residence of ree y th and u in granites and crustal protoliths implications for the chemistry of crustal melts a systematic study with laser ablation icp ms scanning electron microscopy and electron microprobe revealed that 70 95 wt of ree except eu y th and u in granite rocks and crustal protoliths reside within reeythu rich accessories whose nature composition and associations change with the rock aluminosity the accessory assemblage of peraluminous granites migmatites and high grade rocks is composed of monazite xenotime in low ca varieties apatite zircon thorthosilicate uraninite and betafite pyrochlore metaluminous granites have allanite sphene apatite zircon monazite and thorthosilicaie peralkaline granites have aeschinite fergusonite samarskite bastnaesite fluocerite allanite sphene zircon monazite xenotime and th orthosilicate granulite grade garnets are enriched in nd and sm by no less than one order of magnitude with respect to amphibolite grade garnets granulitegrade feldspars are also enriched in lree with respect to amphibolite grade feldspars accessories cause non henrian behaviour of ree y th and u during melt solid partitioning because elevated fractions of monazite xenotime and zircon in common migmatites are included within major minerals their behaviour during anatexis is controlled by that of their host settling curves calculated for a convecting magma show that accessories are too small to settle appreciably being separated from the melt as inclusions within larger minerals biotite has the greatest tendency to include accessories thereby indirectly controlling the geochemistry of ree y th and u we conclude that ree y th and u are unsuitable for petrogenetical modelling of granitoids through equilibrium based trace element fractionation equations

regional metallogeny of tungsten tin polymetallic deposits in nanling region south china abstract the nanling region gains its reputation for abundant mineral resources especially w sn sb bi pb zn li be ta nb and ion adsorption ree within weathering crust as well as uranium these dominant mineral resources are mainly formed in the yanshanian period with intimate genetic relationship to yanshanian granitoids spatially tungsten and tin deposits separately occurred in the eastern and western parts of nanling region respectively the complicated genetic relationships between tungsten tin polymetallic deposits and nanling granitoids demonstrate a regularity for mineralization we named this metallogenic specialization reflected in the aspects of specialized metallogenic compositions age spatiality alteration and its geological background the metallogenic specialization regional metallogeny is important to discover mineralization lay the foundation a new exploration model named five levels basement was proposed in this paper now it became a prospecting guidance in nanling region recently the ongoing prospecting of large tungsten deposits in nanling and its adjacent region using this model indicates a northward expanding for tungsten deposits in the south part of study area and westward expanding for that in the eastern part in practice the model also can be used in deep prospecting e g deep seated bedded or bed like orebodies as well as not limited to tungsten deposits other mineral deposits

sedimentary pachnolite and fluorite from tampa bay florida deltaic deposits of pachnolite and fluorite occur in tampa bay florida as a result of chemical precipitation from a fluoride rich effluent from a phosphate chemical plant the deposits are crusts up to 8 cm in thickness and cover a total of 5 ha crusts range from discontinuous masses to a solid shield with superimposed distributaries these deposits are the only known deposits where pachnolite and fluorite can be shown to have formed in a marine sedimentary environment journal abstract

highly fractionated early cretaceous i type granites and related sn polymetallic mineralization in the jinkeng deposit eastern guangdong se china constraints from geochronology geochemistry and hf isotopes abstract the recently discovered jinkeng deposit located in eastern guangdong province se china is a granite related cassiterite sulfide type sn cu pb zn deposit in the cathaysia block zircon u pb dating of the biotite granite and fine grained granite associated with the deposit yielded concordant ages of 144 7 0 8 ma and 141 1 1 3 ma respectively these ages are consistent within error with the molybdenite re os isochron age of 139 3 2 5 ma for the deposit indicating a temporal link between the emplacement of granitic plutons and polymetallic sn mineralization combined with the regional mineralization ages we propose that the 145 135 ma interval represents another significant period of sn w mineralization in southern china in addition to those already recognized the biotite granite and fine grained granite have similar geochemical characteristics both are weakly peraluminous high k and calc alkaline containing abundant si na and k and low concentrations of fe mg ca and p compared to primitive mantle and unfractionated granitoids they are enriched in rb th u k and pb have relatively high rb sr and low k rb values are depleted in ba sr and ti and have prominent negative eu anomalies eu 0 05 0 19 characteristic of highly fractionated i type granites zircons from these granites have ehf t values ranging from 9 2 to 3 3 and hf model ages tdm2 of 1776 1406 ma suggesting that the granites formed by the partial melting of proterozoic basement material and contain a minor mantle derived component highly fractionated and reduced fo2 below nno magma facilitated the enrichment of sn existing knowledge on the tectonic evolution of this region and new data from this study indicate that the granites and associated sn mineralization in the jinkeng deposit formed in an extensional environment at 140 ma likely related to the rollback of the paleo pacific plate

precise sm nd and u pb isotopic dating of the supergiant shizhuyuan polymetallic deposit and its host granite se china the supergiant shizhuyuan w sn bi mo deposit is hosted by the qianlishan granite a small highly fractionated granitic pluton 10 km 2 with multiple phases of intrusions within the early yanshanian granitoid province of se china strong alteration of skarn and greisen that formed in the contact zone between the first and second phases of granite intrusions and devonian limestone is responsible for the polymetallic mineralizations shrimp u pb zircon analysis indicates that the two early phases of the qianlishan granite formed contemporaneously at 152 2 ma metasomatic minerals garnet fluorite and wolframite separated from the skarn and greisen yield a sm nd isochron age of 149 2 ma that is interpreted as the formation age of the shizhuyuan deposit therefore the mineralization of the supergiant shizhuyuan polymetallic deposit formed contemporaneously with or very shortly after the intrusion of the small highly fractionated qianlishan granite

mineralogy of the msl curiosity landing site in gale crater as observed by mro crism orbital data acquired by the compact reconnaissance imaging spectrometer for mars crism and high resolution imaging science experiment instruments on the mars reconnaissance orbiter mro provide a synoptic view of compositional stratigraphy on the floor of gale crater surrounding the area where the mars science laboratory msl curiosity landed fractured light toned material exhibits a 2 2 m absorption consistent with enrichment in hydroxylated silica this material may be distal sediment from the peace vallis fan with cement and fracture fill containing the silica this unit is overlain by more basaltic material which has 1 m and 2 m absorptions due to pyroxene that are typical of martian basaltic materials both materials are partially obscured by aeolian dust and basaltic sand dunes to the southeast exhibit differences in mafic mineral signatures with barchan dunes enhanced in olivine relative to pyroxene containing longitudinal dunes this compositional difference may be related to aeolian grain sorting

incremental emplacement of the late jurassic midcrustal lopolith like qitianling pluton south china revealed by ams and bouguer gravity data modes of magma emplacement may provide key information on geodynamic tectonic settings of magmatism when the threshold of magma volume and duration of emplacement process is crossed brittle ductile crustal deformation behavior and volumes and rates of magma transfer in the crust the majority of upper crustal granitic intrusions are incrementally emplaced as laccoliths or sills while midcrustal or deeper level granitic intrusions appear to be predominantly emplaced as sills or lopoliths but relatively few examples have been studied we present a case study on the jurassic qitianling pluton from south china which was constructed in the upper part of the middle crust at a depth of 10 15 km to characterize its emplacement mechanism and evolution we have combined field and microscopic observations anisotropy of magnetic susceptibility measurements and bouguer gravity anomaly modeling the main findings are 1 the generally undeformed granite country rock contacts with a narrow thermal aureole 2 irregularly wavy and gradational contacts between the main granite facies 3 dominant subhorizontal magnetic fabrics in the granites with a scattered magnetic foliation 4 rare occurrence of dykes and 5 a subcircular surface and lopolith like pluton geometry accordingly we suggest that the qitianling pluton forms an 25 km wide and 5 km thick lopolith that was incrementally emplaced during a period of tectonic quiescence most likely by under accretion of multiple magma sheets deflected from magma pulses that ascended through pipe like channels the mineralogical and compositional variation of the pluton may be the result of in situ fractionation fractionation at deeper crustal level or variation in source derived melt compositions

chemistry mineralogy and grain properties at namib and high dunes bagnold dune field gale crater mars a synthesis of curiosity rover observations the mars science laboratory curiosity rover performed coordinated measurements to examine the textures and compositions of aeolian sands in the active bagnold dune field the bagnold sands are rounded to subrounded very fine to medium sized 45 500 m with 6 distinct grain colors in contrast to sands examined by curiosity in a dust covered inactive bedform called rocknest and soils at other landing sites bagnold sands are darker less red better sorted have fewer silt sized or smaller grains and show no evidence for cohesion nevertheless bagnold mineralogy and rocknest mineralogy are similar with plagioclase olivine and pyroxenes in similar proportions comprising 90 of crystalline phases along with a substantial amorphous component 35 15 yet bagnold and rocknest bulk chemistry differ bagnold sands are si enriched relative to other soils at gale crater and h 2o s and cl are lower relative to all previously measured martian soils and most gale crater rocks mg ni fe and mn are enriched in the coarse sieved fraction of bagnold sands corroborated by visible near infrared spectra that suggest enrichment of olivine collectively patterns in major element chemistry and volatile release data indicate two distinctive volatile reservoirs in martian soils 1 amorphous components in the sand sized fraction represented by bagnold that are si enriched hydroxylated alteration products and or h 2o or oh bearing impact or volcanic glasses and 2 amorphous components in the fine fraction 40 m represented by rocknest and other bright soils that are fe s and cl enriched with low si and adsorbed and structural h 2o

dark aeolian sediments in martian craters composition and sources our research focuses on the mineralogical characteristics of dark sediment deposits in martian craters dunes dune fields and sand sheets and their local sediment sources carried out on the basis of 70 selected localities morphological analyses reveal dark layers exposed in a number of crater walls showing indications of material transport from the layers downwall to the intracrater deposits additional sites show dark sediment emerging from several craters floors suggesting a dark material source beneath the crater floor spectral analyses of omega and crism data showed for the first time that a direct mineralogical connection exists between the dark layers in the crater walls and the intracrater dune and sand sheet material based on these findings it is shown that these layers are the local sources for the dark aeolian sediment inside the craters spectral analyses further indicate that all deposits are nearly of the same mafic mineralogical composition hinting at a similar origin we conclude that the mineralogical composition points to a volcanic origin of the material the dark layers which we infer to be the material sources might represent layers of volcanic ash almost globally deposited in early noachian times and subsequently covered by regolith groundwater impact erosion and crustal movement led to the highly fragmented situation of the dark layers today however burial protected the layers of dark sediment from chemical alteration caused by surficial fluvial processes impact erosion after the wet periods on mars led to the exposure and mobilization of the material today

zircon u pb and hf o isotopes trace the architecture of polymetallic deposits a case study of the jurassic ore forming porphyries in the qin hang metallogenic belt china abstract the qin hang intra continental porphyry skarn cu polymetallic belt qhmb is among the economically important metallogenic belts in south china the significant differences in the size and metal assemblage of the jurassic magmatic hydrothermal ore deposits in this belt remain as an enigma here we employ zircon u pb and hf o isotopes of the tongshanling and baoshan cu pb zn deposits in the central part of the qhmb to investigate the contrasting metallogenic architecture our sims zircon u pb data indicate that the tongshanling and baoshan granodiorite formed at 160 ma these rocks show high mg values and negative zircon e hf t and high 18 o values suggesting that the magmas of the granodiorite porphyries were mainly generated through the anatexis of older crustal components triggered by the input of mantle derived magma the minor content of amphibole phenocrysts low sr y ratios negative eu anomaly and low zircon ce 4 ce 3 ratios indicate that the porphyries are relatively less oxidized with less water content compared with the ore bearing porphyries in the dexing and yuanzhuding porphyry cu deposits in the northern and southern part of the qhmb suggesting that high magmatic water content and oxidation state are important prerequisites for the formation of large size porphyry skarn copper deposits in the qhmb the positive correlation between zircon e hf t values with the cu reserves as well as zircon 18 o values with the cu cu pb zn ratios of the deposits indicate that the magmatic sources exerted a first order control on the volume and metal assemblage of deposits in the qhmb the hf and nd isotope contour maps indicate that the central part of the qhmb has high potential for pb zn dominated magmatic hydrothermal deposits whereas the northern and southern part of the qhmb are prospective for large cu deposits our results have important implications in formulating regional exploration strategies for jurassic porphyry skarn cu pb zn deposits in the qin hang belt

contrasting zircon hf and o isotopes in the two episodes of neoproterozoic granitoids in south china implications for growth and reworking of continental crust abstract the genetic links among rift magmatism crustal growth and water rock interaction are an important issue about mass and heat transfer between mantle and crust during supercontinent breakup a combined study of hf and o isotopes in zircons from neoproterozoic granitoids in south china provides evidence for growth and reworking of juvenile and ancient crusts with different styles of water rock interactions along rift tectonic zones two generations of the granitoids show contrasting features in both zircon hf and o isotope compositions indicating their distinct petrogenesis the 825 ma granitoids exhibit negative ehf t values of 3 4 0 8 to 1 6 0 8 with old model hf ages of 1 81 0 07 to 1 92 0 10 ga and high 18o values of 8 7 to 10 4 these indicate that the source material of granitoid magmas was derived from melting of paleoproterozoic basement that has the hf isotope signature similar to the enriched mantle but experienced chemical weathering process before anatexis reworking of ancient crust is demonstrated to occur at 825 ma in the orogenic collapse zone with overprinting of subsolidus hydrothermal alteration during magma emplacement in contrast the 760 750 ma bimodal intrusives are characterized by positive ehf t values of 3 5 0 8 to 9 9 0 8 with young model hf ages of 0 94 0 06 to 1 18 0 06 ga and both low and high 18o values of 4 2 to 6 2 relative to 5 3 0 3 for the normal mantle zircon prompt reworking of juvenile crust is suggested to occur at 750 ma in the rifted tectonic zone with occurrence of supersolidus hydrothermal alteration and local low 18o magmatism during supercontinent breakup contributions of the depleted mantle to their magma sources are contrasting in the two episodes of magmatism in association with breakup of the supercontinent rodinia while the change in melt source from the crust to the mantle keeps pace with the advance from continental rifting to supercontinent breakup significant transport of both heat and material from the depleted mantle to the continental crust only occurred along the active rifting zone in either case the growth and reworking of continental crust are episodically associated with rift magmatism

genesis of the xianghualing sn pb zn deposit south china a multi method zircon study abstract the xianghualing sn pb zn deposit is situated near the center of the world class nanling w sn ore belt associated with the highly evolved laiziling granite of jurassic age previous studies focused mainly on geochemical and geochronological features of the mineralization related granite whereas research on the source evolution and geochronology of the ore forming fluids has been limited we carried out precise u pb dating trace element and hf isotopic analyses on magmatic and hydrothermally altered zircons from the skarn stage and sulfide stage ores in the xianghualing deposit zircon u pb dating results from the two ore forming stages show distinct geochronological populations the skarn stage ores contain mainly magmatic and hydrothermally altered zircons in three age clusters 150 ma 220 ma and 420 ma whereas the sulfide stage ores are characterized by abundant old detrital zircons ranging from 497 to 3409 ma with a peak at 800 1000 ma this pattern may indicate that magmatic hydrothermal events in the silurian and triassic were precursors to the main sn mineralization event in the jurassic when circulation of evolved fluids through older sedimentary rocks led to pb zn mineralization the jurassic zircons exhibit high trace element contents e g hf p y nb ta th u and low ti contents eu anomalies nb ta and th u ratios which imply that the laiziling magma experienced significant plagioclase biotite and muscovite fractional crystallization and that it interacted extensively with post emplacement f rich hydrothermal fluids the positive ce anomalies of these zircons ce ce 1 0 226 indicate that the magmatic hydrothermal fluids that led to the jurassic sn mineralization event were reducing the less negative ehf t values of triassic zircons 18 7 to 2 6 compared to the silurian zircons 14 6 to 2 3 suggest more limited interaction between the mantle and the magma source region the jurassic magmatic zircons in the skarns exhibit even more negative ehf t values 30 7 to 6 7 along with tdmc model ages ranging from 1627 to 3134 ma indicating that the jurassic magma was derived from partial melting of old continental crustal basement based on the combined study of zircons in the skarns and sulfide ores we propose a three stage ore genetic model for the xianghualing sn pb zn deposit

mineralogy of an active eolian sediment from the namib dune gale crater mars the mars science laboratory rover curiosity is using a comprehensive scientific payload to explore rocks and soils in gale crater mars recent investigations of the bagnold dune field provided the first in situ assessment of an active dune on mars the chemistry and mineralogy chemin x ray diffraction instrument on curiosity performed quantitative mineralogical analyses of the 150 m size fraction of the namib dune at a location called gobabeb gobabeb is dominated by basaltic minerals plagioclase fo56 olivine and two ca mg fe pyroxenes account for the majority of crystalline phases along with minor magnetite quartz hematite and anhydrite in addition to the crystalline phases a minimum 42 wt of the gobabeb sample is x ray amorphous mineralogical analysis of the gobabeb data set provides insights into the origin s and geologic history of the dune material and offers an important opportunity for ground truth of orbital observations chemin s analysis of the mineralogy and phase chemistry of modern and ancient gale crater dune fields together with other measurements by curiosity s science payload provides new insights into present and past eolian processes on mars

tracking magmatic and hydrothermal nb ta w sn fractionation using mineral textures and composition a case study from the late cretaceous jiepailing ore district in the nanling range in south china abstract the jiepailing mining district in the nanling range in south china is well known for its granite related sn be f mineralization recently drill holes have exposed an nb ta w sn mineralized granitic porphyry and topaz bearing granite greisen at depth which we have studied here using mineral columbite rutile wolframite cassiterite zircon and mica major and trace element compositional data mineral textures and zircon and columbite u pb geochronology our age data shows that the porphyry and the granite and their mineralization formed at 91 89 1 ma in the late cretaceous and thus subsequent to the main ore forming events of the region continuous mineral compositional trends indicate that the studied granitoids are related by progressive fractionation we propose that 1 subhedral euhedral low ta columbite crystallized from melt 2 euhedral subhedral rutile and wolframite and subhedral and subhedral cassiterite up to 30 m in size formed at the magmatic hydrothermal transition of the system and 3 high ta columbite and subhedral cassiterite up to 10 m in size formed from subsolidus hydrothermal fluids in combination with the nb ta w and sn compositions of zircon and mica their textures and compositional variation allow us to track the magmatic to hydrothermal rare metal fractionation concentration mobilization and deposition of the system in detail despite our limited access to it through only two exploration drill cores using the nb ta w and sn concentrations in zircon refractory early crystallized and in micas late equilibrated respectively was particularly useful for tracing the partial loss of sn and w ore components from the intrusion and to constrain the information which is crucial for any rigorous ore exploration

lithospheric electrical structure of south china imaged by magnetotelluric data and its tectonic implications abstract the region of south china mainly consists of the yangtze block in the northwest the cathaysia block in the southeast and the jiangnan orogen in between these two major precambrian continental blocks the yangtze block borders the north china craton in the north and the eastern margin of the tibetan plateau in the west the cathaysia block adjoins the pacific tectonic domain in the east the study of tectonics in this region is of great significance given its important role in understanding the formation of the asia continent under the auspices of sinoprobe project new magnetotelluric mt data were collected along a 1200 km long profile starting from central sichuan basin near suining extending southeastward passing through the yangtze block jiangnan orogen and terminating within the western cathaysia block near ganzhou based on data analysis results 2d inversions were conducted on the dataset resulting model shows that the lithospheric electrical structure of south china is generally resistive which is consistent with the basic feature of stable precambrian tectonic setting the resistive western yangtze block represents the stable archean aged cratonic region of the yangtze basement while the electrically conductive eastern yangtze block is characterized by lithospheric shearing of the strike slip fault system and extensional process that is probably caused by slab roll back of a flatly subducted plate the jiangshao fault performs as a northwestward dipping conductive layer which indicates the lithospheric underthrusting of cathaysia block beneath yangtze block with its frontal edge reaching the area of jishou in the upper mantle to the west of jiangshao fault eastern flank of the xuefengshan mountain marks the overthrusting frontier of the yangtze block as well as its southeastern boundary to the east of jiangshao fault the northwestern boundary of the cathaysia block displays the pattern of wedging tectonics which is characterized by a conductive layer wedging into the cathaysia lithosphere at the depth range of moho

hafnium isotopic heterogeneity in zircons from granitic rocks geochemical evaluation and modeling of zircon effect in crustal anatexis abstract we carried out a geochemical evaluation and modeled the mechanism responsible for varied hf isotopic ratios in magmatic zircons of a single granitic rock specimen five representative granitic samples were selected from southern china based on preliminary hf isotopic data our new dataset of zircon hf isotopes confirmed significant hf isotope variations 5 9 epsilon units for each sample and these zircons show roughly positive th u versus t crystallizing temperature correlations while the lu hf variation is independent from t in addition some zircons show significantly higher ti concentrations in the rims compared to the interiors implying reverse thermal zonation based on the ti in zircon thermometry these geochemical features in zircons suggest open system processes which may have resulted from frequent replenishment we modeled zircon dissolution during crustal anatexis to reveal the hf isotopic evolution in the extracted melts the model suggests that the extracted melts may have extremely variable hf isotope compositions 20 epsilon units if the bulk zr concentration in the source is initially above 100 ppm and the melting is rapid 10 4 yr 1 the decoupled release of zircon hf and non zircon hf from a single crust derived magma source can lead to significant hf isotope variations in a solidified granitic body this work provides an alternative explanation for the hf isotopic heterogeneity in magmatic zircons of granitic rocks which is in contrast to the common interpretation by mixing with mantle derived magmas

geochemistry of a type granites in the huangshaping polymetallic deposit south hunan china implications for granite evolution and associated mineralization abstract the huangshaping granites in hunan province south china were investigated for their geochemical characteristics three types of granites have been petrographically identified quartz porphyry granophyre and granite porphyry whole rock geochemistry suggests that the huangshaping granites especially the granite porphyry exhibit typical a type granite characteristics with their enrichment in si rb u th and nb and significant depletion in ba sr ti eu and p based on the al y and zr contents as well as the ree patterns of the rocks investigated the quartz porphyry and the granophyre are classified as a1 type alkaline granites whereas the granite porphyry is considered as a2 type aluminous granite whole rock and quartz feldspar o isotope data yields a wide range of 18osmow values 11 09 26 32 the granites are characterized by high radiogenic pb isotopic composition the present day whole rock pb isotopic ratios are 206pb 204pb 18 706 19 155 207pb 204pb 15 616 15 711 and 208pb 204pb 38 734 39 296 combining the o pb isotope compositions with major trace and ree geochemistry and regional geology characteristics the huangshaping granites were determined to resemble within plate granites that were mainly derived from a felsic infracrustal source related to continental extension the magma source of the quartz porphyry and the granophyre may have been generated from deeper depths and then ascended rapidly with limited water content and low oxygen fugacity which contributed to cu pb and zn mineralization on the other hand the magma that generated the granite porphyry may have ascended relatively slower and experienced pronounced crystal fractionation upper crustal basement rock contamination assimilation and wall rock interaction producing the sn and w rich granite porphyry this study reveals the crustal extension process and associated magmatic metallogenic activities during 180 150 ma in south hunan

mossbauer mineralogy of rock soil and dust at gusev crater mars spirit s journey through weakly altered olivine basalt on the plains and pervasively altered basalt in the columbia hills 1 the mossbauer spectrometer on spirit measured the oxidation state of fe identified fe bearing phases and measured relative abundances of fe among those phases for surface materials on the plains and in the columbia hills of gusev crater eight fe bearing phases were identified olivine pyroxene ilmenite magnetite nanophase ferric oxide npox hematite goethite and a fe3 sulfate adirondack basaltic rocks on the plains are nearly unaltered fe3 fet px and minor npox and magnetite columbia hills basaltic rocks are nearly unaltered peace and backstay moderately altered woolypatch wishstone and keystone and pervasively altered e g clovis uchben watchtower keel and paros with fe3 fet 0 6 0 9 fe from pyroxene is greater than fe from olivine ol sometimes absent and fe2 from ol px is 40 49 and 9 24 for moderately and pervasively altered materials respectively ilmenite fe from ilm 3 6 is present in backstay wishstone keystone and related rocks along with magnetite fe from mt 10 15 remaining fe is present as npox hematite and goethite in variable proportions clovis has the highest goethite content fe from gt 40 goethite feooh is mineralogical evidence for aqueous processes because it has structural hydroxide and is formed under aqueous conditions relatively unaltered basaltic soils fe3 fet 0 3 occur throughout gusev crater 60 80 fe from ol px 10 30 from npox and 10 from mt pasorobles soil in the columbia hills has a unique occurrence of high concentrations of fe3 sulfate 65 of fe magnetite is identified as a strongly magnetic phase in martian soil and dust

oxygen fugacity of yanshanian granites in south china and implications for metallogeny abstract oxygen fugacity fo 2 of magmas exerts an important control on the speciation of multivalent elements in magmatic hydrothermal processes which has a great significance for mineralization this paper examines the relationships between oxygen fugacity and mineralization associated with yanshanian jurassic to cretaceous granites in south china which hosts many world class w sn cu mo au pb and zn deposits the oxygen fugacities of yanshanian granites were evaluated using published chemical compositions of biotite and the redox states were further constrained with whole rock fe 3 fe 2 as well as zircon ce 4 ce 3 ratios from the literature systematic differences in oxygen fugacity between granites related to cu au mo cu pb zn w sn and w sn mineralization and between ore bearing and barren granites were found log fo 2 values relative to nno buffer are 1 08 to 13 07 average 4 22 for cu au mo related granites 1 01 to 5 36 average 3 51 for cu pb zn related granites 1 51 to 5 68 average 3 78 for w related granites 1 70 to 3 22 average 1 71 for w sn related granites and 5 32 to 2 43 average 0 83 for sn related granites in the biotite fe 3 fe 2 mg 2 ternary and log fo 2 t diagrams the cu au mo related granites are located between the mh and nno buffers and above the mh buffer and sn and w sn related granites are centered around the nno buffer and spread toward the fmq and mh buffers whereas the cu pb zn and w related granites are plotted between the nno and mh buffers similar trends were also observed for whole rock fe 2 o 3 feo ratios and zircon ce 4 ce 3 ratios in areas of cu au mo mineralization ore bearing granites have higher oxygen fugacities than barren granites regional scale variations of oxygen fugacities coupled with changes in la sm and ba th ratios which are considered as proxies of subducted sediments and slab dehydration fluids support the distinction of two metallogenic systems in the yanshanian period in south china a jurassic system related to ne to sw subduction and a cretaceous one related to se to nw subduction of the paleo pacific plate each with a trend of decreasing oxygen fugacities in the direction of subduction

geology and genesis of the hehuaping magnesian skarn type cassiterite sulfide deposit hunan province southern china abstract magnesian skarn type tin deposits are relatively rare in the world the hehuaping cassiterite sulfide deposit in southern china having a total reserve of approximately 130 000 t of tin 50 000 t of lead and 10 000 t of zinc is identified as such type the deposit is related to the late jurassic 157 ma hehuaping medium to coarse grained biotite granite that intruded the middle devonian qiziqiao dolomite formation and the tiaomajian sandstone formation four paragenetic stages of skarn and ore formation have been recognized i prograde stage ii retrograde stage iii cassiterite sulfide stage and iv carbonate stage alteration zoning between fresh granite and unaltered country rocks can be identified the skarn are typified by mg mineral assemblages of forsterite spinel diopside tremolite serpentine talc and phlogopite the geochemistry of various skarn minerals shows a gradually decrease of mg end member and correspondingly an increase of fe and especially mn end members along the process of skarn alteration tin mineralization developed during the late retrograde stage resulted in cassiterite magnetite diopside skarn however the deposition of cassiterite occurred predominantly as cassiterite sulfide veins along fractures and interlayer fracture zones during stage iii the petrogeochemistry of hehuaping granite as well as s and pb isotopic analyses suggest that the ore forming elements have a magmatic source originated from the upper crust the h o isotopic and fluid inclusion analyses indicate that high temperature ore forming fluids in early anhydrous skarn stage stage i are also magmatic origin in comparison the retrograde fluids are characterized by relatively low salinity 2 to 10 wt nacl equiv and low temperature 220 to 300 c suggesting a mixed origin of meteoric waters with magmatic fluids the major ore forming stage iii fluids are characterized by lower temperature 170 to 240 c and salinity 1 to 6 wt nacl equiv indicating fluid mixing could be an efficient tin mineralizing mechanism meteoric waters are dominant in stage iv resulting in a further lowering of temperature 130 to 200 c and salinity 0 4 to 1 wt nacl equiv

mineralogy and fluvial history of the watersheds of gale knobel and sharp craters a regional context for the mars science laboratory curiosity s exploration a 500 km long network of valleys extends from herschel crater to gale knobel and sharp craters the mineralogy and timing of fluvial activity in these watersheds provide a regional framework for deciphering the origin of sediments of gale crater s mount sharp an exploration target for the curiosity rover olivine bearing bedrock is exposed throughout the region and its erosion contributed to widespread olivine bearing sand dunes fe mg phyllosilicates are found in both bedrock and sediments implying that materials deposited in gale crater may have inherited clay minerals transported from the watershed while some topographic lows of the sharp knobel watershed host chloride salts the only salts detected in the gale watershed are sulfates within mount sharp implying regional or temporal differences in water chemistry crater counts indicate progressively more spatially localized aqueous activity large scale valley network activity ceased by the early hesperian though later hesperian amazonian fluvial activity continued near gale and sharp craters

mesozoic magmatism and granitic dome in the wugongshan massif jiangxi province and their genetical relationship to the tectonic events in southeast china abstract in se china a mesozoic granitic dome coeval to extensional tectonics is exposed in the wugongshan massif its center is occupied by mesozoic granitoids and granitic gneisses and the e w trending late paleozoic mesozoic pingxiang and anfu basins are located along its northern and southern sides respectively in this paper the petrological geochemical major incompatible and rare earth elements and isotopic characteristics of the granitoids and granitic gneisses of this dome allow us to constrain their geodynamic evolution the wugongshan mesozoic k feldspar enriched granitoids consist of six granitic bodies and lie within a paleozoic metamorphic basement the caledonian shanzhuang granodiorite containing some dioritic enclaves occurs in the study area and is a calc alkaline type granodiorite characterised by lower sio2 and composed of andesine biotite quartz hornblende magnetite and sphene the mesozoic granitoids either indosinian plutons or yanshanian bodies show a geochemical affinity of peraluminous s type granite having higher sio2 k2o contents al k na 2ca enriched in rb th and depleted in eu they also exhibit lree enriched patterns and marked negative eu anomalies the yanshanian plutons also contain characteristic minerals such as sillimanite garnet and monazite the wugongshan mesozoic granitoids have higher isr values 0 70981 0 72885 and lower end t 10 6 to 14 7 an average of 12 6 than those of the early paleozoic shanzhuang granodiorite the mesozoic granitoids were likely derived from ancient sedimentary rocks by partial melting the wugongshan mesozoic granitoids contain three petrological zones that is an early cretaceous massive granitic zone in the core zone i a foliated granitic zone zone ii and a triassic granitic gneissic zone in the outer rim zone iii the petrological and geochemical features of massive granitoids zone i are similar to those of foliated granites zone ii and of granitic gneisses zone iii in this mesozoic dome moreover geometric and kinematic features within the ductile parts units 2 and 3 are also similar to those within the brittle part unit 1 of the dome all these features show that the geologic evolution of the wugongshan doming is a continuous process lasting from triassic to early cretaceous time published 40ar 39ar and k ar ages in the wugongshan mesozoic granitic rocks fall into two major age fields corresponding to two geodynamic events of intracontinental deformation and magmatic activity the first tectonothermal event dated at 226 259 ma on the granitic gneisses in the outer rim of dome can be linked to indosinian collision between the south china plate and the north china plate during triassic time the second event took place during the early yanshanian dated at 180 120 ma on the granites of the core of dome and are responsible for final doming of the wugongshan plutons this event may be related to a westward subduction of the paleo pacific oceanic plate under the se china continent during late jurassic early cretaceous time

zircon records multiple magmatic hydrothermal processes at the giant shizhuyuan w sn mo bi polymetallic deposit south china abstract the supergiant shizhuyuan w sn mo bi polymetallic deposit is located in the nanling range and is intimately related to the qianlishan granite complex intruded during the late jurassic period the complex consists of three intrusive phases porphyritic biotite granite pbg equigranular biotite granite ebg and porphyritic granite dyke in this work the distinct geochemical features of magmatic and hydrothermally altered zircons from the qianlishan complex are used to reveal the magmatic hydrothermal evolution of the deposit whole rock geochemistry and mineralogy show that ebg samples have experienced stronger fractional crystallization than pbg samples zircon u pb dating constrains the intrusive episodes at 155 153 ma and 152 ma for the pbg and ebg respectively and subsequent hydrothermal events revealed by hydrothermal zircon ages at 154 153 ma and 152 150 ma hydrothermally altered zircon and paragenetic mineral inclusions from ebg samples show textures and compositional properties suggesting they were intensely altered by a zirconium saturated aqueous fluid type 1 enriched in most trace and metallogenic elements e g zr rees hf p u th nb ta ti pb al fe mg ca mn w and sn and volatiles f cl li co2 and h2o this fluid was relatively lower in temperature pressure and oxygen fugacity average ce4 ce3 11 2 type 2 fluid represented by hydrothermally altered zircons found in pbg was depleted in trace elements and had a relatively higher temperature and pressure and low fo2 ce4 ce3 2 12 29 16 type 3 fluid as evidenced by fluid altered zircons from the greisenized granite was likely a further evolved product of the type 2 fluid given its moderate cargo of most trace elements but also with exceedingly low ce4 ce3 values 2 9 33 45 the type 3 fluids might be precursors of w sn mineralizing fluids whereas the type 1 fluids were likely to represent mature ore forming fluids which were activated during the late skarn stage but before the retrograde mineralization stage compared with the fo2 of pbg and ebg magmas calculated by non altered magmatic zircons average ce4 ce3 31 47 and 49 21 it seems that the hydrothermal fluids generated by them became more reduced during the further evolution a progressive process can thus be divided pbg type 2 type 3 ebg type 1 with the gradual accumulation of ore forming materials the enrichment of most elements in hydrothermal zircons further indicates a substitution of y rees p hf u th ti nb ta ca k fe and mn for zr4 and si4 in the zircon lattice most fluid altered zircons exhibit a similar 176hf 177hf distribution range 11 to 6 but evidently elevated 176lu 177hf and 176yb 177hf ratios with magmatic ones this indicates that three types of hydrothermal fluids were magmatic derived whereas lu and yb were highly mobile during the hydrothermal event based on the results a magmatic hydrothermal evolution model is presented for shizhuyuan zircons this research highlights the use of zircon as a powerful tool in revealing the complex magmatic hydrothermal processes and perhaps mineralization potential in highly evolved granite associated mineralization systems

multiple stages of aqueous alteration along fractures in mudstone and sandstone strata in gale crater mars the mars rover curiosity in gale crater conducted the first ever direct chemical and mineralogical comparisons of samples that have clear parent unaltered and daughter altered relationships the mineralogy and chemistry of samples within and adjacent to alteration halos in a sandstone formation were established by the chemistry and mineralogy chemin x ray diffraction xrd instrument and the alpha particle x ray spectrometer apxs respectively the stimson formation sandstones unconformably overlie the murray mudstone formation and represent the youngest stratigraphic unit explored by curiosity to date aqueous alteration of the parent sandstone resulted in a loss of half of the original crystalline mineral phases and a three fold increase in x ray amorphous material aqueous fluids extensively leached mg al mn fe ni zn and other elements from the parent material decreased the pyroxene to feldspar ratio by a factor of two introduced ca and mixed cation sulfates and both passively and actively enriched the silica content leaching of mg al mn fe ni and zn and enrichment of si and s are also observed in alteration halos in the underlying mudstone these observations are consistent with infiltration of subsurface fluids initially acidic and then alkaline propagating along fractures crosscutting the stimson sandstone and murray mudstone the geochemistry and mineralogy suggest a complicated diagenetic history with multiple stages of aqueous alteration under a variety of environmental conditions e g both low and moderate ph the formation of these alteration halos post dates lithification of the sandstones and mudstones and represents one of the youngest hydrogeologic events presently known to have occurred in gale crater

compositional variations in sands of the bagnold dunes gale crater mars from visible shortwave infrared spectroscopy and comparison with ground truth from the curiosity rover during its ascent up mount sharp the mars science laboratory curiosity rover traversed the bagnold dune field we model sand modal mineralogy and grain size at four locations near the rover traverse using orbital shortwave infrared single scattering albedo spectra and a markov chain monte carlo implementation of hapke s radiative transfer theory to fully constrain uncertainties and permitted solutions these predictions evaluated against in situ measurements at one site from the curiosity rover show that x ray diffraction measured mineralogy of the basaltic sands is within the 95 confidence interval of model predictions however predictions are relatively insensitive to grain size and are nonunique especially when modeling the composition of minerals with solid solutions we find an overall basaltic mineralogy and show subtle spatial variations in composition in and around the bagnold dunes consistent with a mafic enrichment of sands with cumulative aeolian transport distance by sorting of olivine pyroxene and plagioclase grains furthermore the large variations in fe and mg abundances 20 wt at the bagnold dunes suggest that compositional variability may be enhanced by local mixing of well sorted sand with proximal sand sources our estimates demonstrate a method for orbital quantification of composition with rigorous uncertainty determination and provide key constraints for interpreting in situ measurements of compositional variability within martian aeolian sandstones

mineralogical characterization of mars science laboratory candidate landing sites from themis and tes data abstract data from the mars global surveyor thermal emission spectrometer tes and the mars odyssey thermal emission imaging system themis instruments are used to assess the mineralogic and dust cover characteristics of landing regions proposed for the mars science laboratory msl mission candidate regions examined in this study are eberswalde crater gale crater holden crater mawrth vallis miyamoto crater nili fossae trough and south meridiani planum compositional units identified in each region from tes and themis data are distinguished by variations in hematite olivine pyroxene and high silica phase abundance whereas no units are distinguished by elevated phyllosilicate or sulfate abundance though phyllosilicate minerals have been identified in all sites using near infrared observations these minerals are not unambiguously detected using either tes spectral index or deconvolution analysis methods for some of the sites small phyllosilicate outcrop sizes relative to the tes field of view likely hinder phyllosilicate mineral detection porous texture and or small particle size 15 possibly up to 40 of a high silica phase such as amorphous silica or zeolite high silica phase abundance over phyllosilicate bearing surfaces in mawrth vallis is higher than that of surrounding surfaces by 10 15 with the exception of these high silica surfaces in mawrth vallis regions examined in this study exhibit similar bulk mineralogical compositions to that of most low albedo regions on mars the msl scientific payload will thus be able to provide important information on surface materials typical of low albedo regions in addition to investigating the origin of phyllosilicate and or sulfate deposits with the exception of gale crater all of the landing sites have relatively low dust cover compared to classic high albedo regions tharsis arabia and elysium and to previous landing sites in gusev crater utopia planitia and chryse planitia

apxs derived chemistry of the bagnold dune sands comparisons with gale crater soils and the global martian average we present apxs data for the active bagnold dune field within the gale impact crater msl mission we derive an apxs based average basaltic soil abs composition for mars based on past and recent data from the msl and mer missions this represents an update to the taylor and mclennan 2009 average martian soil and facilitates comparison across martian datasets the active bagnold dune field is compositionally distinct from the abs with elevated mg ni and fe suggesting mafic mineral enrichment and uniformly low levels of s cl and zn indicating only a minimal dust component a relationship between decreasing grain size and increasing felsic content is revealed the bagnold sands possess the lowest s cl of all martian unconsolidated materials gale soils exhibit relatively uniform major element compositions similar to meridiani planum and gusev crater basaltic soils mer missions however they show minor enrichments in k cr mn and fe which may signify a local contribution the lithified eolian stimson formation within the gale impact crater is compositionally similar to the abs and bagnold sands which provide a modern analogue for these ancient eolian deposits compilation of apxs derived soil data reveals a generally homogenous global composition for martian soils but one that can be locally modified due to past or extant geologic processes that are limited in both space and time

mineralogy and stratigraphy of the gale crater rim wall and floor units the curiosity rover has detected diverse lithologies in float rocks and sedimentary units on the gale crater floor interpreted to have been transported from the rim to understand their provenance we examine the mineralogy and geology of gale s rim walls and floor using high resolution imagery and infrared spectra while no significant differences in bedrock spectral properties were observed within most thermal emission imaging system and compact reconnaissance imaging spectrometer for mars crism scenes some crism scenes of rim and wall rocks showed olivine bearing bedrock accompanied by fe mg phyllosilicates hydrated materials with 2 48 m absorptions in gale s eastern walls are spectrally similar to the sulfate unit in mount sharp aeolis mons sedimentary strata on the gale floor southwest of the landing site likely coeval with the bradbury units explored by curiosity also are hydrated and or have fe mg phyllosilicates spectral properties of these phyllosilicates differ from the al substituted nontronite detected by crism in mount sharp suggesting formation by fluids of different composition geologic mapping of the crater floor shows that the hydrated or hydroxylated materials are typically overlain by spectrally undistinctive erosionally resistant cliff forming units additionally a 4 km impact crater exposes 250 m of the gale floor including finely layered units no basement rocks are exposed thus indicating sedimentary deposits 250 m beneath strata studied by curiosity collectively the data indicate substantial sedimentary infill of gale crater including some materials derived from the crater rim lowermost thin layers are consistent with deposition in a lacustrine environment interbedded hydrated hydroxylated units may signify changing environmental conditions perhaps in a drying or episodically dry lake bed

crustal formation in the nanling range south china block hf isotope evidence of zircons from phanerozoic granitoids abstract granitic rocks are the principle agent of crustal differentiation therefore their origins yield important information on crustal formation and reworking an extensive survey of zircon hf isotopes from granitic rocks in a large region can provide a profile of crustal characteristics that may be further linked to previous crustal evolution in this study we measured u pb ages and hf isotope compositions of zircon grains extracted from twenty five jurassic five triassic and two ordovician granitic plutons from the nanling range south china block scb combined with the published lu hf isotopic data for the granitic rocks in the studied and adjacent areas three domains with different crustal formation histories have been identified in the southern part of the scb eastern side middle part and western side the eastern side extends to the coastal area of the scb with dominant hf crustal model ages tdm2 in zircons falling within the range of 2 2 1 6 ga the middle part is partly coincided with the low nd model age belt proposed by chen and jahn 1998 with zircon hf tdm2 ranging from 1 6 to 1 0 ga the western side covers the westernmost nanling range and the western end of the jiangnan orogen in which the granitoids have zircon hf tdm2 model ages spanning 2 2 1 8 ga the paleo to meso proterozoic model ages of the phanerozoic granitoids in the nanling range imply a long term crustal reworking zircons from the western and eastern sides have an average ehf 155 ma at around 10 about 4 epsilon units lower than the middle part ehf 155 ma 6 hf tdm2 histogram from the western nanling range is similar to that of the neoproterozoic granitoids in northern guangxi province to the west but much lower to the granites in the middle part to the east the eastern side has a broader range of hf model ages in zircons with the main peak low to ca 1 6 ga suggesting the reworking of mesoproterozoic crust however granitoids in the middle part have zircon hf tdm2 ages at 1 6 1 0 ga which indicates the incorporation of younger crust materials into the magma sources the hf model ages of granitoids as well as four zircon xenocrysts with ages around 920 ma within the mesozoic granitoids in the middle part indicate that the middle part has similar crustal features with the eastern jiangnan orogen we propose that this low tdm2 granite belt is probably part of the early neoproterozoic arc continent collision belt between different continents possibly yangtze and cathaysia during the early assembling processes while the granitoids in the western and eastern sides have similar crustal compositions

late jurassic sn metallogeny in eastern guangdong se china coast evidence from geochronology geochemistry and sr nd hf s isotopes of the dadaoshan sn deposit abstract the newly discovered dadaoshan sn deposit is located in the eastern guangdong sn w province coastal se china the sn mineralization hosted in jurassic porphyritic granite and the lower jurassic jinji formation sedimentary wall rocks is considered to be granite related in this study the porphyritic granite was la icp ms zircon u pb dated to be 153 2 1 2 ma consistent with the syn mineralization molybdenite re os age of 152 6 1 8 ma the porphyritic granite samples are weakly peraluminous a cnk 1 0 1 1 and high k calc alkaline the rocks contain high sio2 72 9 75 6 wt moderate rb sr 5 9 and low ree 136 223 ppm they are enriched in f li rb and sn depleted in ba sr p zr th nb and y and have distinct negative eu anomalies eu 0 09 0 18 suggesting that the porphyritic granite is highly fractionated i type granite the calculated initial 87sr 86sr 0 711582 0 715173 relatively low nd t 9 48 to 8 54 tdm2 1638 1814 ma and the zircon ehf t 14 2 to 5 1 two stage model ages 1528 2103 ma all suggest that the granite was mainly crustal derived with little mantle input sulfur isotopic compositions for the sulfides arsenopyrite and chalcopyrite 34s 1 1 to 1 4 average 0 1 imply a dominantly magmatic sulfur source the calculated zircon ce4 ce3 and eun eun ratios of the dadaoshan granite range from 1 0 to 112 mean 31 7 and from 0 04 to 0 37 mean 0 14 respectively indicating a low oxygen fugacity for the magma the reducing and highly fractionated nature of the dadaoshan granitic magma may have played a key role in the sn mineralization it was previously argued that the jurassic sn w mineralization and its causative magmatism were largely confined in the south china interior e g the nanling range our new data suggest that the late jurassic sn w mineralization and its causative magmatism actually extended to the se china coastal area the dadaoshan granite may have been generated from partial crustal melting led by underplating of mantle derived magmas in an extensional environment regional extension may have been related to the west directed flat slab subduction and delamination of the paleo pacific izanagi plate beneath the south china block another suite of early cretaceous sn w bearing granitic rocks in eastern guangdong may have mainly been crustal derived with minor mantle input and likely occurred under back arc extensional setting led by the paleo pacific subduction rollback

zircon u th pb hf isotopes of the basement rocks in northeastern cathaysia block south china implications for phanerozoic multiple metamorphic reworking of a paleoproterozoic terrane abstract the cathaysia block records a complex tectonic history the understanding of which is central to the debate on the evolution of the south china block and its position in various supercontinent assemblies here we investigate two key formations from this block the mayuan group in the northern fujian province northeastern cathaysia block and its equivalent the badu group in southwestern zhejiang province previous studies traced the paleoproterozoic records from the badu group whereas a neoproterozoic age was proposed for the mayuan group the rocks sampled in this study from both groups show similar mineral assemblages of garnet sillimanite biotite plagioclase quartz k feldspar muscovite graphite as well as high contents of sio 2 and al 2 o 3 typical of amphibolite to granulite facies metapelitic rocks zircon u pb data yield two discordia intercept ages of 1990 ma and 2450 ma from one sample and discordia intercept ages of 3 5 ga 2 5 ga 1 86 ga and 233 ma from another in the badu group zircons in two samples from the mayuan group yield intercept ages of 1859 ma and 249 ma in one sample and 2 6 ga 1 87 ga 257 ma and a weighted mean 206 pb 238 u age of 248 ma in the other the ca 1 86 1 87 ga and 230 250 ma ages are interpreted to represent the time of metamorphic reworking because zircon grains of these ages tend to have low th u ratios flat hree patterns and unzoned internal texture as revealed by cathodoluminescene cl images these results confirm that the badu group is a paleoproterozoic lithostratigraphic unit and also suggest that at least part if not all of the mayuan group is paleoproterozoic evidence for paleozoic metamorphic reworking that is considered to have affected the whole of cathaysia block is not revealed in this study in contrast our data clearly show obvious mesozoic metamorphic reworking at ca 230 250 ma zircon hf t values range from 19 to 11 with a peak at 5 5 and show t dm c hf ranging from 1 9 to 4 1 ga with a peak at ca 2 7 3 0 ga suggesting that a major crustal growth took place during this time this interpretation is consistent with the previously suggested crustal growth peaks of 2 7 ga and 2 9ga a synthesis of the reliable geochronological data gathered so far on phanerozoic metamorphic reworking of the northeastern cathaysia block reveals that the imprints of these tectonothermal events is differently distributed in the different zones rocks metamorphosed during the paleozoic tectonothermal event dominantly occur in the western zone whereas those reworked by high grade metamorphism during the mesozoic tectonothermal event mainly outcrop in the eastern zone our study alerts the previous notion of a uniform distribution of the reworked rocks by high grade metamorphism all across the northeastern cathaysia block and provides new insights on the evolution of the south china block

geochronological geochemical and sr nd hf isotopic constraints on the petrogenesis of late cretaceous a type granites from the sibumasu block southern myanmar se asia abstract the late cretaceous to paleogene granitoids occur widespread in the sibumasu block within myanmar se asia which show a close association with tin tungsten mineralization however the precise timing petrogenesis and tectonic significance of these granitoids are poorly constrained so far in this study we present a detailed study on geochronology elemental and sr nd hf isotopic geochemistry for the hermyingyi and taungphila granites in southern myanmar with the aim of determining their petrogenesis and tectonic implications la icp ms u pb dating of zircon grains from the two granites yield ages of 69 70 ma indicating a late cretaceous magmatic event these granitic rocks are weakly peraluminous and belong to the high k calc alkaline series they are both characterized by high sio2 k2o na2o feot feot mgo and ga al ratios and low al2o3 cao mgo p2o5 and tio2 contents enriched in rb th u and y but depleted in ba sr p and eu suggesting an a type granite affinity moreover they display prominent tetrad ree patterns and non charac trace element behavior which are common in late magmatic differentiates with strong hydrothermal interaction or deuteric alteration the granites belong to a2 type and probably formed at a high temperature and anhydrous condition they have zircon ehf t values from 12 4 to 10 0 and whole rock end t values from 11 3 to 10 6 with paleoproterozoic tdm2 ages 1741 1922 ma for both hf and nd isotopes geochemical and isotopic data suggest that these a type granites were derived from partial melting of the paleoproterozoic continental crust dominated by metaigneous rocks with tonalitic to granodioritic compositions without significant input of mantle derived magma and followed by subsequent fractional crystallization by integrating all available data for the regional tectonic evolution in se asia and adjacent regions we attribute the formation of the late cretaceous a type granites to a back arc extension in the hinterland behind the subduction zone which is induced by the rollback of the flat neo tethyan subducting slab around ca 70 ma

segregation of olivine grains in volcanic sands in iceland and implications for mars abstract basaltic sands cover several plains in volcanic regions on earth and dominate the aeolian sediments on mars but basaltic sands are not as well characterized as felsic sands the lambahraun sandy lava plain in iceland was chosen as a martian analog to study the physical sorting of basaltic sands the strong winds affecting the plain and its young age

hybrid genesis of jurassic fayalite bearing felsic subvolcanic rocks in south china inspired by petrography geochronology and sr nd o hf isotopes abstract fayalite bearing felsic fbf magmatic rocks are a special type of granitic rocks with controversial origins a suite of fayalite and ferrosilite bearing subvolcanic rocks namely the xishan fbf rocks in south china is investigated in this study the xishan fbf rocks have high sio 2 contents of 69 70 wt high k 2 o na 2 o ratios of 1 71 1 95 and high feo t feo t mgo ratios of 0 88 0 89 fayalite fo 7 3 9 6 and ferrosilite fs 74 1 76 5 minerals are found in the xishan fbf rocks according to the unmix function of isoplot the zircon u pb ages and initial hf isotope compositions are categorized into two groups with ages of 156 6 ma and 151 5 ma and e hf t values of 7 1 and 5 2 respectively the minerals show 18 o values of 8 8 9 8 for zircon 6 0 8 1 for fayalite and 7 0 8 2 for ferrosilite the oxygen isotope fractionations between ferrosilite and fayalite opx ol vary from 0 8 to 1 5 which indicates disequilibrium crystallization whole rock analyses show high initial 87 sr 86 sr ratios of 0 7169 to 0 7180 and negative e nd t values of 7 3 to 6 8 zircon analyses show e hf t values of 9 1 to 3 8 and 18 o values of 8 8 9 8 so whole rock and zircon isotopes indicate a crustal signature based on these mineralogical and geochemical data the xishan fbf rocks were attributed to a type granites and derived from the mixing of two batches of crustal magmas which were all derived from the partial melting of ancient igneous protolith under the conditions of high temperature 683 893 c moderate water 3 5 wt and low oxygen fugacity lg f o 2 1 21 such rigorous physical conditions may be common for the fbf igneous rocks all over the world which may be the primary factors controlling occurrence of the fbf rocks in limited volume and quantity

hf isotopic compositions of the standard zircons and baddeleyites used in u pb geochronology abstract zircon and baddeleyite u pb geochronological dating is widely used in solid earth sciences and the advent of rapid in situ methods of analysis such sims and icp ms has re emphasized the importance of having uniform standards recently it has been shown that hf isotopic data can provide important information on these minerals since they contain high concentrations of hf but have low lu hf ratios which results in negligible age correction however the complex internal structures that result from multiple thermal events such as inherited cores and metamorphic overgrowths require that the hf isotopic data be measured with high spatial resolution however the isobaric interferences of 176 yb and 176 lu on 176 hf hamper the precise determination of the 176 hf 177 hf ratio during in situ laser ablation mc icpms analysis it is shown here that mass biases of yb yb and hf hf change with time during analyses and behave differently for solutions and solid material therefore it is suggested that the mean yb value of the individual spot be used to obtain the precise isotopic composition for in situ zircon and baddeleyite hf isotopic analyses for low yb hf 176 yb 177 hf yb value have little effect on the accuracy of the hf isotopic composition however the appropriate yb isotopic abundance is necessary for high yb hf 176 yb 177 hf 0 001 zircons and baddeleyites since the interference of 176 yb on 176 hf is significant using the mean yb value of the individual spot and newly published yb isotopic abundance data six standard zircons and two standard baddeleyites have been investigated using a neptune mc icpms with 193 nm laser for zircons the obtained 176 hf 177 hf ratios are 0 282307 31 2sd for 91500 0 282680 31 2sd for temora 0 281729 21 2sd for cz3 282177 17 2sd for cn92 1 0 282983 17 2sd for fm0411 and 281234 11 2sd for phalaborwa the baddeleyites from phalaborwa and sk10 2 have 176 hf 177 hf ratios of 0 281238 12 and 0 282738 13 2sd these results agree well with the values obtained by the solution method and indicate that these standards have different hf isotopic compositions in which the extremely low 176 lu 177 hf and 176 yb 177 hf values of cz3 zircon and phalaborwa baddeleyite make them excellent standards for machine calibration during in situ zircon hf isotopic measurement with the other standards being more suitable for the development of the correction method

improvements of precision and accuracy in in situ hf isotope microanalysis of zircon using the laser ablation mc icpms technique abstract we have developed a new analytical technique for precise and accurate in situ hf isotope ratio measurements for zircons by means of laser ablation multiple collector inductively coupled plasma mass spectrometry la mc icpms newly designed sample cell and n 2 mixing technique provided higher elemental sensitivity with smoother signal intensity profiles in order to improve the accuracy of the hf isotope ratio analysis previously reported correction methods for isobaric interferences on 176 hf by 176 yb and 176 lu were rigorously evaluated and we found that the use of independent mass bias factors for hf and yb in the isobaric interference correction resulted in more reliable hf isotopic data in order to test the reliability of the hf isotopic data from 35 m diameter ablation pits that are smaller than the typical size of most zircon grains lu hf isotopes for three zircons harvard 91500 antarctic zircon pma7 and acasta zircon ay199 were measured the present 176 hf 177 hf isotope ratio of 0 282321 46 2 s d and initial 176 hf 177 hf isotope ratio of 0 282315 47 2 s d were obtained for zircon standard 91500 the resulting present 176 hf 177 hf isotope ratio shows an excellent agreement with the previously reported data our in situ isotopic data revealed that the lu hf ratio varied significantly within the 91500 grain 176 lu 177 hf 0 000130 0 000345 suggesting the existence of slight isotopic heterogeneity in present 176 hf 177 hf approximately 15 ppm for antarctic zircon pma7 despite the smaller size of the single grain 50 100 m wide 80 300 m long and the presence of various mineral inclusions resulting analytical precision for the initial 176 hf 177 hf ratio was 128 ppm 0 281208 36 2 s d for acasta zircon ay199 despite the high yb hf 0 05 and lu hf 0 01 isotope ratios with the early archean crystallization age 3 74 ga resulting analytical precision for the initial 176 hf 177 hf ratio was 187 ppm 0 280160 52 2 s d these results demonstrate clearly that in situ hf isotope ratio microanalysis developed here has the potential to become a significant tool for zircon lu hf isotopic study

ore genesis and geodynamic setting of the lianhuashan porphyry tungsten deposit eastern guangdong province se china constraints from muscovite 40 ar 39 ar and zircon u pb dating and hf isotopes the lianhuashan deposit has long been regarded as a typical tungsten porphyry deposit located in the eastern guangdong province in the southeastern coastal metallogenic belt scmb la mc icp ms zircon u pb dating of the quartz porphyry yielded a weighted mean 206pb 238u age of 137 3 2 0 ma which is interpreted as the emplacement age of the quartz porphyry hydrothermal muscovite yielded a plateau 40ar 39ar age of 133 2 0 9 ma which is consistent with the zircon u pb age suggesting that the tungsten mineralization is genetically related to the quartz porphyry combined with previous studies we suggest that there is a 145 135 ma episode linking the granitic magmas with w sn ore systems in the scmb zircon ehf t values of the quartz porphyry are in range of 3 8 to 0 9 and the two stage hf model ages tdm2 are 1 1 1 4 ga which is younger than the basement rocks in the cathaysia block 1 8 2 2 ga signifying that the quartz porphyry was predominantly derived from melting of mesoproterozoic crust containing variable amounts of mantle components in combination with the newly recognized coeval alkaline bimodal magmatism and a type granites in eastern guangdong we suggest that the 145 135 ma w sn metallogenic event of the scmb is related to a geodynamic setting of large scale lithospheric extension and thinning which can be ascribed to melting of the crust caused by mantle upwelling triggered by the oblique subduction of the izanagi plate

quantitative compositional analysis of martian mafic regions using the mex omega reflectance data 1 methodology uncertainties and examples of application abstract the mars express observatoire pour la mineralogie l eau les glaces et l activite omega collected an unprecedented visible and near infrared hyperspectral dataset covering the low albedo regions of mars we investigate the ability to infer modal abundance of surfaces of these regions from a radiative transfer model developed by shkuratov et al shkuratov y starukhina l hoffmann h arnold g 1999 icarus 137 235 246 and adapted to basaltic surfaces by poulet and erard poulet f erard s 2004 j geophys res 109 e2 doi 10 1029 2003je002179 from omega measurements of mafic surfaces we develop several sensitivity tests to assess the extent to which the model can be applied to predict pyroxene composition high calcium phase and low calcium phase abundance of almost neutral components plagioclase in the near infrared wavelength as well as grain sizes by using a library of selected end members results of the sensitivity tests indicate that the scattering model can estimate both abundances and grain sizes of major basaltic materials of low albedo regions within uncertainties 5 to 15 vol the model is then applied to data from dissected cratered terrains located in terra meridiani the derived grain size including uncertainties is in the 50 500 m range this is consistent with the thermal inertia and albedo of this region which indicates a fine sand sized surface with little dust the abundances of plagioclase 43 57 and pyroxenes 35 45 10 including 11 5 of low calcium phase are in good agreement with previous basalt like compositions of low albedo regions from thermal infrared spectral measurements the method presented in this paper will provide a valuable tool for evaluating the modal mineralogy of other mafic regions of mars observed in the near infrared wavelength range

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

regularization of mars reconnaissance orbiter crism along track oversampled hyperspectral imaging observations of mars mars reconnaissance orbiter compact reconnaissance imaging spectrometer for mars crism hyperspectral image data have been acquired in an along track oversampled ato mode with the intent of processing the data to better than the nominal 18 m pixel ground resolution we have implemented an iterative maximum log likelihood method mlm that utilizes the instrument spectral and spatial transfer functions and includes a penalty function to regularize the data products are produced both in sensor space and as projected hyperspectral image cubes at 12 m pixel preprocessing steps include retrieval of surface single scattering albedos ssa using the hapke function and disort based radiative modeling of atmospheric gases and aerosols resultant ssa cubes are despiked to remove extrema and tested to ensure that the remaining data are poisson distributed an underlying assumption for the mlm algorithm implementation two examples of processed ato data sets are presented ato0002ec79 covers the route taken by the curiosity rover during its initial ascent of mount sharp in gale crater ssa data are used to model mineral abundances and grain sizes predicted to be present in the namib barchan sand dune sampled and analyzed by curiosity crism based results compare favorably to in situ results derived from curiosity s measurement campaign ato0002ddf9 covers marathon valley on the cape tribulation rim segment of endeavour crater ssa spectra indicate the presence of a minor component of fe 3 and mg 2 smectites on the valley floor and walls localization to 12 m pixel provided the detailed spatial information needed for the opportunity rover to traverse to and characterize those outcrops that have the deepest absorptions the combination of orbital and rover based data show that the smectite bearing outcrops in marathon valley are impact breccias that are basaltic in composition and that have been isochemically altered in a low water to rock environment

geochemical factors revealing the differences between the xitian and dengfuxian composite plutons middle qin hang belt implications to the w sn mineralization abstract the xitian and dengfuxian ore fields located in the middle qin hang belt are known for hosting large scale w sn polymetallic deposits the xitian ore field hosts a series of small to large scale sn w deposits including skarn quartz vein and structurally altered rock type whereas the dengfuxian ore field mainly contains a medium scale quartz vein type w deposit these granitic rocks are composed of ore barren triassic and ore related jurassic granites in this study la icp ms zircon u pb dating of three representative samples from dengfuxian triassic granites dtg xitian jurassic granites xjg and dengfuxian jurassic granites djg yields weighted mean 206pb 238u ages of 231 2 2 5 ma 152 5 1 2 ma and 155 9 1 6 ma respectively chemical compositions of the xitian triassic granites xtg and dtg indicate that they belong to relatively lower fractionated granites whereas the xjg and djg are highly fractionated granites the xtg and dtg have similar lu hf isotopic compositions which have peak ehf t values of ca 5 9 and tdmc ages of ca 1 57 ga and peak ehf t values of ca 5 7 and tdmc ages of ca 1 57 ga respectively however the xjg have higher peak ehf t values of ca 5 4 and younger tdmc ages of ca 1 52 ga than those of the djg with peak ehf t values of ca 7 6 and tdmc ages of ca 1 70 ga respectively furthermore the xtg have end t values of 10 5 to 9 40 and nd model ages tdm2 of 1 86 to 1 76 ga which are similar to those of the dtg with end t values of 11 7 to 9 67 and nd model ages tdm2 of 1 95 to 1 79 ga wu et al 2016 cai et al 2015 the xjg have end t values of 11 0 to 9 1 and younger tdm2 ages of 1 69 1 84 ga which are fairly distinct to the reported nd isotopes of the djg cai 2013 it is proposed that the xtg and dtg were originated from the similar magma chamber and formed from partial melting of the proterozoic basement rocks of the south china block scb at low temperatures ca 690 c and oxygen fugacity log fo2 values of ca 17 involved with a certain amount of mantle derived magma magmas of the xjg and djg might be mainly originated from the partial melting of proterozoic basement rocks of the scb in contrast the formation of xjg and djg are involved with a considerable and little mantle derived magma respectively in addition the magma temperatures and log fo2 values of xjg are of ca 856 c and ca 15 respectively which are higher than those of the djg ca 716 c and ca 17 that the xitian and dengfuxian triassic granites did not induce w sn mineralization is likely attributed to their low fractionated signatures the key factors leading to the sn w mineralization in the xitian ore field and w mineralization in the dengfuxian ore field might be magma source and temperature since additional sn could be provided by the mantle and or released by melting of those sn bearing minerals at high temperatures over than 780 c

constraints on the timing and genetic link of the large scale accumulation of proximal w sn mo bi and distal pb zn ag mineralization of the world class dongpo orefield nanling range south china abstract the world class dongpo orefield located in the nanling range south china is famous for its large scale accumulation of w sn mo bi pb zn ag deposits which includes the giant shizhuyuan w sn mo bi jinchuantang sn bi yejiwei sn cu and congshuban pb zn ag deposits the polymetallic mineralization around the qianlishan pluton exhibits systematic zoning and comprises proximal w sn mo bi skarn greisen and distal pb zn ag veins however the timing and genetic link of its proximal skarn greisen w sn mo bi and distal vein type pb zn ag mineralization are not well constrained here we present systematic geochronological data to constrain the geochronological framework and genetic model of the giant dongpo orefield the muscovite 40ar 39ar age of the greisen type ore in the shizhuyuan w sn mo bi deposit is 151 1 ma which is consistent with the formation of the skarn type ore and the qianlishan pluton thus indicating that they are genetically related and both formed contemporaneously at 151 ma the large scale accumulation of w sn mo bi in the shizhuyuan deposit may have occurred in a short duration of 1 ma the muscovite 40ar 39 ar ages 155 5 1 1 and 156 8 1 1 ma and molybdenite re os age 153 8 4 2 ma of the ma naoshan w sn fe mn pb zn deposit as well as the zircon u pb age 152 7 0 9 ma of the yejiwei sn cu deposit in the dongpo orefield are consistent with the age of the qianlishan pluton thus indicating that the proximal skarn greisen w sn mo bi mineralization in the dongpo orefield is genetically related to the qianlishan pluton in addition the rb sr dating of sphalerite indicates that the vein type pb zn ag mineralization in the congshuban area formed at 152 2 ma which is consistent with the la mc icp ms zircon u pb age 156 155 ma of the equigranular biotite granite indicating that the distal vein type pb zn ag mineralization is genetically associated with the qianlishan equigranular biotite granite by integrating the high precision geochronological data of this study with those of previous studies the new genetic model of the large scale accumulation of w sn mo bi pb zn ag in the dongpo orefield suggests that the proximal skarn greisen w sn mo bi and distal vein pb zn ag mineralization in the dongpo orefield are genetically related to the qianlishan pluton and that the mineralization type is mainly controlled by the characteristics of the wall rock

fe isotopic fractionation during the magmatic hydrothermal stage of granitic magmatism abstract felsic intrusive magmatic systems are more complex than volcanic systems as they involve prolonged magmatic processes in addition to potentially multiple phases of magmatic hydrothermal activity within a single pluton in particular the competition between exsolved magmatic fluids and crystallizing minerals for elements and isotopes during the magmatic hydrothermal stages of evolution of these systems remains unclear despite fluid exsolution being one of the key steps in ore formation this study focuses on a suite of representative late jurassic w sn mineralization related granites within the nanling range of southern china and investigates the behavior of fe isotopes during magmatic differentiation and magmatic hydrothermal processes recorded within these granites the granites in the study area have variable 56fe values relative to irmm 014 ranging from 0 12 0 04 0 42 0 01 these values do not correlate with bulk rock geochemical indicators of fluid exsolution e g zr hf nb ta k rb and f cl ratios qualitatively indicating that fluid exsolution has an insignificant effect on fe isotopic fractionation we further quantified the relative contributions of fluid exsolution and crystal fractionation on bulk rock fe isotopic variability using a rayleigh fractionation model this modeling indicates that fluid exsolution can only generate a

mars surface diversity as revealed by the omega mars express observations the observatoire pour la mineralogie l eau les glaces et l activite omega investigation on board the european space agency mars express mission is mapping the surface composition of mars at a 0 3 to 5 kilometer resolution by means of visible near infrared hyperspectral reflectance imagery the data acquired during the first 9 months of the mission already reveal a diverse and complex surface mineralogy offering key insights into the evolution of mars omega has identified and mapped mafic iron bearing silicates of both the northern and southern crust localized concentrations of hydrated phyllosilicates and sulfates but no carbonates and ices and frosts with a water ice composition of the north polar perennial cap as for the south cap covered by a thin carbon dioxide ice veneer

jurassic magmatism related pb zn w mo polymetallic mineralization in the central nanling range south china geochronologic geochemical and isotopic evidence from the huangshaping deposit abstract the nanling range in south china is characterized by extensive mesozoic magmatism and coeval nonferrous and rare metal mineralization huangshaping is a world class pb zn w mo polymetallic skarn deposit in the central nanling range magmatic rocks occurring in this ore district include quartz porphyry granite porphyry granophyre dacite porphyry and aplite with only the first three granitoids genetically associated with polymetallic mineralization most of the orebodies are constrained within the contact zones as skarn and veins between these granitic stocks and the carbonate wall rocks since the age of the quartz porphyry is still controversial and studies of the dacite porphyry and aplite are absent we focus on these magmatic rocks first la icp ms zircon u pb dating suggests that the crystallization ages of the quartz porphyry dacite porphyry and aplite are 154 3 1 9 ma 158 1 0 8 ma and 148 4 3 4 ma respectively combined with previously published age data we infer the evolutionary sequence of magmatic rocks should be dacite porphyry quartz porphyry granite porphyry granophyre aplite the quartz porphyry dacite porphyry and aplite yield high contents of high field strength elements zr nb ce y 255 440 ppm high ratios of 10 000 ga al 2 6 3 2 and prominent depletions in ba sr eu p and ti indicating their crustal affinities to a type granites they have negative end t values 9 4 to 7 0 and high initial pb isotopic ratios 206pb 204pbi 18 307 18 644 207pb 204pbi 15 689 15 742 208pb 204pbi 38 589 38 986 suggesting that they were probably derived by partial melting of ancient granulitic crustal materials the sulfide minerals exhibit a wide range of 34sv cdt values from 22 6 to 24 2 with 206pb 204pb of 17 669 19 708 207pb 204pb of 15 492 15 714 and 208pb 204pb of 37 880 39 789 indicating that sulfur lead and other associated metals were derived from a mixture of magmatic components and the carboniferous wall rocks fluid inclusions in pyrrhotite sphalerite and marmatite samples have 3he 4he ratios of 0 12 to 1 53 ra with calculated mantle helium proportions of 1 3 to 18 9 indicating a predominantly crustal origin for the ore fluids with minor inputs from the mantle the huangshaping deposit is a typical example of the genetic relationship both spatially and temporally between jurassic magmatism and polymetallic metallogeny in the nanling range

element geochemistry mineralogy geochronology and zircon hf isotope of the luxi and xiazhuang granites in guangdong province china implications for u mineralization abstract the luxi and xiazhuang granitic plutons are parts of the guidong granite belt in northern guangdong province china they occur next to each other and have similar crystallization ages however the xiazhuang pluton hosts several important uranium u ore deposits whereas the luxi pluton does not this study compares the two plutons using whole rock geochemistry biotite compositions zircon u pb ages by la icpms and in situ zircon hf isotope data by la mc icpms to understand the fundamental controls results show that the two plutons have similar ages 237 ma for the luxi pluton and 234 ma for the xiazhuang pluton they also have similar geochemical features that are characteristic of s type granites zircons from both plutons have negative e hf t values 9 to 12 and a paleoproterozoic two stage hf model age t dm2 1838 ma to 2025 ma suggesting that their parental magmas were all derived from paleoproterozoic metasedimentary rocks the geochemical and petrological data suggest that these two plutons crystallized from magmas derived from the same parent at different stages the parental magma of the xiazhuang pluton is more evolved than that of the luxi pluton this factor plus different physical chemical conditions such as temperature volatile components and oxidation state resulted in higher u content and favorable u bearing species in the xiazhuang magmatic hydrothermal system u occurs mainly as uraninite in the xiazhuang pluton which facilitates u transfer from granite into co 2 rich hydrothermal fluid to form u ore deposits in contrast u occurs mainly as ree bearing minerals in the luxi magmatic system preventing u transfer to associated hydrothermal fluids as a result the xiazhuang pluton hosts several important uranium ore deposits whereas the luxi pluton is ore barren

crustal growth event in the cathaysia block at 2 5 ga evidence from chronology and geochemistry of captured zircons in jurassic acidic dykes

mineralogy fluid inclusion petrography and stable isotope geochemistry of pb zn ag veins at the shizhuyuan deposit hunan province southeastern china the shizhuyuan polymetallic deposit is located in the central part of the nanling region southeastern china and consists of proximal w sn mo bi skarns and greisens and distal pb zn ag veins the sulfides and sulfosalts in the distal veins formed in three distinct stages 1 an early stage of pyrite and arsenopyrite 2 a middle stage of sphalerite and chalcopyrite and 3 a late stage of galena ag sn and bi bearing sulfides and sulfosalts and pyrrhotite combined sulfide and sulfosalt geothermometry and fluid inclusion analyses indicate that the early stage of mineralization occurred at a temperature of 400 c and involved boiling under hydrostatic pressure 200 bar with the temperature of the system dropping during the late stage to 200 c laser raman analysis indicates that the fluid inclusions within the studied minerals are dominated by h2o although some contain carbonate solids and ch4 gas vein hosted sulfides have 34s values of 3 8 6 3 that are interpreted as indicative of a magmatic source of sulfur the mineralization process can be summarized as follows an aqueous fluid exsolved on final crystallization of the qianlishan pluton ascended along fracture zones cooled to 400 c and boiled under hydrostatic conditions and with decreasing temperature and sulfur fugacity sulfide and sulfosalt minerals precipitated successively from the ag cu zn fe pb sb as s bearing fluid system

zircon geochronology and geochemistry of the xianghualing a type granitic rocks insights into multi stage sn polymetallic mineralization in south china abstract highly evolved sn polymetallic mineralization related granites are intensively developed in the nanling range of south china in this study two types of granitic rocks albite granite and greisenized granite from the laiziling pluton in the xianghualing area were studied to elucidate magma evolution and the genesis of mineralization the a type xianghualing granitic rocks are characterized by high sio2 69 16 85 04 rb 759 2110 ppm ta 17 2 50 8 ppm nd 2 8 82 4 ppm and 87sr 86sr 0 907275 4 181262 and low mgo 0 01 0 98 tio2 0 01 0 03 sr 1 4 70 2 ppm ba 1 4 132 5 ppm eu 0 03 0 21 ppm and 143nd 144nd 0 512283 0 512326 the whole rock end t values range from 6 3 to 6 0 with t2dm ages of 1426 1454 ma the zircon ehf t values mostly range from 10 to 5 with dominant tdmc values of 1400 1800 ma this suggests that the xianghualing granitic rocks were derived from partial melting of mesoproterozoic basement rocks in the cathaysian block in a lithospheric extension setting zircon u pb dating yielded five age clusters proterozoic 900 ma n 9 silurian 430 ma n 4 triassic 220 ma n 16 jurassic 150 ma n 62 and cretaceous 80 ma n 28 zircon internal textures trace element contents and hf isotopic compositions indicate that they formed from a range of sources including residual zircons from the magma source region detrital zircons from local sediments zircons captured from pre existing magmatic rocks with obvious mantle signatures magmatic and fluid altered zircons and late stage hydrothermal zircons this suggests significant fractional crystallization weak wall rock assimilation contamination and intense fluid differentiation metasomatism during the genesis of the xianghualing granitic rocks m type ree tetrad effects are seen not only in bulk rock compositions but also in individual zircon grains indicating that highly fractionated and reduced f rich fluids played an important role in the formation of sn polymetallic mineralization guided by the major mesozoic w sn ore forming events occurring in the cathaysian block of south china a multi stage genetic model is proposed for the xianghualing granitic minerogenic system initial enrichment of w sn in the triassic 220 ma dominant sn polymetallic metal precipitation in the jurassic 150 ma and superimposed mineralization in the cretaceous 80 ma

isotopic and paleomagnetic constraints on the mesozoic tectonic evolution of south china in order to better constrain the paleogeographic evolution of south china we measured sm nd and rb sr isotopic compositions for 23 mesozoic granites that crop out throughout the area tightly grouped neodymium depleted mantle model ages 1 4 0 3 ga suggest the region is underlain by relatively homogeneous proterozoic crust and fail to define crustal provinces neither the isotopic nor geologic data suggest that a mesozoic suture exists however granites possessing anomalously high sm 8 ppm and nd 45 ppm concentrations relatively high initial epsilon neodymium 4 to 8 and high but variable initial 87sr 86sr 0 759 to 0 713 form a northeast trending zone that coincides with two prominent mesozoic basins southeast of the zone lie the majority of mesozoic intrusives and upper triassic to lower cretaceous extensional basins found in south china mesozoic paleomagnetic poles are well clustered northwest of the zone pre cretaceous poles southeast of it are discordant with respect to those from the northwest the only recognized tectonostratigraphic terrane in south china lies southeast of the zone the terrane is bordered by a northeast trending sinistral fault that was active in the mesozoic other faults in south china have similar attitudes ages and sense of shear together the observations suggest that the mesozoic tectonic regime in south china consisted of strike slip activity plus concomitant rifting as terranes or fragments of similar crust were transported north along sinistral faults the zone defined by the granites enriched in nd and sm demarcates displaced terranes to the southeast from relatively stable land to the northwest

u pb geochronology and ree geochemistry of zircons from palaeoproterozoic paragneiss clasts in the mesozoic kamiaso conglomerate central japan evidence for an archean provenance abstract sensitive high resolution ion microprobe shrimp u pb analyses of zircons from a pelitic gneiss clast from the jurassic kamiaso conglomerate in central japan show that most grains are 1850 1950 ma but six are 2400 ma including a very old one 3254 14 ma the shrimp data give chronological evidence for previously unrecognized igneous activity from 1850 to 1950 ma the existence of archean zircons allows us to consider the evolutionary history of the archean crust in eastern asia chondrite normalized ree patterns of the individual zircons determined by shrimp show that the 2400 3250 ma zircons have large positive ce and small negative eu anomalies whereas the 1850 1950 ma zircons have small positive ce and significantly negative eu anomalies these differences in the ree abundances for the 2400 3250 and 1850 1950 ma zircons may reflect the composition of the melt that produced the zircons and reveal the possibility of a geological constraint on the origin of kamiaso zircons

trace elements u pb ages and hf isotopes of zircons from mesozoic granites in the western nanling range south china implications for petrogenesis and w sn mineralization abstract the e w trending nanling range located in the southern part of the south china block scb is characterized by widespread intra continental mesozoic granitoids and accompanying w sn polymetallic ore deposits detailed studies are presented on trace elements u pb ages and lu hf isotopes in zircons from the mesozoic a2 type like granitoids including the qianlishan qitianling xianghualing huashan guposhan niumiao tong an jinziling and jinjiling plutons from the western nanling range la icp ms u pb analyses of zircon indicate that these granites intruded mainly from ca 160 150 ma two types of zircon magmatic and late magmatic hydrothermal with similar ages can be distinguished based on their zircon trace element compositions the late magmatic hydrothermal zircons have high contents of metallogenic elements e g w and sn and may be closely related with the ore deposits the ehf t values of zircons from the mesozoic granitoids are mildly negative to positive indicating the reworking of both old and young crustal components the significant involvement of mesozoic juvenile mantle derived materials in the source can be excluded because of the rare occurrences of mafic rocks with radiogenic isotopic signatures in the area the average crustal residence age patterns of the mesozoic granites in the western nanling range are similar to those of the neoproterozoic magmatic rocks in the eastern part of the jiangnan orogen which may represent the neoproterozoic collisional belt between the yangtze and cathaysia blocks considering the specific isotopic and metallogenic features of the mesozoic granitoids in the study area we propose that the western nanling range may represent a western extension of neoproterozoic arc continent collisional belt in south china the mesozoic granitoids of this area may have been generated mainly by reworking of deeply buried neoproterozoic arc related volcanic sedimentary materials due to thermal perturbations triggered by the subduction of the paleo pacific plate in mesozoic time

initiation of zn pb mineralization in the pingbao pb zn skarn district south china constraints from u pb dating of grossular rich garnet abstract in this study we discuss the application of u pb dating on u rich common pb bearing grossular rich garnet and the issues of common pb correction grossular rich garnet samples were collected from the baoshan and huangshaping areas of the pingbao skarn district hunan south china the baoshan garnet comprises gr64 3 and34 0 to and99 0 gr0 2 gr grossular and andradite with minor spessartine 0 43 1 45 almandine 0 0 61 and pyrope 0 01 0 91 the huangshaping 304 garnet comprises gr41 7 and56 0 to gr70 2 and25 9 with minor spessartine 1 42 2 10 whereas the huangshaping 301 garnet comprises gr62 0 and26 6 spe11 2 to gr74 5 and20 9 pyr2 5 spe2 1 spe spessartine pyr pyrope the baoshan garnet grains are subhedral to euhedral with well developed core rim textures and contain approximately 1 10 ppm u the huangshaping 304 garnet is also euhedral with grains size ranging from several to tens of millimeters the core rim textured garnet grains are compacted together with interstitial quartz and contain about 5 10 ppm u the huangshaping 301 garnet is anhedral to tabular with interstitial quartz and magnetite and contains up to 579 ppm u in situ u pb dating of the baoshan huangshaping 304 and 301 garnet samples yielded consistent anchored y intercept ages at 162 6 2 9 ma n 60 mswd 1 5 160 2 1 5 ma n 59 mswd 1 9 and 160 9 0 3 ma n 60 mswd 4 1 respectively these ages are consistent with the new and published zircon and titanite u pb ages 162 160 ma indicating that the garnet u pb ages are reliable and the technique is robust we suggest that the non u bearing mineral correction has involved in the third party common pb ratio which is believed to be a better correction for the system common pb

genesis of the giant shizhuyuan w sn mo bi pb zn polymetallic deposit south china constraints from zircon geochronology and geochemistry in skarns abstract the giant shizhuyuan w sn mo bi pb zn polymetallic skarn type deposit which lies in the world famous nanling w sn metallogenic belt has a close affinity with the qianlishan granite complex previous studies focused on the qianlishan granitoids rather than relevant skarns where the evolutionary processes of skarn forming fluids mineralized fluids and sources of metals are debated this study carried out systematic epma and la icpms zircon u pb dating major and trace element and lu hf isotopic analyses for three types of skarns ore free greisen stockwork and sulfide bearing skarns at shizhuyuan the whole skarn zircons were classified into six age clusters 125 187 ma 235 ma 345 509 ma 677 772 ma 811 921 ma and 1000 ma and three genetic types detrital magmatic and hydrothermally altered among them the majority of the skarn zircons are of detrital origin 345 to 2225 ma peaking at 410 ma 710 ma and 905 ma and showing a wide range of th u ratios 0 05 7 09 they share similar characteristics of zircons hosted by devonian strata in south china suggesting the inheritance from wall rock the magmatic zircons in skarns can be further subdivided into two clusters triassic 235 ma and jurassic 150 ma which are derived from the corresponding granite ore free skarn contains only detrital zircons that have experienced the weakest alteration indicating the minor participation of granitic fluid the greisen stockwork skarn consists of both detrital zircons and jurassic magmatic hydrothermal zircons implying that granitic and stratigraphic materials may both contribute greatly to the w sn polymetallic mineralization sulfide bearing skarn includes abundant detrital zircon a few of triassic zircons but no jurassic zircons indicating that the latest sulfide mineralization was dominated by sediments rather than granitic rocks the two mineralized skarn zircons display elevated concentrations of most trace elements e g u ree ti y p nb and ta coupled with decreased si and zr which reflects strong fluid rock reaction the lowest ratios of ce ce 1 22 89 78 mean 24 13 in greisen stockwork skarn zircons reveal the most reducing environment for the main w sn mineralizing event jurassic zircons are homogeneous in 176hf 177hf 0 282352 0 282454 and ehf t 11 58 to 7 27 in well accord with local granitic rocks triassic zircons have variable ehf t 9 5 to 1 6 values suggesting more mantle input of precursor pluton before the jurassic main mineralization event based on the zircon geochronology in skarns we speculate that concealed triassic magmatism exists in the deep shizhuyuan area consequently a three stage ore forming model was established for the giant shizhuyuan deposit this study further illustrates that zircon can be used as an important indicator for ore genesis in complex metallogenic systems

elemental and sr nd isotopic systematics of the early mesozoic volcanic sequence in southern jiangxi province south china petrogenesis and tectonic implications elemental and sr nd isotopic results are presented for the early mesozoic volcanic sequence 172 ma in southern jiangxi province south china the sequence is voluminously composed of 45 subalkaline basaltic rocks group 1 5 high mg andesite dacites group 2 and 50 rhyolites group 3 the group 1 rocks are characterized by la yb cn 3 8 7 2 eu eu 0 65 1 15 nb la 0 64 0 99 87sr 86sr t 0 70602 0 70822 and end t 1 63 to 0 11 similar to those of an emii like source the group 2 rocks have mg 0 42 0 60 sio2 60 24 66 71 mgo 2 65 5 54 ni 24 102 ppm and cr 84 266 ppm classified as high mg andesitic rocks these rocks are more enriched in liles and lree with more significant negative eu anomaly 0 63 0 79 are more depleted in hfses with nb la ratios of 0 40 0 56 and have lower end t 9 44 to 7 78 and higher 87sr 86sr t 0 70985 0 71016 in comparison with the group 1 rocks they most likely originated from metasomatised veins in the lithospheric mantle the origination of the group 1 and group 2 magma suggests the development of a peridotite plus vein lithospheric mantle during early mesozoic era beneath the interior of the cathaysian block the group 3 rhyolites are characterized by high sio2 72 75 77 97 zr 99 290 ppm hf 3 9 9 7 ppm and ga al 2 76 3 87 and significant nb ta ba sr and p ti depletions these rhyolites exhibit sr nd isotopic compositions 87sr 86sr t 0 70962 0 71104 end t 4 63 to 5 80 similar to the contemporaneous zhaibei and pitou a type granites in the area such characteristics suggest that they might be derived from the underplating basaltic magma contaminated by crustal materials therefore an early mesozoic rifting model in response to intracontinental lithospheric extension is proposed to account for the early mesozoic volcanism in southern jiangxi province south china

data for s isotopic geochemistry zircon and cassiterite u pb geochronology of the haobugao sn polymetallic deposit southern great xing an range ne china abstract the southern great xing an range sgxr is the most important tin polymetallic metallogenic belt in north china the lack of previous research on the genesis of the tin mineralization especially its exact age prevents development of a deep understanding of tin deposits in this area haobugao sn polymetallic deposit is a large skarn type deposit in the huangang ganzhuermiao sn fe cu pb zn ag metallogenic belt in the sgxr the ore body occurs in the contact zone between a yanshanian intrusion and permian dashizhai formation marble 34 s v cdt values of sulfides from the haobugao sn polymetallic deposit range from 4 7 to 3 5 with an average of 0 65 and these values strongly indicate a deep magmatic source for the sulfur in the ore minerals of the deposit in this paper we also report the results of la icp ms u pb dating of tin mineralization in no i ore body and of the underlying granite cassiterite from no 1 ore body deposited at 139 0 6 ma and the closely associated granite has an age of 142 9 1 6 ma the similar ages indicate that the tin mineralization was produced by early cretaceous magmatic hydrothermal activity these results together with the ages of other tin deposits and related granites indicate extensive granitic magmatism and tin mineralization during the early cretaceous in the southern segment of the great xing an range

dating the giant zhuxi w cu deposit taqian fuchun ore belt in south china using molybdenite re os and muscovite ar ar system abstract the recently discovered zhuxi w cu ore deposit is located within the taqian fuchun ore belt in the southeastern edge of the yangtze block south china its inferred tungsten resources based on new exploration data are more than 280 mt by 2016 at least three paragenetic stages of skarn formation and ore deposition have been recognized prograde skarn stage retrograde stage and hydrothermal sulfide stage secondly greisenization marmorization and hornfels formation are also observed scheelite and chalcopyrite are the dominant metal minerals in the zhuxi deposit and their formation was associated with the emplacement of granite stocks and porphyry dykes intruded into the surrounding carboniferous carbonate sediments huanglong and chuanshan formations and the neoproterozoic slate and phyllites the scheelite was mostly precipitated during the retrograde stage whereas the chalcopyrite was widely precipitated during the hydrothermal sulfide stage a muscovite 40ar 39ar plateau age of about 150 ma is interpreted as the time of tungsten mineralization and molybdenite re os model ages ranging from 145 9 2 0 ma to 148 7 2 2 ma for the subsequent hydrothermal sulfide stage of activity as the time of the copper mineralization our new molybdenite re os and muscovite 40ar 39ar dating results along with previous zircon u pb age data indicate that the hydrothermal activity from the retrograde stage to the last hydrothermal sulfide stage lasted up to 5 myr from 150 6 1 5 to 145 9 1 ma and is approximately coeval or slightly later than the emplacement of the associated granite porphyry and biotite granite the new ages reported here confirm that the zhuxi tungsten deposit represents one of the mesozoic magmatic hydrothermal mineralization events that took place in south china in a setting of lithospheric extension during the late jurassic 160 150 ma it is suggested that mantle material played a role in producing the zhuxi w cu mineralization and associated magmatism

mars global digital dune database and initial science results 1 a new mars global digital dune database mgd3 constructed using thermal emission imaging system themis infrared ir images provides a comprehensive and quantitative view of the geographic distribution of moderate to large size dune fields area 1 km2 that will help researchers to understand global climatic and sedimentary processes that have shaped the surface of mars mgd3 extends from 65 n to 65 s latitude and includes 550 dune fields covering 70 000 km2 with an estimated total volume of 3 600 km3 this area when combined with polar dune estimates suggests moderate to large size dune field coverage on mars may total 800 000 km2 6 times less than the total areal estimate of 5 000 000 km2 for terrestrial dunes where availability and quality of themis visible vis or mars orbiter camera narrow angle moc na images allow we classify dunes and include dune slipface measurements which are derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification for dunes located within craters the azimuth from crater centroid to dune field centroid referred to as dune centroid azimuth is calculated and can provide an accurate method for tracking dune migration within smooth floored craters these indicators of wind direction are compared to output from a general circulation model gcm dune centroid azimuth values generally correlate to regional wind patterns slipface orientations are less well correlated suggesting that local topographic effects may play a larger role in dune orientation than regional winds

a rhythmic source change of the neoproterozoic basement meta sedimentary sequences in the jiangnan orogen implications for tectonic evolution on the southeastern margin of the yangtze block abstract the amalgamation of south china block and its role in the assembly and breakup of rodinia supercontinent have been hotly debated in recent decades however the intensity of accreted arcs around south china and the following exhumation were poorly constrained here we present combined u pb dating and hf isotopic analyses of detrital zircons for a stratigraphic section of the upper shuangqiaoshan group in the eastern part of the jiangnan orogen jo u pb dating results suggest a general younging trend of the maximum depositional ages from the anlelin to the xiushui formations of the upper shuangqiaoshan group indicating a co magmatic sedimentation in association with continental arc magmatism along the se margin of the yangtze block the anlelin and xiushui formations were constrained to form in the periods of ca 845 836 ma and ca 835 815 ma respectively provenance analysis suggests two sources for these neoproterozoic basement sequences neoproterozoic zircons with positive ehf t values represent detritus derived from the arc related magmatic rocks to the southeast whereas 1000 ma zircons and the other neoproterozoic detrital zircons with negative ehf t values are proposed to be sourced from the interior of the yangtze block to the northwest simultaneously the hf isotope results of detrital zircons indicate that there was a rhythmic source change for the sediments in the upper shuangqiaoshan group with the amounts of two separate sources from the yangtze block to the west and from the arc terranes to the east increasing alternatively this provides solid evidence for a bidirectional water flow and supports a back arc basin setting for the deposition of the sediments combined with the published u pb and hf isotopic data for detrital zircons from the neoproterozoic folded sedimentary sequences in the jo we calculated the relative contribution of arc derived crustal materials in the basement sequences of the jo the calculations suggest that the proportion increases progressively from west to east and the back arc basins represented by the folded sedimentary sequences could be divided into three regions plus an arc terrane region to the east this comparison further suggests that the orientation of neoproterozoic accretion on the southeastern margin of the yangtze block was in a w e direction and the jo in neoproterozoic may not have extended 1500 km as what we see today

petrogenesis of the late mesozoic guposhan composite plutons from the nanling range south china implications for w sn mineralization voluminous granite plutons were emplaced in the late mesozoic in the nanling range south china accompanied by large scale polymetallic deposits most plutons are composite composed of major phase granites and highly differentiated late stage granites previous studies have proposed fractionation of both granite types and polymetallic deposits from a common magma we choose to study the ages chemistry and nd hf isotopes of the guposhan complex from the range and propose a different model for the origin of the granite and relationship with associated polymetallic mineralization in the nanling range the major phase granites of the guposhan complex contain medium coarse grained biotite granite and hornblende bearing biotite granite with mafic microenclaves mmes emplaced at 161 1 ma on the contrary the late stage granite is fine grained with apparent zircon ages of 154 3 ma the major phase granites show large variation in chemical compositions and in whole rock nd and zircon hf isotope ratios with end t 6 0 to 1 9 and ehf t 4 5 to 1 5 respectively we suggest that their origin is attributable to a magma mixing process between felsic magma derived from melting of proterozoic basement rocks and mantle derived mafic magma the mafic magma could be represented by the parental magma of the mmes within the plutons which have low sio2 high mgo and high end t values up to 1 8 the late stage granite shows end t and ehf t values similar to the major phase granites but are chemically more evolved sio2 75 80 more reduced and water deficient and in particular are fluorine bearing numerical geochemical modeling and the petrological data indicate that the late stage granite was produced during a new thermal event rather than being produced due to fractional crystallization of the earlier major phase granite the polymetallic deposits are genetically linked with the late stage granite we suggest that a break off of the flat subducted pacific slab beneath the cathaysia block in the late mesozoic resulted in the upwelling of asthenosphere and formation of basaltic magma that underplated and triggered partial melting of the basement rocks forming felsic melts and followed by mixing of the mafic and felsic magmas in an extensional regime

petrogenesis of jurassic fractionated i type granites in southeast china constraints from whole rock geochemical and zircon u pb and hf o isotopes abstract whole rock geochemical and sr nd hf isotopic data and zircon in situ u pb ages and hf o isotopes are reported for twelve granitic intrusions from inland to coastal areas of the cathaysia block southeast se china in order to constrain their magma sources and petrogenesis they are mainly composed of biotite granites with minor granodiorites zircon u pb dating by la icpms and sims methods gave emplacement ages of 165 154 ma for these rocks which are metaluminous to weakly peraluminous a cnk 0 95 1 10 with variable sio 2 contents and high k 2 o contents they are all depleted in high field strength elements hfses and enriched in light rare earth elements lrees and large ion lithophile elements liles and show negative sr ba and eu anomalies in the spidergrams petrographic and geochemical features suggest the granodiorites that contain hornblende to be typical of i type while the biotite granites without hornblende are fractionated i type granites their variable major and trace element concentrations are due to fractional crystallization of feldspar biotite hornblende and accessory minerals including apatite allanite and monazite moreover our data indicate significant variations in isotopic compositions of these granitoids from inland to coastal areas the inland granites from the lapu fogang xinfengjiang and baishigang plutons have relatively high initial 87 sr 86 sr ratios 0 7105 0 7155 and low e nd t 11 2 to 7 3 and e hf t 10 9 to 6 3 values for whole rocks and variable 18 o values of 7 69 9 25 and e hf t values of 13 5 to 6 7 for zircons in contrast the coastal granites from the longwo wushikeng lianhuashan shigushan chiliao hulutian mantoushan and fenghuang plutons show relatively low initial 87 sr 86 sr ratios 0 7056 0 7110 and high e nd t 7 6 to 6 2 and e hf t 6 5 to 2 8 values for whole rocks together with e hf t values of 7 2 to 3 9 and 18 o values of 6 69 8 38 for zircons the spatial isotopic variations suggest that these jurassic granitoids were generated by different percentage mixing of mantle and ancient paleoproterozoic crust derived magmas with subsequently minor crustal assimilation our results highlight that jurassic fractionated i type granites occur widely from inland to coastal areas of se china arguing against the previous view that jurassic granites occur only in inland while coastal granites are mainly cretaceous the widespread occurrence of jurassic granitoids in se china is attributed to ascending of mantle derived magmas which provide heat for partial melting of lower crustal materials in an extensional setting

a possible linkage between highly fractionated granitoids and associated w mineralization in the mesozoic yaogangxian granitic intrusion nanling region south china abstract the yaogangxian ygx w deposit in the central nanling w province south china is one of the largest w deposits worldwide both vein type wolframite and skarn type scheelite orebodies were exposed in ygx these scheelite and wolframite mineralization are spatially associated with the ygx granitic intrusion the exposed intrusion contains two main intrusive phases lower zone coarse grained two mica granite and upper zone fine grained muscovite granite an integrated study of whole rock geochemistry la icp ms zircon u pb geochronology and zircon hf isotopic geochemistry of the ygx granitic intrusion was undertaken to constrain its magmatic source and petrogenesis cassiterite la icp ms u pb dating was also undertaken to constrain the connection between the intrusion and hydrothermal w mineralization zircon u pb dating yielded weighted mean ages of 161 3 and 157 2 ma for the two mica and muscovite granites respectively cassiterite crystals from wolframite quartz veins display growth zonation under cathodoluminescence and have a weighted mean zircon u pb age of 158 2 ma the formation of the muscovite granite and related w mineralization in the ygx deposit was thus initiated during the early yanshanian the ygx granites display typical metaluminous to strongly peraluminous characteristics with high sio2 73 5 79 1 wt and k2o 3 0 5 0 wt contents they are enriched in heavy rare earth elements rees comparative to light rees notably they exhibited strong negative eu anomalies and are depleted in sr ba p and ti in addition muscovite granites in ygx are more significantly enriched in heavy rees relative to light rees than two mica granites indicating that the former experienced higher degree fractionation than the latter zircon grains of the ygx granitoids have strongly negative ehf t 15 to 10 3 with two stage hf model ages of 2 15 1 86 ga indicating a magma source of reworked ancient crustal material without obvious involvement of juvenile materials the results of petrology and geochemistry indicate that the ygx granitic intrusion is a highly fractionated s type granite emplaced during widespread 160 150 ma granitic magmatism in the nanling region further evolution to late stage for multiphase ygx granitic intrusion is needed to enrich ore forming elements after magmatic emplacement it is suggested that the extensional environment of continental lithosphere caused by the northwest subduction of the paleo pacific plate may play an key role in the genesis of ygx s type granite w rich proterozoic basement rocks and fractional crystallization may provide material for the formation of the granite related tungsten mineralization

silicic volcanism on mars evidenced by tridymite in high sio2 sedimentary rock at gale crater tridymite a low pressure high temperature 870 c sio2 polymorph was detected in a drill sample of laminated mudstone buckskin at marias pass in gale crater mars by the chemistry and mineralogy x ray diffraction instrument onboard the mars science laboratory rover curiosity the tridymitic mudstone has 40 wt crystalline and 60 wt x ray amorphous material and a bulk composition with 74 wt sio2 alpha particle x ray spectrometer analysis plagioclase 17 wt of bulk sample tridymite 14 wt sanidine 3 wt cation deficient magnetite 3 wt cristobalite 2 wt and anhydrite 1 wt are the mudstone crystalline minerals amorphous material is silica rich 39 wt opal a and or high sio2 glass and opal ct volatile bearing 16 wt mixed cation sulfates phosphates and chlorides perchlorates chlorates and has minor tio2 and fe2o3t oxides 5 wt rietveld refinement yielded a monoclinic structural model for a well crystalline tridymite consistent with high formation temperatures terrestrial tridymite is commonly associated with silicic volcanism and detritus from such volcanism in a lake gale catchment environment can account for buckskin s tridymite cristobalite feldspar and any residual high sio2 glass these cogenetic detrital phases are possibly sourced from the gale crater wall rim central peak opaline silica could form during diagenesis from high sio2 glass as amorphous precipitated silica or as a residue of acidic leaching in the sediment source region or at marias pass the amorphous mixed cation salts and oxides and possibly the crystalline magnetite otherwise detrital are primary precipitates and or their diagenesis products derived from multiple infiltrations of aqueous solutions having variable compositions temperatures and acidities anhydrite is post lithification fracture vein fill

evolved gas analyses of sedimentary rocks and eolian sediment in gale crater mars results of the curiosity rover s sample analysis at mars instrument from yellowknife bay to the namib dune the sample analysis at mars instrument evolved gas analyzer sam ega has detected evolved water h2 so2 h2s no co2 co o2 and hcl from two eolian sediments and nine sedimentary rocks from gale crater mars these evolved gas detections indicate nitrates organics oxychlorine phase and sulfates are widespread with phyllosilicates and carbonates occurring in select gale crater materials coevolved co2 160 248 2373 820 gc co2 g and co 11 3 320 130 gc co g suggest organic c is present in gale crater materials five samples evolved co2 at temperatures consistent with carbonate 0 32 0 05 0 70 0 1 wt co3 evolved no amounts to 0 002 0 007 0 06 0 03 wt no3 evolution of o2 suggests oxychlorine phases chlorate perchlorate 0 05 0 025 1 05 0 44wt clo4 are present while so2 evolution indicates the presence of crystalline and or poorly crystalline fe and mg sulfate and possibly sulfide evolved h2o 0 9 0 3 2 5 1 6 wt h2o is consistent with the presence of adsorbed water hydrated salts interlayer structural water from phyllosilicates and possible inclusion water in mineral amorphous phases evolved h2 and h2s suggest reduced phases occur despite the presence of oxidized phases nitrate oxychlorine sulfate carbonate sam results coupled with chemin mineralogical and apxs elemental analyses indicate that gale crater sedimentary rocks have experienced a complex authigenetic diagenetic history involving fluids with varying ph redox and salt composition the inferred geochemical conditions were favorable for microbial habitability and if life ever existed there was likely sufficient organic c to support a small microbial population

hydrothermal zircon geochronology age constraint on nanling range tungsten mineralization southeast china abstract the nanling range southeast china is well known for its wolframite bearing quartz vein wqv tungsten deposit this study focuses on the geochemistry and geochronology of zircons from the wqv and challenges the current view of the tungsten mineralization in the nanling range the features of the wqv zircons include 1 pale brown murky brown or orange red color and translucence under microscope 2 110 101 type crystal form 3 weak cathodoluminescence 4 enrichment of hf ranging from 1 97 to 7 83 wt hfo2 u ranging from 0 02 to 3 97 wt uo2 th ranging from 0 to 0 65 wt tho2 and p ranging from 0 to 1 82 wt p2o5 and 5 presence of solid hydrothermal and ore minerals and fluid inclusions these features indicate that the wqv zircons crystallized from hydrothermal fluids during tungsten mineralization the in situ la icpms u pb results of the wqv zircons from five different tungsten deposits in the nanling range yield similar ages ranging from 134 4 1 9 ma to 132 9 1 5 ma approximately 20 million years younger than proposed tungsten ore ages 155 5 ma several mineralization characteristics and field observations also cast doubt on the current model nanling range tungsten ore is the result of orthomagmatic processes the zircon characterization method provided in this study could be applied to tungsten metallogenic research in other parts of the world

u pb lu hf and trace element characteristics of zircon from the felbertal scheelite deposit austria new constraints on timing and source of w mineralization abstract combined in situ u pb lu hf and trace element la icp ms analyses were performed on zircons from the w mineralized k1 k3 orthogneiss and associated aplite gneiss from the felbertal scheelite deposit the textural and trace element characteristics suggest the presence of magmatic and hydrothermal zircon magmatic zircons have low concentrations of w 0 108 3 77 ppm nb 5 04 48 ppm u 691 3079 ppm b 0 26 6 57 ppm and ree y 640 4576 ppm and form euhedral cl bright cores with distinct oscillatory zoning zone a saturation of p in the granitic melt causing apatite crystallization explains the presence of two sub types of cl bright zircon cores distinguished by distinct p and ca concentrations and variable positive ce anomalies higher trace element abundances and lower zr hf ratios occur in cl dark zircons with weak oscillatory zoning zone b overgrowing the zircon cores and in granular textured zircons restricted to the aplite gneiss the increase in trace elements in zircon can be linked to the differentiation of the granitic melt and prolonged zircon crystallization during the transition from the late magmatic to the hydrothermal stage cl dark unzoned texture less domains zone b in k1 k3 orthogneiss zircons and granular textured zircons from the aplite gneiss have supra chondritic y ho ratios 29 62 indicating zircon growth in the presence of f rich hydrothermal fluids exsolved from the evolved k1 k3 melt zone b zircons have the highest concentrations of w 4 3 11 4 ppm nb 63 405 ppm b 7 3 135 ppm ree y 0 31 1 87 mass and u 1 23 5 56 mass they are interpreted as hydrothermal and related to w mineralizing fluids magmatic and hydrothermal zircon has identical u pb and lu hf isotopic signature indicating the same source the in situ u pb concordia ages of zircons of four k1 k3 orthogneisses and one aplite gneiss confine the emplacement period of this granitic series between 341 0 ma and 336 2 ma the initial hf t values ranging from 7 6 to 4 3 indicate a crustal protolith the felbertauern augengneiss is similar it yielded a u pb concordia age of 338 5 1 3 ma and initial hf t between 6 8 and 5 3 on the contrary zircons from the granatspitz gneiss yielded discordant u pb ages late carboniferous to early permian and the hf t values scatter between 3 1 and 2 5 excluding any relation with the k1 k3 orthogneiss our new la icp ms data corroborate the genetic relationship of the w mineralization at felbertal with the early carboniferous k1 k3 orthogneiss series the k1 k3 orthogneiss was part of a larger magmatic suite that developed during the variscan orogeny in the pre alpine basement of the tauern window in the visean

u pb zircon ages of granites from the southern margin of the yangtze block timing of neoproterozoic jinning orogeny in se china and implications for rodinia assembly abstract neoproterozoic jinningian bendong granodiorite and sanfang and yuanbaoshan granites occurred in northern guangxi southern margin of the yangtze block se china and were generally considered to be of orogenic origin that is the collision between the yangtze and huanan blocks during the jinning orogeny these granites were intruded into the mesoproterozoic sibao metamorphic basement and covered unconformably by the neoproterozoic danzhou metasediments they are dominantly peraluminous asi 1 18 1 29 and have low initial end values of 4 8 to 7 6 indicating derivation from a supracrustal source with strong enrichment in rb k and th and relatively low zr hf and higher rare earth elements they are similar to post collision granites zircon u pb ages of 819 9 826 10 and 824 4 ma were obtained for the bendong granodiorite and the sanfang and yuanbaoshan granites respectively by both shrimp and conventional dating methods the age result precludes the existence of any late mesoproterozoic grenville age granitic magmatism in the southern margin of yangtze block together with previous age determinations of ophiolites along the southern margin of the yangtze block the jinning orogeny is referred to the neoproterozoic orogeny which took place between 1 0 and 0 80 ga and likely ended at 0 82 ga the granite formation age of 0 82 ga also supports the basal boundary age of 0 80 ga for the post orogenic sinian system which is probably stratigraphically correlated with the adeladean system in south australia as the link between australia east antarctica and laurentia in the configuration of the supercontinent rodinia the collision between the yangtze and huanan blocks during the neoproterozoic jinning orogeny probably marks the termination of the rodinia assembly

a study of low albedo deposits within amazonis planitia craters evidence for locally derived ultramafic to mafic materials 1 we studied low albedo deposits in the floors of craters within the amazonis planitia region using infrared data from mars global surveyor thermal emission spectrometer tes and mars odyssey thermal emission imaging system themis high resolution visible images from the mars orbiter camera and themis and topographic data from the mars orbiter laser altimeter these deposits are found within subdued to sharp rimmed craters that impacted into thick basaltic lava flows from olympus mons these lava flows flooded the region and were subsequently eroded by aeolian processes tes spectral modeling of the low albedo deposits reveals a mineralogy that is dominated by mafic minerals olivine pyroxene with a derived bulk chemistry that ranges from ultramafic to mafic 40 52 wt sio2 in composition these bulk compositions are comparable to some martian lithologies but represent some of the lowest silica contents identified on mars the compositional range could be produced by either primary igneous processes or subsequent alteration by aeolian processes the spatial distribution of the compositions reveals weak to absent groupings and does not distinguish between the igneous or aeolian scenarios in some craters possible local sources have been identified within the crater walls floors and interiors local sources may be present in additional craters but obscured by dust no regional sources were identified within a reasonable distance in terms of sand transport but may also be obscured by dust therefore the low albedo deposits probably resulted from aeolian erosion of local intracrater basaltic materials that were subsequently redistributed within the floors of these craters

petrogenesis of jurassic a type granites associated with cu mo and w sn deposits in the central nanling region south china relation to mantle upwelling and intra continental extension abstract the central nanling region in south china was the site of uplift extensional deformation granite magmatism and hydrothermal activity from 180 to 150 ma information on the age petrological characteristics major and trace element contents whole rock sr and nd and zircon hf isotopic compositions of granitic plutons were synthesized to constrain the sources evolutionary processes and uplift cooling rates of intrusions that host cu mo and w sn deposits in this region the older 180 160 ma cu mo related granitoids are less differentiated a1 type alkaline rocks with faster cooling and uplift rates they have younger nd and hf two stage model ages and higher end t and ehf t values that indicate mantle derived magmas were moderately contaminated by upper crust the younger 160 150 ma w sn related granites are more differentiated a2 type aluminous rocks with slower cooling and uplift rates they have older nd and hf two stage model ages and lower end t and ehf t values that require more upper crustal contamination the time space distribution and characteristics of these granitoids and ore deposits are indicative of centralized mantle upwelling and gradational crustal extension the older rapidly uplifted less contaminated granitoids with cu mo mineralization occur near the center of an intra continental extension bulge produced by mantle upwelling whereas the younger slowly uplifted more contaminated granitoids with w sn mineralization occur on the periphery the results suggest that metals in the cu mo deposits may have come from the mantle whereas those in the world class nanling w sn polymetallic deposits were derived from early mesoproterozoic 1 4 1 6 ga crustal basement of the cathaysia block in south china