controlling mechanisms for molybdenum isotope fractionation in porphyry deposits the qulong example molybdenite bearing porphyry deposits are the predominant supplier of molybdenum to industrialized society and one of the main hosts of mo in the upper continental crust the mo isotope compositions 98 95mo normalized to nist3134 equals 0 of molybdenite show considerable variation 1 62 to 2 27 but the factors controlling this variability remain poorly constrained this information is critical for underpinning genetic models of porphyry deposits understanding elemental cycling and utilizing the 98 95mo of marine sediments as a paleoredox proxy using the well characterized qulong porphyry cu mo deposit tibet as an example here we discuss how rapid cooling facilitated by mixing hot magmatic fluid with cold meteoric water can be a controlling factor on efficient mineralization and then tackle how fluid evolution regulates molybdenum isotope fractionation molybdenites which preferentially partition isotopically light mo rayleigh fractionation precipitated from a single fluid will develop a heavier 98 95mo composition over time and this also creates heterogeneous 98 95mo between molybdenite grains whereas a fluid undergoing multiple episodes of intensive boiling will gradually lose its isotopically heavy mo to the vapor phase molybdenites crystallizing successively from the residual liquid will then have lighter 98 95mo over time however when mineralization efficiency becomes too low a negligible variation in 98 95mo of molybdenite is observed given that the mineralization efficiency i e the amount of mo crystallized as molybdenite from the fluid rarely reaches 100 and molybdenite favors isotopically light mo the presence of a residual fluid with isotopically heavy mo is inevitable this residual fluid may then become trapped in alteration halos hence 98 95mo has the potential to aid in locating the mineralization center e g lighter 98 95mo toward the orebody the residual fluid may also feed surface hydrological systems and eventually impact mo cycling our study highlights that understanding the controls of isotope fractionation is critical to bridge the gap between ore formation and elemental cycling and that other transition metals e g cu fe and zn may follow similar trajectories

geology of the don manuel igneous complex central chile implications for igneous processes in porphyry copper systems the don manuel igneous complex and associated porphyry copper mineralization in the andean cordillera of central chile demonstrate similarities between intrusive complexes associated with porphyry copper deposits and arc volcanoes that generate porphyritic volcanics the don manuel igneous complex intrusions progressed from quartz monzonite through rhyolite and biotite tonalite to intermediate porphyritic and basaltic andesite dikes which intrude the older units mineralization is associated with the biotite tonalite and intermediate porphyries which also contain the greatest abundance of mafic enclaves zoning patterns within plagioclase phenocrysts suggest that the later intermediate porphyries comprise a hybridized suite formed by magma mixing new zircon u pb ages and whole rock ar ar ages indicate that the don manuel igneous complex was emplaced between ca 4 and 3 6 ma the time scale for the episodic intrusion of the don manuel igneous complex units is similar to observed episodicity of eruption and degassing events in active arc volcanoes observations from the don manuel igneous complex are consistent with the close spatial and temporal association of mineralization with episodic intrusion and interaction between silicic and mafic magmas during emplacement the observations are also consistent with the hypothesis that mafic magma provides a source of sulfur for porphyry copper deposit formation

synchroneity of meltwater pulse 1a and the bolling warming new evidence from the south china sea a twofold decrease in long chain n alcane n nonacosane concentrations in a downcore record from the northern south china sea indicates a rapid drop in the supply of terrigenous organic matter to the open south china sea during the last deglaciation paralleled by an equally rapid increase in sea surface temperatures corresponding with the bolling warming at 14 7 ka the sudden drop in terrigenous organic matter delivery to this marginal basin is interpreted to reflect a short term response of local rivers to rapid sea level rise strongly implying that the bolling warming and the onset of meltwater pulse mwp 1a are synchronous this phase relation contrasts with the widely cited onset of this mwp 1a ca 14 ka and implies that previous studies postulating a weakening of deep water formation in the north atlantic due to massive meltwater discharge during mwp 1a need to be reevaluated

pulsed magmatic fluid releasing in the formation of the taoxihu sn polymetallic deposit eastern guangdong se china evidence from fluid inclusions cassiterite u pb geochronology and stable isotopes abstract the taoxihu deposit is a newly discovered sn polymetallic deposit in eastern guangdong se china the mineralization is related to an early cretaceous highly fractionated i type granite porphyry the ore forming process is divided into six stages i e garnet stage i quartz fluorite biotite stage ii quartz biotite cassiterite sulfides stage iii main mineralization quartz vein with minor sulfides and cassiterite stage iv quartz k feldspar biotite cassiterite sulfides stage v and quartz k feldspar chlorite sulfides stage vi fluid inclusion study shows that the hydrothermal fluids from stage ii salinity 5 9 to 13 2 wt and th 302 to 382 c to stage iv salinity 0 2 to 5 9 wt and th 275 to 315 c are of h2o co2 ch4 salt composition and show a trend of systematically decreasing temperature and salinity from early to late stages in contrast the fluids in stage v salinity 6 5 to 13 9 wt and th 223 to 343 c and stage vi salinity 6 0 to 11 8 wt and th 140 to 300 c are of the h2o salt compositional system and demonstrate also a trend of decreasing temperature and salinity with time representing a distinct hydrothermal event h o isotope data indicate that these two different fluid systems are all initially of magmatic origin in view of the almost identical cassiterite u pb ages of stage iii 139 7 1 1 ma and stage v 139 8 1 6 the two hydrothermal events are interpreted to represent two pulses of magmatic fluid releasing from the same magma chamber the first pulse is characterized by an initially single phase co2 bearing magmatic fluid that was subsequently subject to unmixing or phase separation in relation to hydraulic fracturing and decompression which lead to the main phase mineralization whereas the second pulse is the release of residual co2 free magmatic fluid which mixed with meteoric water and resulted in the second phase of mineralization

asian summer monsoonal variations during the holocene revealed by huguangyan maar lake sediment record abstract high resolution records of summer monsoonal evolution in the holocene are essential to paleoclimate reconstruction but are hard to obtain here we provide a continuous well dated high resolution record from huguangyan maar lake located in the west pacific climate regime multi proxies including chlorophyll a toc sr rb ratio and magnetic susceptibility have been used to reconstruct the monsoon variations in the holocene higher chlorophyll a values are related with stronger summer monsoon and vice versa high temporal resolution radiocarbon dating enables us to divide summer monsoon evolution stages summer monsoon in zhanjiang area was strongest in the early holocene but began to decline at 6080 yr bp and weakened substantially since about 3600 yr bp the transition around 6080 yr bp supported by our high resolution dating lags the previous estimates by 1700 years the decreasing summer solar radiation at 30 n through the holocene is probably responsible for gradually weakened summer monsoon the anti phased co variation of summer monsoon intensity and enso activity throughout the holocene suggests that they could be interlinked driven together by solar radiation at orbital scale

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

fluid inclusion characteristics and molybdenite re os geochronology of the qulong porphyry copper molybdenum deposit tibet the qulong porphyry copper and molybdenum deposit is located at the southwest margin of the lhasa terrane and in the eastern region of the gangdese magmatic belt it represents china s largest porphyry copper system with 2200 million tonnes of ore comprising 0 5 cu and 0 03 mo the mineralization is associated with miocene granodiorite monzogranite and quartz diorite units which intruded into jurassic volcanic units in a post collisional indian asian tectonic setting field observations and core logging demonstrate the alteration and mineralization at qulong are akin to typical porphyry copper systems in subduction settings which comprise similar magmatic hydrothermal potassic propylitic and phyllic alteration assemblages molybdenite re os geochronology confirms the relative timeframe defined by field observations and core logging and indicates that the bulk copper and molybdenum at qulong were deposited within 350 000 years between 16 10 0 06 0 08 without and with decay constant uncertainty and 15 88 0 06 0 08 ma this duration for mineralization is in direct contrast to a long lived intrusive episode associated with mineralization based on previous zircon u pb data our fluid inclusion study indicates that the ore forming fluid was oxidized and contained na k ca fe cu mo cl and s the magmatic hydrothermal transition occurred at 425 c under lithostatic pressure while potassic propylitic and phyllic alteration occurred at hydrostatic pressure with temperature progressively decreasing from 425 to 280 c the fluid inclusion data presented here suggests that there has been 2 3 km of erosion at qulong after its formation and this erosion may be related to regional uplift of the lhasa terrane

ti diffusion in quartz abstract we have measured ti diffusion in quartz under dry 1 atm conditions experiments were performed using synthetic and natural quartz and a tio2 powder source with ti profiles obtained by rutherford backscattering spectrometry rbs over the temperature range 700 1150 c the following arrhenius relation was obtained for diffusion parallel to 001 d ti 7 10 8 exp 273 12 kj mol 1 r t m 2 sec 1 similar diffusivities were obtained for both synthetic and natural quartz and for a range of ti source materials including natural titanite powder and rutile quartz single crystal diffusion couples although ti diffusion appears slightly slower in the direction normal to c this difference is not great using these diffusion parameters calculations indicate that distances over which diffusional alteration of ti concentrations in quartz could occur in a million years would be on order of 500 m at 800 c and 15 m at 600 c the arrhenius relation above should be broadly applicable and may find application in constraining metamorphic histories under conditions where the ti in quartz geothermometer can be reasonably applied this relation can also be used to constrain peak temperatures and cooling histories from observations of exsolved rutile needles in quartz and the width of the ti depleted zone that develops around the growing needles finally these findings may find utility in evaluating crystal residence times in magmatic systems when coupled with observations of the sharpness of zoning patterns in quartz

marine palynological record for tropical climate variations since the late last glacial maximum in the northern south china sea the upper part 191 1439 cm of the marine sediment core md05 2906 from the northern south china sea scs was palynologically investigated the chronology suggested that it covered the record since 19 calendar kiloyears before present cal ka bp and revealed a detailed environmental change history since the late last glacial maximum lgm during the late lgm due to the lowered sea level 100 m lower and the shortened distance from the shore to the study site the pollen concentration was very high the pollen assemblages were dominated by non arboreal taxa especially artemisia pollen before 15 cal ka bp abundant subtropical and tropical pollen taxa were still important components and a south subtropical climate prevailed during the late lgm the coexistent rich artemisia pollen possibly was not derived from near shores but was derived mainly from the northern exposed continental shelf in the east china sea ecs after 15 cal ka bp with the rise in the sea level and enhanced distance from the pollen source areas to the core site pollen concentrations started to decline gradually however during the late deglaciation and early holocene the higher concentrations of many pollen taxa reoccurred which cannot be attributed to the sea level changes pinus pollen deposited in the core which is considered to be mostly water carried based on many modern pollen surveys also started to dramatically increase at the same time therefore the higher pollen concentration with more pinus and typha an aquatic plant pollen indicated a notably enhanced terrestrial runoff and precipitation during the last deglaciation holocene transition 11 3 9 4 cal ka bp we inferred that a strong summer monsoon occurred at this time during the late lgm deglaciation transition period the pollen assemblage reflected a gradually warming climate and the climate fluctuations derived from the high latitudes were not well identified this study suggests that solar insolation played a crucial role in controlling the east asian monsoon and hydrological cycle in the northern scs

timing of meltwater pulse 1a and climate responses to meltwater injections the temporal relationship between meltwater pulse 1a mwp 1a and the climate history of the last deglaciation remains a subject of debate by combining the greenland ice core project d18o ice core record on the new greenland ice core chronology 2005 timescale with the u th dated barbados coral record we conclusively derive that mwp 1a did not coincide with the sharp bolling warming but instead with the abrupt cooling of the older dryas to evaluate whether there is a relationship between meltwater injections north atlantic deep water nadw formation and climate change we present a high resolution record of nadw flow intensity from eirik drift through the last deglaciation it indicates only a relatively minor 200 year weakening of nadw flow coincident with mwp 1a our compilation of records also indicates that during heinrich event 1 and the younger dryas there were no discernible sea level rises and yet these periods were characterized by intense nadw slowdowns shutdowns clearly deepwater formation and climate are not simply controlled by the magnitude or rate of meltwater addition instead our results emphasize that the location of meltwater pulses may be more important with nadw formation being particularly sensitive to surface freshening in the arctic nordic seas

copper deposition during quartz dissolution by cooling magmatic hydrothermal fluids the bingham porphyry abstract scanning electron microscope cathodoluminescence imaging is used to map successive generations of fluid inclusions in texturally complex quartz veinlets representing the main stage of ore metal introduction into the porphyry cu au mo deposit at bingham utah following conventional fluid inclusion microthermometry laser ablation inductively coupled plasma mass spectrometry la icpms is applied to quantify copper and other major and trace element concentrations in the evolving fluid with the aim of identifying the ore forming processes textures visible in cathodoluminescence consistently show that the bulk of vein quartz q1 characterized by bright luminescence crystallized early in the vein history cu fe sulfides are precipitated later in these veins in a microfracture network finally filled with a second generation of dull luminescing q2 quartz mapping of brine and vapor inclusion assemblages in these successive quartz generations in combination with la icpms microanalysis shows that the fluids trapped before and after cu fe sulfide precipitation are very similar with respect to their major and minor element composition except for copper copper concentrations in inclusions associated with ore formation drop by two orders of magnitude in a tight pressure temperature interval between 21 and 14 mpa and 425 350 c several hundred degrees below the temperature of fluid exsolution from the magma copper deposition occurs within a limited p t region in which sulfide solubility shows strong normal temperature dependence while quartz solubility is retrograde this permits copper sulfide deposition while secondary vein permeability is generated by quartz dissolution the brittle to ductile transition of the quartz feldspar rich host rocks occurs in the same temperature range which further enhances vein reactivation and promotes cooling and expansion of fluids ascending across the transition from lithostatic to hydrostatic conditions

the development and fracturing of plutonic apexes implications for porphyry ore deposits porphyry ore deposits are generally located above plutonic apexes described as finger like extrusions from a large underlying silicic magma chamber fractures and faults that concentrate around these shallow structures allow mineral enriched hydrothermal and magmatic fluids to circulate and exchange heat and mass with the host rock plutonic apexes however are not necessarily mineralized the physical mechanisms invoked for their development and fracturing are focused on the role of volatile pressure and we have no clear explanation on the associated thermo mechanical processes here we present a a semi quantitative scenario to explain how significant relief could form at the magma chamber roof to give apexes frozen within the shallow crust and b the results of our numerical modeling of fracturing at plutonic apexes we suggest that morphologic instabilities expressed by two directional corrugations crests and troughs at the crystallizing roof of the magma chamber could arise at the top of large silicic batholiths as a result of thermo mechanical interactions between the reservoir and its surroundings the corrugated roofs could form with local apexes several kilometers high given that a local extensional tectonic regime would surround such systems crystallization of the apexes would promote a concentration of fractures and faults in their vicinity in modeling the thermo mechanical regime around a plutonic apex to show how fractures and faults could develop we tested different values for temperature contrasts extension rates and magma viscosity two main regimes can be identified depending on the rheological contrast between the magma and its host rock the one a single thick fault connecting the apex to the surface analogous to a breccia pipe and the other a network of fractures surrounding the apex analogous to a stockwork where two apexes are close together one will cluster the shear stresses regardless of its vertical extension and thus only a single fracture will develop we thus infer that barren apexes can be located near mineralized apexes if the distance between them is no greater than the thickness of the brittle layer which in turn is highly dependent on local thermal and mechanical conditions

ti diffusion in quartz inclusions implications for metamorphic time scales quartz inclusions in garnet from samples collected from the staurolite zone in central new england are zoned in cathodoluminescence cl the cl intensity is interpreted to be a proxy for ti concentration and the zoning attributed to ti diffusion into the quartz grains driven by ti exchange between quartz and enclosing garnet as a function of changing temperature the cl zoning has been interpreted using a numerical diffusion model to constrain the time scales over which the diffusion has occurred temperature time histories are sensitive to the presumed peak temperature but not to other model parameters the total time of the metamorphic heating and cooling cycle from around 450 c to the peak temperature 550 600 c back to 450 c is surprisingly short and encompasses only 0 2 2 million years for peak temperatures of 600 550 c the metamorphism was accompanied by large scale nappe and dome formation and it is suggested that this occurred as a consequence of in sequence thrusting resulting in a mid crustal ductile duplex structure

scanning electron microscope cathodoluminescence analysis of quartz reveals complex growth histories in veins from the butte porphyry copper deposit montana scanning electron microscope cathodoluminescence sem cl analysis of quartz reveals textures that cannot be observed using optical microscopy or backscattered electrons these cryptic textures yield insight into timing and physical conditions of quartz growth especially in environments with multiple quartz precipitation events hydrothermal quartz from quartz sulfide veins in the porphyry copper deposit in butte montana was analyzed by sem cl revealing the following textures euhedral growth zones wide nonluminescing bands that cut across multiple quartz grains rounded luminescent quartz grain cores with euhedral overgrowths nonluminescing splatters of quartz connected by networks of cobweb like nonluminescing quartz in otherwise luminescent quartz concentric growth zones and wide nonluminescent grain boundaries these textures indicate that many veins have undergone fracturing dilation growth of quartz into fluid filled space quartz dissolution and recrystallization of quartz precipitation and dissolution textures indicate that early quartz molybdenite veins formed as a result of pressure fluctuations between lithostatic and hydrostatic at high temperatures and later pyrite quartz veins formed near hydrostatic pressure in response to temperature decrease through and beyond the field of retrograde quartz solubility

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

mineral thermometry and fluid inclusion studies of the pea ridge iron oxide apatite rare earth element deposit mesoproterozoic st francois mountains terrane southeast missouri usa mineral thermometry and fluid inclusion studies were conducted on variably altered and mineralized samples from the mesoproterozoic pea ridge iron oxide apatite ioa rare earth element ree deposit in order to constrain p t conditions fluid chemistry and the source of salt and volatiles during early magnetite and later ree mineralization scanning electron microscopy sem cathodoluminescence and sem backscatter electron images show that quartz and rutile precipitated before during and after magnetite and ree mineral growth ti in quartz and zr in rutile equilibration temperatures range from 350 to 750 c in the amphibole magnetite hematite and silicified zones where t increased during magnetite and quartz growth and dropped precipitously after fracturing and brecciation late drusy quartz cements within a ree rich breccia pipe record the lowest t 315 400 c liquid vapor rich and hypersaline hematite calcite fluid inclusions are common and liquid co 2 is present locally salinities define three populations saline 10 27 wt nacl equiv hypersaline 34 60 wt nacl equiv and dilute 0 10 wt nacl equiv the wide range of eutectic melting temperatures 67 to 19 c suggests that saline inclusions trapped variable proportions of a cacl mgcl fecl bearing fluid end member and an nacl kcl fluid end member homogenization temperatures and pressures of these saline inclusions suggest they were trapped when fluids unmixed into brine and vapor at t the na cl na k and cl br ratios of fluid inclusion extracts provide evidence for mixtures of magmatic hydrothermal fluids and evaporated seawater extracts from magnetite hematite and pyrite plot in the magmatic hydrothermal field indicating that fe was derived from a magmatic source their enrichments in mg and ca are consistent with a mafic magmatic source the positive correlation between na mg and na ca ratios may be due to halite saturation or albitization of igneous rocks extracts from barite in the ree rich breccia pipes are enriched in na and br and plot near the seawater evaporation trend he is highly enriched relative to ne and ar in fluid inclusion extracts which precludes air as a source of he although the he is mostly of crustal origin pyrite with a 3 he 4 he r r a of 0 1 contains up to 12 mantle he many extracts have low 20 ne 22 ne ratios due to nucleogenic production of 22 ne in high f o minerals such as fluorapatite or f biotite the arrays of data for 3 he 4 he r r a and 22 ne 20 ne suggest that volatiles were derived from two sources a moderate f mafic magma containing mantle he and a high f silicic magma with crustal he together with other evidence cited in this report these data 1 support a magmatic hydrothermal origin for the mesoproterozoic magnetite apatite deposit with ore fluids derived from a concealed mafic to intermediate composition intrusion 2 suggest that the ree minerals in breccia pipes were either derived from apatite or precipitated in response to decompression and cooling during breccia pipe formation 3 provide evidence for the influx of basinal brine magmatic fluids from granitic intrusions and meteoric water after breccia pipe formation and 4 show that pea ridge was relatively unaffected by the late paleozoic mississippi valley type mvt pb zn system in overlying cambrian sedimentary rocks

intensity of quartz cathodoluminescence and trace element content in quartz from the porphyry copper deposit at butte montana textures of hydrothermal quartz revealed by cathodoluminescence using a scanning electron microscope sem cl refl ect the physical and chemical environment of quartz formation variations in intensity of sem cl can be used to distinguish among quartz from superimposed mineralization events in a single vein in this study we present a technique to quantify the cathodoluminescent intensity of quartz within individual and among multiple samples to relate luminescence intensity to specific mineralizing events this technique has been applied to plutonic quartz and three generations of hydrothermal veins at the porphyry copper deposit in butte montana analyzed veins include early quartz molybdenite veins with potassic alteration pyrite quartz veins with sericitic alteration and main stage veins with intense sericitic alteration cl intensity of quartz is diagnostic of each mineralizing event and can be used to fingerprint quartz and its fluid inclusions isotopes trace elements etc from specific mineralizing episodes furthermore cl intensity increases proportional to temperature of quartz formation such that plutonic quartz from the butte quartz monzonite bqm that crystallized at temperatures near 750 c luminesces with the highest intensity whereas quartz that precipitated at 250 c in main stage veins luminesces with the least intensity trace element analyses via electron microprobe and laser ablation icp ms indicate that plutonic quartz and each generation of hydrothermal quartz from butte is dominated by characteristic trace amounts of al p ti and fe thus in addition to cl intensity each generation of quartz can be distinguished based on its unique trace element content aluminum is generally the most abundant element in all generations of quartz typically between 50 and 200 ppm but low temperature main stage quartz containing 400 to 3600 ppm al is enriched by an order of magnitude relative to all other quartz generations phosphorous is present in abundances between 25 and 75 ppm and p concentrations in quartz show little variation among quartz generations iron is the least abundant of these elements in most quartz types and is slightly enriched in cl dark quartz in pyrite quartz veins with sericitic alteration titanium is directly correlated with both temperature of quartz precipitation and intensity of quartz luminescence such that bqm quartz contains hundreds of ppm ti whereas main stage quartz contains less than 10 ppm ti our results suggest that ti concentration in quartz is controlled by temperature of quartz precipitation and that increased ti concentrations in quartz may be responsible for increased cl intensities

geology and geochronology of the tiegelongnan porphyry epithermal cu au deposit tibet china formation exhumation and preservation history abstract the tiegelongnan rongna deposit is a giant porphyry epithermal cu au deposit within the duolong porphyry district in the south qiangtang terrane central western tibet china the deposit is centered on multiphase granodiorite porphyry gp intrusions intruded in jurassic sandstone phase 1 and 2 gp are associated with biotite and sericite alteration whereas gp3 and 4 occur in middle and shallow parts of the deposit affected by sericite and advanced argillic alteration alunite kaolinite dickite pyrophyllite sericite alteration is pervasive in the deep part of the deposit replacing biotite alteration and hosting porphyry stage chalcopyrite bornite pyrite molybdenite mineralization advanced argillic alterationis associated with epithermal stage high sulfidation tennantite enargite bornite and digenite mineralization overprints the sericite and biotite alteration from the shallow part of the deposit the top of the tiegelongnan hydrothermal system was weathered with a layer of supergene oxidation and enrichment zone exhumated and covered by andesite and gravel muscovite sampled from deep sericite alteration yields a 40ar 39ar age of 120 9 0 8 ma which is consistent with previously reported hydrothermal biotite 40ar 39ar age of 121 1 0 6 ma molybdenite re os ages of 121 2 0 6 and 119 0 1 4 ma and gp 1 and 2 zircon u pb ages of 121 5 1 5 120 2 1 0 ma la icp ms results and 118 7 0 9 ma sims result phase 3 gp 3 yields a ca id tims zircon u pb age of 119 9 0 2 ma which constrains the age of porphyry magmatic hydrothermal events the porphyry system was then unroofed weathered and superimposed by discrete stages of advanced argillic alteration and high sulfidation mineralization two pulses of alunite events yield 40ar 39ar ages of 116 3 0 8 ma and 111 7 1 0 ma which represent the principal epithermal alteration and mineralization ages at tiegelongnan the first alunite pulse age is consistent with younger porphyry gp4 age of 116 2 0 4 ma zircon la icp ms age weathering and exhumation of the porphyry epithermal deposit were continuing until the cover of andesite at 110 ma and by post andesite gravel the andesite was affected by a younger weak hydrothermal alteration at 108 7 0 7 ma constrained by a muscovite 40ar 39ar age another barren alunite yields a 40ar 39ar age of 100 6 2 0 ma which may represent the youngest hydrothermal event the long life span discrete hydrothermal activities from 120 to 100 ma in the tiegelongnan deposit is consistent with the long lasting tectonic magmatic events of the bangong nujiang suture zone the discrete epithermal mineralization events at tiegelongan are younger than the porphyry mineralization events which is analogous to several other epithermal deposits worldwide the 10 m y exhumation history at tiegelongan is slower than the typical and rapid erosion history of 1 2 m y porphyry deposits in low altitude tropical climates regions and during a specific abrupt uplift pulse in the andean region the slow exhumation at tiegelongnan is interpreted to be an integrated result of an arid climate environment relatively flat topography and a slow uplift condition during cretaceous in central western tibet

high resolution evidence from southern china of an early holocene optimum and a mid holocene dry event during the past 18 000 years abstract computer models suggest that the holocene optimum for east asian summer monsoon precipitation occurred at different times in different regions of china previous studies indicate that this time transgressive holocene optimum should have been experienced about 3000 yr ago in southern china in this study we describe a section which allows us to test this timing directly we have closely examined high resolution eutrophic peat mud sequences covering the past 18 000 cal yr at dahu jiangxi on the southern boundary of the mid subtropical zone in china late pleistocene successions in the dahu record indicate cooler and much wetter conditions relative to synchronous events in north central china our results indicate that the holocene optimum occurred between ca 10 000 and 6000 cal yr ago in southern china consistent with the global pattern conditions were relatively dry and cold from 6000 to 4000 cal yr ago our data also support the conclusion that the last deglaciation to early holocene in the south was much wetter resulting in the formation of dense broad leaved forests which could have acted to moderate land temperature 10 000 to 6000 cal yr ago yielding a stable early holocene climate after 6000 cal yr forest reduction led to unstable land temperatures and possibly to a northerly shift of the subtropical high pressure system whatever the mechanism these changes resulted in decreased precipitation between 6000 and 4000 cal yr b p in southern china

a 20 000 year high resolution pollen record from huguangyan maar lake in tropical subtropical south china abstract a high resolution pollen record from huguangyan maar lake near the south china sea spanning the past 20 400 yr bp has been presented aimed to provide an improved understanding of the response of the regional vegetation in tropical subtropical south china to climatic variations since the late last glacial maximum the results reveal the strong control of the asian summer monsoon asm strength on vegetation via orbitally induced variations in northern hemisphere summer solar insolation the trend of climatic evolution of the region consists of change from a warm temperate northern subtropical climate 20 400 18 700 cal yr bp to a southern subtropical climate 16 500 11 500 cal yr bp during the last deglaciation followed by a stepwise environmental shift from a tropical climate 11 500 8200 cal yr bp to a southern subtropical climate 8200 6600 cal yr bp and finally to a middle northern subtropical climate the bolling allerod warming is characterized by the highest percentages of evergreen quercus but the lowest percentages of xerophytic gramineae throughout the record suggesting intensified warm wet conditions during 15 000 13 000 cal yr bp by contrast the younger dryas is characterized by a marked decrease in subtropical evergreen broad leaved plants but a significant increase in herbaceous taxa representing a brief cold reversal during 13 000 12 000 cal yr bp the occurrence of two major cooling events at 8 2 and 6 6 kyr bp both of which are characterized by dramatic decreases in tropical evergreen broad leaved plants is supposed to be linked to a distinct weakening of the asm and southward migration of the intertropical convergence zone associated with marked declines in atlantic meridional overturning circulation the subsequent brief intervals of high herbaceous pollen percentages but low percentages of tropical taxa correspond to high el nino southern oscillation enso activity supporting a link between the weakening of solar isolation driven asm strength and a gradual intensification of enso

time scales of porphyry cu deposit formation insights from titanium diffusion in quartz porphyry dikes and hydrothermal veins from the porphyry cu mo deposit at butte montana contain multiple generations of quartz that are distinct in scanning electron microscope cathodoluminescence sem cl images and in ti concentrations a comparison of microprobe trace element profiles and maps to sem cl images shows that the concentration of ti in quartz correlates positively with cl brightness but al k and fe do not after calibrating cl brightness in relation to ti concentration we use the brightness gradient between different quartz generations as a proxy for ti gradients that we model to determine time scales of quartz formation and cooling model results indicate that time scales of porphyry magma residence are 1 000s of years and time scales from porphyry quartz phenocryst rim formation to porphyry dike injection and cooling are 10s of years time scales for the formation and cooling of various generations of hydrothermal vein quartz range from 10s to 10 000s of years these time scales are considerably shorter than the 0 6 m y overall time frame for each porphyry style mineralization pulse determined from isotopic studies at butte montana simple heat conduction models provide a temporal reference point to compare chemical diffusion time scales and we find that they support short dike and vein formation time scales we interpret these relatively short time scales to indicate that the butte porphyry deposit formed by short lived episodes of hydrofracturing dike injection and vein formation each with discrete thermal pulses which repeated over the 3 m y generation of the deposit

shrimp u pb and 40ar 39ar age constraints for relating plutonism and mineralization in the boulder batholith region montana the composite boulder batholith montana hosts a variety of mineral deposit types including important silver rich polymetallic quartz vein districts in the northern part of the batholith and the giant butte porphyry copper molybdenum pre main stage system and crosscutting copper rich main stage vein system in the southern part of the batholith previous dating studies have identified ambiguous relationships among igneous and mineralizing events mineralizing hydrothermal fluids for these types of deposits and magma for quartz porphyry dikes at butte have all been considered to be late stage differentiates of the boulder batholith however previous dating studies indicated that the boulder batholith plutons cooled from about 78 to 72 ma whereas copper rich main stage veins at butte were dated at about 61 ma recent efforts to date the porphyry copper molybdenum pre main stage deposits at butte resulted in conflicting estimates of both 64 and 76 ma for the mineralizing events silver rich polymetallic quartz vein deposits elsewhere in the batholith have not been dated previously to resolve this controversy we used the u s geological survey stanford shrimp rg ion microprobe to date single age domains within zircons from plutonic rock samples and 40 ar 39 ar geochronology to date white mica biotite and k feldspar from mineral deposits u pb zircon ages are rader creek granodiorite 80 4 1 2 ma unionville granodiorite 78 2 0 8 ma pulpit rock granite 76 5 0 8 ma butte granite 74 5 0 9 ma altered steward type quartz porphyry dike i 15 roadcut 66 5 1 0 ma altered steward type quartz porphyry dike continental pit 65 7 0 9 ma and quartz monzodiorite of boulder baldy big belt mountains 66 2 0 9 ma zircons from rader creek granodiorite and quartz porphyry dike samples contain archean inheritance the 40 ar 39 ar ages are muscovite silver rich polymetallic quartz vein basin district 74 4 0 3 ma muscovite silver rich polymetallic quartz vein boulder district 74 4 1 2 ma muscovite early dark micaceous vein continental pit 63 6 0 2 ma biotite early dark micaceous vein continental pit 63 6 0 2 ma potassium feldspar early dark micaceous vein continental pit 63 to 59 ma and biotite biotite breccia dike continental pit 63 6 0 2 ma outlying silver rich polymetallic quartz veins of the basin and boulder mining districts probably are directly related to the 74 5 ma butte granite whereas steward type east west quartz porphyry dikes and butte pre main stage deposits are parts of a 66 to 64 ma magmatic mineralization system unrelated to emplacement of the boulder batholith the age of the crosscutting main stage veins may be about 61 ma as originally reported but can only be bracketed as younger than the 64 ma pre main stage mineralization and older than the about 50 ma eocene lowland creek intrusions the 66 ma age for the quartz monzodiorite of boulder baldy and consideration of previous dating studies in the region indicate that small ca 66 ma plutonic systems may be common in the boulder batholith region and especially to the east the approximately 64 ma porphyry copper systems at butte and gold mineralization at miller mountain are indicative of regionally important mineralizing systems of this age in the boulder batholith region resolution of the age and probable magmatic source of the butte pre main stage porphyry copper molybdenum system and of the silver rich polymetallic quartz vein systems in the northern part of the boulder batholith documents that these deposits formed from two discrete periods of hydrothermal mineralization related to two discrete magmatic events

magma evolution leading to porphyry au cu mineralization at the ok tedi deposit papua new guinea trace element geochemistry and high precision geochronology of igneous zircon

how do metals escape from magmas to form porphyry type ore deposits abstract many precious and base metals cu au ag mo w sn in porphyry type deposits are extracted from a granitic to granodioritic silicate melt and transported by magmatic hydrothermal fluids to the site of ore deposition metals abundance increases from some ppb in the melt to in ore bodies assuming a unique magmatic source for metals it implies an exceptional combination of enrichment process acting over up to 4 orders of magnitude previous models of magma differentiation and hydrothermal circulations omitted to consider the role of metal segregation during magma chamber evolution models for the formation and evolution of intrusions have recently shifted from the so called melting storage assimilation homogenization mash paradigm basically steady state to the mantle melting segregation ascent emplacement m m sae paradigm dynamic and discontinuous in time successive magma injections of variable compositions progressively build the magma chamber this is supported by field relations e g cross cutting dykes and stocks textures e g partially resorbed enclaves or mineral fabrics geochemistry e g hybridization signatures and age dating aswell as istopic studies as melt crystallizes and forms a mush 50 crystals volatiles also exsolve forming a magmatic volatile phase mvp while melt motion slows down metals partition between the three phases melt crystals and mvp they generally prefer the mvp owing to more favorable partition coefficients this is indicated by metal content in coeval melt and fluid inclusions with homogenization temperatures above 600 c or in volcanic fumaroles here by simulating the physical interactions between the three phases we suggest a model of fluid sparging during which metals segregate towards the mvp by diffusion and are further transported by advection as metal complexes the model also provides estimates of metal enrichment an undimensional peclet number rules the competition between diffusion and advection basically scaling with respect to the inverse of the product of melt viscosity by metal diffusivity d the threshold value of the peclet number between diffusion and advection is roughly 10 9 fast diffusive metals au cu ag w readily diffuse from silicate melt and towards bubbles of the mvp to escape the mush through tubular structures the mvp must overcome a critical gas saturation level about 20 vol usually reached after several magma injections advection then takes over and transports the metal enriched mvp towards the top of the magma chamber this leads to nearly coeval 1 separation between a high salinity liquid phase and a low salinity vapor phase 2 fluid rock interactions resulting in potassic advanced argillic and phyllic alterations and 3 metal deposition the metal enrichment scales as the ratio between partition coefficient i e related to the gradient in chemical potential diffusivity i e related to the gradient of concentration and melt viscosity i e related to the gradient of momentum the rates at which all such gradients relax determe metals enrichment inducing chemical and physical instabilities leading to a cyclic process the whole cycle also encompasses the case of a partial non completed full enrichment yielding to barren intrusions a tentative model generalizes the sparging fluid model to other metal deposits linked to an intrusion such generalization should be interpreted as predicting metal enrichment by 3 4 orders of magnitude rather than predicting an exact value

oxygen isotope and palaeotemperature records from six greenland ice core stations camp century dye 3 grip gisp2 renland and northgrip oxygen isotope variations spanning the last glacial cycle and the holocene derived from ice core records for six sites in greenland camp century dye 3 grip gisp2 renland and northgrip show strong similarities this suggests that the dominant influence on oxygen isotope variations reflected in the ice sheet records was regional climatic change differences in detail between the records probably reflect the effects of basal deformation in the ice as well as geographical gradients in atmospheric isotope ratios palaeotemperature estimates have been obtained from the records using three approaches i inferences based on the measured relationship between mean annual 18o of snow and of mean annual surface temperature over greenland ii modelled inversion of the borehole temperature profile constrained either by the dated isotopic profile or iii by using monte carlo simulation techniques the third of these approaches was adopted to reconstruct holocene temperature variations for the dye 3 and grip temperature profiles which yields remarkably compatible results a new record of holocene isotope variations obtained from the northgrip ice core matches the grip short term isotope record and also shows similar long term trends to the dye 3 and grip inverted temperature data the northgrip isotope record reflects i a generally stronger isotopic signal than is found in the grip record ii several short lived temperature fluctuations during the first 1500 yr of the holocene iii a marked cold event at ca 8 2 ka the 8 2 ka event iv optimum temperatures for the holocene between ca 8 6 and 4 3 ka a signal that is 0 6 stronger than for the grip profile v a clear signal for the little ice age and vi a clear signal of climate warming during the last century these data suggest that the northgrip stable isotope record responded in a sensitive manner to temperature fluctuations during the holocene copyright 2001 john wiley sons ltd

ti content in huguangyan maar lake sediment as a proxy for monsoon induced vegetation density in the holocene the provenance of element ti in huguangyan maar lake hgy sediment has been under debate since yancheva et al 2007a proposed its eolian source from the chinese loessplateau clp and applied it as a proxy for asian wintermonsoon we performed a comprehensive study on ti carryingminerals and ti uxes in lake sediments wall rocks andloess from the clp here we show that the chemicalcompositions and morphological features of magnetite the most important ti carrier in hgy surface sediments are identical to those in wall rocks around the lake butsubstantially different from those in clp loess samples ourcalculated modern eolian ti ux from the clp is negligiblecompared to the average total ti ux to hgy and ti uxfrom catchment erosion can provide enough ti indicating tiin hgy sediment are predominantly from wall rock erosion inverse correlation between total organic carbon toc vegetation density and ti ca ratio terrestrial input in theholocene suggests monsoon induced vegetation densitypredominates over runoff in controlling ti input to hgy s ratio represents toc directly mediated reductive diagenesisof iron oxides magnetite preservation rather than anoxic oxic condition at the bottom water induced by wintermonsoon our record shows a decreased vegetation density increased ti input and weakened reductive diagenesisthrough the holocene driven by a weakened summermonsoon

titaniq a titanium in quartz geothermometer titanium is one of many trace elements to substitute for silicon in the mineral quartz here we describe the temperature dependence of that substitution in the form of a new geothermometer to calibrate the titaniq thermometer we synthesized quartz in the presence of rutile and either aqueous fluid or hydrous silicate melt at temperatures ranging from 600 to 1 000 c at 1 0 gpa the ti contents of quartz in ppm by weight from 13 experiments increase exponentially with reciprocal t as described by text log left x text qtz text ti right 5 69 pm 0 02 frac 3765 pm 24 t k application of this thermometer is straightforward typically requiring analysis of only one phase quartz this can be accomplished either by epma for crystallization temperatures above 600 c or by sims for temperatures down to at least 400 resulting temperature estimates are very precise usually better than 5 c potentially allowing detailed characterization of thermal histories within individual quartz grains although calibrated for quartz crystallized in the presence of rutile the thermometer can also be applied to rutile absent systems if tio2 activity is constrained

assessment of vertical contamination of cd pb and zn in soils around a former ore smelter in wallonia belgium concentrations of trace elements cd co cr cu ni pb and zn and major elements ca mg k fe al and mn as well as phkcl and total organic carbon toc were measured on 22 profiles located in a 3 km radius of a former ore treatment plant in wallonia belgium the enrichment factor ef vertical impoverishment factor vif and availability ratio ar were used as diagnostic tools of contamination and migration of cd pb and zn in profiles the data revealed that the soil profiles are significantly contaminated the ranges of efs for cd 17 3570 pb 1 2883 and zn 2 309 are very broad with the higher ef in the topsoil of the profiles vifs of subhorizons are rarely above 1 in the few cases with vif 1 the main factor explaining is the soil type in particular colluvic regosols luvisols and cambisols with shale load cd pb and zn ars are strongly correlated with toc and to a lesser extent with phkcl pb and zn ars are influenced by soil type while land use only has an effect on zn ar the cd availability is independent of these two factors the contents of trace elements measured in soil profiles are very high especially in topsoil at present the cd pb and zn vertical distribution shows a low migration from topsoil to deeper levels however we must not discount the hazard of a future potential transfer

getting granite dikes out of the source region whether a dike can propagate far from a magma reservoir depends upon the competition between the rate at which propagation widens the dike and the rate at which freezing constricts the aperture available for magma flow various formulations are developed for a viscous fluid at temperature t sub m intruding a growing crack in an elastic solid the initial solid temperature equals t sub m at the source and decreases linearly with distance from the source if t sub m is the unique freezing temperature of the fluid dike growth is initially self similar and an essentially exact solution is obtained if t sub m is above the solidus temperature the solution is approximate but is designed to overestimate the distance the dike may propagate the ability of a dike to survive thermally depends primarily upon a single parameter that is a measure of the ratio of the dike frozen margin thickness to elastic thickness perhaps more intuitively one may define a minimum distance from the essentially solid reservoir wall to the point at which the host rock temperature drops below the solidus necessary for dikes to propagate far into subsolidus rock it is concluded that for reasonable material properties and source conditions most basalt dikes will have little difficulty leaving the source region but most rhyolite dikes will be halted by freezing soon after the magma encounters rock at temperatures below the magma solidus while these results can explain why granitic dikes are common near granitic plutons but rare elsewhere the potentially large variation in magmatic systems makes it premature to rule out the possibility that most granites are transported through the crust in dikes nonetheless these results highlight difficulties with such proposals and suggest that it may also be premature to rule out the possibility that most granite plutons ascend as more equidimensional bodies

rutile saturation in hydrous siliceous melts and its bearing on ti thermometry of quartz and zircon the tio2 solubility of rutile saturated hydrous siliceous melts has been investigated at p 1 gpa and t 650 1000 c for several representative felsic compositions the dissolution of a rutile crystal into a tio2 undersaturated melt provides information on both tio2 solubility and ti diffusion results of this study confirm that tio2 solubility is strongly dependent on both temperature and melt composition but not on the amount of h2o present for a given t t io2 content decreases as the melts become more felsic the solubility of tio2 is given by log ti ppm 7 95 5305 t 0 124fm

reconstruction of climate and vegetation changes of lake bayanchagan inner mongolia holocene variability of the east asian monsoon a high resolution pollen and pediastrum record spanning 12 500 yr is presented for lake bayanchagan 115 21 e 41 65 n and 1355 m a s l southern inner mongolia individual pollen taxa pt mat and the pft affinity scores pft mat were used for quantitative climatic reconstruction from pollen and algal data both techniques indicate that a cold and dry climate similar to that of today prevailed before 10 500 cal yr b p the wettest climate occurred between 10 500 and 6500 cal yr b p at which time annual precipitation was up to 30 60 higher than today the early holocene increases in temperature and precipitation occurred simultaneously but mid holocene cooling started at approximately 8000 cal yr b p 1500 yr earlier than the drying vegetation reconstruction was based on the objective assignment of pollen taxa to the plant functional type the results suggest that this region was dominated by steppe vegetation throughout the holocene except for the period 9200 to 6700 cal yr b p when forest patches were relatively common inner mongolia is situated at the limit of the present east asian monsoon and patterns of vegetation and climate changes in that region during the holocene probably reflect fluctuations in the monsoon s response to solar insolation variations the early to middle holocene monsoon undoubtedly extended to more northern latitudes than at present

magnetism of the huguangyan maar lake sediments southeast china and its paleoenvironmental implications abstract the huguangyan hgy lake a typical maar lake in the southeast of china is sensitive to the evolution of the asian monsoon system including the east asian summer monsoon easm and the indian summer monsoon ism so far the mechanism of how magnetic properties of the hgy lake sediments respond to climate changes has not been well determined in this study we performed a detailed mineral magnetic analysis on the high resolution hgy sediments results revealed that finer grained magnetite superparamagnetic and single domain magnetite mixed with a small amount of goethite and hematite is the dominant magnetic mineral which is consistent with the magnetic properties of the red weathered soils collected from the catchments but differs greatly from that of the aeolian inputs therefore magnetic minerals of the hgy sediments were originated mainly from the lake catchment rather than the wind blown dust inputs considering the high tephra wall relative elevation of 10 20 m and great precipitation surface runoff by rainfall is interpreted as the main process to transport red soils into the lake the magnetic records of hgy sediments revealed that the summer monsoon was enhanced at the early holocene and then declined abruptly at the mid late holocene 5 5 kyr cal bp this pattern strongly mimics the evolution pattern of ism but is inconsistent with the easm thus we suggest that the magnetic records from hgy have the great potential to investigate the evolution of ism

the last glacial termination a major puzzle of paleoclimatology is why after a long interval of cooling climate each late quaternary ice age ended with a relatively short warming leg called a termination we here offer a comprehensive hypothesis of how earth emerged from the last global ice age a prerequisite was the growth of very large northern hemisphere ice sheets whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation the southern hemisphere westerlies shifted poleward during each northern stadial producing pulses of ocean upwelling and warming that together accounted for much of the termination in the southern ocean and antarctica rising atmospheric co2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres

holocene periodicity in north atlantic climate and deep ocean flow south of iceland climate fluctuations during the past millennium are relatively well documented1 on a longer timescale there is growing evidence of millennial scale variability of holocene climate at periodicities of 2 500 and 950 years possibly caused by changes in solar flux 2 3 and 1 500 years maybe related to an internal oscillation of the climate system 4 5 6 but the involvement of deep water masses in these holocene climate changes has yet to be established here we use sediment grain size data from the iceland basin to reconstruct past changes in the speed of deep water flow the study site is under the influence of iceland scotland overflow water isow the flow of which is an important component of the thermohaline circulation that modulates european climate flow changes coincide with some known climate events the little ice age and the mediaeval warm period and extend over the entire holocene epoch with aquasi periodicity of 1 500 years the grain size data indicate afaster isow flow when the climate of northern europe is warmer however a second mode of operation is observed in the early holocene when warm climate intervals are associated with slower isow flow at that time the melting remnant of land based glacial age ice may have provided a sufficient source of fresh water to the ocean to reduce isow flow south of iceland

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

from a long lived upper crustal magma chamber to rapid porphyry copper emplacement reading the geochemistry of zircon crystals at bajo de la alumbrera nw argentina the formation of world class porphyry copper deposits reflect magmatic processes that take place in a deeper and much larger underlying magmatic system which provides the source of porphyry magmas as well as metal and sulphur charged mineralising fluids reading the geochemical record of this large magmatic source region as well as constraining the time scales for creating a much smaller porphyry copper deposit are critical in order to fully understand and quantify the processes that lead to metal concentration within these valuable mineral deposits this study focuses on the bajo de la alumbrera porphyry copper deposit in northwest argentina the deposit is centred on a dacitic porphyry intrusive stock that was mineralised by several pulses of porphyry magma emplacement and hydrothermal fluid injections to constrain the duration of ore formation we dated zircons from four porphyry intrusions including pre syn and post mineralisation porphyries based on intersection relations between successive intrusion and vein generations using high precision ca id tims based on the youngest assemblages of zircon grains which overlap within analytical error all four intrusions were emplaced within 29 ka which places an upper limit on the total duration of hydrothermal mineralisation re os dating of hydrothermal molybdenite fully overlaps with this high precision age bracket however all four porphyries contain zircon antecrysts which record protracted zircon crystallisation during the 200 ka preceding the emplacement of the porphyries zircon trace element variations ti in zircon temperatures and hf isotopic compositions indicate that the four porphyry magmas record a common geochemical and thermal history and that the four intrusions were derived from the same upper crustal magma chamber trace element zoning within single zircon crystals confirms a fractional crystallisation trend dominated by titanite and apatite crystallisation however zircon cathodoluminescence imaging reveals the presence of intermediate low luminescent dark growth zones in many crystals from all intrusions characterised by anomalously high th u and ree concentrations and transient excursions in trace element ratios a return to the same fractionation trend after this excursion excludes external compositional forcing such as magma mixing instead we interpret the dark zones to record zircon crystallisation during a transient event of rapid growth that resulted from mafic magma injection into the base of the magma chamber releasing a co2 rich vapour phase into the dacitic crystal mush we propose that this vapour phase then migrated upwards to the apical part of the magma chamber from where it was expelled together with successive batches of magma to form the porphyry copper deposit within a short time span of less than a few 10 000 years the short duration of host rock emplacement hydrothermal alteration and mineralisation presented in this study provides critical constraints on fluid storage in magma chambers and the genesis of large porphyry copper deposits

cathodoluminescence and trace element zoning in quartz phenocrysts and xenocrysts quartz phenocrysts and xenocrysts are a common component of volcanic rocks but rarely contribute to our understanding of magmatic or eruptive processes due to an apparent internal chemical and structural homogeneity scanning electron microscopy cathodoluminescence imaging sem cl and secondary ion mass spectroscopy ion microprobe analysis sims are used here to demonstrate that quartz crystals in volcanic rocks show hitherto unrecognised internal structural and chemical zoning two contrasting crystal morphologies have been studied porphyritic euhedral bipyramidal quartz crystals in dacite from bonne nuit bay jersey uk show fine scale growth zoning in sem cl zones are narrow 1 40 m wide planar parallel to crystal faces and overgrow more broadly zoned rounded cores these crystals are interpreted to have formed at small degrees of undercooling by diffusion controlled growth quiescent magma conditions are indicated by the preservation of an al rich diffusive boundary layer which has not been removed by melt shearing during convection in contrast rounded and embayed porphyritic quartz grains in a quartz dacite from the esperanza mine e1 salvador northern chile show broad internal sem cl zones with irregular boundaries some of which are truncated by grain margins indicating dissolution crystal rounding may occur by dissolution or melting due to thermal or thermal chemical disequilibrium with surrounding melt and embayments by gas bubble enhanced convective dissolution are consistent with the development of incipient ocelli textures strings of amphibole inclusions adjacent to quartz rims several episodes of rounding can be recognised in some xenocrysts ion microprobe sims analysis of quartz from both samples shows that a1 contents are higher in areas of bright cl emission previous studies of cl in quartz have suggested that several factors control luminescence although a1 substitution for si in sio4 tetrahedra may be partly responsible for sem cl zoning recorded in volcanic quartz additional mechanisms including the effect of growth rate on defect density probably also play a major role

trace elements in hydrothermal quartz relationships to cathodoluminescent textures and insights into vein formation high resolution electron microprobe maps show the distribution of ti al ca k and fe among quartz growth zones revealed by scanning electron microscope cathodoluminescence sem cl from 12 hydrothermal ore deposits formed between 100 and 750 c the maps clearly show the relationships between trace elements and cl intensity in quartz among all samples no single trace element consistently correlates with variations in cl intensity however in vein quartz from five porphyry cu mo au deposits cl intensity always correlates positively with ti concentrations suggesting that ti is a cl activator in quartz formed at 400 c ti concentrations in most rutile bearing vein quartz from porphyry copper deposits indicate reasonable formation temperatures of 750 c using the titaniq geothermometer titanium concentrations of 10 ppm in all veins that formed at temperatures 350 c suggest a broad correlation between ti concentrations and temperature of quartz precipitation in quartz from most deposits formed at 2000 ppm but in high temperature quartz al concentrations are consistently in the range of several hundred ppm aluminum concentrations in quartz reflect the al solubility in hydrothermal fluids which is strongly dependent on ph aluminum concentrations in quartz therefore reflect fluctuations in ph that may drive metal sulfide precipitation in hydrothermal systems

new 40ar 39ar and u th he dating for the zhunuo porphyry cu deposit gangdese belt southern tibet implications for pulsed magmatic hydrothermal processes and ore exhumation and preservation understanding the magmatic hydrothermal cooling and exhumation history is fundamental for investigating porphyry deposit formation and preservation in the zhunuo porphyry copper deposit of southern tibet hydrothermal biotite related to early potassic alteration likely formed from 14 7 0 3 ma zircon u pb age to 14 23 0 13 ma molybdenite re os age and cooled below the closure temperature for 40ar 39ar system at 13 91 0 05 ma hydrothermal biotite 40ar 39ar plateau age the 40ar 39ar spectra of another hydrothermal biotite sample that was selectively replaced by chlorite record the timing of late phyllic alteration at 13 53 0 08 ma zhunuo hydrothermal alteration and mineralization likely ceased at 13 09 0 07 ma based on the 40ar 39ar plateau age of the fresh magmatic biotite crystals the biotite 40ar 39ar systematics have not been reset by 12 0 ma post mineralization granite porphyry within ore district which is likely due to rapid cooling and or absence of fluid exsolution for the granite porphyry in combination with previous zircon u pb and molybdenite re os data two pulses of magmatic hydrothermal activity from 14 78 0 11 to 14 44 0 05 ma and from 14 23 0 13 to 13 53 0 08 ma can be recognized at zhunuo u th he thermochronological data on zircon and apatite from the inter mineralization monzogranite porphyry suggest three cooling events characterized by first stage magmatic cooling at a rate of 1850 c m y and two later phases of uplift and exhumation at 70 c m y and 10 c m y approximately 1 4 km thickness of materials have been removed from the zhunuo miocene monzogranite porphyry during uplift and erosion including a large volume of ore

a 400 000 year record of vegetational and climatic changes from a volcanic basin leizhou peninsula southern china abstract the tianyang lake in leizhou peninsula is an enclosed crater formed during the early to middle pleistocene over 200 m of diatomaceous mud and clay were deposited in the last 400 000 years providing a continuous middle and late quaternary lacustrine sequence for paleoenvironmental studies the pollen record spans the last four glacial interglacial cycles equivalent to oxygen isotope stages ois 10 to 1 during most of the glacial phases fagaceous monsoon forest was replaced by altitudinal vegetation indicating a regional landscape transformation on the peninsula the montane forest reached down to the lowland by at least 600 m during the ois 6 and 8 in a cool and relatively wet condition with temperature estimated to be more than 4 c lower than present a further lowering of the montane forest belts by about 800 1000 m occurred in the ois 4 2 as implied by the appearance of many temperate elements during the last glacial maximum this mixed forest subsequently gave way to the poaceae grassland a savanna vegetation type favored by drier and cooler climatic conditions this drastic change implies a more significant drop in temperature and precipitation than the previous three glacial periods ois 10 8 and 6 it is thus inferred that the weakening of summer monsoon was more significant towards the end of the late pleistocene particularly during the last glacial maximum lgm

mineral deposits of canada a synthesis of major deposit types district metallogeny the evolution of geological provinces and exploration methods wayne d goodfellow editor 1 068 pp geological association of canada mineral deposits division special publication no 5 2007 hardcover isbn 13 978 1 897095 24 9 price members cdn 60 00 non members cdn 80 00 following in the footsteps of other landmark reviews of major ore producing countries such as australia hughes 1990 solomon and groves 1994 and south africa anhaeusser and maske 1986 this substantial 1 000 pages monograph is a great achievement that should be in every geologic research library in the world in many ways it sets a new standard most notably in that all figures and photographs are in color and that the entire volume is available in electronic form both as an included dvd and mostly on the gac website it is common in such compendia to have a spectacular cover photo or frontispiece to catch the reader s attention and this book does not disappoint the frontispiece photo is of a 61 8 kg sample from the dome mine timmins ontario and is stated to contain 20 wt percent gold at today s prices the gold alone would be worth 1 5 million dollars

evolution of middle late triassic granitic intrusions from the badaguan cu mo deposit inner mongolia constraints from zircon u pb dating geochemistry and hf isotopes abstract the great xing an range in the eastern part of the central orogenic belt is one of the major polymetallic metallogenic belts in china the badaguan cu mo deposit in the erguna massif forms part of this belt and is a typical porphyry deposit associated with multiple granitic intrusions which are temporally and genetically related to the formation of this deposit in this paper we present new zircon u pb ages hf isotopic data and whole rock major and trace element geochemistry on the badaguan granitoids zircon u pb data indicate that the intrusions formed during two major phases ca 244 237 ma and ca 232 229 ma the middle triassic ca 244 237 ma phase is represented by a suite of medium k calc alkaline granite k feldspar granite biotite granite and porphyritic granite with i type affinities in general they are enriched in light rare earth elements lrees and large ion lithophile elements liles and depleted in heavy rare earth elements hrees and high field strength elements hfses their zircon ehf t values and two stage model ages tdm2 range from 1 5 to 8 5 with a mean value of 4 9 and from 732 to 1366 ma with a mean value of 959 ma respectively in contrast the late triassic ca 232 229 ma intrusions dominantly comprise a suite of high k calc alkaline i type granite porphyry and granodiorite porphyry these rocks are enriched in liles and lrees but depleted in hrees and hfses such as nb ta and ti their ehf t and tdm2 values range from 3 4 to 6 2 with a mean value of 5 0 and from 865 to 1047 ma with a mean value of 942 ma respectively these results suggest that the primary magmas of the middle and late triassic intrusive rocks were co magmatic and were mainly derived from the partial melting of juvenile thickened lower crust in addition the primary magma forming the middle triassic complex also assimilated a small amount of ancient crustal material and experienced a remarkable degree of fractional crystallization prior to its emplacement in contrast the source magma of the late triassic complex probably underwent interaction between of minor mantle derived melt and crustal components prior to emplacement the cu in badaguan deposit was likely sourced from the mantle derived melt whereas the mo was contributed by the host rocks with high mo contents

pulsed magmatic fluid release for the formation of porphyry deposits tracing fluid evolution in absolute time from the tibetan qulong cu mo deposit the magmatic hydrothermal evolution of porphyry style mineralization in the shallow crust that is linked to magmatic processes at depth has been extensively studied using bulk sample isotopic analysis combined with relative timing constraints however a lack of evaluation of the fluid evolution process against an absolute time frame limits further understanding of the ore forming process here we quantify the fluid evolution process within an absolute time frame for the first time by integrating new in situ oxygen isotope data from the qulong porphyry cu mo deposit tibet with existing fluid inclusion data and high precision re os dates of co precipitated hydrothermal quartz and molybdenite respectively we demonstrate that vein quartz records primary oxygen isotopic compositions and reached oxygen isotope equilibrium with ore forming fluids and therefore is an archive of the isotopic composition and source of the ore forming fluids the 18oquartz and 18ofluid values in absolute time show periodic fluctuations that indicate the presence of three intermittent pulses of magmatic fluid flux which have been balanced by meteoric water as such the flux of magmatic fluid during ore formation was pulsed rather than being continuous the overall highest 18ofluid in the first pulse of mineralization with a gradual decrease to the second and third pulses is suggestive of a progressive reduction in the magmatic component of the hydrothermal fluids and by inference the mineralizing potential of the hydrothermal fluids this view is supported by a decrease in sulfide bearing fluid inclusions and metal grade through time our findings favor multiple fluid release events from a single cooling magmatic reservoir although multiple fluid melt recharge events remain a competitive alternative an additional implication is that the magmatic reservoir may have a lifespan of hundreds of thousands of years with fluid release events occurring over tens of thousands of years

holocene east asian summer monsoon records in northern china and their inconsistency with chinese stalagmite δ18o records abstract monsoon precipitation over china exhibits large spatial differences it has been found that a significantly enhanced east asian summer monsoon easm is characterized by increased rainfall in northern china and by reduced rainfall in southern china and this relationship occurs on different time scales during the holocene this study presents results from a diverse range of proxy paleoclimatic records from northern china where precipitation variability is traditionally considered as an easm proxy our aim is to evaluate the evolution of the easm during the holocene and to compare it with all of the published stalagmite 18 o records from the asian monsoon region in order to explore the potential mechanism s controlling the chinese stalagmite 18 o we found that the intensity of the easm during the holocene recorded by the traditional easm proxy of moisture or precipitation records from northern china is significantly different from the chinese stalagmite 18 o records the easm maximum occurred during the mid holocene challenging the prevailing view of an early holocene easm maximum mainly inferred from stalagmite 18 o records in eastern china in addition all of the well dated holocene stalagmite 18 o records covering a broad geographical region exhibit a remarkably similar trend of variation and are statistically well correlated on different time scales thus indicating a common signal however in contrast with the clear consistency in the 18 o values in all of the cave records both instrumental and paleoclimatic records exhibit significant spatial variations in rainfall on decadal to centennial time scales over eastern china in addition both paleoclimatic records and modeling results suggest that holocene east asian summer monsoon precipitation reached a maximum at different periods in different regions of china thus the stalagmite 18 o records from the easm region should not be regarded as a reliable indicator of the strength of the east asian summer monsoon furthermore modern observations indicate that the moisture for precipitation in the east asian monsoon region is mainly derived from the indian ocean the moisture transport route from the indian ocean to the east asian monsoon region during the holocene is almost identical to that of modern precipitation therefore the strong correlation of 18 o records in the easm and indian summer monsoon ism regions and the similarity of the pattern of latitudinal changes in 18 o values in stalagmites and in modern meteoric precipitation along the water vapor transport route further suggests that the stalagmite 18 o records from the easm region are essentially a signal of the isotopic composition of precipitation which is determined mainly by changes in the 18 o of atmospheric vapor in the upstream source region over the indian ocean and indian monsoon region via the upstream depletion mechanism finally the main trends of the stalagmite 18 o records are strongly correlated with the known evolution of the ism and therefore these records reflect the history of the ism rather than that of the easm our findings support the conclusion that easm variability is mainly controlled by northern hemisphere summer insolation and was strongly modulated by ice volume during the last deglaciation and early holocene which delayed the response of the easm maximum to peak insolation forcing

alunite 40ar 39ar and zircon u pb constraints on the magmatic hydrothermal history of the zijinshan high sulfidation epithermal cu au deposit and the adjacent luoboling porphyry cu mo deposit south china implications for their genetic association

giant porphyry deposits characteristics distribution and tectonic controls more than half of the 25 largest known porphyry copper deposits defined in terms of contained copper metal formed during three time periods the paleocene to eocene eocene to oligocene and middle miocene to pliocene these giant deposits are clustered within three provinces central chile northern chile and southwest arizona northern mexico other giant deposits occur in montana utah panama peru argentina irian jaya mongolia and iran compressive tectonic environments thickened continental crust and active uplift and erosion were associated with the formation of many of these deposits calc alkalic magmas are most favorable for the formation of giant porphyry copper deposits although several of the largest systems are associated with high k calc alkalic intrusions the 25 largest gold rich porphyry deposits are concentrated in the southwest pacific and south america with other occurrences in eurasia british columbia alaska and new south wales many of the deposits formed in the last 13 m y the largest of the deposits are associated with high k calc alkalic intrusions many calc alkalic porphyritic intrusions have also produced giant gold rich porphyries in the last 20 m y the formation of giant porphyry copper molybdenum and copper gold deposits in the circum pacific region has been closely associated with subduction of aseismic ridges seamount chains and oceanic plateaus beneath oceanic island and continental arcs in several examples these tectonic perturbations have promoted flat slab subduction crustal thickening uplift and erosion and adakitic magmatism coeval with the formation of well endowed porphyry and or epithermal mineral provinces similar tectonic features are inferred to be associated with the giant porphyry copper molybdenum provinces of northern chile eocene oligocene and southwest united states cretaceous paleocene topographic and thermal anomalies on the downgoing slab appear to act as tectonic triggers for porphyry ore formation other factors such as sutures in the overriding plate permeability architecture of the upper crust efficient processes of ore transport and deposition and in some cases formation and preservation of supergene enrichment blankets are also vital for the development of high grade giant ore deposits a low grade geochemical anomaly may be the final product of mineralization if ore forming processes do not operate efficiently even in the most favorable geodynamic settings

teleconnection of climatic events between east asia and polar high latitude areas during the last deglaciation abstract from observations of continuous aeolian and swamp sediment sequences augmented by a detailed 14 c chronology 13 c and organic c analyses we can demonstrate century to millennium scale fluctuations in east asian monsoon palaeoclimatic events we also infer significant precipitation variability within the last deglaciation the major climatic zones that have been recognised in europe and find counterparts in east asia are the bolling allerod 14 750 12 800 cal yr b p and the younger dryas 12 800 11 600 cal yr b p the last deglaciation sediment sequences are characterised by frequent facies changes reflecting climate instability these frequent abrupt climatic events correlate well with fluctuations recorded in high latitude and polar areas as represented by the greenland ice core gisp 2 and a core from the north sea this indicates a palaeoclimate teleconnection between the high latitude and polar areas and the east asian monsoon areas through cold air mass activity and the related atmospheric pressure system

combined zircon molybdenite and cassiterite geochronology and cassiterite geochemistry of the kuntabin tin tungsten deposit in myanmar

multiphase magma intrusion ore enhancement and hydrothermal carbonatisation in the siah kamar porphyry mo deposit urumieh dokhtar magmatic zone nw iran abstract the siah kamar mo deposit skmd is located at the northwestern termination of the urumieh dokhtar magmatic zone and it is the only porphyry mo ore reserve in iran the exploration program documented 39 2 mt proved reserves 539 ppm mo and 66 4 mt probable reserves 266 ppm mo in this study field and petrographic investigations integrated with geochemical fluid inclusion and quartz chemistry and geochronological u pb zircon re os molybdenite and rb sr multimineral isochron studies are used to propose a metallogenic model for the mo mineralisation in the skmd the geology of the skmd is characterized by the emplacement of a multiphase oligocene basic intermediate at ca 33 30 ma to acidic 29 28 ma magmatic suite which intruded the eocene volcanic country rocks the alteration zone about 4 3 km in size and with a general nw se trend is centered within the main basic porphyry stock grading from an inner potassic sodic zone to peripheral phyllic propylitic halos the late acidic magmatic products stocks and dykes intruded and post dated the main alteration zone two stage mo mineralisation is recognised including i stage 1 disseminated molybdenite coeval with the formation of potassic sodic alteration and minor microscale fsp bt qz po veinlets and ii stage 2 high grade molybdenite carbonate sericite structurally controlled stockwork veining fluid inclusion systematics combined with titaniq thermometry documents a mineralising fluid system compatible with a transition from high temperature up to ca 600 c magmatic to epithermal 250 c conditions during progressive cooling exhumation and mixing with meteoric sources at shallow crustal conditions ca 7 3 km the re os molybdenite dating constrains the high grade mo ore formation at ca 29 28 ma attesting for the intimate linkage between the main mo mineralisation and the acidic magmatic phase in the area the rb sr geochronology of the potassic sodic alteration zones confirms the two stage magmatic mineralisation scenarios overlapping within errors with the results obtained from the u pb zircon geochronology and constraining the formation of the potassic sodic and phyllic alteration at ca 33 and 28 ma respectively our results document an uncommon scenario of two stage porphyry mo mineralisation associated with intensive late stage carbonate precipitation and achieved during a long lasting and multiphase magmatic pulses of oligocene age we highlight the dominant role of acidic fluid neutralisation for further ore enrichment during polyphase magma intrusion as the dominant factor controlling the mo mineralisation in the skmd comparison at a regional scale indicates that parameters such as longevity of magma supply progressive magma crystallization differentiation and the presence of a possible pre enriched crustal material should be considered responsible for the mo endowment in the udmz

mineral equilibria and zircon garnet and titanite u pb ages constraining the ptt path of granite related hydrothermal systems at the big bell gold deposit western australia the big bell deposit 75 t gold is located in a narrow spur of the meekatharra greenstone belt yilgarn craton western australia two ore bodies are located in a calcic potassic contact alteration zone overprinting lineated granodiorite dykes and amphibolite almandine cummingtonite hornblende skarn 1 3 g t au 1700 g t as 330 g t w and the muscovite microcline gneiss 3 5 g t au 580 g t sb 620 g t w of the main lode genetic models vary from pre to post metamorphic replacement hornblende plagioclase pairs in amphibolite constrain peak metamorphic temperature to 670 50 c in contrast garnet biotite thermometry provides estimates of 578 50 and 608 50 c for garnet cordierite biotite schist bordering the skarn and enveloping the main lode garnet cordierite and garnet hornblende pairs extend the range of fluid temperature to 540 65 c well below peak metamorphic temperature at 540 600 c the alteration assemblage andalusite sillimanite constrains pressure to 300 400 mpa corresponding to 11 14 km crustal depth published u pb ages indicate that metamorphism took place in the aureole of the southeast granodiorite tonalite batholith 2740 2700 ma followed by gold mineralization at 2662 5 ma and by the emplacement of biotite granite and sn ta nb granite pegmatite dykes at 2625 2610 ma amphibolite xenoliths in granite northwest of the deposit record the lowest temperature 628 50 c suggesting it lacks a metamorphic aureole the rare metal dykes are spatially associated with epidote albite and andradite diopside skarns 1 5 g t au mined where enriched in the weathered zone we analysed hydrothermal zircon intergrown with andradite concordant u pb ages of 2612 7 and 2609 10 ma confirm the presence of a second granite related system the zircons display oscillatory zoning and have low th u ratios 0 05 0 08 low th titanite from an albite granite dyke has a concordant but reset u pb age of 2577 7 ma

trace elements and cathodoluminescence of quartz in stockwork veins of mongolian porphyry style deposits the combination of scanning electron microscope cathodoluminescence cl fluid inclusion analysis and high resolution electron probe microanalysis of al ti k and fe in vein quartz has yielded results permitting a greater understanding of the complex mineralisation of the central oyu tolgoi and zesen uul porphyry style deposits southern mongolia these data demonstrate the relationship between quartz precipitation dissolution and ore deposition as the mineralising fluid chemistry changed through time four major quartz generations are identified in the a type veins from the stockworks of both the central oyu tolgoi oti to otiv and zesen uul deposits zui to zuiv despite differences in the associated alteration and mineralisation style the observed cl textures and trace element signatures of the quartz generations are comparable between deposits the oti and zui stage formed both the primary network of a type veins and pervasive silicification of the host rock using the ti in quartz geothermometer crystallisation temperatures for oti and zui of between 598 c and 880 c are indicated the main stage of sulphide mineralisation was accompanied by the dissolution of pre existing quartz oti and zui and precipitation of a weakly luminescent generation of quartz otii and zuii with a low ti content reflected in a calculated temperature drop from approximately 700 c to 340 c in central oyu tolgoi and 445 c in zesen uul otii and zuii stage quartzes show high and variable al concentrations the next stage of quartz in both deposits otiii and zuiii forms a fine network of veins in cracks formed in pre existing quartz otiii and zuiii quartz contain measurable fluid inclusions of moderate salinity 3 17 1 wt nacl eq entrapped in the temperature range 256 c to 385 c otiii and zuiii are not related to any sulphide mineralisation the final otiv and zuiv stages are characterised by quartz calcite micro breccias that penetrate the a type veins based on the calculated entrapment temperatures the otiv zuiv stage crystallised between 212 c and 335 c and the quartz is characterised by elevated but variable al and fe contents the cl and trace element signatures of the oti to otiii and zui to zuiii stages of the two mongolian porphyries show similar features to those observed in porphyry style deposits from other regions this suggests that a common sequence of quartz crystallisation occurs during the formation of early veins in many porphyry copper systems

new insights into the glacial latitudinal temperature gradients in the north atlantic results from uk 37 sea surface temperatures and terrigenous inputs abstract sea surface temperatures sst and input of continental materials have been reconstructed from the study of the long chain alkenones and n alkanes respectively in a core located in the western side of the mid atlantic ridge md952037 37 05 n 32 02 w 2630 m depth both the long and short term variability recorded by the temperatures and the planktonic 18o are basically the same over the last 280 kyr showing a clear glacial interglacial evolution comparison with core su90 08 located only 6 north and directly influenced by the cold polar waters associated with the polar front during glacial times revealed different climatic conditions during glacial periods at both locations whereas core md952037 recorded similar sst values during the last two glacial periods ca 14 15 c the northern core displayed colder conditions during isotopic stage 2 8 10 c than in stage 6 13 15 c these results indicate the existence of a well developed steep north south gradient between 37 and 43 n during the last glacial period but not during stage 6 which suggests a southern expansion of the polar front during the last glacial maximum

mineralized breccia clasts a window into hidden porphyry type mineralization underlying the epithermal polymetallic deposit of cerro de pasco peru cerro de pasco peru is known for its large epithermal polymetallic zn pb ag cu bi mineralization emplaced at shallow level a few hundred meters below the paleo surface at the border of a large diatreme dome complex porphyry style veins crosscutting hornfels and magmatic rock clasts are found in the diatreme breccia and in quartz monzonite porphyry dikes such mineralized veins in clasts allow investigation of high temperature porphyry style mineralization developed in the deep portions of magmatic hydrothermal systems quartz in porphyry style veins contains silicate melt inclusions as well as fluid and solid mineral inclusions two types of high temperature 600 c quartz molybdenite chalcopyrite pyrite veins are found in the clasts early thin 1 2 mm and sinuous ht1 veins are crosscut by slightly thicker up to 2 cm and more regular ht2 veins the ht1 vein quartz hosts co2 and sulfur rich high density vapor inclusions two subtypes of the ht1 veins have been defined based on the nature of mineral inclusions hosted in quartz i ht1bt veins with inclusions of k feldspar biotite rutile and minor titanite and ii ht1px veins with inclusions of actinolite augite titanite apatite and minor rutile using an emplacement depth of the veins of between 2 and 3 km 500 to 800 bar derived from the diatreme breccia architecture and the supposed erosion preceding the diatreme formation multiple mineral thermobarometers are applied the data indicate that ht1 veins were formed at temperatures 700 c ht2 veins host assemblages of polyphase brine inclusions generally coexisting with low density vapor rich inclusions trapped at temperatures around 600 c rhyolitic silicate melt inclusions found in both ht1 and ht2 veins represent melt droplets transported by the ascending hydrothermal fluids la icp ms analyses reveal a chemical evolution coherent with the crystallization of an evolved rhyolitic melt quartz from both ht1 and ht2 veins also contains secondary low temperature 300 c brine and aqueous fluid inclusions that record the cooling of the system both vein types are locally crosscut and or reopened by a pre diatreme polymetallic event consisting of pyrite sphalerite with chalcopyrite disease galena chalcopyrite tetrahedrite tennantite and minor quartz la icp ms analyses of mineral and high temperature fluid inclusions hosted in ht1 and ht2 veins and in situ secondary ion mass spectrometry oxygen isotope analyses of vein quartz indicate a magmatic signature for the mineralizing fluids with no major meteoric water input and allow reconstruction of the source and chemical evolution of fluids that formed these porphyry style veins as snapshots of the early and deep mineralizations at cerro de pasco this detailed study of the porphyry type mineralization hosted in clasts offers a unique opportunity to reconstruct the late magmatic and early hydrothermal evolutions of porphyry mineralization underlying the world class cerro de pasco epithermal polymetallic zn pb ag cu bi deposit

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

a 20 m y long lived successive mineralization in the giant dahutang w cu mo deposit south china abstract the connection between prolonged granitic magmatism and the formation of giant tungsten w polymetallic deposits has long been disputed in this study we present 6 mica ar ar plateau ages and 22 molybdenite re os model ages data on the newly discovered giant dahutang w cu mo deposit in south china which is one of the largest w deposits in the world new and published zircon u pb mica ar ar and molybdenite re os age data reveal that the mesozoic dahutang magmatism and mineralization occurred in two major periods 1 the late jurassic ca 153 147 ma forming the hydrothermal breccia large wolframite bearing quartz vein and scheelite dominated disseminated veinlet type orebodies which is mainly associated with the emplacement of porphyritic biotite granite 2 the late jurassic to early cretaceous ca 146 130 ma forming the cu mo w sn mineralization overprinting the late jurassic w mo cu orebodies which is mainly related to the successively emplacement of the early cretaceous granites we suggest that continuous accumulation of mineralization for a long period of time 151 130 ma have contributed to the formation of the giant dahutang deposit

relationships between sem cathodoluminescence response and trace element composition of hydrothermal vein quartz laser ablation icp ms data of hydrothermal vein quartz with zonation in scanning electron microscope cathodoluminescence reveal two groups of trace elements one that co varies in concentration with luminosity and another that remains uniform throughout bright luminosity correlates with a high total abundance of trace elements in early quartz including al up to 410 g g ti up to 240 g g k up to 330 g g li up to 8 g g na up to 36 g g and fe up to 20 g g up to 20 times lower concentrations of these elements are associated with dark luminosity in late quartz concentrations of p 21 g g ga 0 3 g g ge 1 3 g g sn 1 5 g g cu 0 3 g g and ag 0 1 g g demonstrate no relationship with luminosity charge balance cannot be achieved for bright luminescent quartz unless the presence of up to 6 g g h not analyzed by la icpms or interstitial al3 is invoked interestingly the inferred 6 g g h remains constant for quartz containing more than 10 mol total trace elements and might represent the solubility of h in hydrothermal quartz at temperatures between 450 and 700 c la icpms results indicate that the fluid chemistry determines the quartz trace element pattern which may serve as a monitor for the chemical environment from which quartz crystallized ratios of na al and ti al are uniform whereas k al evolves toward lower values with decreasing luminosity combined evidence including quartz vein textures silica solubility data and estimates of the temperature of quartz growth suggest that early quartz crystallized fast but late quartz grew more slowly at 350 to 425 c it is speculated that the higher the quartz growth rate is the more trace elements are incorporated into quartz besides the temperature dependence known from the literature clearly growth rate temperature and fluid chemistry are important parameters affecting luminosity however their relative importance may vary from case to case

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

time scales of magmatic processes from modeling the zoning patterns of crystals the advent of polarized light microscopy in the middle of the 19th century allowed mineralogists and petrologists interested in igneous rocks to recognize the widespread occurrence of fine scale heterogeneities in the optical properties of minerals e g see young 2003 for details the interpretation of mineral zoning patterns as archives of magmatic processes has been with us for some time e g larsen et al 1938 tomkeieff 1939 the development of the electron microprobe in the 1960 s allowed mineral zoning profiles to be quantitatively analyzed and modeled e g bottinga et al 1966 moore and evans 1967 enhanced textural observations permitted recognition of many kinds of detailed structures during the growth and dissolution of magmatic minerals fig 1 e g anderson 1983 pearce and kolisnik 1990 and these processes were also explored using experimental and numerical models e g albarede and bottinga 1972 lofgren 1972 kirkpatrick et al 1976 loomis 1982 major element zoning patterns are routinely measured and with the arrival of the ion microprobe the identification of heterogeneous distribution of trace elements opened the window for more realistic and sophisticated scenarios and models fig 1 e g kohn et al 1989 blundy and shimizu 1991 singer et al 1995 we now measure abundances of naturally occurring isotopes at the scale of tens of micrometers e g davidson et al 2007a ramos and tepley 2008 and this allows in situ dating of crystals e g cooper and reid 2008 figure 1 a nomarski dic image of a plagioclase crystal from a gabbroic xenolith of volcan san pedro costa et al 2002 the crystal shows a well defined core and a rim separated by an oscillatory zoned interval ion microprobe analysis pits and the trace of the electron microprobe traverse between the pits are evident b major

illumination of vein quartz textures in a porphyry copper ore deposit using scanned cathodoluminescence grasberg igneous complex irian jaya indonesia vein quartz from the grasberg igneous complex in irian jaya indonesia displays a wide range of features when observed using scanned cathodoluminescence imaging on the electron microscope examination of seventeen samples revealed concentric growth zoning quartz filled microfractures dark luminescence near sulfides changes in crystal size and orientation from vein edges to vein centers turbid growth zoning and the truncation of concentric growth zoning individual features observed along two large photomosaic traverses from vein margins to vein centers coupled with trace element analyses from the electron microprobe allow determination of a detailed history of fracture infilling the two traverses indicate a simple two stage history of crystal growth into an open fracture followed by mechanical closing of the fracture with resulting microfractures electron microprobe trace element analyses show that the fe content of quartz reaches values of up to 4900 ppm in dark luminescent regions near sulfide crystals and decreases smoothly to 200 ppm along traverses away from the sulfides the solution to the diffusion equation coupled with existing experimental data about fe diffusion in sio2 indicate the duration of the diffusion was perhaps on the order of thousands of years

porphyry cu mo stockwork formation by dynamic transient hydrothermal pulses mineralogic insights from the deposit at butte montana the systematic distribution of vein and alteration mineral assemblages in porphyry cu deposits largely arises from changes in the temperature and pressure of fluids that traversed fractures throughout the hydrothermal system magmatic and hydrothermal minerals record the complex history of the fluctuating temperature and pressure regime as hydrothermal fluids transfer heat from their magmatic source to cold wall rock in response to lithostatic to hydrostatic pressure variations we examine the thermal profile of the porphyry cu mo deposit in butte montana by determining formation temperatures for magmatic and hydrothermal samples representing different time frames and depths within the deposit in context with sample pressure estimates we use three independent mineral thermobarometers ti in quartz zr in rutile and x mg ti in biotite from which we estimate that final dike injection temperature and hence the initial magmatic hydrothermal fluid temperature was 700 c while the ambient host rock temperature was 450 to 500 c we find a magmatic hydrothermal continuum represented in hydrothermal veins ranging from 710 to

trace element diffusion and incorporation in quartz during heating experiments heating of quartz crystals in order to study melt and high temperature fluid inclusions is a common practice to constrain major physical and chemical parameters of magmatic and hydrothermal processes diffusion and modification of trace element content in quartz and its hosted melt inclusions have been investigated through step heating experiments of both matrix free quartz crystals and quartz crystals associated with sulfides and other minerals using a linkam ts1500 stage magmatic and hydrothermal quartz were successively analyzed after each heating step for cu al and ti using electron probe micro analyzer after the last heating step quartz crystals and their hosted melt inclusions were analyzed by laser ablation inductively coupled plasma mass spectrometry and compared to unheated samples heated samples reveal modification of cu li na and b contents in quartz and modification of cu li ag and k concentrations in melt inclusions our results show that different mechanisms of cu li and na incorporation occur in magmatic and hydrothermal quartz heated magmatic quartz records only small up to a few ppm enrichment in cu and na mostly substituting for li by contrast heated hydrothermal quartz shows enrichment up to several hundreds of ppm in cu li and na which substitute for originally present h this study reveals that the composition of both quartz and its hosted melt inclusions may be significantly modified upon heating experiments leading to erroneous quantification of elemental concentrations in addition each quartz crystal also becomes significantly enriched in cu in the sub surface layer during heating we propose that sub surface cu enrichment is a direct indication of cu diffusion in quartz externally sourced from both the surrounding sulfides as well as the copper pins belonging to the heating device our study shows that the chemical compositions of both heated quartz and its hosted inclusions must be interpreted with great caution to avoid misleading geological interpretations

superlakes megafloods and abrupt climate change about 8200 years ago the climate of much of the northern hemisphere cooled abruptly for a period of about 200 years in their perspective clarke et al examine the most likely culprit for this cooling an outburst of fresh water from a vast ice dammed glacial lake in north america the superlake had formed when the kilometers thick ice sheet covering much of north america disintegrated when the ice dam became unstable fresh water flooded from the lake into the north atlantic it remains unclear how this fresh water affected ocean circulation or whether the outburst occurred in more than one stage but the timing points strongly to the outburst flood as the trigger of the 8200 year climate event

diffusion and partition coefficients of minor and trace elements in magnetite as a function of oxygen fugacity at 1150 oc lattice diffusion coefficients and partition coefficients have been determined for li mg al sc ti cr v mn co ni cu zn ga y zr nb mo in lu hf ta and u in single crystals of natural magnetite as a function of oxygen fugacity fo2 at 1150 c and 1 bar by equilibration with a synthetic silicate melt reservoir most experiments were run for twelve hours which was sufficient to generate diffusion profiles from 25 to 1000 m in length the results were checked at one condition with two additional experiments at 66 9 and 161 h the profiles were analysed using scanning laser ablation inductively coupled plasma mass spectrometry diffusion coefficients d were calculated by fitting data from individual element diffusion profiles to the conventional diffusion equation for one dimensional diffusion into a semi infinite slab with constant composition maintained in the melt at the interface equilibrium magnetite melt partition coefficients are given by the ratio of the interface concentrations to those in the melt plots of log d as a function of log fo2 produce v shaped trends for all the investigated elements representing two different mechanisms of diffusion that depend on fo2 2 3 and fo2 2 3 diffusion coefficients at a given fo2 generally increase in the order cr mo ta v ti al hf nb sc zr ga in lu y ni u zn mn mg co li cu thus cu contents of magnetites are most susceptible to diffusive reequilibration whereas the original content of cr should be best preserved

economic geology clues to hidden copper deposits economic grade deposits of copper are hard to find the aluminium content of magmatic rocks at the surface may provide an indicator of ore deposits buried deep below

petrology of the yerington batholith nevada evidence for evolution of porphyry copper ore fluids the jurassic yerington batholith western nevada is a composite pluton that contains several centers of porphyry copper mineralization and is exposed in structural cross section at paleodepths ranging from 0 to 8 km within these exposures the mcleod hill quartz monzodiorite bear quartz monzonite and luhr hill granite form successive intrusions that are in turn volumetrically smaller approximately 75 19 and 6 vol respectively more deeply emplaced tops at 65 km 3 luhr hill granite the low cu content approximately 10 ppm of the granite would allow extraction of approximately 50 ppm cu from it during crystallization these data suggest an orthomagmatic model in which both high and low density saline aqueous fluids formed during exsolution of water from the crystallizing luhr hill granite and from which salts cu fe and s strongly partitioned into the high density ore fluid low density fluids may have risen from the magma as a vapor plume mineralization occurred when fluid overpressures caused fracturing of wall rock and upward intrusion of granite porphyry dikes and high density saline ore fluids both the f sub o 2 path during subsolidus cooling and the deposition of most s as chalcopyrite pyrite in ore suggest that reduction of magmatic s to sulfide may have been a mechanism for oxidation of magmatic ferromagnesian silicate and fe ti oxide minerals

can economic porphyry copper mineralization be generated by a typical calc alkaline melt numerical simulation of chlorine and copper partitioning between a crystallizing melt and exsolving aqueous fluids indicates that typical calc alkaline magmas contain sufficient copper chlorine and water to produce economic porphyry copper mineralization neither an elevated copper content in the magma nor an additional large volume of magma are required to provide metals or volatiles the most important variables that determine the volume of melt necessary to produce sufficient copper are the degree of compatible behavior displayed by copper the ratio of initial water in the melt to the water saturation level and the initial chlorine water ratio of the melt the absolute values for initial water in the melt and water content at saturation are relatively unimportant in determining the required melt volume the bulk salinity of the exsolved fluid may vary from 2 0 wt nacl to saturation levels 84 wt nacl at 700 c indicating that boiling is not necessary to produce high salinity brines at appropriate p t xnacl conditions the magmatic aqueous fluid separates into a saline liquid which transports most of the copper and a low salinity vapor the salinities of the two immiscible phases are governed by the p t conditions while the bulk fluid salinity determines the mass fractions of liquid and vapor formed pressure quenching causes rapid crystallization of the aplitic groundmass in porphyritic rocks associated with copper mineralization and significantly reduces the amount of chlorine and copper partitioning to the aqueous fluid this results in abrupt and possibly large reductions in fluid salinity and causes copper to become concentrated in the melt as copper is transported from the melt by the earliest exsolving fluids in deep 2 0 kbar systems and by late exsolving fluids in shallow 0 5 kbar systems the relative timing of pressure quenching aplite formation and fluid transport of copper from the melt can vary significantly in systems produced under different confining pressures model results incorporating petrologic constraints determined for yerington nevada are in good agreement with observed mineralization