potential analogues for paleoclimatic variations in eastern interior alaska during the past 14 000 yr atmospheric circulation controls of regional temperature and moisture responses the paleoclimatic history of a region can be viewed as a series of surface temperature and moisture anomalies through time the effects of changes in large scale climatic controls e g insolation major circulation controls can be mediated by the influence of smaller scale controls e g topographic barriers coastlines this may result in heterogenous surface climatic responses at the regional and sub regional scale divergent paleoclimatic trajectories between regions may be explainable in terms of such meso scale patterns using modern analogues for paleoclimate we examine how the sequence of climatic variations in eastern interior alaska during the interval 12 000 0 14c yr bp could have been generated by specific atmospheric circulation patterns fossil pollen and lake level records document the long term trends in temperature and effective moisture for the region water balance modelling provides additional estimates of paleoprecipitation synoptic climatological patterns are described using the modern instrumental record of upper level and sea level pressure surface temperature and precipitation at 12 000 14c yr bp eastern interior alaska was cooler and drier than present a situation generated today by a southward displacement of the jet stream conditions warmer and drier than present at 9000 14c yr bp may have been generated by increased ridging north of alaska and a weakened westerly circulation warmer wetter conditions than present possibly prevailed in the late middle holocene these might reflect ridging over alaska and troughing further west cool wet conditions feature enhanced westerly flow into alaska through an eastward shift in the east asian trough and positive pressure anomalies in the north pacific they may be analogous to cold periods of the little ice age the analogues demonstrate how surface conditions in other parts of beringia may sometimes be similar to while at other times different from those in the eastern interior these broader spatial patterns provide hypotheses about past climates that can be tested with paleoclimatological data for example the widespread positive temperature anomalies associated with the warm dry 9000 14c yr bp analogue fit with the expansion northward of the eastern siberian treeline the anomalously cool conditions in northeast siberia associated with the warm wet analogue may explain the continued late middle holocene treeline advance in alaska while there was retreat in siberia

monsoonal variability in the northeastern arabian sea during the past 5000years geochemical evidence from laminated sediments abstract a high resolution laminated sediment record from the oxygen minimum zone in the northeastern arabian sea off pakistan was studied to reconstruct climatic variations to infer the monsoon driven moisture history in the northeastern arabian sea during the past 5000 years we have used three types of independant proxies 1 varve thickness 2 stable isotope ratios of planktic foraminifera and 3 inorganic geochemical composition on the basis of these proxies we have subdivided the sedimentary record into five intervals the first time interval from 5000 to 3900 yr bp period i is dominated by summer monsoon activity deduced from ti al zr al k al and sr ca ratios and oxygen isotope data of planktonic foraminifera slightly enhanced winter monsoon conditions can be inferred for the period from 3900 to about 3000 yr bp period ii maximum precipitation during enhanced winter monsoon activity at about 3100 yr bp was followed by an onset of aridification at 3000 yr bp which continued until about 2000 2200 yr bp period iii the textural mineralogical and geochemical data suggest that this aridification was a gradual century scale process rather than an abrupt event comparison to late holocene records in nw and sw india the near east and tropical africa supports our interpretation that period iii from 3000 to 2000 yr bp is characterized by a gradual change in the atmospherical moisture budget over much of this area reduced monsoonal rainfall may be linked to variations of eurasian snow cover as deduced from varve thickness and element to al ratios period iv from 2000 to about 1500 yr bp is characterized by a summer monsoon dominated sequence with higher precipitation than during period iii the 18o record shows an abrupt shift at 2000 yr bp coinciding with an increase of varve thickness which suggests a cooling of surface waters in the northern arabian sea present day conditions in the makran area were established at 1500 yr bp period v based on inorganic geochemical data and meteorological records at several stations in the makran we conclude that period v is dominated by precipitation during the winter season here declined rainfall associated with the summer monsoon may be related to a less northward position of the intertropical convergence zone itcz during summer and a stronger influence of winter monsoon linked phenomenona

palaeoenvironmental signals in ancient urban setting the heavy rainfall record in sumhuram a pre islamic archaeological site of dhofar s oman a case study of an archaeological section in the pre islamic town of sumhuram third century bc fifth century ad dhofar s oman is presented sedimentological and palynological data have been integrated with the aim of finding signals of natural processes within an urban context two main types of deposits alternate in the section anthropogenic ad and waterlain wd the presence of laminated sediments within the wd deposits suggesting short term street flooding from heavy rainfall encouraged the development of a targeted palynological sampling strategy the results of the pollen analysis in these laminated sediments e g high pollen concentrations particularly of wet environment plants clumped pollen grains long distance pollen grains and overall good state of preservation suggest a stronger monsoonal influence than the present and high precipitation in s oman between 204 bc and ad 130

climatic signal of ice melt features in southern greenland the stratigraphie record of melt features in intermediate depth polar ice cores has provided valuable data on past summer climate1 3 the thermal drilling technique used in previous studies precluded extending this record beyond a few hundred years recently however a 901 m deep ice core was mechanically drilled in southern greenland the excellent core quality and improved techniques for measuring melt features have resulted in an 2 200 yr record with consistently high quality data we report here that the temporal variations in melt feature abundance expressed as annual melt per cent amp provide proxy data on summer climate that can complement other records extending back thousands of years the amp profile indicates that relatively warm summers prevailed from about ad 950 until ad 1500 culminating in the thirteenth and fourteenth centuries the periods from about 300 to 150 bc ad 350 to 550 and ad 1550 to 1800 had relatively little summer melting

reconstructed summer degree days in central alaska and northwestern canada since 1524 abstract three time series based on precisely dated annual tree ring widths have been used to reconstruct june plus july degree days for the central alaska and northwestern canada region the time series are the longest recently developed chronologies for the area and represent 57 core samples from 27 trees the degree day reconstruction extending back to a d 1524 exhibits much year to year variation and extended warming and cooling trends including a general warming trend from about 1840 to 1960 the reconstruction is in agreement with some subaretic glacial information and with data of percentage melting from arctic ice cores this and similar reconstructions can provide quantitative information to compare with general circulation and energy budget models for longer time periods than are available in recorded meteorological data

abrupt post glacial climate events in west asia and north africa monsoon domains regions beyond the present or past penetration of the indian and african monsoons have experienced several large and abrupt climatic fluctuations over the past 13 14c kyr pollen and lake records from west asia western tibet and rajasthan east africa ethiopia and west africa western sahara sahel and subequatorial africa were selected on the basis of chronological control sensitivity of both site and environmental indicators to climate change the continuity of the record and interdisciplinary control of the palaeoclimatic interpretation conditions wetter than those of today prevailed during the early mid holocene period but major dry spells are recorded at all sites during the intervals 11 0 9 5 kyr bp 8 7 kyr bp and 3 4 kyr bp several records also suggest dry events of minor amplitude around 6 kyr bp potential boundary forcings of insolation and sea surface and tropical land surface conditions are discussed the solar radiation accounts for the general envelop of the post glacial monsoon fluctuations but explains neither the timing nor the amplitude of the short term changes in spite of apparent covariation between fluctuations in sea surface conditions in the north atlantic and the monsoon record no direct mechanism could be found relating the intensity of the oceanic thermohaline conveyor belt to the monsoon strength changes in tropical land surface conditions soil moisture negative feedback and changes in ch4 production from wetlands provide a more satisfactory hypothesis for explaining abrupt reversal events

light rings in subarctic conifers as a dendrochronological tool abstract light rings are characterized by one or a very few latewood cell layers an indication of shortened growing seasons and are particularly frequent in black spruce picea mariana mill bsp at the treeline in quebec the construction of a light ring chronology spanning the period ad 1398 1982 showed that the highest frequency 25 of light rings among 160 trees and krummholz occurred in 1593 1620 1634 1784 1816 1817 1853 1969 and 1972 these diagnostic rings be a useful cross dating tool for dendroecologists working with living and dead krummholz with a low growth variability about two thirds of the 65 light ring years coincide with years or triads of major volcanic eruptions the climatic conditions low temperature occurring at the end of the growing season in part induced by the climatic effect of volcanism seem to initiate light rings

temperature dependence of sulfide and sulfate solubility in olivine saturated basaltic magmas abstract the sulfur concentration at pyrrhotite and anhydrite saturation in primitive hydrous basaltic melt of the 2001 2002 eruption of mt etna was determined at 200 mpa t 1050 1250 c and at log fo2 from fmq to fmq 2 2 fmq is fayalite magnetite quartz oxygen buffer at 1050 c au sample containers were used a double capsule technique using a single crystal olivine sample container closed with an olivine piston embedded in a sealed au80pd20 capsule was developed to perform experiments in s bearing hydrous basaltic systems at t 1050 c pyrrhotite is found to be a stable phase coexisting with melt at fmq fmq 0 3 whereas anhydrite is stable at fmq 1 4 fmq 2 2 the s concentration in the melt increases almost linearly from 0 12 0 01 to 0 39 0 02 wt s at fes saturation and from 0 74 0 01 to 1 08 0 04 wt s at anhydrite saturation with t ranging from 1050 1250 c the relationships between s concentration at pyrrhotite and or anhydrite saturation mgo content of the olivine saturated melt t and log fo2 observed in this study and from previous data are used to develop an empirical model for estimating the magmatic t and fo2 from the s and mgo concentrations of h2o bearing olivine saturated basaltic melts the model can also be used to determine maximum s concentrations if fo2 and mgo content of the melt are known the application of the model to compositions of melt inclusions in olivines from mt etna indicates that the most primitive magmas trapped in inclusions might have been stored at log fo2 slightly higher than fmq 1 and at t 1100 1150 c whereas more evolved melts could have been trapped at t 1100 c these values are in a good agreement with the estimates obtained by other independent methods reported in the literature

holocene migration of lodgepole pine pinus contorta var latifolia in southern yukon canada a palynological reconstruction n 25 profiles suggests that the northern extent of lodgepole pine pinus contorta var latifolia engelmann ex s watson occurred between 59 and 60 n latitude in

late stage anhydrite gypsum siderite dolomite calcite assemblages record the transition from a deep to a shallow hydrothermal system in the schwarzwald mining district sw germany abstract the majority of hydrothermal vein systems of economic interest occur at relatively shallow crustal levels although many of them formed at significantly greater depths their present position is a consequence of uplift and erosion although many aspects of their formation are well constrained the temporal chemical evolution of such systems during uplift and erosion is still poorly understood these vein minerals comprise calcite dolomite ankerite siderite magnesite anhydrite and gypsum forming the last gangue assemblages in jurassic and tertiary sulphide fluorite quartz barite veins of the schwarzwald mining district sw germany mineral textures of samples from nine localities reveal that in these sequences mineral precipitation follows a recurring pattern early calcite is followed by anhydrite or gypsum siderite and or dolomite this succession may repeat up to three times in situ la icp ms u pb age dating of 15 carbonates from three subsequent generations of the late stage vein assemblage yield robust ages between 20 and 0 6 ma each mineral sequence forms in a distinctive period of about 2 5 ma these ages clearly relate these late stage mineral phases to the youngest geological episode of the schwarzwald which is associated with the cenozoic rhine graben rifting and basement uplift based on thermodynamic modelling the formation of the observed mineral assemblages required an deeply sourced mg fe and so4 rich fluid b which was episodically mixed with a shallow crustal hco3 rich fluid a as a consequence of fluid mixing concentrations of mg fe and so4 temporarily increased and initiated the formation of the observed sulphate carbonate mineral sequences this discontinuous large scale vertical fluid mixing was presumably directly related to episodes of active tectonics associated with the cenozoic strike slip regime of the upper rhine graben analogously episodic fluid mixing is a major key in the formation of older jurassic to early tertiary pb zn fluorite quartz barite assemblages in the same specific vein systems albeit involving different fluid compositions late stage hydrothermal 20 70 c vein assemblages reported in this study record the transition from deep 2 km to very shallow 0 1 km crustal conditions as a consequence of successive uplift increasing proportions of shallower and cooler 50 70 c fluids could take part in such mixing processes associated changes in the fluid composition caused the vein mineralogy to change from sulphide quartz fluorite barite to calcite anhydrite gypsum siderite dolomite as the system passively ascended closer to the surface

high oxidation governed fluid evolution in the naruo porphyry cu au deposit tibet china abstract the naruo porphyry cu au deposit is the third discovered large deposit in the duolong metallogenic district previous research has mainly focused on the geochemistry of the ore bearing granodiorite porphyry however the metallogenesis is also poorly understood based on mapping using outcrops and geological drill cores the alteration zones were outlined and the sequence of veins was also identified furthermore fluid inclusion microthermometry and raman composition analyses were conducted a boiling fluid system is indicated by the coexisting aqueous brine and vapor inclusions in all vein types daughter metal minerals bearing brine inclusions are the major fluid inclusion types in all veins suggesting that the naruo porphyry cu au deposit was formed by high salinity fluids thus the measured data of the brine inclusions are mainly used for the interpretation of fluid evolution in the early quartz magnetite veins brine fluid inclusions exhibit high homogenization temperatures greater than 500 c and diverse salinities 30 1 61 5 wt nacl equiv while in the later magnetite absent chalcopyrite bearing quartz sulfide veins the homogenization temperatures of aqueous and brine inclusions are below 440 c suggesting that the magnetite mostly precipitated at temperatures higher than 440 c in the even later quartz pyrite chalcopyrite veins the homogenization temperatures of the brine inclusions are mainly below 300 c implying that the temperature range from 440 c to 300 c is the main copper mineralization interval the precipitation temperature of chalcopyrite fits the fact that the copper ore body is present within the potassic and early phyllic alteration zones hematite and magnetite are common within high salinity inclusions in all vein types indicating the high oxidation property of the ore forming fluid high oxidation facilitates the scavenging of sulfur and chalcophile metals into magmatic hydrothermal systems moreover hematite or magnetite deposition can facilitate the reduction of sulfate to sulfide and decrease ph values ultimately affecting sulfide precipitation and hydrothermal alteration the constant high oxidation is crucial for the metallogenesis of the naruo porphyry cu au deposit

fluid fluid interactions in magmatic hydrothermal ore formation hydrothermal ore deposits have provided some of the first geological evidence for the interaction of multiple fluids in the earth s interior including fluid mixing as well as fluid phase separation physical evidence comes from veins and breccias documenting the impact of fluids in breaking rocks and creating fracture permeability for ore formation as a result of the fluid expansion that is commonly associated with phase separation between melts and multiple fluids chemical evidence of fluid fluid interaction includes the precipitation of minerals in veins as a result of fluid boiling or mixing between chemically contrasting fluids fluid inclusions record interactions of multiple fluids especially in magmatic hydrothermal ore deposits and associated igneous rocks fig 1 in recent years fluid inclusions have contributed to a more quantitative understanding of the role of fluid fluid interactions since new microanalytical techniques allow determination of element concentrations in all types of fluids from low density vapor through aqueous and hypersaline liquids to hydrous salt melts roedder 1984 samson et al 2003 figure 1 geological evidence for fluid phase separation in ore forming magmatic hydrothermal systems a bonanza grade gold 1 wt that was precipitated together with fine grained pyrite in a fluidized breccia resulting from instantaneous boiling and expansion of magmatic fluids ascending from an underlying andesite porphyry intrusion the breccia consists of adularia sericite altered clasts of sedimentary wall rock s and nodules of originally colloidal pyrite with bright specks of gold p g both cemented by roscoelite r vanadium rich muscovite and late calcite c zone vii ore body porgera papua new guinea ronacher et al 2004 b bladed manganocalcite the characteristic habit of calcite precipitated from aqueous epithermal fluids as a result of the ph change following loss of co2 to a separating vapor phase madan bulgaria kostova et al 2004 c growth band in a euhedral quartz

mobility and h2o loss from fluid inclusions in natural quartz crystals petrographic observations on quartz crystals from the mole granite australia and other localities shed new light on the mechanisms of post entrapment modification of fluid inclusions these modifications include migration away from pseudosecondary trails changes in fluid salinity and density shape distortion and the formation of sweat haloes around strongly deformed inclusions increases in fluid salinity which usually are associated with inclusion migration indicate water losses of up to 50 however la icp ms analysis of unmobilized and mobilized inclusions of the same trail reveals basically unchanged ratios of major and trace element cations with the exception of li which seems to be incorporated into the crystal lattice during migration despite the fact that all these modifications are closely related to deformation processes they occur not only in mechanically deformed quartz but also in free standing crystals in the latter samples stress has been generated internally as a result of brazil twinned growth and compositional zonation these observations and their interpretation leads to a list of practical criteria that should help in differentiating between reliable and suspect fluid inclusions in other samples

geochronology and geochemistry of porphyritic intrusions in the duolong porphyry and epithermal cu au district central tibet implications for the genesis and exploration of porphyry copper deposits abstract the duolong district in central tibet hosts a number of porphyry as well as high sulfidation epithermal copper gold deposits and prospects associated with voluminous calc alkaline volcanism and plutonism in this study we present new geochronological geochemical isotopic and mineralogical data for both economically mineralized and barren porphyritic intrusions from the duobuza and naruo porphyry cu au deposits zircon u pb analyses suggest the emplacement of economically mineralized granodiorite porphyry and barren granodiorite porphyry at naruo deposit took place at 119 8 1 4 ma and 117 2 0 5 ma respectively four molybdenite samples from the naruo deposit yield an isochron re os age of 119 5 3 2 ma indicating mineralization occurred synchronously with the emplacement of the early granodiorite porphyry at duobuza deposit the barren quartz diorite porphyry intruded at 119 5 0 7 ma and two economically mineralized intrusions intruded at 118 5 1 2 ma granodiorite porphyry and 117 5 1 2 ma quartz diorite porphyry respectively petrographic investigations and geochemical data indicate that all of the porphyritic intrusions were oxidized water rich and subduction related calc alkaline magmas zircons from the porphyritic intrusions have a wide range in the ehf 0 11 1 indicating that they were sourced from mixing of mantle derived mafic and crust derived felsic melts moreover the variation of trace element content of plagioclase phenocrysts indicates that the magma chambers were recharged by mafic magmas comparison of the composition of amphibole phenocrysts indicates the porphyry copper gold mineralization at duolong was generated in magma chambers at low crystallization temperatures and pressures 754 to 791 c 59 m to 73 mpa n 8 and under highly oxidizing conditions nno 2 2 to 2 7 n 8 in contrast barren intrusions were sourced from the magma chambers with higher crystallization temperatures and pressures 816 to 892 c 111 to 232 mpa n 22 that were less oxidizing nno 0 6 to 1 6 n 22 the requirement for a thermal contrast is supported by the declining of ti content in magnetite crystals in barren intrusions 12 550 to 34 200 ppm versus those from economically mineralized intrusions 600 to 3400 ppm moreover the v content in magnetite crystals from economically mineralized intrusions 990 to 2510 ppm is lower than those recorded from barren intrusions 2610 to 3510 ppm which might reflect the variation in oxidation state of the magma the calculated water solubility of the magma forming the economically mineralized intrusions 3 2 3 7 wt is lower than that of magma forming the barren intrusions 4 6 6 4 wt based on the chemical physical characteristics of economically mineralized magma our study suggests that the development of porphyry cu au mineralization at duolong was initiated by shallow level emplacement of a magma that crystallized at lower temperatures and pressures experimental studies show that copper and water solubilities in silicate melts decrease with falling temperatures and pressures indicating metals and ore forming fluids are more likely to be released from a magma reservoir emplaced at shallow crustal levels we propose the magnetite might be a convenient exploration tool in the search for porphyry copper mineralization because the variations in ti and v content of mineral concentrates and rock samples are indicative of barren versus mineralized intrusions

stability and abundance of the trisulfur radical ion s 3 in hydrothermal fluids the interpretation of sulfur behavior in geological fluids and melts is based on a long standing paradigm that sulfate sulfide and sulfur dioxide are the major sulfur compounds this paradigm was recently challenged by the discovery of the trisulfur ion s 3 in aqueous s bearing fluids from laboratory experiments at elevated temperatures however the stability and abundance of this potentially important sulfur species remain insufficiently quantified at hydrothermal conditions here we used in situ raman spectroscopy on model thiosulfate sulfide and sulfate aqueous solutions across a wide range of sulfur concentration 0 5 10 0 wt acidity ph 3 8 temperature 200 500 degrees c and pressure 15 1500 bar to identify the different sulfur species and determine their concentrations results show that in the low density 0 2 g cm 3 vapor phase h2s is the only detectable sulfur form by contrast in the denser liquid and supercritical fluid phase together with sulfide and sulfate the trisulfur radical ion s 3 is a ubiquitous and thermodynamically stable species from 200 degrees c to at least 500 degrees c in addition the disulfur radical ion s is detected at 450 500 degrees c in most solutions and polymeric molecular sulfur with a maximum abundance around 300 degrees c in s rich solutions these results combined with revised literature data allow the thermodynamic properties of s 3 to be constrained enabling quantitative predictions of its abundance over a wide temperature and pressure range of crustal fluids these predictions suggest that s 3 may account for up to 10 of total dissolved sulfur s tot at 300 500 degrees c in fluids from arc related magmatic hydrothermal systems and more than 50 s tot at 600 700 degrees c in s rich fluids produced via prograde metamorphism of pyrite bearing rocks the trisulfur ion may favor the mobility of sulfur itself and associated metals au cu pt mo in geological fluids over a large range of depth and provide the source of these elements for orogenic au and porphyry epithermal cu au mo deposits furthermore the ubiquity of s 3 in aqueous sulfate sulfide systems offers new interpretations of the kinetics and mechanisms of sulfur redox reactions at elevated temperatures and associated mass dependent and mass independent fractionation of sulfur isotopes

triggers for the formation of porphyry ore deposits in magmatic arcs porphyry ore deposits supply much of the copper molybdenum gold and silver used by humans a review of the main processes that trigger porphyry ore formation suggests that sulphide saturation of the magmas that supply the metals could be the overriding mechanism that helps control the temporal and spatial distribution of the ore deposits

the origin and pre cenozoic evolution of the tibetan plateau different hypotheses have been proposed for the origin and pre cenozoic evolution of the tibetan plateau as a result of several collision events between a series of gondwana derived terranes e g qiangtang lhasa and india and asian continent since the early paleozoic this paper reviews and reevaluates these hypotheses in light of new data from tibet including 1 the distribution of major tectonic boundaries and suture zones 2 basement rocks and their sedimentary covers 3 magmatic suites and 4 detrital zircon constraints from paleozoic metasedimentary rocks the western qiangtang amdo and tethyan himalaya terranes have the indian gondwana origin whereas the lhasa terrane shows an australian gondwana affinity the cambrian magmatic record in the lhasa terrane resulted from the subduction of the proto tethyan ocean lithosphere beneath the australian gondwana the newly identified late devonian granitoids in the southern margin of the lhasa terrane may represent an extensional magmatic event associated with its rifting which ultimately resulted in the opening of the songdo tethyan ocean the lhasa northern australia collision at similar to 263 ma was likely responsible for the initiation of a southward dipping subduction of the bangong nujiang tethyan oceanic lithosphere the yarlung zangbo tethyan ocean opened as a back arc basin in the late triassic leading to the separation of the lhasa terrane from northern australia the subsequent northward subduction of the yarlung zangbo tethyan ocean lithosphere beneath the lhasa terrane may have been triggered by the qiangtang lhasa collision in the earliest cretaceous the mafic dike swarms ca 284 ma in the western qiangtang originated from the panjal plume activity that resulted in continental rifting and its separation from the northern indian continent the subsequent collision of the western qiangtang with the eastern qiangtang in the middle triassic was followed by slab breakoff that led to the exhumation of the qiangtang metamorphic rocks this collision may have caused the northward subduction initiation of the bangong nujiang ocean lithosphere beneath the western qiangtang collision related coeval igneous rocks occurring on both sides of the suture zone and the within plate basalt affinity of associated mafic lithologies suggest slab breakoff induced magmatism in a continent continent collision zone this zone may be the site of net continental crust growth as exemplified by the tibetan plateau c 2012 international association for gondwana research published by elsevier b v all rights reserved

a 930 year ring width chronology from moisture sensitive white spruce picea glauca moench in northwestern canada a 930 year tree ring chronology was constructed from living and subfossil white spruce picea glauca moench from the campbell dolomite upland northwest territories canada response function analy sis using climate data from nearby inuvik indicates that 69 of the variation in ring widths can be explained by monthly precipitation and temperature ring width is most strongly correlated with high precipitation between february and may there is also a significant negative relationship between ring widths and tempera tures during the previous growing season periods of slow radial growth at ad 1820 1855 1700 1710 1585 1610 1395 1405 1260 1300 and 1125 1170 are assumed to be associated with times of increased moisture stress periods of rapid growth at ad 1925 1940 1770 1780 1725 1740 1510 1560 1215 1260 and 1185 1205 likely reflect higher precipitation and or decreased moisture stress this chronology is the oldest yet published from northwestern canada and the first that provides a dendrohydrolo

paleoenvironmental changes during the last 4000 yr in the tigray northern ethiopia in the tigray region at the northern ethiopian highlands paleoenvironmental reconstruction based on several infilled valley deposit sequences suggests that the past 4000 yr comprised three major wetter periods ca 4000 3500 yr b p 2500 1500 yr b p and 1000 960 yr b p during which soils were formed and two degradation episodes ca 3500 2500 yr b p and 1500 1000 yr b p during which there was an increase of sediment yield from the slopes into the valleys for the past 1000 yr and in particular since the early 17th century stratigraphic records together with historic chronicles suggest increasing aridity although difficulties arise in distinguishing between natural and human impacts particularly in a region with a long established agricultural background stratigraphical and proxy paleoclimatic data have indicated climate as the main controlling factor responsible for the environmental changes in the tigray

the origin of monsoons abstract the monsoon is interpreted as an intertropical convergence zone itcz substantially away more than 10 from the equator and the existence of the itcz does not have to rely on land sea contrast land sea contrast can provide a favorable longitudinal location for the itcz but this role can be replaced by sea surface temperature contrast in the longitudinal direction thus the interpretation of the monsoon presented herein differs from the long held fundamental belief that its basic cause is land sea thermal contrast on the continental scale in the sense that the existence of landmass is not considered a necessary condition for monsoons through general circulation model experiments support has been found for this interpretation the asian and australian summer monsoon circulations are largely intact in an experiment in which asia maritime continent and australia are replaced by ocean with sea surface temperature sst taken from that of the surrounding oceans thus in these areas land sea c

contribution of mafic melt to porphyry copper mineralization evidence from mount pinatubo philippines and bingham canyon utah usa mount pinatubo in the philippines known for its cataclysmic eruption in 1991 hosts several porphyry copper deposits and active geothermal systems an underlying mafic melt supplied much of the sulphur for the dacitic magma and its injection into the dacitic magma chamber triggered the eruption the eruption caused purging of the sulphur rich fluid from the dacite to the atmosphere and extensive fracturing similar events took place at bingham canyon utah site of the largest copper and gold deposit in north america at 38 ma the bingham canyon mineralization took place beneath an active stratovolcano and pyroclastic flows contemporaneous with the mineralization show evidence for magma mingling ascent of mafic melt supplied sulphur and chalcophile elements to the felsic magma which consolidated to form the bingham stock and its underlying magma chamber injections of the mafic melt caused periodic eruptions of felsic magma to form the stratovolcano and deposition of sulphide minerals in highly fractured rocks in and around the stock

a ring width based reconstruction of june july minimum temperatures since ad 1245 from white spruce stands in the mackenzie delta region northwestern canada abstract we present a reconstruction of june july minimum temperatures since ad 1245 for the mackenzie delta region based on a 29 site network of white spruce picea glauca ring width series most but not all trees experienced a divergent temperature growth response similar to the divergence that has affected other white spruce trees across yukon and alaska however divergence in the study region began as early as ad 1900 and we have documented our methods to avoid including divergent signals in the reconstruction calibration verification testing based on local temperature data and multi century coherence with nearby and large scale temperature proxy records confirm that our reconstruction is robust the reconstruction shows cool conditions in the late 13th early 18th and early 19th centuries corresponding with solar minima and increased volcanism these cool periods are interrupted by warm periods consistent with early to mid 20th century warmth the late 20th century is the warmest interval and the last decade is estimated to be 1 4 c warmer than any decade before the mid 20th century the reconstructed climate history corroborates other proxy based inferences and supports the notion that high latitude regions such as the mackenzie delta have experienced rapid warming in recent decades that is exceptional in the last eight centuries

cenozoic epeirogeny of the arabian peninsula from drainage modeling it is generally accepted that the arabian peninsula has been uplifted by subcrustal processes positive residual depth anomalies from oceanic crust in the red sea and in the gulf of aden suggest that a region surrounding this peninsula is dynamically supported admittance calculations surface wave tomography studies and receiver function analyses all imply that regional topography is generated and maintained by some combination of mantle convective circulation and lithospheric thickness changes despite these significant advances the spatial and temporal uplift rate history of the arabian peninsula is not well known here we show that a regional uplift rate history can be obtained by jointly inverting 225 longitudinal river profiles that drain this peninsula our strategy assumes that shapes of individual river profiles are controlled by uplift rate history and moderated by erosional processes we used local measurements of incision rate to calibrate the relevant erosional parameters in our inverse algorithm uplift rate is permitted to vary smoothly as a function of space and time but upstream drainage area remains invariant we also assume that knickzone migration is not lithologically controlled implications of these important assumptions have been investigated our results suggest that the arabian peninsula underwent two phases of asymmetric uplift during the last 20 30 ma at rates of 0 05 0 1 mm a 1 the southwestern flank of the peninsula has been uplifted by 1 5 2 5 km regional stratigraphic constraints the age and composition of volcanism paleosol formation incised peneplains emergent marine terraces and thermochronometric measurements corroborate our calculated patterns of uplift progressive development of three domal swells along the western margin of the peninsula is consistent with localized upwelling of hot asthenospheric mantle

last millennium northern hemisphere summer temperatures from tree rings part i the long term context abstract large scale millennial length northern hemisphere nh temperature reconstructions have been progressively improved over the last 20 years as new datasets have been developed this paper and its companion part ii anchukaitis et al in prep details the latest tree ring tr based nh land air temperature reconstruction from a temporal and spatial perspective this work is the first product of a consortium called n trend n orthern hemisphere tre e ring n etwork d evelopment which brings together dendroclimatologists to identify a collective strategy for improving large scale summer temperature reconstructions the new reconstruction n trend2015 utilises 54 records a significant expansion compared with previous tr studies and yields an improved reconstruction with stronger statistical calibration metrics n trend2015 is relatively insensitive to the compositing method and spatial weighting used and validation metrics indicate that the new record portrays reasonable coherence with large scale summer temperatures and is robust at all time scales from 918 to 2004 where at least 3 tr records exist from each major continental mass n trend2015 indicates a longer and warmer medieval period 900 1170 than portrayed by previous tr nh reconstructions and by the cmip5 model ensemble but with better overall agreement between records for the last 600 years future dendroclimatic projects should focus on developing new long records from data sparse regions such as north america and eastern eurasia as well as ensuring the measurement of parameters related to latewood density to complement ring width records which can improve local based calibration substantially

high cu concentrations in vapor type fluid inclusions an artifact abstract studies of natural fluid inclusions have shown that cu commonly occurs at higher concentrations in vapor type inclusions than in coexisting brine inclusions a phenomenon which has been interpreted to arise from copper partitioning into the vapor phase in the first part of this study we attempted to experimentally reproduce this behavior in hydrothermal experiments covering a range of p t conditions 600 800 c 70 130 mpa fluid compositions nacl kcl fecl 2 0 5 6 6 wt s fluid acidities quench fluid ph 0 3 10 and sulfur speciation h 2 s dominated to so 2 dominated however as in several other studies we did not succeed in reproducing conditions under which cu partitions into the vapor phase in view of recent observations that quartz hosted fluid inclusions can diffusively loose or gain cu after entrapment we set out to determine if the evidence from natural fluid inclusions could be compromised for this purpose we synthesized vapor and brine inclusions from cu h 2 o nacl s fluids at 800 c 130 mpa and re equilibrated them in slightly different fluids at 800 c 70 mpa measuring some inclusions by la icp ms after each step vapor inclusions indeed experienced a dramatic increase in cu from 0 3 0 03 to 5 7 3 3 wt while brine inclusions remained largely unmodified leading to a change in the partition coefficient d cu vap brine from a true value i e before re equilibration of 0 4 0 05 to an apparent value of 8 3 4 9 the requirements for substantial diffusional gain of cu in fluid inclusions are a change in the ph of the surrounding fluid from 1 to more neutral and the presence of s in the pre existing fluid inclusions these requirements are also fulfilled in nature cooling magmatic hydrothermal fluids experience a change from acidic to more neutral ph due to buffering along the feldspar mica join and natural vapor inclusions typically contain significant amounts of sulfur a reversal experiment performed on natural quartz hosted fluid inclusions from the erongo granite namibia showed that this process can be reversed with the measured d cu vap brine value of 11 9 3 being modified to 0 06 0 04 thus d cu vap brine values 1 measured on natural fluid inclusions in quartz are likely a secondary feature caused by post entrapment copper diffusion realistic d cu vap brine values in porphyry cu environments are between 0 11 and 0 15 and reconstructed vapor brine mass ratios are in the order of 4 9 this suggests that the main transporting agent of cu at the porphyry level are brines and that models based on copper into the vapor phase are incorrect

early middle holocene environmental changes and pre neolithic human occupations as recorded in the cavities of jebel qara dhofar southern sultanate of oman abstract numerous palaeoenvironmental and archaeological studies from southern arabia yemen and oman have revealed strong relations between phases of human settlements and climate change linked to the indian monsoon system analyses on speleothems cave fills lacustrine deposits and palaeo mangroves have shown that during the early to mid holocene a humid optimum culminated around 9000 8000 cal bp new results on inland speleothems and cave sediments from the jebel qara southern oman are crucial in our depiction of early and mid holocene climatic evolution and cultural dynamics of the region these aspects are discussed here based on new archaeological surveys excavations geoarchaeological and micromorphological studies aiming to better understand connections with terminal pleistocene and early holocene autochthonous cultures of southern arabia our results suggest that the final pleistocene was marked by strong aridity which promoted a widespread thermoclastism within rock shelter and deposition of aeolian sand in contrast the transition towards the holocene is marked since c 12 000 cal bp by a progressive increasing in environmental humidity which permitted the formation of thick strata of peridesert loess after this phase the environmental humidity of the jebel increased and permitted the existence of a large community of land snails the latter were exploited by early holocene hunter gatherers who lived in the rock shelters between c 10 500 9500 cal bp and left consistent accumulations of land shells escargotieres the maximum of holocene humidity was reached between 9000 and 8000 cal bp regional aquifer were recharged and the deposition of calcareous tufa at the entrance of caves started lasting up to c 4500 cal bp c and o stable isotopes from calcareous tufa highlights in accordance with several regional records the progressive decline of the intensity of the indian ocean monsoon and the transition towards arid conditions in this phase the area was abandoned and archaeological communities possibly relocated along the coast of central and southern oman where they exploited the mangrove environment

tibetan basement rocks near amdo reveal missing mesozoic tectonism along the bangong suture central tibet the u pb and 4 0 ar 3 9 ar studies of a unique exposure of crystalline basement along the jurassic early cretaceous bangong suture of central tibet reveal previously unrecognized records of mesozoic metamorphism magmatism and exhumation the basement includes cambrian and older orthogneisses that underwent amphibolite facies metamorphism coeval with extensive granitoid emplacement at 185 170 ma the basement cooled to 300 c by 165 ma and was exhumed to upper crustal levels in the hanging wall of a south directed thrust system during early cretaceous time we attribute jurassic metamorphism and magmatism to the development of a continental arc during bangong ocean subduction and early cretaceous exhumation to northward continental underthrusting of the lhasa terrane beneath the qiangtang terrane we speculate that a jurassic arc extended regionally along the length of the bangong suture but in all other places in tibet has been buried either depositionally or structurally beneath supracrustal assemblages

timing of the southward retreat of the itcz at the end of the holocene humid period in southern arabia data model comparison new pollen data from omani mangroves kwar al jaramah 22 49 n 59 76 e and filim 20 61 n 58 17 e in addition to previously published paleohydrological records from southern arabia improve our understanding of the timing and amplitude of the southward retreat of the indian monsoon influence in southern arabia along a north south transect comparison with simulations performed with the ipsl climate model considering both snapshot experiments and transient simulations from 6000 cal yr bp to the present confirm the latitudinally time transgressive nature of the humid arid transition at the end of the holocene humid period this occurred in two steps respectively dated at around 5000 and 2700 cal yr bp at around 5000 cal yr bp the southward itcz shift was orbitally driven and led to the abrupt aridification at kwar al jaramah and the progressive increase of dryness at filim as the mean position of the itcz was centered ca 22 30 n at 2700 cal yr bp aridity was fully in place over all of southern arabia due to increased climate variability more intense rainy events during the last millennium however may have contributed to the discrete hydrological improvement without any impact on the regional vegetation which has remained desert to the present day

late holocene palaeoenvironmental history of khawr rawri and khawr al balid dhofar sultanate of oman abstract the coastal wetlands in dhofar sultanate of oman provide a record of late holocene palaeoenvironmental history the age of the surface sediments at some selected sites in the estuaries locally known as khawrs and qurms ranges from 750 to 390 calendar years cal y bc to present geomorphological data suggest that prior to 270 420 cal y ad these estuaries were open to the sea and received a high input of fresh water from the mountains at least from 270 420 cal y ad onwards the physiography of the estuaries changed as a consequence of dwindling fresh water input from the mountains as a result the open estuaries changed into barrier dominated estuaries with periodical input of saline and fresh water palynological data indicate that the estuaries are mainly filled with i pollen and spores from the surrounding vegetation ii a regional input of pollen and spores through surface and subsurface runoff from mountains coastal plain and wadis iii pollen and spores from east africa and the indian subcontinent brought in by the monsoon between 750 390 cal y ad and 270 420 cal y ad the local input of khawr taxa prevailed whereas from 270 420 cal y ad to present coastal plain and wadi taxa prevail both geomorphological and palynological data suggest the ancient centers of trade such as samhuram at khawr rawri ca 100 bc 100 ad and zafar at khawr al balid 12th 15th centuries ad were affected by important hydrological changes related to desertification of the region as a consequence of a weakening sw summer monsoon

rivers of the hadramawt watershed yemen during the holocene clues of late functioning recent geoarchaeological investigations have been carried out in the thick silty alluvial formations of the northern hadramawt basin yemen field data was combined with a compilation of palaeoenvironmental records published from arabia and its margins research performed on palaeolakes and other geoarchives indicates that the wet early mid holocene has little in common with the continuously arid period after 5 2 ka bp the data sets allowed the authors to propose new perspectives for the holocene palaeohydrological evolution of southern arabia which was more variable and contrasting than previously thought furthermore these data provide the opportunity to go deeper into the holocene and to present a new precise palaeohydrological framework for the late holocene 7 0e2 0 ka bp river functioning fluvial aquifer dynamics and types of sedimentation are closely related to the rainfall regime length and intensity monsoonal or mediterranean and to the landscape conditions in the upper watersheds the development of fluvial palaeosols in the hadramawt valleys often associated with high levels of the aquifers is clearly in phase with humid periods until the beginning of the first millennium bc 5 9e5 3 4 8e4 5 and 4 0e2 7 ka river behaviour also impacted neolithic and early bronze age settlement systems in this lowland area as phases of floodplain stability favour site location the hyperarid 4 2 ka event is associated with an unprecedented fluvial detrital phase with high energy discharges in the entire hadramawt basin

holocene forcing of the indian monsoon recorded in a stalagmite from southern oman a high resolution oxygen isotope record from a thorium uranium dated stalagmite from southern oman reflects variations in the amount of monsoon precipitation for the periods from 10 3 to 2 7 and 1 4 to 0 4 thousand years before the present ky b p between 10 3 and 8 ky b p decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in greenland ice cores indicating that early holocene monsoon intensity is largely controlled by glacial boundary conditions after approximately 8 ky b p monsoon precipitation decreases gradually in response to changing northern hemisphere summer solar insolation with decadal to multidecadal variations in monsoon precipitation being linked to solar activity

a 263 year record of summer temperature for northern quebec reconstructed from tree ring data and evidence of a major climatic shift in the early 1800 s abstract tree ring data are used to reconstruct 263 years of summer temperatures at a site located near the northern tree line in central western quebec a chronology comprising 20 ring density time series is used in conjunction with a chronology comprising 20 ring width time series in the regression analyses the increased precision of the temperature estimates obtained by using density data as an additional proxy time series places the reconstruction and its interpretation on a firmer basis than it is when only ring width data are used the results are considerably improved over the use of either tree ring parameter alone the temperature reconstruction reflects a major cooling event in the early nineteenth century comparisons with other temperature and proxy data series support the idea of a global cooling event with a persistence of the cool period of about three decades in high latitude north america and of much shorter duration in other regions of the world volcanic activity in the early 1800 s is suggested as partially responsible for the cooling event but is considered inadequate as cause for the extended period of low temperatures in the locale of this reconstruction

high oxidation magmatic evolution in the naruo porphyry cu deposit tibet china abstract the naruo porphyry cu deposit is the third largest deposit discovered in the duolong metallogenic district previous research has focused mainly on the geochemistry of the ore bearing granodiorite porphyry the metallogenesis remains poorly understood in the present work on the basis of outcrops and drilling core geological mapping phases of early mineralization diorite two inter mineralization granodiorite porphyries and late mineralization granodiorite porphyry have been distinguished furthermore the alteration zones were outlined and the vein sequence was identified the diorite and three porphyry phases were subjected to laser ablation inductively coupled plasma mass spectrometry la icp ms zircon u pb dating and in situ hf isotope analyses as well as bulk major element trace element and sr nd isotopic analyses molybdenite re os dating was also conducted the zircon u pb dating results show that the diorite and porphyry intrusions were emplaced at about 120 ma and the molybdenite re os isochron age is 118 8 1 9 ma this indicates that the naruo porphyry cu deposit was formed during a continuous magmatic hydrothermal process all of the diorite and granodiorite porphyry samples showed arc magmatic characteristics moreover the moderate 87 sr 86 sr i ratios and low e nd t and e hf t values of the diorite and porphyry intrusions suggest the source region of the juvenile lower crust the lower 87 sr 86 sr i and 143 nd 144 nd i ratios and higher e nd t values and incompatible element concentrations than those in the granodiorite porphyry samples indicate a two stage magmatic generation process for the intrusions the early mineralization diorite has a high cu concentration implying that the source is enriched in cu however the slightly lower cu content of the late mineralization granodiorite porphyry samples might imply cu release from magmas and deposition within the metallogenic stage the multiple stages of intrusions and subsequent volcanism within the duolong metallogenic district together with high sr y features indicate persistent magmatism during the metallogenic epoch which is necessary for maintaining the activity of magmatic hydrothermal and mineralization processes thus the high cu content in the source region mantle derived melt upwelling and multiple stages of persistent magmatism were favorable for the formation of the naruo porphyry cu deposit the high fe 2 o 3 feo ratios of the diorite and granodiorite porphyry intrusions show very high oxidation features which is coincident with estimated magmatic oxidation state calculated by the zircon trace element compositions the high oxidation facilitates sulfur and chalcophile metals to be scavenged into the magmatic hydrothermal systems which is crucial for the metallogenesis of the naruo porphyry cu deposit

cessation of ice wedge development during the 20th century in spruce forests of eastern mackenzie delta northwest territories canada ice wedges are presently inactive in white spruce picea glauca forests of eastern mackenzie delta as shown by the absence of vein ice above ice wedges the maintenance of intact breaking cables and the abundance of rootlets propagating across ridge trough sequences at spruce forest sites near surface ground cooling rates and minimum near surface temperatures from the years 2003 2005 were above ice wedge cracking thresholds ground thermal conditions associated with cracking were recorded at a tundra peatland with active ice wedges annual mean permafrost temperatures at the spruce forest sites ranged from 1 8 to 2 9 c whereas at the tundra peatland the permafrost was colder than 6 c although winter air temperatures are similar throughout the study region deeper snow cover thicker active layers and warmer permafrost account for the more gradual seasonal cooling and warmer near surface temperatures recorded at the subarctic forest sites the subtle ridge to trough relief 12 35 cm of permafr

multiple hydroclimatic controls over recent sedimentation in proglacial mirror lake southern selwyn mountains northwest territories varves from mirror lake northwest territories 62 n 128 w reveal significant but changing climatic influences on discharge and sedimentation on a decadal scale during the late 20th century the complex hydroclimatic signal within the sediments indicates the difficulty in identifying a quantitative relationship between varve thickness and a single climatic variable regression of recent varve thickness with local meteorological data shows july temperature as the dominant control over sediment accumulation in contrast the dampening effects of increased snowfall on glacier ablation and resultant runoff reduce sediment delivery although the impact of snowfall does not appear to significantly weaken the relationship between summer temperature and varve formation periods when multiple climatic factors control sediment delivery are characterized by distinctive varves containing two prominent silt units thus the mirror lake hydrological system appears to shift between two general states the first state

coherent response of arabian sea upwelling and pollen transport to late quaternary monsoonal winds the indian summer monsoon causes large seasonal changes in the environments of both eastern africa and the arabian sea here we compare time series 140 kyr long of selected pollen types and foraminiferal upwelling faunas preserved in marine sediments to identify the frequencies of their variability and the coherence and phase of the terrestrial and marine responses to monsoonal circulation during interglacial intervals the pollen and upwelling records of the western arabian sea indicate stronger monsoons and are both coherent and in phase at periodicities near the precession of the earth s rotational axis 23 kyr we conclude that the strength of the monsoonal southwesterlies accounts for this high coherence of marine and terrestrial records during interglacial intervals low correlation during glacial phases indicates weaker monsoons and some decoupling of these two records these data indicate that two distinct modes of monsoon variability may exist an interglacial mode with strong monsoons and effective coupling of terrestrial and marine records and a glacial mode with both weaker monsoons and decreased linkage between arabian sea pollen and upwelling records

dendroclimatic reconstruction of summer temperatures in northwestern canada since a d 1638 based on age dependent modeling abstract ring widths from five picea glauca stands at the alpine treeline in northwestern canada are used to investigate climate growth responses and to develop a long reconstruction of summer temperatures response function and linear regression analyses indicate that the radial growth response of these trees to climate varies with age and site at most sites the period of significant positive response to growing season temperatures declines with tree age age dependent and standard age independent models are then used to develop two reconstructions of june july temperatures for northwestern canada extending back to a d 1638 calibration statistics were similar for both models but the standard model performed poorly during verification the reconstruction produced using age dependent modeling suggests june july temperatures were cooler than present throughout most of the past 350 years with the exception of the late 18th century particularly cool periods occurred at 1700 and in the mid 19th century in constast the standard model suggests that temperatures were similar to or warmer than present during the last 350 years the age dependent reconstruction compares favorably with other proxy climate records from northern north america age dependent dendroclimatic modeling can provide a sensitive record of recent climatic change that allows the inclusion of previously rejected sites into dendroclimatic analyses

a matter of divergence tracking recent warming at hemispheric scales using tree ring data 1 no current tree ring tr based reconstruction of extratropical northern hemisphere enh temperatures that extends into the 1990s captures the full range of late 20th century warming observed in the instrumental record over recent decades a divergence between cooler reconstructed and warmer instrumental large scale temperatures is observed we hypothesize that this problem is partly related to the fact that some of the constituent chronologies used for previous reconstructions show divergence against local temperatures in the recent period in this study we compiled tr data and published local regional reconstructions that show no divergence against local temperatures these data have not been included in other large scale temperature reconstructions utilizing this data set we developed a new completely independent reconstruction of enh annual temperatures 1750 2000 this record is not meant to replace existing reconstructions but allows some degree of independent validation of these earlier studies as well as demonstrating that tr data can better model recent warming at large scales when careful selection of constituent chronologies is made at the local scale although the new series tracks the increase in enh annual temperatures over the last few decades better than any existing reconstruction it still slightly under predicts values in the post 1988 period we finally discuss possible reasons why it is so difficult to model post mid 1980s warming provide some possible alternative approaches with regards to the instrumental target and detail several recommendations that should be followed in future large scale reconstruction attempts that may result in more robust temperature estimates

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