned portions of brown titanite grains are igneous in origin white cross cutting zones probably formed during a previously unrecognized event that caused partial dissolution of earlier titanite and reprecipitation of a slightly younger generation of brown titanite colorless titanite replaced and grew over the magmatic titanite during the permian alleghanian orogeny these isotopic data indicate that titanite like zircon can contain multiple age components coupling shrimp microanalysis with empa and sem results on dated zones as presented in this study is an efficient and effective technique to extract additional chronologic data to reveal the complexities of igneous crystallization and metamorphic growth

geochronology of the giant beiya gold polymetallic deposit in yunnan province southwest china and its relationship with the petrogenesis of alkaline porphyry abstract the beiya gold polymetallic deposit located at the junction of the sanjiang tethys himalaya orogenic belt and the yangtze craton in southwestern china is the largest gold deposit in the region mineralization mainly occurs in skarn which formed along the contacts between porphyry intrusions and limestone host rocks the ore formation process is suggested to be closely related to the himalayan age alkaline porphyries u pb dating of magmatic zircons from the beiya quartz syenite porphyry yields a weighted average 206 pb 238 u ages of 36 07 0 43 ma n 25 mswd 1 17 calculated isochron age of five molybdenite samples from beiya is 34 7 1 6 ma mswd 0 99 initial 187 os of 0 21 0 16 ppb which indicates that mineralization is coeval with the intrusion of the beiya alkaline porphyry this age is also in agreement with the results of apatite fission track analysis in the porphyry magmatic zircon e hf t values range from 7 4 to 0 1 which correspond to the two stage hf model with ages between 1112 ma and 1588 ma this finding suggests that the main source of porphyry was probably melting of thickened mesoproterozoic lower crust triggered by partial melting of the lithospheric mantle zircon ce iv ce iii ratios of ore related porphyry are high given that all eu n eu n ratios are above 0 4 which demonstrates that the magma source of the porphyry was highly oxidized which was favorable for cu au mineralization the medium re concentrations in molybdenite re 2 08 20 54 ppm suggest that the ore forming materials were characterized by mixed crustal mantle sources mineralization in the beiya deposit was one of the many metallogenic events related to the india eurasia collision that was responsible for the fertile deep sourced magmatism

in situ la icp ms u pb dating of metavolcanics of norrbotten sweden records of extended geological histories in complex titanite grains in situ u pb dating of a variety of mineral phases is an important goal in petrology this study reports data chiefly from titanite but also from rutile and apatite obtained using the laser ablation la icp ms methodology on polished thick sections in order to retain as much petrologic information as possible and allowing trace element analyses from adjacent areas to the u pb analyses the samples analysed come from svecofennian intermediate to acid volcanic rocks of the porphyry group within the major iron ore province of norrbotten northern sweden where titanite is a common phase associated with the mineralisation using a laser beam of 30 45 m in diameter accurate and relatively precise 2 3 2 on 206pb 238u ratios data can be obtained on titanite similar precision on pb u ratios can be obtained in rutile but accuracy cannot be assessed because of the lack of well characterised standards however the data are a priori accurate as they are geologically reasonable apatite shows reverse discordance which could be explained by a number of scenarios however the 207pb 206pb ages are fairly precise 1 3 2 and the calculated age is geologically reasonable suggesting that the data may be accurate the titanite grains studied show complex internal structures rare earth element ree analysis by la icp ms demonstrates that the core and rim zones are distinct and supports a model for two stage evolution in two out of three samples with the rims in these samples being enriched in total ree and particularly in lree in one sample and displaying a positive y anomaly in contrast to the cores in situ u pb analysis reveals that core zones from all samples retain distinct older ages of c 2050 ma whereas the reworked rims have either distinct younger or strongly reset ages the older cores are interpreted as representing the first alteration metamorphism of the volcanic pile titanite rims record a u pb age of 1870 24 ma 2 at luossavaara and 1826 15 ma 2 at the smaller fe oxide apatite body at gruvberget in both cases the ages are consistent with previous age determinations from the fe oxide apatite deposits a sample from malmberget records a slightly different scenario where u pb ages spread along concordia from c 1920 to 1708 ma we attribute this pattern to metamorphic reworking of primary metasomatic titanite rutile ages from inclusions within the core of gruvberget titanite essentially mimic the ages obtained from the surrounding titanite and suggest that they have undergone the same history apatite inclusions within titanite at malmberget record a younger age of 1584 12 ma 2 which we attribute to later events known to have affected the area these data indicate that the porphyry group volcanics must be at least c 2050 ma in age in contrast to previous age determinations from zircon which suggested a deposition age of c 1960 to 1880 ma the large grain size of the titanites studied coupled with the ability for the first time to obtain in situ u pb ages from small areas has allowed probing of this hitherto unrecognised event smaller zircon grain size coupled with extremely saline hot pressurised high p t metasomatic fluids relating to regional magnetite apatite mineralisation in the period 1900 to 1800 ma may have resulted in resetting of zircon u pb systematics 2007 elsevier b v all rights reserved

formation of magmatic titanite and titanite ilmenite phase relations during granite alteration in the tribec mountains western carpathians slovakia abstract in this study formation of titanite in carboniferous i type granites granitoids from the tribec mountains slovakia and its subsequent alteration products are described titanite occurs in early magmatic differentiates of i type granites granitoids calculation of model mineral equilibria in the system k 2 o cao feo al 2 o 3 tio 2 sio 2 h 2 o o 2 kcfatsho indicates that titanite forms in granites granitoids as a consequence of a reaction between titanomagnetite biotite and anorthite in a fluid rich environment under relatively oxidizing conditions during the later stages of magma crystallisation evidence for this reaction can be found in low temperature inclusions of ti rich magnetite and biotite inclusions in the titanite as well as in the formation of titanite not only interstitially but also locally in quartz the titanite alteration process has lead to the complete replacement of titanite by ilmenite quartz ree bearing epidote and allanite while preserving the characteristic euhedral diamond shape of the former titanite completely altered titanite grains become optically opaque due to the presence of ilmenite the formation of ree bearing epidote and allanite is probably due to the release of ree from the titanite during alteration this can be explained by model hydration reactions such as titanite anorthite annite h 2 o ilmenite clinozoisite muscovite quartz calculation of mineral equilibria involving magmatic precursor minerals such as plagioclase and biotite indicate that the formation of ilmenite from titanite requires an influx of h 2 o and or an increase in f o 2 titanite with the highest degree of ilmenite replacement occurs in a strongly mylonitized granite in which the rock forming minerals have been replaced by sericite epidote and chlorite this breakdown of titanite to ilmenite is a common phenomenon in some granites from the southwest area of the tribec mountains indicating widespread late stage fluid activity associated with high f o 2 during the subsolidus cooling

sediment transport by burrowing mammals marin county california abstract field observations suggest that burrowing activity is the primary mode of sediment transport currently active in a small grassland drainage basin in marin county california spatial concentrations of the 1 150 gopher mounds surveyed vary from 0 16 mounds m on interfluves to 0 32 mounds m on sideslopes and in the topographic hollow with localized concentrations of up to 2 88 mounds m on the margins of the colluvial deposit simple models of sediment transport by burrowing activity yield estimates of between 0 91 and 2 33 cm3 cm yr for the basin as a whole with absolute minimum and maximum rates of 048 and 6 31 cm3 cm yr i these values are similar to those previously estimated for this area lehre 1982 and are nearly an order of magnitude less than average long term sediment transport rates at the same site reneau 1988 key words sediment transport erosion rates bioturbation introduction burrowing animals disturb and transport soil in environments ranging from alpine tundra to humid grasslands hansen and morris

combined oxygen isotope and u pb zoning studies of titanite new criteria for age preservation this material is based upon work supported by the u s national science foundation award ear 0838058 the u s department of energy office of basic energy sciences under award number de fg02 93er14389 and geological society of america student research grant 9224 10 wiscsims is partially supported by nsf ear 1053466 and 1355590

trace element incorporation in titanite constraints from experimentally determined solid liquid partition coefficients titanite liquid partition coefficients for most of the trace elements relevant in petrogenetic studies are provided for titanite saturated liquids equilibrated at 1 5 gpa and 850 c starting from lamproitic compositions the high compatibility observed for ree hfse sr v and sc and the strong incompatibility observed for actinides large ion lithophile and light elements are discussed in terms of available crystal chemical mechanisms for incorporation and crystal structure control the exchange vectors na1ca 1 and al1ti 1 allow local charge balance to be achieved after incorporation of ree3 and r5 at the ca and ti site respectively the significant amounts of h measured are also relevant in this regard the exchange mechanism being oh 1o 1 at the o1 site the incorporation of u4 and th4 at the ca site is scarce and is likely balanced by that of mg2 at the ti site both these substitutions are responsible for strong structural strain titanite can thus be considered an important repository for ree and hfse in metamorphic and igneous rocks and its role must be accounted for when modelling trace element residence during metamorphic reactions and late magmatic crystallisation history due to the measured differences in compatibility titanite crystallisation increases the values of nb ta and lree hree ratios in residual liquids the similar compatibility of u and pb makes titanite suitable for u pb geochronology of igneous rocks only after common pb correction finally this study confirms that the titanite end member is not suitable for radioactive waste disposal due to the discussed crystal chemical constraints and that titanite based waste forms should contain high amounts of na and mg2

u pb re os and 40ar 39ar geochronology of the nambija au skarn and pangui porphyry cu deposits ecuador implications for the jurassic metallogenic belt of the northern andes new u pb re os and 40ar 39ar dates are presented for magmatic and hydrothermal mineral phases in skarn and porphyry related ores from the nambija and pangui districts of the subandean zone southeastern ecuador nambija has been one of the main gold producing centers of ecuador since the 1980s due to exceptionally high grade ores average 15 g t but frequently up to 300 g t au pangui is a recently discovered porphyry cu mo district the geology of the subandean zone in southeastern ecuador is dominated by the i type subduction related jurassic zamora batholith which intrudes triassic volcanosedimentary rocks the zamora batholith is in turn cut by porphyritic stocks which are commonly associated with skarn formation and or porphyry style mineralization high precision u pb and re os ages for porphyritic stocks u pb zircon associated prograde skarn u pb hydrothermal titanite and retrograde stage skarn re os molybdenite from veins postdating gold deposition of the nambija district are all indistinguishable from each other within error 145 ma and indicate a late jurassic age for the gold mineralization previously gold mineralization at nambija was considered to be early tertiary based on k ar ages obtained on various hydrothermal minerals the new jurassic age for the nambija district is slightly younger than the 40ar 39ar and re os ages for magmatic hydrothermal minerals from the pangui district which range between 157 and 152 ma mineralization at nambija and pangui is associated with porphyritic stocks that represent the last known episodes of a long lived jurassic arc magmatism 190 to 145 ma a jurassic age for mineralization at nambija and pangui suggests that the northern andean jurassic metallogenic belt which starts in colombia at 3 n extends down to 5 s in ecuador it also adds a new mineralization style au skarn to the metal endowment of this belt

in situ la icpms trace elements and u pb analysis of titanite from the mesozoic ruanjiawan w cu mo skarn deposit daye district china abstract in this paper we present u pb ages and trace element compositions of titanite from the ruanjiawan w cu mo skarn deposit in the daye district eastern china to constrain the magmatic and hydrothermal history in this deposit and provide a better understanding of the u pb geochronology and trace element geochemistry of titanite that have been subjected to post crystallization hydrothermal alteration titanite from the mineralized skarn the ore related quartz diorite stock and a diabase dike intruding this stock were analyzed using laser ablation inductively coupled plasma mass spectrometry la icpms titanite grains from the quartz diorite and diabase dike typically coexist with hydrothermal minerals such as epidote sericite chlorite pyrite and calcite and display irregular or patchy zoning these grains have low lree hree and high th u and lu hf ratios coupled with negative eu and positive ce anomalies the textural and compositional data indicate that titanite from the quartz diorite has been overprinted by hydrothermal fluids after being crystallized from magmas titanite grains from the mineralized skarn are texturally equilibrated with retrograde skarn minerals including actinolite quartz calcite and epidote demonstrating that these grains were formed directly from hydrothermal fluids responsible for the mineralization compared to the varieties from the quartz diorite stock and diabase dike titanite grains from the mineralized skarn have much lower ree contents and lree hree th u and lu hf ratios they have a weighted mean 206 pb 238 u age of 142 2 ma mswd 0 7 2 in agreement with a zircon u pb age of 144 1 ma mswd 0 3 2 of the quartz diorite and thus interpreted as formation age of the ruanjiawan w cu mo deposit titanite grains from the ore related quartz diorite have a concordant u pb age of 132 2 ma mswd 0 5 2 which is 10 12 ma younger than the zircon u pb age of the same sample and thus interpreted as the time of a hydrothermal overprint after their crystallization this hydrothermal overprint was most likely related to the emplacement of the diabase dike that has a zircon u pb age of 133 1 ma and a titanite u pb age of 131 2 ma the geochronological results thus reveal two hydrothermal events in the ruanjiawan deposit an early one forming the wu cu mo ores related to the emplacement of the quartz diorite stock and a later one causing alteration of the quartz diorite and its titanite due to emplacement of diabase dike it is suggested that titanite is much more susceptible to hydrothermal alteration than zircon results from this study also highlight the utilization of trace element compositions in discriminating titanite of magmatic and hydrothermal origins facilitating a more reasonable interpretation of the titanite u pb ages

preserved zr temperatures and u pb ages in high grade metamorphic titanite evidence for a static hot channel in the himalayan orogen abstract titanite grains from 800 c gneisses of the c 6 km thick greater himalayan sequence of central nepal were analyzed for zr in titanite temperatures and u pb ages to investigate the formation and evolution of a former weak mid crustal channel in the himalaya laser ablation icp ms depth profiles and spot analyses of titanite zr and u pb isotopic compositions are inconsistent with diffusional reequilibration on scales greater than 1 2 m and instead data appear to faithfully record both temperature and age titanite records protracted heating from 700 750 c at 37 ma to 775 c at 24 ma and possibly slight cooling to 765 c at 20 ma such temperatures exceed partial melting reactions in associated metapelites and imply profoundly weak rheologies i e a hot channel yet predate initiation of the bounding main central thrust and south tibetan detachment systems by as much as 15 myr evidently thick but weak crustal channels may remain stationary with respect to the convergence direction for 10 myr even during one of earth s biggest continent continent collisions

late alteration in titanite catisio5 redistribution and remobilization of rare earth elements and implications for u pb and th pb geochronology and nuclear waste disposal abstract translucent dark coloured titanites from a wide variety of geological environments are commonly partly replaced by very fine grained aggregates of ree rich minerals including allanite monazite and bastnasite rutile quartz calcite apatite and chlorite along grain fractures and boundaries the aggregates of ree rich minerals are bordered by an irregular zone of altered titanite which by secondary ion mass spectrometry sims is considerably lower in rees u and th than the adjacent unaltered matrix light rees and th are differentially depleted in the altered zone and correspondingly enriched in secondary minerals additionally hrees and u have been lost to the external system the loss of hrees being in proportion to the increase in atomic number natural radiation damage was not an important factor in promoting the late alteration of titanite titanite which has been subjected to late hydrothermal activity would not remain a closed system in respect to either u or th decay series and therefore cannot be used for u pb and th pb geochronology the observed leaching and partial dissolution of titanite under hydrothermal conditions are generally consistent with laboratory experimentation indicating that proper isolation from any communication with hydrothermal fluids is essential in the application of titanite based ceramics for the immobilization of radioactive waste

porphyry cu au and associated polymetallic fe cu au deposits in the beiya area western yunnan province south china abstract the alkaline porphyries in the beiya area are located east of the jinshajiang suture as part of a cenozoic alkali rich porphyry belt in western yunnan the main rock types include quartz albite porphyry quartz k feldspar porphyry and biotite k feldspar porphyry these porphyries are characterised by high alkalinity k2o na2o 10 high silica sio2 65 high sr 400 ppm and 87sr 86sr 0 706 ratio and were intruded at 65 5 ma between 25 5 to 32 5 ma and about 3 8 ma respectively there are five main types of mineral deposits in the beiya area 1 porphyry cu au deposits 2 magmatic fe au deposits 3 sedimentary polymetallic deposits 4 polymetallic skarn deposits and 5 palaeoplacers associated with karsts the porphyry cu au and polymetallic skarn deposits are associated with quartz albite porphyry bodies the fe au and polymetallic sedimentary deposits are part of an ore forming system that produced considerable au in the beiya area and are characterised by low concentrations of la ti and co and high concentrations of y yb and sc the cenozoic porphyries in western yunnan display increased alkalinity away from the triassic jinshajiang suture distribution of both the porphyries and sedimentary deposits in the beiya area are interpreted to be related to partial melting in a disjointed region between upper mantle lithosphere of the yangtze plate and gondwana continent and lie within a shear zone between buried palaeo tethyan oceanic lithosphere and upper mantle lithosphere caused by the subduction and collision of india and asia

geochemical and u pb age constraints on the occurrence of polygenetic titanites in uhp metagranite in the dabie orogen abstract relict magmatic titanite was identified in the core of a few titanite grains with the overgrown rim of metamorphic titanite in uhp metagranite in the dabie orogen la icpms u pb dating gave neoproterozoic ages for the magmatic titanite but triassic ages for the metamorphic titanite the magmatic and metamorphic titanites are clearly distinct by differences in petrological and geochemical compositions the magmatic titanite occurs as residual cores that show bright bse the presence of allanite and quartz inclusions low contents of cao al2o3 and tio2 but high contents of fe2o3 and mgo in trace elements the magmatic titanite exhibits high ree and hfse contents distinctly negative eu anomalies with flat mree hree patterns and high th u ratios in contrast the metamorphic titanite occurs as rims and grains of homogeneously dark bse that contain inclusions of epidote quartz k feldspar rutile biotite and phengite and have relatively high contents of cao al2o3 and tio2 but low contents of fe2o3 and mgo and relatively low ree and hfse contents slightly negative eu anomalies with hree depletion relative to mree and low th u ratios the zr in titanite thermometry yields 727 to 877 c at 0 5 to 1 0 gpa for the magmatic titanite and 729 to 870 c at 1 5 to 2 0 gpa for the metamorphic titanite the neoproterozoic u pb chronometric system of magmatic titanite survived the triassic continental subduction zone hp uhp metamorphism this suggests a relatively high closure temperature of 800 c for the titanite u pb system the metamorphic titanite is principally a product of retrograde metamorphism during decompression exhumation at the transition from hp eclogite facies to amphibolite facies therefore titanite holds a great potential to geochronological and petrogenetic studies of continental subduction zone metamorphic rocks

laser ablation icp ms titanite u th pb dating of hydrothermal ore deposits a case study of the tonglushan cu fe au skarn deposit se hubei province china abstract titanite from the tonglushan cu fe au skarn deposit daye district eastern china has been successfully dated by laser ablation inductively coupled plasma mass spectrometry la icp ms hydrothermal titanite from both skarn ores and calcite veins cutting the ore bodies are characterized by having much lower ree and th u and lu hf ratios compared to their magmatic equivalents from the ore related yangxin quartz diorite intrusion and a late stage albitite dike titanite from the yangxin quartz diorite and an albitite dike which intrudes both the quartz diorite intrusion and ore bodies yield weighted mean 206pb 238u ages of 136 0 1 5 ma and 120 6 2 3 ma 2 respectively in agreement within analytical uncertainty to their 208pb 232th ages in situ analysis of epidote enclosed hydrothermal titanite in thin sections of a skarn ore sample yields a mean 206pb 238u age of 135 9 1 3 ma and 208pb 232th age of 138 2 4 5 ma whereas titanite in calcite from a calcite dominated vein cross cutting the skarn ore body has consistent 206pb 238u and 208pb 232th ages of ca 121 ma the data thus reveal two independent hydrothermal events the earlier event was responsible for the known cu fe au skarn mineralization at tonglushan and throughout the daye district and was caused by coeval magmatism that has resulted in the emplacement of the yangxin quartz diorite the later event previously unrecognized was associated with a second magmatic pulse as represented by the albitite dikes and provides potential for discovering new mineral deposits at tonglushan and possibly over the daye district this study represents the first direct dating of skarn deposits using titanite u th pb geochronometer and signifies the utilization of titanite for precise dating of hydrothermal ore formation

in situ la icp ms u pb geochronology and trace elements analysis of polygenetic titanite from the giant beiya gold polymetallic deposit in yunnan province southwest china abstract the beiya gold polymetallic deposit located in the middle of the jinshajiang ailaoshan alkaline porphyry metallogenic belt is one of the largest gold deposits in china the mineralization mainly occurs in skarn along the intrusive contacts between the alkaline porphyries and middle triassic limestone in this paper we present u pb age as well as major and trace element geochemistry of titanite from the beiya deposit and distinguish the titanite into a magmatic and a hydrothermal suite our study indicates that the titanite from the ore related porphyry and from the mineralized skarn is texturally and geochemically very different the euhedral envelope shaped titanite from the ore related porphyry has lower feo f hfses nb ta and lu hf together with higher tio2 and th u than the subhedral titanite from the mineralized skarn the titanite from the porphyry also displays higher lree hree and more subtle negative eu anomaly than its mineralized skarn counterpart this suggests a magmatic and a hydrothermal origin for respectively the titanite from the ore related porphyry and from the mineralized skarn in situ magmatic titanite u pb dating has yielded an eocene age of 36 0 5 9 ma consistent with the porphyry zircon u pb age 36 07 0 43 ma obtained in previous studies hydrothermal titanite has yielded a weighted average 206pb 238u age of 33 1 1 0 ma mswd 2 0 which represents the age of the retrograde skarn alteration and the maximum age for the gold mineralization together with the previous molybdenite re os age we have further constrained the beiya gold polymetallic metallogeny to 33 1 34 1 ma the mineralization age is slightly younger than the porphyry emplacement indicating that the beiya metallogeny was likely to be a post magmatic hydrothermal product of the himalayan orogenic event the ree characteristics of hydrothermal titanite also reveal that the ore forming fluids may have been derived from a highly oxidized magma

additional evidence of an upper tropospheric zonal eddy relationship during winter abstract a zonal wind oscillation with a period of about 15 35 days is isolated over the middle latitudes of the northern hemisphere during winter a systematic relationship between the zonal winds and wind departures from zonal symmetry eddies is found for nine prominent zonal wind oscillation cycles taken from six 120 day winters this zonal eddy relationship consists of an oscillation between anomalous zonal flow and anomalous meridional flow which is strongest across north america from 150 w to 0

in situ la mc icp ms trace element and nd isotopic compositions and genesis of polygenetic titanite from the baogutu reduced porphyry cu deposit western junggar nw china abstract titanite sphene catisio 5 is sensitive to changes in temperature oxygen and water fugacity and fluid composition in order to understand formation processes and the nature of hydrothermal fluids various types of titanite from cu ores at the baogutu reduced porphyry cu deposit were chosen for detailed study magmatic titanite is associated with biotite plagioclase and k feldspar whereas hydrothermal titanite occurs with k feldspar chlorite actinolite and calcite the formation of hydrothermal titanite was related to hydration of igneous minerals under high f h 2 o whereas the widespread replacement of ilmenite by titanite without magnetite indicates a relatively low oxygen fugacity magmatic titanite has low al high fe y sn zr nb and ree contents relative to hydrothermal titanite on the basis of the zr in titanite and al in chlorite geothermometers formation temperatures for magmatic and hydrothermal titanite are estimated to be 687 739 c and 250 670 c respectively the gradual decrease in ree y and sn contents from magmatic to late hydrothermal titanite was probably caused by precipitation of ree bearing minerals magmatic and hydrothermal titanites have similar chondrite normalized ree patterns with negative eu anomalies and relatively flat hree randomly selected titanites have nd isotopic compositions similar to the host rocks thus both magmatic and hydrothermal titanite are believed to have been predominantly derived from a mantle source