increased arctic sea ice volume after anomalously low melting in 2013 changes in arctic sea ice volume are difficult to quantify five years of satellite data reveal a reduction in autumn sea ice volume in 2010 2012 but a sharp increase in 2013 and 2014 suggesting that ice volume can recover quickly

a 1 78 ga large igneous province in the north china craton the xiong er volcanic province and the north china dyke swarm abstract the 1 78 ga xiong er volcanic province xvp and coeval north china giant mafic dyke swarm ncds are the most important magmatic events occurring after the amalgamation of the north china craton ncc the xvp consists of 3 7 km of extrusive volcanics and some feeder dykes sills located along the southern margin of the ncc and extending over an area 0 06 m km2 compositions vary from basalt to rhyolite but are predominantly intermediate in terms of silica content there are also minor sedimentary intercalations and pyroclastic units the sedimentary interlayers indicate an environment changing from continental facies to oceanic facies up section the xvp is characterized by fractional crystallization from an em i type mantle source and both continental arc andean type and rift environments have been proposed the ncds is widespread in the central ncc with an outcrop area 0 1 m km2 and are exposed at variable depths up to 20 km deepest in the north dyke compositions vary from basalt to andesite and dacite but are dominantly mafic and comprise two series of magmatism previous studies revealed that the ncds recorded assimilation and fractional crystallization of an em i type magma source with a minor dm contribution in the younger magmas both syn collisional and intra continental anorogenic environments have been proposed spatial and petrogenic correlations suggest a cogenetic relationship between the ncds and xvp and considered together they define a large igneous province lip of 0 1 m km2 in area and 0 1 m km3 in volume which is also notable for its continuous compositional range from mafic to felsic with no gap at intermediate compositions the petrology is explained by a common magma source that undergoes a silica poor and iron enriched fractionation trend at depth followed by a silica rich and iron poor fractionation trend in shallow level magma conduits dykes and surface lavas a mantle plume is favored as the cause of this 1 78 ga north china lip

modeling global sea ice with a thickness and enthalpy distribution model in generalized curvilinear coordinates abstract a parallel ocean and ice model poim in generalized orthogonal curvilinear coordinates has been developed for global climate studies the poim couples the parallel ocean program pop with a 12 category thickness and enthalpy distribution ted sea ice model although the poim aims at modeling the global ocean and sea ice system the focus of this study is on the presentation implementation and evaluation of the ted sea ice model in a generalized coordinate system the ted sea ice model is a dynamic thermodynamic model that also explicitly simulates sea ice ridging using a viscous plastic rheology the ted model is formulated such that all the metric terms in generalized curvilinear coordinates are retained following the pop s structure for parallel computation the ted model is designed to be run on a variety of computer architectures parallel serial or vector when run on a computer cluster with 10 parallel processors the parallel performance of the poim is close to that of a correspon

snow dunes a controlling factor of melt pond distribution on arctic sea ice 1 the location of snow dunes over the course of the ice growth season 2007 08 was mapped on level landfast first year sea ice near barrow alaska landfast ice formed in mid december and exhibited essentially homogeneous snow depths of 4 6 cm in mid january by early february distinct snow dunes were observed despite additional snowfall and wind redistribution throughout the season the location of the dunes was fixed by march and these locations were highly correlated with the distribution of meltwater ponds at the beginning of june our observations including ground based light detection and ranging system lidar measurements show that melt ponds initially form in the interstices between snow dunes and that the outline of the melt ponds is controlled by snow depth contours the resulting preferential surface ablation of ponded ice creates the surface topography that later determines the melt pond evolution

exsolution of magmatic volatile phases from cl enriched mineralizing granitic magmas and implications for ore metal transport abstract to understand cl dissolution in aluminosilicate liquids and the exsolution of cl rich magmatic volatile phases experiments were conducted to determine the solubility of nacl kcl and h2o in felsic liquids at 0 5 and 2 kbar the cl content of h2o poor nacl saturated and kcl saturated silicate liquids is low i e 1 3 wt to very low i e 0 2 wt and varies with changes in pressure and composition the cl concentration increases with the f concentration and the molar al na ca mg si ratio of the liquid and decreases with increasing activity of h2o in the system exsolution of a volatile phase depends on the partial pressures of all dissolved volatiles and low cl solubilities in nacl saturated and kcl saturated silicate liquids imply that exsolution of a cl bearing volatile phase will occur early in cl bearing granitic magmas i e prior to extensive melt crystallization and or at comparatively low water fugacities the solubility behavior of h2o and cl is very similar to that of co2 and h2o in felsic liquids small quantities of co2 are known to facilitate volatile phase exsolution holloway 1976 and in a similar manner volatile phases may exsolve early in cl enriched granite magmas whereas 5 to 6 wt dissolved h2o is necessary for volatile phase exsolution from a co2 free and cl free haplogranite liquid at 2 kbar and 800 c a cl rich brine will exsolve if the liquid contains only 1 wt h2o and 0 26 wt cl at the same conditions these new solubility data are interpreted in light of h2o f and cl concentrations in felsic liquids determined from silicate melt inclusions to constrain the exsolution of cl bearing magmatic volatile phases from mineralizing granitic magmas felsic magmas genetically associated with cu porphyry and mo porphyry mineralization contain sufficient h2o and cl to become saturated with respect to a hypersaline brine without strong pressure reduction boiling of the volatile phase i e exsolution of immiscible vapor and brine or strong volatile enrichment resulting from extensive crystal fractionation experiments were also conducted to investigate the solubility of mo in highly saline volatile phases coexisting with granitic liquids at 2 and 0 5 kbar the apparent partition coefficient for mo in the volatile phase s relative to silicate liquid d mo is defined as the computed concentration of mo in a volatile phase or phases the measured concentration of mo in granite glass d mo ranges from 8 to 80 as the nacl and kcl content of the volatile phase s increases from 15 to 90 wt because mo does not complex with cl in aqueous fluids it appears that mo solubility may be a strong function of the activity of na and k in alkali chloride rich volatile phases

prograde evolution and geothermal affinities of a major porphyry copper deposit the cerro colorado hypogene protore i region northern chile the middle eocene 51 8 0 6 ma hypogene protore underlying the supergene orebody of the cerro colorado porphyry cu mo deposit i region chile exhibits features not commonly documented in such hydrothermal systems early stage alteration of upper cretaceous plagioclase phyric andesite generated a sub horizontal blanket of pervasive extremely fine grained but texture preserving biotite 35 modal albite 40 magnetite 3 alteration 8 km 2 in area but lacking sulfide minerals at least seventy percent of the chalcopyrite pyrite stockwork mineralization was emplaced during the subsequent main stage alteration which comprises with decreasing depth quartz albite sericite chlorite clay smectite quartz sericite clay and andalusite diaspore pyrophyllite assemblages the deposit is apparently unique among documented central andean porphyry systems in the association of the highest grade copper mineralization with intermediate argillic alteration the subsequent transitional stage phyllic i e quartz sericite pyrite tourmaline alteration was associated with the emplacement of molybdenite rich breccia bodies the occurrence of undumortieri tized tourmaline veinlets cutting andalusite diaspore assemblages confirms that much of the advanced argillic alteration took place during the main stage early stage alteration was the product of nonboiling cool trapping temperature ca 380 c low salinity 8 wt nacl equiv fluids which added substantial k na mg fe 2 cl f and water to the host andesite the initial main stage fluids boiling at a paleodepth of ca 2 5 to 3 0 km were up to 160 c hotter 544 c and highly saline 52 wt nacl equiv as these fluids rose they cooled to 320 c were diluted to 37 wt nacl equiv deposited sulfides and leached k na ca mg fe 2 and cl from the host rocks yielding diverse broadly contemporaneous intermediate and advanced argillic alteration facies pressure estimates require that low density 0 3 g cm 3 and thus more acidic fluids were primarily responsible for the formation of the quartz sericite clay and shallow advanced argillic alteration subsequent phyllic alteration was similarly caused by boiling fluids which were hot 486 c and saline 47 wt at depth but cooler 334 c dilute 8 wt and vapor dominated at shallower levels even terminal stage pyrite veins formed at temperatures as high as 450 c albeit from low salinity 8 wt fluids following a major prograde thermal transition from the early to the main stage each sulfide depositing alteration episode at cerro colorado was generated by a pulse of high temperature fluid which cooled and diluted as it rose such changes in fluid characteristics temperature and alteration relationships are well documented in numerous geothermal fields where potassic alteration generally develops at ca 270 to 350 c and are likely to occur at an early stage in any hydrothermal system in which magmatic fluids exsolving at relatively high pressures ascend into the near surface environment the initial alteration at cerro colorado plausibly developed under conditions similar to those in nonexplosive geothermal systems in which hydrothermal fluids cool and disperse laterally at shallow depths extensive zones of biotite rich alteration generally barren and with a hornfelsic appearance occur in many andesite hosted porphyry copper deposits but few data are available elsewhere for mineralogical pressure temperature or metasomatic exchange relationships in such systems cerro colorado may however be representative of a subclass of porphyry copper deposits exhibiting unusually close analogies with geothermal systems

a first assessment of icebridge snow and ice thickness data over arctic sea ice we present a first assessment of airborne laser and radar altimeter data over snow covered sea ice gathered during the national aeronautics and space administration operation icebridge mission we describe a new technique designed to process radar echograms from the university of kansas snow radar to estimate snow depth we combine icebridge laser altimetry with radar derived snow depths to determine sea ice thickness results are validated through comparison with direct measurements of snow and ice thickness collected in situ at the danish greenarc 2009 sea ice camp located on fast ice north of greenland the icebridge instrument suite provides accurate measurements of snow and ice thickness particularly over level ice mean icebridge snow and ice thickness agree with in situ measurements to within 0 01 and 0 05 m respectively while modal snow and ice thickness estimates agree to within 0 02 and 0 10 m respectively icebridge snow depths were correlated with in situ measurements r 0 7 for an averaging length of 55 m the uncertainty associated with the derived icebridge sea ice thickness estimates is 0 40 m the results demonstrate the retrieval of both first year and multiyear ice thickness from icebridge data the airborne data were however compromised in heavily ridged ice where snow depth and hence ice thickness could not be measured techniques developed as part of this study will be used for routine processing of icebridge retrievals over arctic sea ice the limitations of the greenarc study are discussed and recommendations for future validation of airborne measurements via field activities are provided

sea ice circulation around the beaufort gyre the changing role of wind forcing and the sea ice state sea ice drift estimates from feature tracking of satellite passive microwave data are used to investigate seasonal trends and variability in the ice circulation around the beaufort gyre over the multi decadal period 1980 2013 our results suggest an amplified response of the beaufort gyre ice circulation to wind forcing especially during the late 2000s we find increasing anticyclonic ice drift across all seasons with the strongest trend in autumn associated with increased ice export out of the southern beaufort sea into the chukchi sea a flux gate analysis highlights consistency across a suite of drift products despite these seasonal anticyclonic ice drift trends a significant anticyclonic wind trend occurs in summer only driven in part by anomalously anticyclonic winds in 2007 across all seasons the ice drift curl is more anticyclonic than predicted from a linear relationship to the wind curl in the 2000s compared to the 1980s 1990s the strength of this anticyclonic ice drift curl amplification is strongest in autumn and appears to have increased since the 1980s up to 2010 in spring and summer the ice drift curl amplification occurs mainly between 2007 and 2010 these results suggest non linear ice interaction feedbacks e g a weaker more mobile sea ice pack enhanced atmospheric drag and or an increased role of the ocean the results also show a weakening of the anticyclonic wind and ice circulation since 2010 this article is protected by copyright all rights reserved

isotopic and element geochemical study of jinduicheng superlarge porphyry mo deposit in east qinling area this paper made a systemic study of isotopic and element geochemical characteristics of the ore bearing porphyry wall rocks ores pyrites in the ore and mineralized wall rocks in the jinduicheng mo deposit with a discussion on the origin of the ore forming materials the results indicate that the jinduicheng ore bearing porphyry is enriched with light rare earth elements lree and has obvious fractionation between lree and hree as well as indistinct or no negative eu anomalies eu 0 70 0 96 four pyrite samples are enriched with lree and have slightly negative eu and no ce eu 0 64 0 81 ce 0 88 1 03 anomalies in addition their chondrite normalized ree patterns are similar to those of jinduicheng porphyry and other types of ores all these characteristics indicate that the ore bearing hydrothermal fluids were derived from the porphyry lead sulfur carbon and hydrogen oxygen isotopic characteristics show that the ore forming materials of the jinduicheng deposit had the same source as the porphyry and they were all derived from the lower crust and the upper mantle immobility isocon diagrams were plotted based on the element transform formula during alteration the slope of the immobility isocon straight line represents the fundamental ratio of the rock mass before alteration to the rock mass after alteration these diagrams show that mo was consistently and significantly added to the country rocks from the jinduicheng porphyry all this has led the authors to reach the concludion that the ore forming materials were mainly derived from the porphyry instead of from the wall rocks the jinduicheng porphyry mo deposit was formed during the transforming stage of the qinling orogen from compression to extension in mesozoic cenozoic period influenced by the slab breaking off and underplating of basaltic magma from the boundary between the crust and the mantle the thickening lower crust at the south edge of the north china plate was subjected to partial melting and generated granitic magma with the magma migrating upward to the upper crust along the structural loci the ore forming fluid generated by magmatic condensation and fractionation filled the cracks and replaced the wall rocks and finally resulted in the formation of the jinduicheng mo deposit

advances in study of porphyry molybdenum deposits porphyry molybdenum deposits the most important molybdenum resources in the world are spatially temporally and genetically associated with porphyritic intrusions based on a summarization of researches on porphyry molybdenum deposits in western cordillera of north america and china this paper deals with such aspects of porphyry molybdenum deposits as their classification co genetic igneous rocks mineralization and alteration characteristics with the emphasis placed on transportation and deposition of molybdenum characteristics of ore forming fluids and sources of magmas and metals of these deposits

genesis and evolution of the leimengou porphyry mo deposit in west henan province east qinling dabie belt china constraints from hydrothermal alteration fluid inclusions and stable isotope data abstract the leimengou mo deposit is located in the east qinling dabie metallogenic mo belt located at the southern margin of the north china craton the deposit is hosted within the mesozoic leimengou granite porphyry pluton and at the contact between the granite and late archean gneisses in light of mineral assemblage and crosscutting relationships among veinlets the mineralization and alteration can be classified in four distinct stages 1 a mo barren pre mineralization stage of alteration characterized by massive k feldspar alteration of the granite porphyry 2 a k feldspar quartz vein stage that formed veinlets with minor molybdenite 3 a quartz sulfide veinlet stage which is the main stage of mineralization and 4 post mineralization quartz calcite vein stage stage 1 alteration is associated with fluid inclusions of low medium salinity 2 4 13 1 wt naclequiv that homogenized at medium to high temperatures 238 476 c stage 2 mineralization is associated with fluid inclusions that homogenized at 201 389 c and that have salinities of 2 0 13 6 wt naclequiv fluid inclusions that formed during stage 3 have homogenization temperatures of 205 370 c and corresponding salinities of 1 0 17 6 wt naclequiv to 31 4 40 6 wt naclequiv indicative of fluid immiscibility and mixing of hydrothermal fluids with meteoric water stage 4 h2o nacl fluids were trapped at lower temperatures 148 246 c and have salinities of 1 7 7 9 wt naclequiv stages 1 to 4 have calculated 18ofluid values of 3 6 4 3 2 7 2 8 0 6 2 3 and 3 2 to 3 8 respectively with dfluid values of 72 to 80 83 to 90 68 to 82 and 81 to 90 respectively these results are consistent with the fluid inclusion data outlined above and suggest that early fluids were exsolved from the granitic magma and underwent progressive mixing with meteoric water molybdenum was initially transported from the crystallizing magma in a hot alkaline and oxidized fluid while decreasing temperatures and ph water rock interaction and fluid immiscibility during fluid ascent resulted in its precipitation and deposition

the bingham canyon porphyry cu mo au deposit iii zoned copper gold ore deposition by magmatic vapor expansion fluid inclusion microthermometry and laser ablation icpms microanalysis are combined with geological and textural observations to reconstruct the spatial and temporal evolution of magmatic fluids that formed the subvolcanic porphyry cu au mo ore deposit at bingham canyon utah the bingham canyon orebody is exposed over 1 6 km vertically and has the shape of an inverted cup with distinct metal zoning fluid inclusions in the barren but highly veined and potassically altered deep center of the system have intermediate density 0 6 g cm 3 and a salinity of 7 wt percent nacl equiv they have subequal concentrations of na k fe and cu and contain minor co2 the intermediate density fluids were trapped as a single phase mostly at 500 c and 800 bars the au cu rich center near the top of the orebody contains low density vapor inclusions 0 2 g cm 3 coexisting with brine inclusions containing 45 wt percent nacl equiv the vertical transition of different inclusion types indicates phase separation of the single phase input fluid upon volume expansion associated with a pressure drop to 200 100 bars mass balance calculation based on all analyzed inclusion components indicates that the mass of the vapor phase exceeded that of the brine by 9 1 the vapor contained cu as its dominant cation 1 5 wt and contributed about 95 percent of the total amount of copper transported to the base of the orebody bornite chalcopyrite and native gold were precipitated in a narrow temperature interval from 430 to 350 c into secondary pore space created by local redissolution of vein quartz as a result of retrograde quartz solubility in the vapor dominated fluid system intermediate density fluid inclusions in the deepest parts of the peripheral copper ore zone have identical density and composition including similar gold contents as those in the deep center microthermometry and statistical estimation of phase proportions in the inclusions show that the vapor in the peripheral cu rich but au poor ore zone remained denser and the separating brine was less saline 36 wt nacl equiv compared to vapor and brine in the central au cu ore zone this indicates that the peripheral fluids experienced a lower degree of phase separation due to slightly higher fluid pressure at equivalent temperature compared to more strongly expanding fluids in the center of the system the systematic zoning of au cu within the ore shell despite compositionally similar input fluids is interpreted to have resulted from slightly different pressure temperature density evolution paths of magmatic fluids copper was selectively precipitated in the peripheral ore zone in contrast to complete coprecipitation of au and cu in the central upflow zone of the vapor plume the formation of particularly rich cu au ore in the center of the upward expanding fluid plume is consistent with published experimental data showing that the solubility of metals in hydrous vapor decreases sharply with falling pressure due to destabilization of the hydration shell around metal complexes in expanding vapor this interpretation supports the classic vapor plume model for porphyry copper ore formation but additionally emphasizes the role of sulfur bearing complexes as a key chemical control on magmatic hydrothermal metal transport and the deposition of cu and au in porphyry ores our interpretation of selective cu au precipitation as a function of vapor density can explain the more general observation that most gold rich porphyry copper deposits are formed in shallow sub volcanic environments whereas deeper seated porphyry cu mo deposits are generally gold poor

the relationship of mantle derived fluids to gold metallogenesis in the jiaodong peninsula evidence from d o c s isotope systematics abstract the largest gold district in china is the jiaodong peninsula where three types of gold deposits are recognized quartz vein fracture altered and breccia types the first two developed along a group of ne trending faults and are hosted by granitic intrusions dated at 160 to 150 ma biotite granite and 130 to 126 ma granodiorite and by metamorphic rocks of the precambrian crystalline basement the breccia type gold system is mainly located around the northern margin of the jiaolai cretaceous basin where mineralisation is controlled by both detachment fractures and ne trending faults this study is based on stable isotope determinations from ten gold deposits including linglong jiaojia sanshandao cangshang wang ershan dayigezhuang denggezhuang pengjiakuang fayunkuang and dazhuangzi as well as the linglong jurassic biotite granite guojialing cretaceous granodiorite and archean gneiss the stable isotope systematics reflect the style of the three types of gold deposits but also show that they belong to the same metallogenic system in which the hydrothermal fluids were derived from a mantle fluid reservoir and mixed with crustal fluids the ore forming age is later than both the jurassic biotite granite and cretaceous granodiotite but overlaps with the 121 to 114 ma ages of lamprophyre and diabase dykes the hydrothermal fluids that were responsible for both gold mineralisation and the retrograde alteration of the diabase and lamprophyre dykes are similar and represent a co 2 and potassium rich system this fluid system is interpreted to be the consequence of cretaceous lithospheric thinning asthenospheric upwelling and mantle degassing in eastern china

late mesozoic felsic magmatism and mo au pb zn mineralization in the southern margin of the north china craton a review abstract the widespread large scale mo au pb zn mineralization in the southern margin of the north china craton ncc is spatially and temporally associated with the voluminous late mesozoic granitic magmatism relationship between the granitic magmatism and ore mineralization has been extensively investigated in the last decade however controversy still exists regarding the magma source metallogeny and geodynamic settings this paper systematically reviews the major features of the mesozoic granitic magmatism and associated mo au pb zn mineralization in the southern margin of the north china craton including temporal and spatial variations of magmatic rocks composition of ore fluids sources of ore metals and metallogeny the granitic rocks were mainly formed in late mesozoic and emplaced in two stages the early stage 158 128 ma granites are of typical i type derived from remelting of ancient crust of the southern margin of the ncc with input of mantle material under lithospheric thinning tectonic regime the late stage 127 112 ma granites include a type and or highly fractionated i type granites which commonly contain more fractions of mantle materials as exhibited by more depleted isotopic signatures suggestive of an intracontinental extensional setting mo mineralization 155 130 ma related to the early stage granitic magmatism includes mainly of porphyry or porphyry skarn type with ore metals mainly derived from the mixed source of the mantle and crust whereas the late stage mo mineralization 127 116 ma is mainly of porphyry type with the ore metals from similar sources with more input of mantle materials pb zn deposits 144 130 ma associated with the early stage granitic magmatism are mainly of hydrothermal vein and skarn types whereas those 125 117 ma related to the late stage granites are of hydrothermal vein type the pb zn deposits are most likely distal products of the mo deposits together forming a metallogenic system au deposits are located in the xiaoqinling and xiong ershan areas and were formed during middle jurassic to early cretaceous 163 118 ma mostly from 132 to 120 ma the ores mainly occur in quartz veins and altered rocks and are hydrothermal magmatic in origin with au derived from a mixed source of crust and mantle

interdecadal changes in snow depth on arctic sea ice snow plays a key role in the growth and decay of arctic sea ice in winter it insulates sea ice from cold air temperatures slowing sea ice growth from spring to summer the albedo of snow determines how much insolation is absorbed by the sea ice and underlying ocean impacting ice melt processes knowledge of the contemporary snow depth distribution is essential for estimating sea ice thickness and volume and for understanding and modeling sea ice thermodynamics in the changing arctic this study assesses spring snow depth distribution on arctic sea ice using airborne radar observations from operation icebridge for 2009 2013 data were validated using coordinated in situ measurements taken in march 2012 during the bromine ozone and mercury experiment bromex field campaign we find a correlation of 0 59 and root mean square error of 5 8 cm between the airborne and in situ data using this relationship and icebridge snow thickness products we compared the recent results with data from the 1937 1954 1991 soviet drifting ice stations the comparison shows thinning of the snowpack from 35 1 9 4 to 22 2 1 9 cm in the western arctic and from 32 8 9 4 to 14 5 1 9 cm in the beaufort and chukchi seas these changes suggest a snow depth decline of 37 29 in the western arctic and 56 33 in the beaufort and chukchi seas thinning is negatively correlated with the delayed onset of sea ice freezeup during autumn

isotope geochemistry of the tieluping silver lead deposit henan china a case study of orogenic silver dominated deposits and related tectonic setting the tieluping silver deposit which is sited along ne trending faults within the high grade metamorphic basement of the xiong er terrane in the qinling orogenic belt is part of an important recently discovered mesozoic orogenic type ag pb belt ore formation includes three stages an early barren quartz pyrite stage e an intermediate polymetallic sulfide ore stage m and a late barren carbonate stage l carbon sulfur and lead isotope systematics indicate that the e stage fluids are deeply sourced the l stage fluids are shallow sourced meteoric water whereas the m stage fluids are a mix of deep sourced and shallow sourced fluids sulfur and lead isotope data show that the ore forming fluids must have originated from a source with elevated radiogenic lead and low 34s values that differs significantly from exposed geologic units in the xiong er terrane the lower crust and the mantle this supports the view that the carbonate shale chert sequences of the guandaokou and luanchuan groups south of the machaoying fault might be the favorable sources although little is known about their isotopic compositions a tectonic model that combines collisional orogeny metallogeny and hydrothermal fluid flow is proposed to explain the formation of the tieluping silver deposit during the mesozoic collision between the north china craton and south china block early mid triassic indosinian orogeny crustal slabs containing the carbonate shale chert sequences of the guandaokou and luanchuan groups locally rich in organic matter carbonaceous shale were thrust northwards beneath the xiong er terrane along the machaoying fault metamorphic devolatilisation of this underthrust slab probably provided the ore forming fluids to develop the ag pb ore belt which includes the tieluping silver deposit fluids and magmas were emplaced during extensional stages related to the jurassic cretaceous yanshanian orogeny

coastline responses to changing storm patterns 1 researchers and coastal managers are pondering how accelerated sea level rise and possibly intensified storms will affect shorelines these issues are most often investigated in a cross shore profile framework fostering the implicit assumption that coastline responses will be approximately uniform in the alongshore direction however experiments with a recently developed numerical model of coastline change on a large spatial domain suggest that the shoreline responses to climate change could be highly variable as storm and wave climates change large scale coastline shapes are likely to shift causing areas of greatly accelerated coastal erosion to alternate with areas of considerable shoreline accretion on complex shaped coastlines including cuspate cape and spit coastlines the alongshore variation in shoreline retreat rates could be an order of magnitude higher than the baseline retreat rate expected from sea level rise alone

an ultra wideband microwave radar for measuring snow thickness on sea ice and mapping near surface internal layers in polar firn sea ice is generally covered with snow which can vary in thickness from a few centimeters to 1 m snow cover acts as a thermal insulator modulating the heat exchange between the ocean and the atmosphere and it impacts sea ice growth rates and overall thickness a key indicator of climate change in polar regions snow depth is required to estimate sea ice thickness using freeboard measurements made with satellite altimeters the snow cover also acts as a mechanical load that depresses ice freeboard snow and ice above sea level freeboard depression can result in flooding of the snow ice interface and the formation of a thick slush layer particularly in the antarctic sea ice cover the center for remote sensing of ice sheets cresis has developed an ultra wideband microwave radar capable of operation on long endurance aircraft to characterize the thickness of snow over sea ice the low power 100 mw signal is swept from 2 to 8 ghz allowing the air snow and snow ice interfaces to be mapped with 5 cm range resolution in snow this is an improvement over the original system that worked from 2 to 6 5 ghz from 2009 to 2012 cresis successfully operated the radar on the nasa p 3b and dc 8 aircraft to collect data on snow covered sea ice in the arctic and antarctic for nasa operation icebridge the radar was found capable of snow depth retrievals ranging from 10 cm to 1 m we also demonstrated that this radar can be used to map near surface internal layers in polar firn with fine range resolution here we describe the instrument design characteristics and performance of the radar

geophysical and atmospheric controls on ku x and c band backscatter evolution from a saline snow cover on first year sea ice from late winter to pre early melt abstract this study investigates changes in ku x and c band microwave backscatter co polarized ratio and dual frequency ratios to changes in in situ measured snow thermophysical properties driven by surface radiation measurements during a 7 day transition from late winter to pre early melt on a highly saline snow cover on smooth first year ice a surface based ku x and c band microwave scatterometer system is used near coincident with in situ thermophysical snow measurements a frequency dependent penetration depth model is utilized to simulate diverse variations in ku x and c band penetration during fluctuating snow thermophysical and atmospheric conditions these results helped improve the interpretation of observed changes in ku x and c band backscatter overall dielectric loss associated with presence of brine throughout the snow volume is observed to be the governing factor affecting microwave penetration our results indicate significant differences in observed microwave backscatter and derived co polarized ratio and dual frequency ratios for all three frequencies during the transition from cold late winter phase to warm pre early melt onset phase c band demonstrates the greatest increase in backscatter and co pol ratios followed by x and ku bands the dual frequency ratio combinations clearly demonstrate their ability to separate sensitivities in frequencies by characterizing changes in backscatter during the 7 day transition our results indicate strong direct influence of downwelling shortwave and longwave radiation on snow brine volume and dielectric properties which drives changes to ku x and c band microwave backscatter and its associated co polarized ratio and dual frequency ratios our results demonstrate the ability of an observational multi frequency active microwave approach to illustrate frequency polarization and incidence angle dependent changes in microwave backscatter from snow covers on first year ice at varying atmospheric and snow thermophysical conditions

decline in arctic sea ice thickness from submarine and icesat records 1958 2008 1 the decline of sea ice thickness in the arctic ocean from icesat 2003 2008 is placed in the context of estimates from 42 years of submarine records 1958 2000 described by rothrock et al 1999 2008 while the earlier 1999 work provides a longer historical record of the regional changes the latter offers a more refined analysis over a sizable portion of the arctic ocean supported by a much stronger and richer data set within the data release area dra of declassified submarine sonar measurements covering 38 of the arctic ocean the overall mean winter thickness of 3 64 m in 1980 can be compared to a 1 89 m mean during the last winter of the icesat record an astonishing decrease of 1 75 m in thickness between 1975 and 2000 the steepest rate of decrease is 0 08 m yr in 1990 compared to a slightly higher winter summer rate of 0 10 0 20 m yr in the five year icesat record 2003 2008 prior to 1997 ice extent in the dra was 90 during the summer minimum this can be contrasted to the gradual decrease in the early 2000s followed by an abrupt drop to 55 during the record setting minimum in 2007 this combined analysis shows a long term trend of sea ice thinning over submarine and icesat records that span five decades

thermal conductivity and heat transfer through the snow on the ice of the beaufort sea 1 eighty nine point measurements of the thermal conductivity ks of the snow on the sea ice of the beaufort sea were made using a heated needle probe average values ranged from 0 078 w m 1 k 1 for new snow to 0 290 w m 1 k 1 for an ubiquitous wind slab ks increased with increasing density consistent with published equations but could also be reliably estimated from the metamorphic state of the snow using measured values of ks and snow stratigraphy the average bulk value for the full snowpack was 0 14 w m 1 k 1 in contrast ks inferred from ice growth and temperature gradients in the snow was 0 33 w m 1 k 1 the mismatch arises in part because the second estimate is based on measurements from an aggregate scale that includes enhanced heat flow due to two and three dimensional snow and ice geometry a finite element model suggests that the complex geometry produces areas of concentrated heat loss at the snow surface these hot spots however increase the apparent conductivity only by a factor of 1 4 not enough to fully explain the mismatch nonconductive heat transfer mechanisms like natural and forced air convection may also be operating in the snowpack though the ubiquitous presence of low permeability wind slabs potentially limits their effectiveness the relative contributions of effects due to snow and ice geometric and nonconductive processes within the snowpack remain uncertain

effect of frequent winter warming events storms and snow on sea ice growth a case from the atlantic sector of the arctic ocean during the n ice2015 campaign

recent changes in arctic sea ice melt onset freezeup and melt season length 1 in order to explore changes and trends in the timing of arctic sea ice melt onset and freezeup and therefore melt season length we developed a method that obtains this information directly from satellite passive microwave data creating a consistent data set from 1979 through present we furthermore distinguish between early melt the first day of the year when melt is detected and the first day of continuous melt a similar distinction is made for the freezeup using this method we analyze trends in melt onset and freezeup for 10 different arctic regions in all regions except for the sea of okhotsk which shows a very slight and statistically insignificant positive trend 0 4 d decade 1 trends in melt onset are negative i e toward earlier melt the trends range from 1 0 d decade 1 for the bering sea to 7 3 d decade 1 for the east greenland sea except for the sea of okhotsk all areas also show a trend toward later autumn freeze onset the chukchi beaufort seas and laptev east siberian seas observe the strongest trends with 7 d decade 1 for the entire arctic the melt season length has increased by about 20 days over the last 30 years largest trends of over 10 d decade 1 are seen for hudson bay the east greenland sea the laptev east siberian seas and the chukchi beaufort seas those trends are statistically significant at the 99 level

tectonic implications from re os dating of mesozoic molybdenum deposits in the east qinling dabie orogenic belt abstract the east qinling dabie molybdenum belt is part of a larger east west trending metallogenic belt in eastern china most of the molybdenum deposits occur as porphyry or porphyry skarn type but there are also some vein type deposits following systematic re os dating of molybdenite from 13 deposits and comparisons with two previously dated deposits we have recognized that the molybdenum mineralization in the east qinling dabie belt was developed during hydrothermal activity linked to magmatism and the emplacement of granitoid stocks three pulses of granitoid magmatism and mo mineralization are recognized corresponding to significant tectonic events in the east qinling dabie belt vein type deposits dated at 233 221 ma were formed in detachment fractures indicating localized extension within the collisional setting of the north china and yangtze cratons i type and transitional i and s type granites and related mineralization dated at 148 138 ma may have formed part of a continental magmatic arc with widespread magmatism and back arc extension caused by subduction of the izanagi or paleopacific plate beneath the eurasian continent in a wnw ese direction in the late jurassic early cretaceous both s type and transitional s and i type granite associated porphyry molybdenum deposits dated at 131 112 ma are part of an extensive mineralization event throughout east china that can be ascribed to regional large scale lithospheric thinning delamination and thermal erosion

early mesozoic mo mineralization in the qinling orogen an overview abstract as one of the most important mo provinces in the world the qinling orogen is host to mainly late mesozoic late jurassic early cretaceous porphyry mo systems recently additional early mesozoic mainly triassic plus minor early jurassic mo deposits have been identified which occur as fault controlled quartz veins or as carbonatite veins and as such they are fundamentally different from the commonly observed porphyry systems furthermore early mesozoic porphyry systems are also present but they are different from those of late mesozoic age thus early mesozoic mo systems not only offer a new and comprehensive view of the mo metallogenesis but also provide unique insight into the tectonic evolution of the qinling orogen taking into consideration the role of mineral deposits as ideal probes of the geodynamic evolution the known early mesozoic mo deposits in qinling can be classified into three types based on their geological and geochemical features porphyry carbonatite and orogenic systems porphyry mo systems including porphyry porphyry skarn and intrusion related veins are spatially and genetically associated with granitic porphyries they display typical porphyry type alterations and are formed by magmatic water carbonatites are considered as mantle derived igneous rocks and mo mineralization is associated with magmatic fluids orogenic mo systems occur as fault controlled quartz lodes and the ore forming fluids are medium high temperature co2 rich metamorphic fluids spatially early mesozoic porphyry mo systems are concentrated in the western and middle part of the qinling orogen whereas carbonatite veins and orogenic mo systems are located in the northeastern part temporally orogenic mo deposits were the earliest mainly between 220 and 250 ma followed by carbonatite veins mainly between 205 and 225 ma and porphyry mo systems mainly between 190 and 205 ma with some exceptions there is generally a trend of decreasing deposit ages toward the western part of the orogen detailed comparison reveals that the early mesozoic porphyry mo systems in the qinling orogen are different from the late mesozoic ones in terms of their economic importance spatial distribution ore causative intrusions hydrothermal alteration and the ore forming fluids to explain the above geological and geochemical features the triassic qinling is considered as an active continental margin caused by the northward subduction of the mian lue oceanic plate a transition from continental arc to back arc basin is suggested for the formation of triassic orogenic and carbonatite vein mo deposits whereas continental arc is host to the early mesozoic porphyry mo systems

evaluation of operation icebridge quick look snow depth estimates on sea ice we evaluate operation icebridge oib quick look ql snow depth on sea ice retrievals using in situ measurements taken over immobile first year ice fyi and multi year ice myi during march of 2014 good agreement was found over undeformed fyi 4 5 cm mean bias with reduced agreement over deformed fyi 6 6 cm mean bias over myi the mean bias was 5 7 cm but 54 of retrievals were discarded by the oib retrieval process as compared to only 10 over fyi footprint scale analysis revealed a root mean square error rmse of 6 2 cm over undeformed fyi with rmse of 10 5 cm and 17 5 cm in the more complex deformed fyi and myi environments correlation analysis was used to demonstrate contrasting retrieval uncertainty associated with spatial aggregation and ice surface roughness

fluid inclusion geochemistry and magmatic oxygen fugacity of the wenquan triassic molybdenum deposit in the western qinling orogen china abstract the wenquan mo deposit in gansu province china is one of the large porphyry mo deposits in the western qinling orogen that associated with the triassic continental collision between the north china block and south china block in this study detailed fluid inclusions fis analyses were performed on early stage quartz biotite k feldspar veins middle stage quartz polymetallic sulfide veins and late stage sulfide calcite veins four compositional types of fis are observed including pure co2 pc type co2 h2o c type h2o nacl w type and daughter mineral bearing polyphase s type with no halite daughter mineral the early stage quartz contains all the four types which are mainly homogenized between 285 c and 495 c with salinities ranging from 4 2 to 17 6 wt nacl eqv however in the middle stage pc type fis are not observed and s w and c types fis yield homogeneous temperatures th of 200 397 c and salinities of 2 4 13 1 wt nacl eqv late stage quartz contains only w type fis with th of 102 246 c and salinities of 1 2 10 1 wt nacl eqv results indicate that the fluid system evolved from an initial co2 rich magmatic hydrothermal fluid to a late co2 poor meteoric fluid in the early and middle stages it is possible that heterogeneous fis associations may have been trapped from a fluid immiscibility system the dramatically decreasing percentage of pc and c types fis in the ore stage indicates that co2 escaped which is possibly the result of earlier fluid immiscibility and phase separation in addition there are double peaks of th in this stage that are obviously lower than in the early stage showing that meteoric water flowed into and mixed with magmatic fluids thereby cooling the hydrothermal system these results suggest that metal precipitation resulted from fluid immiscibility co2 escape and inflow of meteoric water occurred in the middle stage the initial fluids of the wenquan deposit are characterized by relatively high temperature high salinity high fo2 and are co2 rich and nacl poor indicating that the wenquan deposit is a collisional type porphyry mo deposit the oxygen fugacity fo2 constrained by trace element compositions of zircons from the wenquan mo bearing porphyry is uneven with fmq 10 3 4 68 average of 4 32 which could result from the input of mafic magma and its inhomogeneous mixing with felsic magma such values are still much higher than those of the adjacent contemporaneous mo barren lujing baijiazhuang jiaochangba luchuba and zhongchuan granitic plutons which confirms the affinity between mo mineralization and the oxidized melt system and implies that the wenquan porphyry has relatively high fo2 characteristics for its tectonic location and epoch fluid inclusion initial mineralization depth 8 6 km magma fo2 and the zircon high u yb ratio of the wenquan mo deposit strongly suggest that mo mineralization was related to continental collision rather than oceanic crust subduction this study therefore proposes that the wenquan mo deposit was formed in a rapid crust uplifting setting caused by syn orogenic crustal thickening followed by post orogenic delamination of the lithospheric root during the late triassic

behavior of molybdenum in alkali silicate melts effects of excess sio2 and co2 abstract the effects of excess sio 2 and co 2 on the solubility of molybdenite in hydrous sodium disilicate melts were experimentally determined at 680 bars and 650 c the molybdenite solubility decreases with increasing sio 2 and co 2 under the experimental conditions the mos 2 content of the vapor saturated liquid decreases from 10 wt to 2 5 wt at sio 2 saturation in the presence of co 2 the solubility decreases to 4 6 wt mos 2 and becomes negligible at high p co2 these results are explained as deriving from the increased polymerization and hence decreased nbo si ratio of the melt with increasing sio 2 content and co 2 respectively sulfur dissolves principally as so 4 2 at the relatively high fo 2 of the experiments consequently the effect of sulfur is to lower the mo solubility by effectively decreasing the nbo si ratio of the melt sulfur saturation is therefore likely to be a limiting factor in the mo content of alkali silicate melts because of the chalcophile affinities of molybdenum

geology mineralization and fluid inclusion characteristics of the kensu w mo skarn and mo w cu au alkalic porphyry deposit tien shan kyrgyzstan the kensu deposit is located within a large metallogenic belt of w mo cu mo w au au and pb zn deposits along the late paleozoic active continental margin of tien shan the deposit is related to a small late carboniferous to early permian multiphase gabbro monzonite syenite granite pluton representing an alkaline potassic shoshonitic suite the igneous rocks are related to a deep rooted magmatic source but the pluton emplacement corresponds to shallow porphyry levels the deposit represents an example of a complex w rich alkalic magmatic hydrothermal system that complements the typical mineral deposits related to shoshonitic igneous suites it contains large bodies of w mo skarn of the oxidized type with abundant andradite garnet scapolite k na feldspars and fe oxides magnetite hematite the skarns are overprinted and surrounded by extensive halos of stockwork disseminated porphyry style mo w mo w cu pb zn and au w mineralization with propylitic chlorite amphibole epidote dominated and phyllic quartz sericite carbonate sulfide alteration assemblages consistent with the oxidized nature of the major mineral assemblages the deposit may represent the oxidized lithophile w mo cu au metallogenic type the hydrothermal stages alternate with magmatic phases and fluid inclusion data show the predominance of high temperature 550 450 c high pressure 1 200 700 bars and high salinity 60 45 wt nacl equiv magmatic hydrothermal fluid at prograde and early retrograde skarn stages with its possible direct exsolution from crystallizing magma the general trend of cooling and dilution was complicated by the influx of higher temperature and higher salinity fluid that correlates to the intrusion of quartz monzonite and the initial stages of its degassing and cooling this more advanced phase of magmatic differentiation likely corresponded to the enrichment of residual melt and related magmatic fluids in w and mo intense fluid boiling and phase separation triggered the deposition of molybdoscheelite in skarns that formed at t 625 500 c and p 510 300 bars and continued to a nonboiling fluid at t 420 370 c and p 1 150 750 bars mineralization in propylitic alteration zones was formed by highly to moderately saline nonboiling fluids late quartz sericite carbonate sulfide stage involved both high to low salinity aqueous fluids and co2 rich fluids under decreasing temperature from 400 c to 200 300 c and varying pressure from 1 200 bars to 750 600 bars

arctic sea ice conditions in spring 2009 2013 prior to melt 1 measurements from nasa icebridge airborne surveys in march april 2009 2013 over the western arctic ocean are presented in the context of previous observations to assess changes in the characteristics of the sea ice cover during the last decade taking into account spatial and temporal limitations in the available data following a precipitous drop in the amount and thickness of multiyear my ice in 2007 2008 the characteristics of the ice cover have remained largely consistent through march 2013 the central arctic continues to be dominated by my ice with mean and modal thicknesses of 3 2 m and 2 4 m respectively the southern beaufort and chukchi sea region is a complex mixture of 75 first year ice and 25 my ice icebridge observations indicate that the mean thickness in the beaufort and chukchi seas may have decreased from 2 5 m to as low as 1 6 m over the 5 year period

granite related paleoproterozoic serrinha gold deposit southern amazonia brazil hydrothermal alteration fluid inclusion and stable isotope constraints on genesis and evolution the serrinha gold deposit in the juruena teles pires gold province is spatially and genetically related to the hydrothermal alteration of the i type calc alkaline 1872 12 ma matupa monzogranite in the south central amazonian craton the mineralized areas are characterized by intense hydrothermal alteration of the monzogranite comprising incipient autometasomatism k silicate sodic mn chlorite phyllic carbonate and microcline alteration with partial overprinting of the early alteration by later stages a distal barren propylitic zone is interpreted from drill core the gold mineralization is disseminated in the most altered samples and genetically related to mn chlorite k silicate and phyllic hydrothermal alteration types hydrothermal magnetite and rutile are ubiquitous within pyrite the early serrinha gold mineralization stage is characterized by ag poor gold included in pyrite au ag 7 15 associated with pyrrhotite cubanite and galena the fluids interpreted to be associated with this early auriferous stage were found only in quartz from the mn chlorite alteration and are typically saline 45 57 wt nacl equiv and high temperature 375 and 480 c h2o nacl kcl fluids entrapped at pressures of at least 1 3 kbars the late stage gold mineralization which is coeval with the phyllic alteration occurs either as isolated gold grains or as fracture fillings and or inclusions within pyrite associated with tetradymite galena tsumoite bite hessite ag2te and aikinite pbcubis3 gold grains associated with this late stage are richer in ag au ag 2 5 data from chlorite geothermometry and aqueous carbonic and saline nacl kcl fluid inclusions associated with this second auriferous event indicate p t conditions of 1 5 to 2 4 kbars and 293 to 365 c the occurrence of lower temperature coeval aqueous aqueous carbonic and carbonic fluid inclusions with no postentrapment modification in the k silicate assemblage partially overprinted by phyllic alteration and in phyllic assemblages suggests that fluid immiscibility and or mixing with meteoric water occurred in the hydrothermal system h2o nacl cacl2 fluids contemporaneous with carbonate and late microcline alteration which postdated gold mineralization were entrapped at lower temperatures 172 200 c calculated 18o and d values are 8 2 and 37 per mil respectively for the early saline fluids in equilibrium with the mn chlorite assemblage and 1 7 to 4 7 and 20 to 15 per mil for the late fluids in equilibrium with the phyllic assemblage these data in conjunction with fluid inclusion results suggest that early fluids exsolved from granitic melts and later mixed with meteoric water gold is interpreted to have been initially transported from the crystallizing magma as chlorine complexes in a hot saline acidic and oxidized fluid decrease in temperature during fluid ascent immiscibility or ph increase is interpreted to have caused gold precipitation subsequent dilution of the saline fluid could have been responsible for the deposition of late gold in pyrite fractures based on field petrological mineralogical fluid inclusion and isotopic evidence we propose that serrinha is a typical proximal intrusion related gold deposit similar to porphyry style gold deposits

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

large scale surveys of snow depth on arctic sea ice from operation icebridge 1 we show the first results of a large scale survey of snow depth on arctic sea ice from nasa s operation icebridge snow radar system for the 2009 season and compare the data to climatological snow depth values established over the 1954 1991 time period for multiyear ice the mean radar derived snow depth is 33 1 cm and the corresponding mean climatological snow depth is 33 4 cm the small mean difference suggests consistency between contemporary estimates of snow depth with the historical climatology for the multiyear ice region of the arctic a 16 5 cm mean difference climatology minus radar is observed for first year ice areas suggesting that the increasingly seasonal sea ice cover of the arctic ocean has led to an overall loss of snow as the region has transitioned away from a dominantly multiyear ice cover

the thermal conductivity of seasonal snow twenty seven studies on the thermal conductivity of snow k eff have been published since 1886 combined they comprise 354 values of k eff and have been used to derive over 13 regression equation and predicting k eff vs density due to large and largely undocumented differences in measurement methods and accuracy sample temperature and snow type it is not possible to know what part of the variability in this data set is the result of snow microstructure we present a new data set containing 488 measurements for which the temperature type and measurement accuracy are known a quadratic equation where is in g cm 3 and k eff is in w m 1 k 1 can be fit to the new data r 2 0 79 a logarithmic expression can also be used the first regression is better when estimating values beyond the limits of the data the second when estimating values for low density snow within the data set snow types resulting from kinetic growth show density independent behavior rounded grain and wind blown snow show strong density dependence the new data set has a higher mean value of density but a lower mean value of thermal conductivity than the old set this shift is attributed to differences in snow types and sample temperatures in the sets using both data sets we show that there are well defined limits to the geometric configurations that natural seasonal snow can take

direct evolution of brine from a crystallizing silicic melt at the questa new mexico molybdenum deposit molybdenum mineralization in the southwest orebody at the questa deposit is associated with crystallization of aplite porphyry explosive brecciation and exsolution of magmatic hydrothermal fluids quartz k feldspar fluorophlogopite and molybdenite precipitated from exsolving aqueous fluids and cemented aplite porphyry and andesite wall rock clasts forming a magmatic hydrothermal breccia ore fluid inclusions in quartz in the breccia matrix trapped aqueous fluids that transported and precipitated molybdenum two fluid inclusion populations associated with molybdenite mineralization were identified the largest population commonly contains liquid vapor halite sylvite and one or more opaque daughter crystals these inclusions homogenize between 200 degrees and 500 degrees c and have a prominent mode at 360 degrees to 400 degrees c salinities vary from 31 to 57 wt percent nacl equiv low first ice melting temperatures suggest that additional fluid components possibly calcium or magnesium chlorides may be present approximately 80 percent of these inclusions homogenize by halite dissolution phase equilibria constraints require that these inclusions trapped fluids in the vapor absent field the remaining saline inclusions homogenize to liquid at temperatures above halite dissolution temperatures significantly the saline fluid did not coexist with a low density aqueous fluid a second population of inclusions contains fluids with salinities of 2 7 to 25 0 wt percent nacl equiv and homogenizes by vapor bubble disappearance vapor bubble expansion or critical behavior textural relationships and phase behavior during microthermometry indicate that these inclusions constitute a single population which formed as pressure and temperature fluctuated at near critical conditions pressure changes related to brecciation followed by crystallization and system resealing produced the observed fluids saline fluids were trapped as the system sealed following a major brecciation event these high salinity fluids were produced as the melt under pressure that increased from hydrostatic to lithostatic partitioned increasing amounts of chlorine into the exsolving aqueous fluid renewed fracturing and abrupt pressure decrease to hydrostatic conditions reduced the mass of chlorine partitioning to the exsolving fluid lower salinity fluids exsolved at near critical conditions and were trapped by inclusions that homogenize to liquid to vapor or by critical behavior the lack of cogenetic liquid and vapor rich fluid inclusions and phase equilibria constraints indicate that high salinity fluids or 57 wt nacl equiv were generated directly by the crystallizing magma and were not a product of aqueous fluid immiscibility

evidence for a genetic link between gold silver telluride and porphyry molybdenum mineralization at the golden sunlight deposit whitehall montana fluid inclusion and stable isotope studies the golden sunlight gold silver telluride deposit hosted primarily within the mineral hill breccia pipe is spatially related to a high level late cretaceous multiphase alkaline to subalkaline porphyry system latite porphyries quartz monzodiorite and lamprophyres base metal veins and manganese rhodochrosite mineralization occur up to 2 km from the mineral hill breccia pipe and form part of a regional mineral zonation pattern genetically related to a low grade porphyry molybdenum system alteration associated with this system consists of a proximal zone pervasive in style disseminations and veinlets that is core to the alkaline igneous rocks and a distal zone that is vein controlled proximal alteration is composed of an early barren zone of quartz hematite pyrite and barite as well as a pervasive zone composed of quartz sericite k feldspar base metal sulfides tellurides molybdenite and native gold distal alteration is characterized by the same mineralogy as the precious and base metal zone of the proximal zone except that it is vein controlled and does not contain molybdenite a base metal and rhodochrosite zone occurs farthest from the center of the porphyry system k feldspar alteration occurs as selvages to quartz molybdenite mineralization and as a pervasive replacement of clasts in the mineral hill breccia pipe early whereas quartz sericite alteration is dominantly associated with auriferous veins and the breccia pipe late molybdenite occurs in high veinlet density quartz veins at the margins and deeper portions of the breccia pipe in clasts in prebreccia pipe quartz pyrite k feldspar veinlets as fine grained disseminations in breccia fragments and as rims to fragments of xenolithic latite previously four periods of hypogene mineralization in the breccia pipe were identified stages i and iv constitute asymp 99 percent of the mineralization native gold calavertite and bi tellurides sulfosalts occur in stage i whereas au ag tellurides developed in stage iii minor amounts of base metals are present in stage ii whereas barite dolomite magnesite trace kaolinite and sericite develop in stage iv proterozoic rocks of the lahood formation and the informally named bull mountain group host the breccia pipe and contain strata bound sulfides sulfosalts up to 50 pyrite with minor to trace amounts of chalcopyrite tennantite pyrrhotite sphalerite galena and molybdenite fluid inclusion homogenization temperatures of primary and pseudosecondary aqueous liquid vapor inclusions constant liquid to vapor ratios in quartz pyrite molybdenite veins range from 131 8 degrees to 398 2 degrees c primary and pseudosecondary inclusions with highly variable liquid vapor ratios that coexist with rare three phase co 2 h 2 o and multiphase inclusions one or more solid phases in addition to liquid and vapor also occur in quartz pyrite k feldspar molybdenite veins and indicate periods of intermittent boiling homogenization temperatures for fluid inclusions in stage i auriferous pyrite veins range from 145 degrees to 345 degrees c with salinities of asymp 1 to 10 wt percent nacl equiv values of delta 34 s for sulfides in the mineral hill breccia pipe quartz pyrite k feldspar molybdenite veins proterozoic sedimentary rocks and distal base metal veins range from 12 2 to 3 1 per mil 8 1 to 0 8 per mil 0 7 to 6 1 per mil and 8 9 to 9 5 per mil respectively and suggest a mixed magmatic sedimentary sulfur source calculated delta 18 o values for water in equilibrium with late stage sericite at 170 degrees c vary from 0 7 to 2 8 per mil whereas delta d water values range from 67 to 8 per mil geologic paragenetic fluid inclusion and stable isotope studies are consistent with an early magmatic fluid associated with quartz pyrite k feldspar molybdenite veins that subsequently mixed with meteoric water during stages i to iv breccia pipe hosted and auriferous pyrite vein formation ore forming components e g au ag te cu bi mo and much of the s were most likely derived from the late cretaceous intrusive system with possible contributions from the proterozoic host rocks

comparison of freeboard retrieval and ice thickness calculation from als asiras and cryosat 2 in the norwegian arctic to field measurements made during the n ice2015 expedition we present freeboard measurements from airborne laser scanner als the airborne synthetic aperture and interferometric radar altimeter system asiras and cryosat 2 siral radar altimeter ice thickness measurements from both helicopter borne and ground based electromagnetic sounding and point measurements of ice properties this case study was carried out in april 2015 during the n ice2015 expedition in the area of the arctic ocean north of svalbard the region is represented by deep snow up to 1 12 m and a widespread presence of negative freeboards the main scattering surfaces from both cryosat 2 and asiras are shown to be closer to the snow freeboard obtained by als than to the ice freeboard measured in situ this case study documents the complexity of freeboard retrievals from radar altimetry we show that even under cold below 15 c conditions the radar freeboard can be close to the snow freeboard on a regional scale of tens of kilometers we derived a modal sea ice thickness for the study region from cryosat 2 of 3 9 m compared to measured total thickness 1 7 m resulting in an overestimation of sea ice thickness on the order of a factor 2 our results also highlight the importance of year to year regional scale information about the depth and density of the snowpack as this influences the sea ice freeboard the radar penetration and is a key component of the hydrostatic balance equations used to convert radar freeboard to sea ice thickness

mesozoic molybdenum deposits in the east qinling dabie orogenic belt characteristics and tectonic settings abstract the east qinling dabie orogenic belt accommodates the largest mo ore district in the world it contains 8 43 mt of proven mo metal reserves which accounts for 66 of the total proven chinese mo reserves the mo ore district includes 24 deposits and 12 occurrences with four major types of mo mineral systems i e porphyry porphyry skarn skarn and hydrothermal veins the latter can be further subdivided into quartz vein and carbonatite vein types although mo mineralization in the belt began in the paleoproterozoic 1680 24 to 2044 14 ma all economically significant deposits were formed during the mesozoic re os dating of molybdenite has shown that there are three episodes of mo mineralization i e late triassic 233 221 ma late jurassic to early cretaceous 148 138 ma and early to middle cretaceous 131 112 ma late triassic mo deposits developed as molybdenite quartz veins and carbonatite vein types stable isotope systematics c o s and high contents of re and sr indicate that the carbonatite mo veins are mantle derived porphyry and porphyry skarn mo mineral deposits were formed in the late jurassic to early cretaceous and early to middle cretaceous the late jurassic to early cretaceous granite porphyries that are associated with the mo deposits usually occupy less than 1 5 km2 at the surface and are situated in the east qinling area far west of china s continental margin on the other hand the early to middle cretaceous batholiths and granite porphyries with associated mo deposits are located in the dabieshan area and eastern part of the east qinling area the late jurassic to early creataceous granitoids and related mo deposits possibly formed in a back arc extensional setting of the eurasian continental margin which was probably triggered by the oblique subduction of the izanagi plate the early to middle cretaceous batholiths and granite porphyries are linked to the tectonic regime of lithospheric thinning asthenospheric upwelling and partial melting of the crust induced by a change in izanagi plate motion parallel to the continent margin in the east qinling dabie belt there are vein type pb zn ag deposits surrounding porphyry and or porphyry skarn mo w deposits forming well defined ore clusters the same spatial arrangement i e porphyry mo stockworks and outlying pb zn ag ore veins is also observed at the deposit scale thus mo porphyry stockworks and distal polymetallic veins belong to the same ore system and may reflect an outward temperature decrease from the highly fractionated granite plutons both porphyry stockworks and polymetallic veins can be used as vectors for further prospecting

the inferred formation of a subice platelet layer below the multiyear landfast sea ice in the wandel sea ne greenland induced by meltwater drainage

a review of the geological characteristics and geodynamic setting of the late early cretaceous molybdenum deposits in the east qinling dabie molybdenum belt east china abstract the east qinling dabie molybdenum belt which is located in the nearly east west trending qinling dabie orogen east china is the largest mo belt in the world and is characterized by extensive mesozoic mineralization although the late early cretaceous ca 120 100 ma is the latest stage of the mo mineralization in the east qinling dabie mo belt this period shows relatively intensive mo mineralization such as the world class shapinggou mo deposit all of the late early cretaceous mo deposits are closely related to granitic magmatism some of which are typical porphyry type deposits e g donggou tangjiaping shapinggou homogenization temperatures of fluid inclusions in the late early cretaceous mo deposits range from 115 to 550 c with salinities ranging from 0 02 to 62 1 wt nacl equivalent different amount of co2 have been recognized in the hydrothermal systems of these mo deposits indicating h2o nacl co2 systems the ore forming fluids in these mo deposits were magmatic water mixed with different amount of meteoric water except the donggou deposit the 34s values of sulfides from the late early cretaceous mo deposits have a narrow range of 0 4 6 3 suggesting a deep magmatic source for the sulfur the donggou mo deposit has slightly higher 34s values 7 5 9 4 reflecting that the ore sulfur was mainly derived from magma probably with some upper crust materials available isotopic data show that the ore associated magmas of the late early cretaceous mo deposits were mainly derived from crustal materials probably with some contribution of mantle or newly added crust the donggou tangjiaping and shapinggou mo deposits are genetically related to a type magmatism suggesting that they formed in an extensional setting the late early cretaceous mo deposits in the east qinling dabie mo belt formed in an intraplate extensional setting accompanied by the lithospheric thinning and asthenospheric upwelling

magmatic hydrothermal evolution of the donggou porphyry mo deposit at the southern margin of the north china craton evidence from chemistry of biotite abstract late mesozoic granitoids are widespread in the southern margin of the north china craton ncc occurring commonly as both small porphyritic stocks and large batholiths most of the mo deposits are closely associated with small porphyritic bodies in order to determine the relationship between mo mineralization and the granitoids a systematic geochemical study of biotite from the taishanmiao batholith and the mo mineralization associated donggou porphyry was conducted trace element features of biotites indicate a differentiation trend from rocks of the taishanmiao batholith to those of the donggou porphyry as revealed by systematically decreasing k rb ratios co ba v and ti and increasing cs li ta and tl the contents of mo also increase with the degree of magmatic differentiation the compositions of biotite follow a trend towards more magnesium rich compositions and mostly plot above the nno buffer the fe3 fe2 values of biotite gradually increase from the taishanmiao batholith to the donggou porphyry indicating the progressive increasing fo2 during magmatic differentiation the halogen fugacities of magmatic fluids calculated from biotite compositions show a trend of magmatic differentiation the earlier fluids associated with the taishanmiao batholith are relatively f poor with log fhf fhcl 0 the high degree of melt fractionation and progressive increasing of oxygen fugacity is beneficial to concentrate mo in the residual melt in addition later relatively f rich fluid may be beneficial to extract mo from the melt and thus favorable for mo mineralization

gold deposits in the xiaoqinling xiong ershan region qinling mountains central china the gold rich xiaoqinling xiong ershan region in eastern shaanxi and western henan provinces central china lies about 30 50 km inland of the southern margin of the north china craton more than 100 gold deposits and occurrences are concentrated in the xiaoqinling west xiaoshan middle and xiong ershan east areas late archean gneiss of the taihua group and middle proterozoic metavolcanic rocks of the xiong er group are the main host rocks for the deposits mesozoic granitoids ca 178 104 ma are present in most gold districts but deposits are typically hosted in the precambrian basement rocks hundreds of meters to as far as 10 km from the intrusions and related hornfels zones deposits in the xiaoqinling and xiaoshan areas are best classified as orogenic gold deposits with ores occurring in a number of distinct belts both in quartz veins and disseminated in altered metamorphic rocks alteration assemblages are dominated by quartz sericite pyrite and carbonate minerals the ore forming fluids were low salinity co2 rich and characterized by isotopically heavy 18o four deposits dongchuang wenyu yangzhaiyu and dahu in the xiaoqinling area each contain resources of about 1 moz au some of the gold deposits in the xiong ershan area represent more shallowly emplaced tellurium enriched orogenic systems which include resources of approximately 1 1 5 moz au at shanggong and beiling or tantou others are epithermal deposits e g qiyugou and dianfang that are hosted in volcanic breccia pipes isotopic dates for all gold deposits although often contradictory generally cluster between 172 99 ma and are coeval with emplacement of the post kinematic granitoids the gold deposits formed during a period of relaxation of far field compressional stresses clearly subsequent to the extensive paleozoic early mesozoic accretion of arc terranes and the yangtze craton onto the southern margin of the north china craton hydrothermal and magmatic events occurred locally where extension related precambrian basement uplifting took place along the craton margin fluids for the orogenic gold deposits in the xiaoqinling xiaoshan and xiong ershan areas may have been released from evolving magmas or resulted from prograde metamorphic reactions within the uplift zones alternatively for the epithermal gold deposits at shallower levels in the xiong ershan area gold transporting fluids were mainly exsolved from coeval magmas although meteoric water was also involved in these hydrothermal systems

in situ trace element and sulfur isotope of pyrite constrain ore genesis in the shapoling molybdenum deposit east qinling orogen china abstract the early cretaceous ca 128 ma shapoling vein type molybdenum mo mineralization associated with the huashan intrusion is a newly discovered deposit in the xiong ershan district east qinling china where pyrite is a ubiquitous mineral phase here we present results from an integrated study on the texture in situ trace element chemistry from laser ablation inductively coupled plasma mass spectrometry la icp ms and sulfur isotopic composition using secondary ion mass spectrometry sims with a view to understand the geochemical variation genesis of mo mineralization and ore forming process the distinct textural patterns as revealed by petrographic observations suggest three types of pyrites py1 is composed of coarse grained euhedral pyrite in the wall rock and early barren quartz vein at stage i py2 is represented by subhedral anhedral grains coexisting with molybdenite in quartz veins at stage ii and py3 forms irregular interstitial grains in the quartz k feldspar molybdenite dominated veins at stage iii the mo enrichment mainly occurred in py3 with co ni ratios 1 and 34s values mainly