an outline of the plate tectonics of china china is principally a part of the eurasian plate but the margins of the indian and philippine sea plates are involved in the himalayas and in the coastal range of taiwan respectively within the eurasian plate the cathaysian paleoplate is separated from the angaraian paleoplate by the junggar hegen suture which contains paleozoic ophiolites and rare blueschists the three microplates of the cathaysian paleoplate consist of precambrian cratons and or phanerozoic accretionary fold belts these coalesced precambrian cratons record at least six stages of intense orogeny before cratonization the paleozoic to cenozoic accretionary fold belts of china can be correlated with similar events now found in west pacific andean and atlantic type active continental margins ophiolites occupying many of these tectonic zones provide evidence for the age and igneous history of oceanic crust formed during the paleozoic to cenozoic the presence of blueschist in some of these chinese sutures reveals evidence of large scale subduction and tectonic exhumation during consolidation of the eurasian plate cenozoic collision of the eurasian and indian plates produced deformation and uplift of the himalayas strongly influencing the tectonics of western china in contrast mesozoic tertiary evolution of eastern china is typical basin range geology similar to that of the western united states which included development of deep sedimentary basins along with calc alkaline plutonic and volcanic activity associated with crustal thinning and high heat flow the complicated tectonic evolution of china is greatly illuminated by the presence of ophiolites and blueschists in proterozoic to tertiary convergent boundaries these petrotectonic assemblages provide evidence of an extremely mobile history of plate movement in china

tropical storm induced near inertial internal waves during the cirene experiment energy fluxes and impact on vertical mixing 1 near inertial internal waves niw excited by storms and cyclones play an essential role in driving turbulent mixing in the thermocline and interior ocean storm induced mixing may be climatically relevant in regions like the thermocline ridge in the southwestern indian ocean where a shallow thermocline and strong high frequency wind activity enhance the impact of internal gravity wave induced mixing on sea surface temperature the cirene research cruise in early 2007 collected ship borne and mooring vertical profiles in this region under the effect of a developing tropical cyclone in this paper we characterize the niw field and the impact of these waves on turbulent mixing in the upper ocean niw packets were identified down to 1000 m the maximum depth of the measurements we estimated an niw vertical energy flux of up to 2 5 mw m 2 within the pycnocline which represents about 10 of the maximum local wind power input a non negligible fraction of the wind power input is hence potentially available for subsurface mixing the impact of mixing by internal waves on the upper ocean heat budget was estimated from a fine scale mixing parameterization during the first leg of the cruise characterized by little niw activity the average heating rate due to mixing was 0 06 c month 1 in the thermocline 23 24 kg m 3 isopycnals during the second leg characterized by strong niw energy in the thermocline and below this heating rate increased to 0 42 c month 1 indicative of increased shear instability along near inertial wave energy pathways

subsurface melting of a free floating antarctic iceberg abstract observations near a large tabular iceberg in the weddell sea in march and april 2009 show evidence that water from ice melting below the surface is dispersed in two distinct ways warm salty anomalies in t s diagrams suggest that water from the permanent thermocline is transported vertically as a result of turbulent entrainment of meltwater at the iceberg s base stepped profiles of temperature salinity and density in the seasonal thermocline are more characteristic of double diffusive processes that transfer meltwater horizontally away from the vertical ice face these processes contribute comparable amounts of meltwater o 0 1 m3 to the upper 200 m of a 1 m2 water column but only basal melting results in significant upwelling of water from below the winter water layer into the seasonal thermocline suggesting that these two processes may have different effects on vertical nutrient transport near an iceberg

the impact of salt fingering on the thermohaline circulation under mixed boundary conditions abstract the impact of salt fingers on the thermohaline circulation in a single hemisphere basin under mixed boundary conditions is investigated through scaling analysis and numerical experiments by assuming that the internal density ratio is determined by the surface horizontal density ratio the effect of a double diffusive parameterization on the vertical diffusivity of density k is estimated salt fingers reduce the magnitude of k with the extent of the reduction dependent on the magnitude of the density ratio the reduced diapycnal mixing leads to a diminished thermohaline circulation and modifies the stability criteria for the thermal haline mode transition under mixed boundary conditions quasi equilibrium numerical experiments with the gfdl modular ocean model produce results consistent with the scaling analysis in the reduction of the magnitude of the thermohaline circulation and the change in the critical freshwater forcing required for the existence of the stable thermal mode sensitivity

silurian and devonian paleomagnetic poles from north china and implications for gondwana abstract we have obtained paleomagnetic results from silurian and devonian rocks on the western margin of the north china block ncb ages which previously were thought to be unrepresented throughout north china high unblocking temperature components of magnetization isolated from both the silurian and devonian strata pass fold and reversal tests suggesting that they are primary remanence the corresponding paleopoles at 228 4 e 26 2 n silurian and 228 7 e 34 2 n devonian imply low paleolatitude positions of north china during the middle paleozoic probably adjacent to east gondwana

the contribution of salt fingers to vertical mixing in the north atlantic tracer release experiment abstract the north atlantic tracer release experiment natre was performed in an area moderately favorable to salt fingers however the classic finger signature of a distinct thermohaline staircase caused by upgradient density flux was absent this is likely because mixing by turbulence was sufficiently strong to disrupt the formation of permanent step and layer systems despite the lack of a staircase optical shadowgraph profiles revealed that small scale tilted laminae previously observed in a salt finger staircase were abundant at the natre site using microstructure observations the strength of salt finger mixing has been diagnosed using a nondimensional parameter related to the ratio of the diffusivities for heat and buoyancy the dissipation ratio by examining the dissipation ratio in a parameter space of density ratio r and richardson number ri the signal of salt fingers was discerned even under conditions where turbulent mixing also occurred while the model for turbulence descr

late paleozoic polar wander path for the tarim platform and its tectonic significance abstract stepwise thermal and a f demagnetizations have been carried out on 518 samples 47 sites from the sishichang section across the akesu area in the tarim basin the results lead to a discussion on some problems concerning the tectonic history of the tarim platform and adjacent blocks during the late paleozoic from the late carboniferous until the early permian the tarim platform collided with the kazakhstan block siberian platform and russian platform no large displacements have occurred between these blocks since the mesozoic however the permian pole position of the tarim platform obviously differs from that for the sino korea platform the difference in paleolatitude between the tarim and sino korea platforms in the permian was about 10 their orientations were also different the paleomagnetic result is in contrast to the geologically accepted idea that the two platforms in question occur as a whole in the late paleozoic

observations indicative of rain induced double diffusion in the ocean surface boundary layer double diffusion can result in the formation of thermohaline staircases typically observed in the ocean interior the observations presented here were acquired in the ocean surface boundary layer with the autonomous microstructure air sea interaction profiler an intense rain event rainfall rates of up to 35 mm h resulted in cooler fresher water up to 0 15 practical salinity unit psu over the upper 7 10 m overlaying warmer saltier water a situation potentially conducive to double diffusive mixing although not as crisp as interfaces in the interior ocean because of elevated background mixing a total of 303 thermohaline interfaces were detected within and at the base of the fresh layer with mean changes in temperature t and salinity s across interfaces of 20 10 3 c and 22 10 3 psu respectively these results call for new studies to disambiguate whether such interfaces are formed through double diffusive mixing or shear instabilities and understand any long term impacts on near surface stratification

the relationship between epithermal and porphyry hydrothermal systems within the tavua caldera fiji the shoshonitic tavua caldera in viti levu fiji defines the volcanic center of the tavua volcano the caldera occurs at the intersection of the northeast trending viti levu lineament and a northwest trending lineament locally manifested by the nasivi shear zone fault related subsidence which contributed to the evolution of the tavua caldera the central inner caldera and the structural preparation for mineralization occurred on these two regional fault systems and local concentric normal faults a continuum of mineralization and alteration styles is evident along the nasivi shear zone caused by a northwesterly evolution and migration of intrusion and hydrothermal activity porphyry style subeconomic copper gold mineralization and associated alteration occurred at depth in the nasivi shear zone at the center of the caldera approximately contemporaneously with the development of the inner caldera acid sulfate style epithermal alteration and minor gold mineralization immediately postdated and were superimposed on this porphyry style alteration farther northwest along the nasivi shear zone transitional ac d sulfate to adularia sericite epithermal alteration and minor gold mineralization occur variation in hydrothermal style is considered to reflect an increasing distance from magmatic source combined with an increasing proportion of meteoric water mixing with the hydrothermal fluid northwest of this system at the intersection of the nasivi shear zone and the viti levu lineament the 4 4 m oz adularia sericite style epithermal emperor gold mine occurs high level epithermal mineralization and alteration occur 4 km northeast of the emperor gold mine in an area which has a demonstrable present day hydraulic connection with the mine variations in fluid inclusion homogenization temperatures from the mine indicate that fluids entered the structurally prepared mine area via the nasivi shear zone emperor epithermal mineralization postdated magmatism by approximately 0 4 ma stable isotope data the presence of albitic alteration beneath mineralization and high salinities within the mine indicate that the emperor northern prospects hydrothermal system is related to an intrusion into the nasivi shear zone beneath the mine this is consistent with a demonstrable northwesterly migration of intrusions with time along the nasivi shear zone albitic phyllic and propylitic assemblages comprise the main porphyry style alteration types in the caldera center calculated temperatures of formation of chlorite in these assemblages indicate that these three alteration facies formed in the temperature range 270 degrees to 340 degrees c in good agreement with available fluid inclusion data and the stability ranges of the mineral assemblages kubler indices of illite likewise imply that these assemblages formed at relatively high temperature epithermal lode alteration mineralization at emperor is shown by fluid inclusion data to have formed around 200 degrees c kubler indices of illite confirm that this alteration formed at significantly lower temperatures than did porphyry alteration and that chlorites in the emperor mine have calculated temperatures of formation mostly below 200 degrees c high level epithermal alteration occurring northeast of emperor is inferred to have formed at even lower temperatures

strong indian ocean sea surface temperature signals associated with the madden julian oscillation in late 2007 and early 2008 a moored buoy was recently deployed at 8 degrees s 67 degrees e in the shallow thermocline region of the indian ocean known as seychelles chagos thermocline ridge sctr where the madden julian oscillation mjo is associated with strong sea surface temperature sst variability we use observations from this mooring to describe the oceanic signature of two mjos between november 2007 and february 2008 the four month average upper ocean heat balance was largely between heating by atmospheric forcing 2 0 0 3 degrees c month and a significant cooling by subsurface processes 2 2 0 8 degrees c month consistent with climatological ekman pumping in the region the two mjo events resulted in strong intraseasonal sst variations 1 5 to 2 degrees c in similar to 20 days in the sctr at the mooring site atmospheric fluxes dominated the upper ocean heat balance at the mjo timescale with the net surface heat flux into the ocean decreasing from an average 105 w m 2 during suppressed phases to 15 w m 2 during active phases of the mjo it is difficult to establish if mjo induced variations of subsurface processes also contributed to the cooling because of large uncertainty in this term lateral advection had no systematic fluctuations on mjo timescales but cannot be neglected at the mooring site

equilibrium mineral fluid calculations and their application to the solid solution between alunite and natroalunite in the el indio pascua belt of chile and argentina abstract the effects of temperature and bulk fluid k na on the alunite natroalunite solid solution have been determined at 200 bar and 100 300 c these are conditions typical of magmatic hydrothermal alteration and precious metal mineral deposition in high sulfidation environments which are characterized by the presence of alunite bearing alteration zones our model is based on published experimental parameters which indicate that both alunite and natroalunite are stable over this temperature range and that increased na substitution is favored at higher temperature our calculation results predict that at all temperatures fluids in equilibrium with natroalunite are significantly more na rich than those typical of modern volcanic hydrothermal environments the results also indicate that a large variation in fluid k na is required to precipitate both k and na rich alunite at high temperature assuming near equilibrium conditions at lower temperature much less variation in fluid composition can yield compositions near those of the end members controls on alunite natroalunite solid solution in natural systems were evaluated using electron microprobe data from high sulfidation gold deposits of the el indio pascua belt the results indicate that higher temperatures of deposition correlate with a greater range of na substitution in alunite elevated na content in alunite is also locally attributed to higher concentrations of na in the source fluid as a result of the leaching and alteration of andesitic host rocks dacitic to granitic host lithologies in other regions of the belt are correlative with more k rich alunite compositions the results from this study suggest that the use of alunite k na composition as a guide to mineral exploration should be treated with caution

immiscibility and continuous felsic melt fluid evolution within the rio blanco porphyry system chile evidence from inclusions in magmatic quartz the 5 2 to 3 9 ma late porphyries at rio blanco are spatially associated with hydrothermal tourmaline cemented breccias and a significant cu mo deposit magmatic inclusions in quartz from these rocks are used to better understand late stage magmatic processes particularly those involving melt melt and melt fluid immiscibility inclusions are represented by glass of common rhyolitic composition hereafter type 1 crystallized volatile rich felsic melt type 2 h2o and salt rich fluids and microphenocrysts coexistence of types 1 and 2 material within the same growth plane and within a single inclusion suggests that crystallizing rhyolitic magma separated into two silicate melts volatile poor and volatile rich the volatile rich silicate melt had a prolonged evolution extending below the solidus of volatile poor silicate melt with a progressive reduction of the silicate volatile ratio and ultimately to highly saline fluids the latter may have been the source of hydrothermal fluids that had the potential to transport metals the occurrence of immiscibility in the rio blanco rhyolites may be in some ways comparable to that in volatile rich pegmatites and strongly suggests that this process may be common in other se normal felsic magmas and important in the origin of mineralized porphyries

south east asia as a part of an ordovician gondwanaland a palaeobiogeographic test of a tectonic hypothesis the hypothesis that thailand and malaysia the sibumasu block were adjacent to australia in the early palaeozoic has been tested by an examination of the ordovician sequences and faunas of sibumasu and australia the relatively stenogeographic nautiloids of the two areas are remarkably similar and have a simpson index of 0 92 at the generic level two new genera of discosorids are restricted to the two blocks andgeorgina andmesaktoceras are found elsewhere only in tibet very close affinities are also evident between the gastropod polyplacophoran and rostroconch molluscs the ordovician brachiopod faunas are also very close including the genusspanodonta other very close similarities are found between the upper cambrian trilobite faunas and the ordovician conodonts and stromatoporoids no ordovician faunas younger than upper whiterockian were found during this study in either northern australia or sibumasu and a stratigraphic gap probably exists from the upper whiterockian to the upper ordovician over most of the two blocks these remarkably close faunal similarities are good evidence in favour of the hypothesis that sibumasu was adjacent to australia during the early palaeozoic similarly close faunal relationships between north china south east asia tibet and australia may also suggest close proximity of those blocks during the early palaeozoic

nature and ore formation of the erdaohezi pb zn deposit in the great xing an range ne china abstract the erguna metallogenic belt is a large erdaohezi epithermal polymetallic sulfide pb zn deposit in the northern great xing an range that is associated with andesitic porphyry mineralization mainly occurs at the edges of andesitic porphyry and adjacent jurassic quartz porphyry and volcanic strata hydrothermal alteration minerals mainly include quartz sericite adularia chlorite and calcite while ore minerals include pyrite galena and sphalerite with minor argentite chalcopyrite and tetrahedrite three hydrothermal mineralization stages are recognized three categories of fluid inclusions fis are distinguished in quartz fluorite and sphalerite veins liquid rich gas rich and a few h2o co2 inclusions the stage i fis include all three inclusion types and present high homogenization temperatures 197 233 and salinities 0 7 6 8 wt nacl eq the stage ii fis mainly comprise liquid rich inclusions with a few h2o co2 types and present higher homogenization temperatures 167 190 and slightly higher salinities 0 9 7 6 wt nacl eq than those of stage i stage iii only contains liquid rich inclusions and presents the lowest homogenization temperatures 120 157 and salinities 0 5 4 8 wt nacl eq the ore forming fluids have low temperatures and salinities in an h2o nacl co2 ch4 system the o h isotope data 2 2 to 5 0 and 160 0 to 152 5 respectively suggest that ore forming fluids gradually evolved from mantle primary water to meteoric water sulfur strontium and lead isotopes imply a mixed crustal and mantle source for the ore forming materials sulfide rb sr dating yields a well defined isochron age of 130 5 3 6 ma from the main mineralization stage which is similar to the zircon age of 134 9 0 9 ma for the andesitic porphyry related to mineralization we therefore proposed that erdaohezi is a low sulfidation epithermal pb zn polymetallic deposit and fluid immiscibility was the dominant mechanism of ore deposition mineralization occurred in an early cretaceous back arc extensional setting that was related to the subduction of the paleo pacific plate

origin and evolution of ore forming fluids and genesis of the duhuangling and jiusangou gold deposits in eastern yanbian northeast china the duhuangling and jiusangou gold deposits are located east of the yanbian area northeast china we present the results of systematic studies of the ore geology fluid inclusion fi features and isotopic geochemistry of the two gold deposits four mineralization stages have been defined in each gold deposit pyrite sericite quartz stage i quartz pyrite chalcopyrite arsenopyrite stage ii quartz native gold polymetallic sulfide stage iii and quartz calcite stage iv fis from the two gold deposits are similar and contain five types pure vapor phase v type vapor rich phase rv type liquid rich phase rl type daughter mineral bearing polyphase s type and pure liquid phase l type stage i fis homogenize at temperatures of 350 450 c yielding salinities of 5 40 48 67 wt fis from both stages ii and iii samples homogenize at 160 350 c yielding salinities of 5 71 39 75 wt fis in pyrite from the stage ii have 3he 4he ratios of 0 0069 0 0148 ra and 40ar 36ar ratios o

mesozoic cenozoic rift drift sequence of asian fragments from gondwanaland abstract the university of cambridge atlas map plotting computer program has been used to plot a reconstruction of the dispersal of continental blocks from eastern gondwanaland from the late jurassic 160 ma until the late miocene 10 ma the geological basis for the reconstruction rests on the concept of south tibet burma western thailand malaya and sumatra having been part of the eastern gondwana continent during the late palaeozoic and early mesozoic the reconstruction is also based on the view that these asian continental blocks were rifted from eastern gondwanaland in the late jurassic this rifting episode gave rise to the continental margin of central new guinea and northern australia it was associated with the sea floor spreading anomalies preserved in the floor of the northeastern indian ocean the model considers the indication of crustal uplift in the middle jurassic followed by profound subsidence in the cretaceous and palaeogene exposed in the islands of the outer banda arc from seram to timor and the similar jurassic cretaceous facies in eastern sulawesi implies that these areas formed part of this rifted northern margin of australia in the jurassic subsequent tectonic collision and associated major strike slip movements have deformed and disrupted these rock sequences during the cainozoic the date of the rifting that removed south tibet burma western thailand and malaya from gondwanaland is controversial the indications in favour of the rifting episode having occurred in the jurassic rather than in the permo triassic are stratigraphie structural observations on the northwestern australian shelf in the banda arc and in central new guinea the identification of the continental blocks removed by this rifting is based partly on stratigraphie correlation with the banda arc and new guinea and partly on indications that the age of collision of tibet burma western thailand and malaya with asia was a late cretaceous event and not triassic jurassic as is generally held there are very few reliable land based palaeomagnetic measurements to constrain the movements of these dispersed continental fragments from gondwanaland the computer generated map reconstructions put forward here fit the available indian ocean sea floor spreading data although they are not unique solutions much of the critical ocean floor data associated with the rifting and dispersal of these continental fragments has been destroyed in the tectonic collision processes that occurred at the asian continental margin

diagenesis and metallogenetic mechanisms of the tuanjiegou gold deposit from the lesser xing an range ne china zircon u pb geochronology and lu hf isotopic constraints abstract the tuanjiegou gold deposit is a large sized breccia hosted epithermal gold deposit in heilongjiang province eastern china and was discovered in the late 1950s the scale and unusual metallogenic setting of this gold deposit have made it the focus of many previous studies we systematically analyzed ore samples and volcanic and granitic rocks that are associated with the formation of the deposit by single zircon u pb dating obtaining three distinct concordant groups of u pb ages from dacitic pyroclastic rocks and lavas 119 3 3 3 n 2 113 2 1 1 n 13 and 109 1 1 4 ma n 8 four groups of concordant u pb ages from an ore bearing granite porphyry 112 5 2 2 n 2 107 0 1 2 n 4 103 0 0 70 n 10 and 99 9 1 1 ma n 4 two groups of concordant u pb ages from a pyrite rich quartz vein cemented brecciated and silicified granite porphyry 104 23 0 51 n 16 and 101 3 1 3 ma n 2 and five groups of concordant u pb ages from pyrite rich quartz vein cemented brecciated or chunky ore samples 139 4 to 144 3 n 2 127 4 n 1 113 8 2 1 n 8 101 3 3 4 n 3 and 91 3 ma n 1 combining the whole rock and lu hf isotope geochemistry with the geology of the mining area and these new u pb dates we have redefined the ore deposit related temporal history of the area with formation age of the magma associated with the ningyuancun stage volcanics being 119 1 4 ma and eruption of the volcanics at 113 1 1 ma the granodiorite porphyry and granite porphyry were emplaced at 107 0 1 2 ma and 103 102 ma respectively with ore deposit formation at 102 100 ma the magmato hydrothermal interaction that formed the deposit was closely related to late mesozoic crust mantle interaction with the early stage calc alkaline and high k calc alkaline magmatism in this area potentially being derived from interaction between asthenospheric mantle material and the underplated lower crust however the magmas associated with late stage intrusive calc alkaline and high k calc alkaline magmatism may have been generated during interaction between adakite like magmas derived from the subduction of an oceanic plate and lower crustal material here we suggest that the fluids that formed this deposit formed by interaction with both early and late stage mantle derived magmas and the lower crust with subsequent aggregation after significant igneous differentiation during ore formation the area was in a back arc initial passive rift and continental margin island arc tectonic environment associated with late mesozoic subduction of the pacific plate with metallogenesis occurring during a change in the tectonic environment between the latest early cretaceous and the late cretaceous

noble gases in mafic phenocrysts and xenoliths from new zealand we have determined the elemental and isotopic compositions of noble gases in young subduction related phenocrystic olivine and clinopyroxene samples from the taupo volcanic zone central north island new zealand and in behind arc intraplate phenocrystic and xenolithic olivine samples from the northland and auckland volcanic provinces northern north island new zealand helium isotopic ratios range from morb like 3he4he values of about 11 10 6 to lower values of about 6 10 6 consistent with previous measurements of helium isotopic ratios in subduction related samples 40ar36ar and 21ne22ne ratios range from atmosphere like compositions to maximum values of about 700 and 0 033 respectively in contrast most of the 21ne22neratios are generally indistinguishable from atmospheric values the variations in helium neon and argon isotopic ratios are interpreted as resulting from mixing of 1 a a primordial 3he rich component derived from the upper mantle and characterised by morb like 3he4he ratios of about 12 10 6 2 b a radiogenic 4he rich component derived from crustal materials and characterised by a 3he4he ratio of less than 2 10 7 and 3 c a helium poor atmosphere derived component which dominates the heavier noble gases by combining the helium and argon isotopic results it is possible to estimate the relative contribution of each of these three components to the total 40ar observed in each sample based on the present understanding of the origin and evolution of arc magmas a simple qualitative model of the mechanisms which introduce noble gases to the parent magmas of the samples is developed however it remains uncertain whether the atmospheric and crustal derived noble gas components are introduced to the mantle source regions of the magmas by subduction or alternatively are introduced by interactions between the ascending parent magmas and the overlying crust

vertical heat transfer in the arctic ocean the role of double diffusive mixing 1 microstructure profiles collected in the central amundsen basin are analyzed in order to quantify the role of double diffusive mixing for vertical heat transfer from the atlantic layer in the profiles a persistent but laterally incoherent thermohaline staircase structure is identified in the 200 260 m depth range the staircase contains homogeneous layers with average height of 1 3 m and thin high gradient interfaces with average temperature and salinity jumps of about 0 065 c and 0 015 respectively when inferred from a commonly used diffusive convection parameterization the average vertical heat flux within the staircase is 0 6 w m 2 this is one order of magnitude larger than the molecular diffusion alone and of the same order as the overall heat loss from the atlantic layer in the deep basins of the arctic ocean the parameterization is evaluated using observed turbulent heat fluxes and is found to overestimate diffusive convective fluxes with up to an order of magnitude especially for weak thermal forcing small temperature jumps in staircase staircases coexist with thermohaline intrusions in the vertical temperature and salinity profiles lomonosov ridge is identified as a potential region for formation of intrusions it is found that salt fingering is the dominant process during intrusion growth whereas diffusive convection is the dominant process in maintaining the intrusions at steady state in the deep basins

enhanced diapycnal mixing by salt fingers in the thermocline of the tropical atlantic diapycnal mixing plays a significant role in the ocean s circulation and uptake of heat and carbon dioxide but has not been quantified in salt finger driven thermohaline staircases we recently performed a tracer release experiment in the western tropical atlantic staircase at approximately 400 m depth the observed dispersion implies an effective diapycnal diffusivity for tracer and salt of 0 8 to 0 9 x 10 4 m2 s temperature microstructure data interpreted in terms of a vertical production dissipation balance yields a smaller effective diffusivity for heat of 0 45 0 2 x 10 4 m2 s consistent with salt fingers and well above the mixing ascribable to mechanical turbulence

ice tethered profiler observations of the double diffusive staircase in the canada basin thermocline vertical heat fluxes through the staircase are in the range 0 05 0 3 w m 2 only about one tenth of the estimated mean surface mixed layer heat flux to the sea ice it is thus concluded that the vertical transport of heat from the atlantic water in the central basin is unlikely to have a significant impact to the canada basin ocean surface heat budget icebreaker conductivity temperature depth data from the beaufort gyre freshwater experiment show that the staircase is absent at the basin periphery turbulent mixing that presumably disrupts the staircase might drive greater flux from the atlantic water at the basin boundaries and possibly dominate the regionally averaged heat flux

fluid inclusion noble gas and halogen evidence on the origin of cu porphyry mineralising fluids the naturally occurring noble gas isotopes 40ar 36ar 84kr and 129xe and halogens cl br i have been determined simultaneously in irradiated quartz vein samples by noble gas mass spectrometry quartz vein samples were collected from the potassic and propylitic alteration zones of six porphyry copper deposits pcd bingham canyon utah and silverbell ray mission pinto valley and globe miami in arizona in addition analyses of 3he 4he have been obtained from sulphide minerals hosted by the quartz veins at silverbell ray pinto valley and globe miami the majority of pcd fluids studied have br cl and i cl ratios that overlap those of fluids included in mantle diamond suggesting that the salinity had a juvenile origin the high i cl 121 10 6 mole m in samples from the propylitic zone of silverbell is attributed to the presence of sedimentary formation water 3he 4he ratios have r ra values in the range 0 3 to 1 72 and provide evidence for the involvement of a crustal component in addition to mantle volatiles 40ar 36ar ratios vary from meteoric values of 317 in the propylitic zone of bingham canyon and 323 in the skarn alteration of mission up to 3225 in the potassic zone of pinto valley fluids in both the potassic and propylitic alteration zones of every deposit are a mixture of a low salinity end member comprising meteoric water and air and a high salinity end member consisting of a mixed mantle and crustal fluid the 40ar cl ratio of fluid inclusions at pinto valley 10 4 m is similar to values obtained previously for mantle fluids the 40ar cl value is two orders of magnitude lower at bingham canyon where a depleted 36ar concentration 0 2 10 6 cm3 g below that of air saturated water asw and a range of highly fractionated noble gas compositions f84kr 13 and f129xe 160 indicate that boiling and pulsed fluid flow have occurred

raman microspectrometry of fluid inclusions abstract for many kinds of fluid inclusions the coupling of microthermometry and raman microspectrometry is still the only viable option to obtain compositions of single fluid inclusions a review is given on the basis of 16 years of experience and helped with about 120 references of the instrumentation analytical conditions and methodology of the application of raman microspectrometry to gaseous aqueous and hydrocarbon inclusions and their daughter minerals

new cambrian and ordovician paleomagnetic poles for the north china block and their paleogeographic implications multicomponent magnetization has been revealed in several cambrian and ordovician sedimentary units from localities in hebei and shandong provinces of the north china block ncb a well defined component with lower unblocking temperature is characterized by northerly declination and moderate to steep inclination with both polarities and postdates the late cretaceous folding the pole position derived from the overprinted directions is close to both the cretaceous pole for the ncb as well as the present north pole the overprint is not a simple thermal remanent magnetization but is probably a chemical remanent magnetization imposed at moderately elevated temperature during the major episode of regional deformation in the late mesozoic the higher unblocking temperature characteristic components pass reversal baked contact and fold tests and are internally consistent with rocks of different lithologies from widely distributed localities moreover the data exhibit an overall similarity in the magnetic polarity pattern in the stratigraphic sequence at sampled localities hence the high unblocking temperature characteristic component was probably acquired at or near the time of deposition the cambrian and ordovician paleopoles are somewhat different from the other coeval poles for the ncb which are based on much less data and do not pass as many reliability tests but all imply that the ncb was in the equatorial zone in the early paleozoic

geology mineralogy and fluid inclusion data of the furtei high sulfidation gold deposit sardinia italy the epithermal high sulfidation gold deposit at furtei sardinia italy contains at least 2 15 million metric tons mt at 2 82 g t au 725 000 t oxidized ore 1 375 000 t sulfide ore and 50 000 t mixed ore potential by products are silver and copper the geology of the area features an oligocene miocene volcano sedimentary sequence including andesite porphyry domes and associated block and ash flows pyroclastic flows fall and surge deposits and interlayered epiclastic and sedimentary sequences a phreatic and or phreatomagmatic diatreme breccia also crops out in the mineralized area the volcanic rocks belong to the calc alkaline sardinian magmatism their k ar ages in the area are 23 6 to 25 5 ma hydrothermal circulation affected most of the volcano sedimentary sequence over an area of about 5 km 2 during or immediately after volcanic activity early hydrothermal activity was responsible for the acid alteration typical of high sulfidation deposits with formation of four hypogene alteration types of decreasing intensity silicification advanced argillic alteration argillic alteration and propylitization these alteration styles show a rough spatial zonation silicification consists of massive and vuggy silica veins and bodies these are controlled by preferential structural directions n 140 degrees n 40 degrees and n s and by the contacts between the andesite porphyry domes and the diatreme breccias or between domes and epiclastic pyroclastic sequences the advanced argillic alteration borders vuggy and massive silica alteration zones and is characterized by the widespread presence of kaolinite dickite minerals this alteration pervasively affects the diatreme breccia and epiclastic pyroclastic units advanced argillic alteration grades outward into argillic alteration marked by the presence of montmorillonite which passes to a districtwide propylitic alteration halo the ore stage clearly postdates hydrothermal alteration as indicated by the occurrence of ore minerals in vuggy cavities and fractures in silica bodies the furtei mineralization comprises a surficial oxidized zone of supergene nature and a deeper primary sulfide zone and is largely hosted by the diatreme breccia the sulfide zone up to 300 m of vertical extension is characterized by a vertical zoning of the mineral assemblage at higher levels pyrite enargite luzonite gold are present whereas in the deep zone the above minerals are accompanied by tennantite and tellurides native gold with 0 7 7 8 wt ag occurs as blebs in enargite and luzonite fluid inclusions indicate that the fluid present at the time of alteration and epithermal mineralization had temperatures generally between 190 degrees and 280 degrees c and relatively low salinity max 5 5 wt nacl equiv the local coexistence of liquid and vapor rich inclusions suggests boiling conditions the inclusions were trapped at depths of between 60 and 680 m below the water table the occurrence of high salinity 31 5 44 8 wt nacl equiv high temperature 390 degrees 500 degrees c inclusions in cataclastic hydrothermal quartz suggests that a dense brine of probable magmatic derivation circulated in the furtei system this is consistent with geophysical data suggesting the presence of an intrusion at approximately a 1 to 1 5 km depth a few relatively high salinity around 22 wt nacl equiv low temperature 255 degrees 275 degrees c inclusions may be the result of episodic mixing of deep saline brines with low salinity meteoric fluids late stage barite contains low salinity

a review of shallow ore related granites textures volatiles and ore metals shallow texturally complex granites can be associated spatially introduction and temporally with hydrothermal alteration and mineralization granite related ore deposits include porphyry and skarn the formation of a granite related ore deposit represents the confluence type ores and other hydrothermal deposits that are of many chemical and physical geological factors including magma spatially and temporally associated with granitic sensu composition e g concentrations of ore metals chlorine and water lato rocks in this paper i emphasize characteristics magma oxidation state the relative timing of crystallization magma found in porphyry style cu mo au deposits and some ascent magmatic volatile phase exsolution and the depth of em related systems however my treatment here is not meant placement early magmatic crystallization of ore metal rich minerals to cover the full range of granitic rocks and mineralization coupled with late exsolution of the magmatic volatile phase is that make up the granite related ore systems the forpromoted by deeper emplacement levels and lower magmatic water mation of granite related ore deposits by orthomagmatic concentrations and leads to low eyciencies of removal of compatible hydrothermal processes is dependent upon many physical elements from melts into the magmatic volatile phase s water and chemical magmatic factors including but not limited concentrations in the melt and pressures of crystallization can be to the composition and evolution of the associated estimated from phase equilibria and textural relationships of horn magmas the rate of magma ascent the depth and blende in some felsic systems physical factors avect the dynamics geometry of magma emplacement and the local temof fluid magma melt and volatile phase movement which in turn perature and stress fields at the site of magma emavect the size of zones of alteration and mineralization granite placement detailed studies of the igneous rocks textures can record the partial history of some dynamic processes associated with ore deposits can therefore yield critical miarolitic cavities are good evidence for magmatic volatile phase information regarding the source of metals and ligands exsolution both miarolitic cavities and pegmatitic texture exhibit in the ore generative hydrothermal solutions that are evidence for external nucleation of crystals nucleation controlled operative in the formation of granite related ores in this phenomena expressed as variations in granite textures can result review i will present a series of narratives consistent in from a multiplicity of causes including undercooling of the melt my view with prevailing field and experimental data on textural elements such as pegmatite aplite skeletal crystals and the orthomagmatic hydrothermal theory for the genesis graphic textures can form as a result of undercooling interconnected of some granite related deposits volumes of the magmatic volatile phase allow for advection of some high level granites i e those that are emplaced hydrothermal ore fluids through the magma in shallow granitic at depths of 8 km or less represent the crystallized systems miarolitic cavities can be interconnected consistent with remains of magmas that were associated with subvolcanic this hypothesis ore generative hydrothermal systems therefore studies of shallow granites aimed at understanding magmatic evolution and volatile phase exsolution at shallow levels are necessary if we are to understand ore genesis and the deep inputs to present day geothermal systems as well as evaluate hazards associated with the volcanic

mantle crustal and atmospheric noble gases in ailaoshan gold deposits yunnan province china abstract helium and argon isotopic and elemental compositions of fluids released by crushing pyrite grains are reported from the ailaoshan gold province china the province is a series of gold deposits hosted on a 200 km segment of a major normal fault formed during eocene extension the deposits have been well characterised using conventional geochemical and microthermometric techniques the results of which are consistent with a predominantly high temperature magmatic fluid present in the ore minerals in contrast analyses of noble gases from three gold deposits demonstrate the palaeofluids were a mixture between a mantle derived magmatic fluid and two different low temperature fluids similar to modern groundwaters the specific isotopic and abundance characteristics of helium and argon allow unequivocal identification of both a mantle derived component and a surface derived component to these fluids the magmatic fluid dominates deposits from the northern end of the fault the second groundwater is present only in deposits in the south of the province by assuming fluid inclusion homogenisation temperatures in coexisting quartz are representative of fluid temperature 3he heat ratios can be estimated the 3he heat ratios vary systematically along the fault from 30 10 12 cm3 stp j 1 in the northern deposits to

resolving mantle and crustal contributions to ancient hydrothermal fluids hear isotopes in fluid inclusions from dae hwa wmo mineralisation south korea abstract helium and argon isotopes from fluid inclusions in individual colour zones b c d and e of a large scheelite crystal from the 88 ma dae hwa w mo deposit south korea trace the source and history of the ore fluids a gradual decrease of the fluid 3 he 4 he 3 he 36 ar and 40 ar 36 ar from the core to the edge of the scheelite reflects the progressive dilution of a magmatic fluid by meteoric water and is consistent with the previously observed decrease of 18oh2o and fluid inclusion homogenisation temperatures th shelton et al 1987 the covariation of fluid inclusion he ar isotope systematics with 18o and th defines a magmatic component with 3 he 4 he 1 2 10 6 3 he 36 ar 0 01 and 40 ar 36 ar 1000 anomalously high helium and argon isotope ratios in zone d fluids represents undiluted magmatic noble gases this may reflect local variation in the magmatic gas flux or gas loss due to boiling of the hydrothermal fluids prior to mixing with magmatic gas helium and argon isotope systematics constrain mantle and crustal components in the hydrothermal fluids 40 ar 3 he 4 5 104 are close to the mid ocean ridge basalt value implying that 40ar is mantle in origin radiogenic isotope ratios of the mantle endmember 40 ar 4 he 0 69 0 06 are similar to contemporary geothermal fluids the coincidence of mantle derived he and ar in the fluids is strong evidence that mantle melting during late cretaceous subduction triggered the crystal melting responsible for granite formation 40 ar 4 he of the meteoric fluid 0 007 0 001 is far lower than the crystal production ratio 0 2 implying an origin in crust below 200 c

double diffusive recipes part i large scale dynamics of thermohaline staircases abstractthree dimensional dynamics of thermohaline staircases are investigated using a series of basin scale staircase resolving numerical simulations the computational domain and forcing fields are chosen to reflect the size and structure of the north atlantic subtropical thermocline salt finger transport is parameterized using the flux gradient formulation based on a suite of recent direct numerical simulations analysis of the spontaneous generation of thermohaline staircases suggests that thermohaline layering is a product of the gamma instability associated with the variation of the flux ratio with the density ratio after their formation numerical staircases undergo a series of merging events which systematically increase the size of layers ultimately the system evolves into a steady equilibrium state with pronounced layers 20 50 m thick the size of the region occupied by thermohaline staircases is controlled by the competition between turbulent mixing and double diffusion assuming in acc