crack azimuths on europa time sequence in the southern leading face the formation sequence of prominent ridges and other tectonic lineaments on the southern portion of the leading hemisphere of europa is determined from cross cutting relationships these selected features formed fairly recently relative to most of the surface older lineaments no longer retain clear evidence of cross cutting if we assume that this sequence represents the order of formation of cracks that underlie each lineament and that the orientation of each crack was determined by tidal stress whose azimuth varies monotonically counter clockwise with time the azimuth must have rotated more than 740 which would correspond to the change in tidal stress over two periods of nonsynchronous rotation relative to the direction of jupiter however that interpretation is not necessarily compelling because the observed orientations of cross cutting lineaments are not densely spaced over these cycles in fact the sequence would fit nearly as well into an arbitrary model with rotation in the opposite sense from that predicted by theory this tectonic record may have formed over many more rotational cycles such that typically only a few cracks form per cycle which would be consistent with evidence from considerations of cycloidal crack patterns sets of cracks that cluster near certain azimuth orientations appear to be parts of globe encircling lineament systems and may result from other effects perhaps polar wander that occurred rapidly relative to nonsynchronous rotation

sims zircon u pb geochronology and sr nd isotopes of ni cu bearing mafic ultramafic intrusions in eastern tianshan and beishan in correlation with flood basalts in tarim basin nw china constraints on a ca 280 ma mantle plume zircon sims u pb dating of the poshi hongshishan bijiashan and huangshan ni cu bearing and xiangshan ni cu ti fe bearing mafic ultramafic intrusions in the eastern tianshan and beishan rift yields a relatively restricted range of 278 6 ma to 284 0 ma the histogram of compiled age data of basalts in the tarim basin and mafic ultramafic intrusions in the eastern tianshan and beishan rift has a peak of 280 ma which probably represents the time of mantle plume activity the basalts have lower end t values in the range of 9 2 1 7 and mg of 2 wt indicating that they were generated directly from a peripheral zone of the mantle plume by low degree of melting the mafic ultramafic intrusions have higher end t of 1 3 11 2 and mg of 33 90 and lower tio2

hydrothermal evolution and ore genesis of the hongshi copper deposit in the east tianshan orogenic belt xinjiang nw china constraints from ore geology fluid inclusion geochemistry and h o s he ar isotopes abstract the hongshi lode type copper deposit is located in the kalatag region in the east tianshan xinjiang nw china the lode ore bodies are hosted in the late ordovician to early silurian daliugou formation and the cu mineralization is closely associated with andesite minor amounts of intrusive rocks such as the quartz porphyry are also exposed the country rocks have undergone extensive silicification chlorite alteration and sericite alteration the metallic minerals are pyrite and chalcopyrite with minor magnetite sphalerite and galena the gangue minerals are quartz sericite epidote calcite and chlorite the mineralized veins in the hongshi deposit can be divided into an early quartz pyrite vein stage the main quartz chalcopyrite pyrite sphalerite vein stage and a late quartz calcite chlorite vein stage fluid inclusion petrography shows that two phase liquid rich type i two phase vapor rich type ii and daughter bearing multiphase type iii fluid inclusions are present in the hydrothermal quartz sulfide veins in the hongshi deposit the fluid inclusions in the early stage minerals are mainly type i and type ii with minor type iii their homogenization temperatures and salinities range from 198 c to 315 c with a peak value of 253 c and from 1 40 to 8 81 wt nacl equiv respectively the coexistence of type ii and type iii inclusions and their similar homogenization temperatures but contrasting salinities suggest that fluid boiling processes occurred in the early stage the main stage minerals feature dominantly type i and type ii inclusions with homogenization temperatures and salinities of 168 c 280 c with a peak value of 209 c and 1 40 6 16 wt nacl equiv respectively the late stage minerals feature dominantly type i and type ii inclusions with homogenization temperatures and salinities of 109 c 179 c with a peak value of 157 c and 0 53 3 23 wt nacl equiv respectively the initial ore forming fluids of the hongshi deposit were therefore associated with an h2o nacl system with a near neutral ph low intermediate temperatures and low salinities the oxygen and hydrogen stable isotopic analyses of fis in quartz from the different ore forming stages show that the ore forming fluids were of volcanic origin with gradually increasing proportions of meteoric water during after mineralization the 34s values of chalcopyrite and pyrite from the main ore forming stage vary between 1 9 and 11 9 suggesting a volcanic source the 3he 4he ratios of fluid inclusions in the main stage pyrite mainly range from 0 12 to 1 40 ra and the 40ar 36ar values vary from 310 to 337 all these isotopic characteristics suggest that the ore fluids were likely derived from a combination of crustal and mantle components combining the integrated analysis of ore deposit geology the fluid evolutionary process and h o s he ar isotopes we suggest that the hongshi deposit should be classified as a volcanic subvolcanic hydrothermal copper deposit processes including local fluid unmixing decreasing temperature and fluid mixing may have been responsible for the hydrothermal alteration and cu precipitation

geochemistry and chronology of the early paleozoic diorites and granites in the huangtupo volcanogenic massive sulfide vms deposit eastern tianshan nw china implications for petrogenesis and geodynamic setting abstract the eastern tianshan orogen contains many late paleozoic porphyry cu and magmatic cu ni deposits recent studies demonstrate that several early paleozoic volcanogenic massive sulfide vms cu polymetallic and porphyry cu deposits were discovered in the northern part of eastern tianshan this study presents zircon u pb whole rock geochemical and sr nd isotopic data for granites and diorites from the huangtupo vms cu zn deposit northern part of the eastern tianshan our results can provide constraints on the genesis of intermediate and felsic intrusions as well as early paleozoic geodynamic setting of the northern part of eastern tianshan la icp ms zircon u pb analyses suggest that the granites and diorites were formed at 435 2 ma and 440 2 ma respectively geochemical characteristics suggest that the huangtupo granites and diorites are metaluminous rocks exhibiting typical subduction related features such as enrichment in lile and lree and depletion in hfse the diorites have moderate mg positive end t values 6 4 to 7 3 and young nd model ages indicative of a depleted mantle origin the granites exhibit mineral assemblages and geochemical characteristics of i type granites and they have positive end t values 6 7 to 10 2 and young nd model ages suggesting a juvenile crust origin the early paleozoic vms cu polymetallic and porphyry cu deposits in the northern part of eastern tianshan were genetically related the formation of the early paleozoic magmatic rocks as well as vms and porphyry cu deposits in the northern part of eastern tianshan was due to a southward subduction of the junggar oceanic plate

re os isotopic dating of molybdenite and pyrite in the baishan mo re deposit eastern tianshan nw china and its geological significance the baishan mo re deposit is located in the eastern section of the eastern tianshan orogenic belt nw china the deposit has a grade of 0 06 mo and a high content of rhenium of 1 4 g t rhenium and osmium isotopes in sulfide minerals from the baishan deposit are used to determine the age of mineralization rhenium concentrations in molybdenite samples are between 74 and 250 g g analysis of eight molybdenite samples yields an isochron age of 224 8 4 5 ma 2 pyrite samples have rhenium and osmium concentrations varying in the range 33 4 330 6 ng g and 0 08 0 81 ng g respectively isotope data on seven pyrite samples yield an isochron age of 225 12 ma 2 on the 187re 188os versus 187os 188os plot and an age of 233 14 ma 2 on the 187os versus 187re correlation diagram the ages of molybdenite and pyrite are consistent within the analytical errors combined with field observations the data indicate that mo re mineralization in the baishan deposit is produced by a magmatic hydrothermal event in an intracontinental extensional setting after late paleozoic orogeny the initial 187os 188os ratio of pyrite is 0 3 0 07 the 34s values of molybdenite vary from 0 5 to 3 6 both data indicate that mineralization is derived mainly from a mantle source

genesis of the huangtupo cu zn deposit eastern tianshan nw china constraints from geology rb sr and re os geochronology fluid inclusions and h o s pb isotopes abstract the huangtupo cu zn deposit is a newly discovered volcanogenic massive sulfide vms deposit in the kalatage cu polymetallic belt eastern tianshan nw china the deposit is hosted in early paleozoic volcano sedimentary rocks belonging to the lower member of the daliugou formation the orebodies are generally composed of an upper portion dominated by massive and banded ores and a lower part characterized by disseminated and veinlet ores two periods of mineralization are distinguishable the first one is related to the primary depositional sea floor volcanic hydrothermal activity and can be subdivided into the earlier exhalative sedimentary and later hydrothermal stages and the second one is the supergene period silicification pyritization and sericitization are the major wall rock alteration features and are closely related to mineralization we constrain the timing of mineralization in the huangtupo cu zn deposit through well defined sulfide pyrite chalcopyrite and sphalerite rb sr and pyrite re os isochron geochronology which yield ages of 432 2 3 1 and 425 38 ma respectively the re os age is compatible with the rb sr age suggesting that the deposit formed at ca 432 ma fluid inclusion studies show liquid rich two phase fluid inclusions as the common type in the ore bearing barite and quartz samples the ore forming fluids of barite from the exhalative sedimentary stage homogenize at 367 204 c and are of moderate salinity 14 36 9 21 wt nacl equiv those in quartz from the hydrothermal stage homogenize at 295 158 c and are of moderate to low salinity 6 74 2 74 wt nacl equiv the 18 o 6 9 12 1 and d values 109 to 73 of quartz hosted fluid inclusions and the calculated 18 o values of the ore forming fluid 3 21 to 1 99 suggest that the ore forming fluid formed through mixing of magmatic fluids and deeply circulating seawater the 34 s values of pyrite chalcopyrite and sphalerite exhibit a narrow range of 0 3 to 3 9 and those of two barite samples are 29 1 and 31 the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb ratios of sulfides pyrite chalcopyrite and sphalerite in the ores are 17 999 18 234 15 442 15 723 and 37 703 37 963 respectively these isotopic data suggest that the ore forming materials of the huangtupo cu zn deposit were derived from the volcanic host rocks and seawater sulfate

re os dating of pyrite from the tuolugou stratabound co au deposit eastern kunlun orogenic belt northwestern china abstract the tuolugou cobalt gold deposit in the northeastern margin of the qinghai tibetan plateau and central part of the eastern kunlun orogenic belt is the most recently discovered large cobalt gold discovery in qinghai province nw china exploration to date has identified a cobalt resource of greater than 20 000 t co with significant potential for expansion mineralization is largely confined to an e w striking volcano sedimentary sequence consisting of four lithological units that underwent extensive greenschist facies metamorphism and deformation all orebodies occur in stratiform or lenticular bodies within quartz albitite and sericite quartz schists and are concordant with lithological contacts the ores contain various amounts of pyrite the dominant ore mineral and display massive 80 pyrite banded 30 to 50 pyrite and disseminated re os dating shows that pyrite from different ore types has very low re and os concentrations in the range of 0 122 8 988 ppb and 0 003 0 054 ppb respectively isotope data on seven pyrite samples yield an isochron age of 429 29 ma 2 with an initial 187 os 188 os ratio of 0 2 mean square weighted deviates 7 9 on the 187 re 188 os 187 os 188 os plot which are close to the age of the host strata suggesting that primary cobalt mineralization in the tuolugou deposit may have formed from syngenetic exhalative processes in addition our results not only provide new evidence for plate rifting and mineralization taking place during the early silurian in the eastern kunlun orogenic belt but also suggest that the age of the regionally widespread nachitai group is early paleozoic

geological and geochemical characteristics and ore genesis of the keketale vms pb zn deposit southern altai metallogenic belt nw china article i nfo article history the keketale pb zn volcanogenic massive sulfide vms deposit occurs in the early devonian sequence of the kangbutiebao formation of the southern altai metallogenic belt samb northern xinjiang china all the orebodies are stratabound and hosted by a suite of meta sedimentary rocks intercalated with volcanic rocks major sulfide ores are pyrite sphalerite galena with minor pyrrhotite and rare chalcopyrite massive banded and disseminated ores are the three main types a typical vms type hydrothermal alteration zone is developed around the orebodies because of the overturned strata an intense chlorite pyrite rich crosscutting feeder zone is present immediately above the orebody a sericite zone envelopes the chlorite zone the meta volcanic rocks show decoupled characteristics between the high field strength elements ta zr and hf and large ion lithophile elements rb ba and th all samples plot in the volcanic arc field in ta vs yb discrimination diagrams the 34 s values of the stockwork zone are 1 0 to 4 5 and those of banded or massive ores range from 11 1 to 8 8 indicating that hydrothermal fluids may have had multiple sources and that bacterial sulfate reduction probably played an important role initial 87

recognition of late ordovician yudai porphyry cu au mo mineralization in the kalatag district eastern tianshan terrane nw china constraints from geology geochronology and petrology abstract although the eastern tianshan terrane in xinjiang nw china occupies a critical position in the central asian orogenic belt caob the early paleozoic tectonic evolution and mineralization history of this terrane remain ambiguous the yudai deposit is a newly discovered porphyry cu mo au deposit in the kalatag district of the dananhu island arc a key area containing early paleozoic rocks in the eastern tianshan this paper reports the geologic characteristics molybdenite re os ages zircon la icp ms u pb ages and geochemical and lu hf isotopic findings regarding the ore hosting porphyries in the yudai deposit the yudai ore hosting porphyries include an early diorite porphyry and a late quartz diorite porphyry alteration and mineralization have formed distinct zones around the quartz diorite porphyry with disseminated vein or veinlet cu mo au mineralization types mainly related to potassic alteration e g biotite magnetite and quartz typical of a porphyry cu deposit two molybdenite samples have an re os weighted mean age of 449 5 4 2 ma and exhibit high re contents 2624 to 4704 ppm indicating a mantle component the observed mineralization was probably related to the quartz diorite porphyry which yielded a mean zircon 206pb 238u age of 452 7 2 8 ma the rock samples from the two porphyries mainly plot in the diorite field show metaluminous to weak peraluminous features and belong to tholeiitic to calc alkaline series with k2o na2o ratios of 0 16 0 34 and mg values of 44 2 50 3 the samples also exhibit steep chondrite normalized rare earth element and relatively flat heavy rare earth element patterns indicating residual amphibole with positive eu anomalies eu eu 1 09 1 45 the samples are enriched in large ion lithophile elements relative to high field strength elements typical of arc magma in addition the rocks show adakitic features sr y 47 8 73 5 and present high ba th and low th nb ratios indicating slab fluids the zircons from the quartz diorite porphyry mainly yield high ehf t values 13 5 14 7 and very young two stage hf model ages tdm2 494 556 ma consistent with a depleted mantle origin combined with the arc tectonic setting we propose that the ore metals and ore hosting porphyries at yudai were predominately derived from the partial melting of the amphibole bearing and fluid rich kangguer ocean slab that was subducted northward beneath the dananhu island arc in the late ordovician therefore the evolutionary history of the dananhu island arc can be traced back to the late ordovician the yudai deposit is the first age constrained early paleozoic porphyry cu deposit in the eastern tianshan terrane and the early paleozoic was an important epoch of mineralization on this terrane

strike slip faults on europa global shear patterns driven by tidal stress abstract diurnal tides due to orbital eccentricity may drive strike slip motion on europa through a process of walking in which faults open and close out of phase with alternate right and left lateral shear mapping of five different regions on europa has revealed 121 strike slip faults including astypalaea linea a 800 km long fault with 42 km of right lateral offset at high southern latitudes near astypalaea linea all of the strike slip faults identified were right lateral europa appears to preferentially form right lateral faults in the southern hemisphere and left lateral faults in the northern hemisphere consistent with tidal walking at the five locations nonsynchronous rotation explains the azimuthal orientations and distribution of sense of shear which fit formation 60 to 90 west of their current positions alternatively stress due to differential rotation might also explain the observed shear patterns nearly all identified strike slip faults were associated with double ridges or bands but few were detected along ridgeless cracks even older ones thus cracks without ridges may not have penetrated to a decoupling layer consistent with the models for ridge formation that require cracks to penetrate to a liquid water ocean

new 40ar 39ar ages from the kalatag district in the eastern tianshan nw china constraints on the timing of cu mineralization and stratigraphy abstract the kalatag region in the eastern tianshan of nw china contains a number of economically important cu deposits among these the south meiling vms deposit is hosted in the late ordovician to early silurian dacitic tuff belonging to the daliugou formation the deposit is composed of two domains a concordant massive sulfide ore domain and a discordant vein type ore domain located in the footwall phyllic alteration zone here we report new 40 ar 39 ar ages on sericite from the phyllic alteration zone to better constrain the timing and genesis of mineralization the sericite displays markedly flat 40 ar 39 ar age spectra yielding a 40 ar 39 ar plateau age of 438 8 3 0 ma and an isochron age of 443 0 11 0 ma the 40 ar 39 ar age is in good agreement with the re os age reported earlier placing the timing of cu zn mineralization at 434 2 3 9 ma the age is also consistent with the field relationships that concordant massive sulfide orebody formed later than discordant vein type orebody another deposit at hongshi is hosted in basaltic andesites of the daliugou formation the orebodies cut the phyllic alteration zone indicating that the cu mineralization formed later than the phyllic alteration hydrothermal sericite from the phyllic alteration zone from this deposit yielded flat 40 ar 39 ar age spectra with 40 ar 39 ar plateau ages of 441 5 3 2 ma and 446 4 4 6 ma and isochron ages of 445 8 5 6 ma and 448 8 7 3 ma respectively this age is obviously older than the re os age which is also in conformity with the field relations that quartz sulfide veins cut the sericitization zone our 40 ar 39 ar ages offer precise constraints on early paleozoic cu mineralization in the eastern tianshan orogen these results indicate that the lower unit basaltic andesites of the daliugou formation formed earlier than 446 ma we thus consider that the daliugou formation formed during middle ordovician to early silurian we also propose several metallogenic events in the kalatag area including 1 an early vms cu zn and hydrothermal vein cu mineralization at 440 430 ma 2 porphyry cu and skarn fe mineralization at 390 380 ma and 3 a late cu au mineralization at ca 300 ma these three metallogenic events were coeval with the distinct magmatic pulses in the kalatag area

rotation of europa constraints from terminator and limb positions abstract tidal torques on europa due to jupiter would tend to drive europa s rotation to a rate slightly faster than synchronous unless synchroneity is maintained by a permanent asymmetry in europa s mass distribution moreover global fracture patterns on europa s surface as well as the complex fine scale tectonics revealed by galileo high resolution imagery may be evidence of stress due to nonsynchronous rotation a direct measurement of europa s rotation rate is made from the positions of surface features relative to the terminator in a galileo image and comparing the results with similar measurements of the positions of the same features relative to the terminator in a voyager 2 image taken 17 years earlier any nonsynchronous rotation must be slower than a few tenths of a degree in 17 years a complete rotation in 10 4 years relative to the direction of jupiter

re os dating of chalcopyrite from selected mineral deposits in the kalatag district in the eastern tianshan orogen china the kalatag cu zn au district contains a number of economically important cu deposits in eastern tianshan in xinjiang nw china due to the lack of precise mineralization ages the metallogenesis of this area has long been a matter of debate in this study chalcopyrite re os isotope methods are used to date the south meiling cu zn and hongshi cu deposits in the eastern part of kalatag area the south meiling cu zn deposit is hosted in volcanic sedimentary rocks of the late ordovician to early silurian daliugou formation the deposit consists of two parts a concordant massive sulfide ores and discordant vein type ores located in the footwall strata the principal ore minerals are pyrite chalcopyrite sphalerite minor tetrahedrite galena and pyrrhotite gangue minerals include quartz sericite and barite and minor chlorite plagioclase and carbonate minerals the hongshi cu deposit represents a hydrothermal vein system hosted in the mafic volcanic rocks of daliugou formation the orebodies are associated with quartz veins and controlled by subsidiary faults of the kalatag fault the ore forming process can be divided into the early middle and late stages and is characterized by quartz pyrite quartz chalcopyrite pyrite and quartz carbonate gypsum veins respectively re os analyses of chalcopyrite from the south meiling cu zn deposit yield an isochron age of 434 2 3 9 ma and initial 187os 188os ratio of 0 647 0 098 mswd 0 59 re os analyses of chalcopyrite from the hongshi cu deposit yield an isochron age of 431 8 2 7 ma and initial 187os 188os ratio of 0 165 0 075 mswd 0 77 since chalcopyrite is the primary copper mineral we interpret these isochron ages as the timing of cu mineralization based on field geology and petrographic evidence these results suggest that the re os ages presented here provide for the first time a direct constraint on an early paleozoic cu mineralization event of the eastern tianshan orogen the high initial 187os 188os ratios 0 647 0 098 ratio of 434 ma chalcopyrite from the south meiling deposit suggest that the metal was sourced from a two end member mixing of crust and mantle materials moreover we propose that the vms mineral system and hydrothermal vein system of the kalatag district were related to the south dipping subduction of the kalamaili oceanic plate during the late ordovician silurian

re os dating of low level highly radiogenic llhr sulfides the harnas gold deposit southwest sweden records continental scale tectonic events to obtain geologically meaningful and precise results on low level sulfides that are highly radiogenic blank corrections that account for the extreme difference in the os isotope composition of sample and blank are necessary and the resulting data is best plotted in 187 re 187 os space much like the approach used for molybdenites we here introduce the acronym llhr as a means of characterizing low level and highly radiogenic sulfides use of the traditional 187 re 188 os vs 187 os 188 os plot for llhr sulfides leads to large analytical uncertainties and highly correlated errors as 188 os is poorly determined and can generally be accounted for by the blank we now recognize that llhr sulfides such as those encountered at the harnas au deposit are a common occurrence and characteristic of many crustally affiliated ore systems the harnas au deposit in southwest sweden is located in the mjosa vanern mineral belt that transects from northwest to southeast the prominent geologic fabric of the sveconorwegian province including the mylonite zone the deposit is hosted in a strongly sheared and locally brecciated sulfide bearing quartz vein that crosscuts the foliation of orthogneisses belonging to the 1600 maa mal granitoid suite a 187 re 187 os isochron of 973 34 ma 2 for samples of pyrite and chalcopyrite from outcrops of the harnas alma and silvergruvan veins was obtained the harnas and subsidiary alma veins are au bearing whereas the silvergruvan 2 5 km to the southeast is not of the au bearing type four replicate analyses of an additional pyrite sample from the harnas vein yield a model age of 616 40 ma 95 c l in all samples re and 187 os concentrations are extremely low 0 35 to 7 1 and 0 005 to 0 074 ppb respectively and total common os 0 002 0 028 ppb is less than half the calculated radiogenic 187 os two samples of galena from the harnas vein yielded blank level re and os neither the 973 nor 616 ma time of mineralization is related to development of the mylonite zone at 920 ma or intrusion of the anorogenic bohus blomskog granites at 920 to 900 ma previously proposed sources for generating mjosa vanern mineral belt ore fluids an age of 973 ma for harnas alma silvergruvan suggests that sulfide deposition was associated with the waning stages 0 97 0 90 ga of the sveconorwegian grenvillian orogeny 1 15 0 90 ga postdating metamorphism and deformation that produced a regionally overthickened crust in the northern part of the sveconorwegian province the vein systems for these and numerous other small deposits in the mjosa vanern mineral belt could have resulted from regional exhumation in the late sveconorwegian with associated extension and the development of fracture systems at cooler middle to upper crustal levels in the southern part of the sveconorwegian province dominated by granulitic facies rocks no mineralization is present perhaps due only to increased exhumation and erosion that has exposed deeper crustal levels the late sveconorwegian age 973 ma records the main period of sulfide deposition for the harnas alma silvergruvan vein systems and indicates the robustness of the chronometer within tectonically complex terranes the late neoproterozoic age 616 ma records a later time of pyrite deposition probably associated with shearing and reopening of the harnas vein system because the au mineralization at harnas has been described as associated with shearing and occurring in fracture fillings in early pyrite we suggest that part or all of the au mineralization could have been introduced at 616 ma during reactivation of the vein system the 616 ma age for pyrite suggests a previously unrecognized and much younger mineralizing episode in the harnas region most likely reflecting continental scale extension and the late neoproterozoic opening of the iapetus ocean

sulfide re os and rb sr isotope dating of the kangdian iocg metallogenic province southwest china implications for regional metallogenesis the kangdian iron oxide copper gold iocg metallogenic province contains a number of economically important fe cu deposits in south china and northern vietnam due to the lack of precise mineralization ages the metallogenesis of this province has long been a matter of debate in this study molybdenite re os pyrite re os and rb sr isotope methods are used to date the yinachang and e touchang fe cu deposits in the central part of this province fine grained 0 1 mm molybdenite occurs as veinlets along bandings or fractures of magnetite ores and hydrothermal veins in the yinachang deposit molybdenite separates from magnetite ores have highly reproducible re os model ages of 1654 7 ma whereas those from hydrothermal veins have a much younger re os model age of 1451 6 ma euhedral pyrite grains occur locally along foliations of hematite ores and their proximal alteration assemblages in the e touchang deposit pyrite separates have an re os isochron age of 1487 110 ma and a single grain rb sr isochron age of 1453 28 ma both of which are compatible with the molybdenite re os age of hydrothermal veins from the yinachang deposit the molybdenite age of magnetite ores is in good agreement with zircon u pb ages of dolerite intrusions in the region and is considered to represent the timing of a major ore formation event at 1655 ma the younger re os and rb sr ages likely record a secondary hydrothermal overprint event at 1450 ma which has not been recognized before the mineralization potential and implications of this event need to be investigated in future studies our new isotopic data set hence demonstrates that the kangdian iocg deposits were likely formed at 1655 ma synchronous with the late paleoproterozoic intracontinental rifting event of the western yangtze block

timing of the formation of the changba lijiagou pb zn ore deposit gansu province china evidence from rb sr isotopic dating of sulfides abstract the giant changba lijiagou pb zn deposit is located in the north of the xihe chengxian abbreviated as xicheng ore cluster in gansu province china the orebodies in the deposit are mainly hosted in the marble dolomitic marble and biotite calcite quartz schist of the middle devonian anjiacha formation the genesis of the deposit has previously been argued to be of sedex type sedimentary exhalative type or of epigenetic hydrothermal type this paper reports results of rb sr isotopic dating on sphalerite and pyrite taken from the main orebody which yield an isochron age of 222 3 2 2 ma for eight sphalerite samples and 222 0 3 0 ma for the eight sphalerite samples combined with four pyrite samples indicating that the deposit formed during the late triassic the 87sr 86sri value of the sphalerite is 0 71370 0 00013 and that of the sphalerite and pyrite is 0 71371 0 00014 which are identical within experimental error suggesting that the ore metals are derived mainly from the continental crust by integrating the present results with the regional geology we propose that the changba lijiagou pb zn deposit is a product of regional hydrothermal mineralization processes forced by tectono magmatic activities which took place in the xicheng ore cluster during triassic orogenic processes

tidal reorientation and the fracturing of jupiter s moon europa the most striking characteristic of europa is the network of long linear albedo markings over the surface suggestive of global scale tectonic processes various explanations for the fractures have been proposed freezing and expansion of an early liquid water ocean1 planetary expansion due to dehydration of hydrated silicates2 localization by weak points in the crust generated by impacts3 and a combination of stresses due to planetary volume change and tidal distortions from orbital recession and orbital eccentricity4 5 calculations by yoder6 and greenberg and weidenschilling7 have shown that europa may rotate slightly more rapidly than the synchronous rate with a rotation period reorientation through 360 ranging from 20 to 103 yr if a liquid mantle is present or up to 1010 yr if the satellite is essentially solid7 helfen stein and parmentier8 modelled the stresses due to nonsynchronous rotation and concluded that this could explain the long fractures in part of the anti jovian hemisphere in this note i present a global map of lineaments with long arc lengths 20 or 550 km and compare the lineament orientations to the tensile stress trajectories due to tidal distortions changes in the lengths of three principal semiaxes and to nonsynchronous rotation longitudinal reorientation of two of the principal semiaxes an excellent orthogonal fit to the lineaments is achieved by the stresses due to nonsynchronous rotation with the axis radial to jupiter located 25 east of its present position this fit suggests that nonsynchronous rotation occurred at some time in europa s history

origin of the subduction related carboniferous intrusions associated with the yandong porphyry cu deposit in eastern tianshan nw china constraints from geology geochronology geochemistry and sr nd pb hf o isotopes the yandong porphyry cu deposit is located at the south margin of the dananhu tousuquan arc belt in eastern tianshan northwest china the cu ores comprise mainly disseminations and vein zones in the potassic and phyllic alteration zones and are predominantly hosted in diorite porphyry tonalite and quartz porphyry which intruded into carboniferous qi eshan group volcanic rocks the u pb ages indicate that four intrusions were emplaced between 338 6 2 9 and 326 1 2 6 ma five molybdenite samples yield re os model ages of 333 8 329 5 ma with a weighted average age of 331 8 2 1 ma fourteen pyrite samples have 206pb 204pb of 17 776 18 959 207pb 204pb of 15 410 15 534 and 208pb 204pb of 37 323 38 127 similar to the age corrected data of the yandong tonalite the tonalite shows adakite like characteristics e g high sr y ratios and low y contents and has positive end t and ehf t values and low zircon o isotopes 3 7 4 6 suggesting that the melt was derived from partial melting of a subducted oceanic slab followed by mantle peridotite interaction the diorite porphyry exhibits high mg and low sr y values slightly negative eu anomalies and positive ehf t values indicating a lithospheric mantle source the quartz porphyry with stronger negative eu anomalies less evolved ehf t values and low 18o values 4 7 5 5 was probably derived from mantle melts that experienced mixing with lower crustal materials melts or assimilation the new data suggest that the yandong intrusions formed in an arc setting as the tonalite is genetically linked to the cu mineralization subduction related slab melts must have played a key role in the formation of the yandong deposit

a modified genetic model for the huangshandong magmatic sulfide deposit in the central asian orogenic belt xinjiang western china the huangshandong ni cu deposit is the largest magmatic sulfide deposit discovered to date in the central asian orogenic belt in northern xinjiang western china the host intrusion is a 274 ma composite mafic ultramafic intrusion consisting of four separate intrusive units a large layered gabbroic sequence phase i a sheet like ultramafic body phase ii a dyke like gabbronorite body phase iii and an irregular ultramafic unit phase iv important sulfide mineralization is present in the last three intrusive units predominantly as disseminated and net textured sulfides pyrrhotite pentlandite and chalcopyrite the huangshandong mafic ultramafic intrusive rocks are characterized by arc like geochemical signatures such as low ca content in olivine and negative nb ta anomalies in whole rocks this together with a post subduction setting for the east tianshan in the permian suggests that the source mantle was modified previously by slab derived fluids in the carboniferous the mantle derived magma was ponded in a staging chamber in the lower part of the newly formed arc crust the first batch of magma to arrive at huangshandong was most fractionated and depleted in ni crystallizing fe rich and ni depleted olivine fo67 300 ppm ni the second batch of magma was more primitive crystallizing more primitive olivine fo81 84 the third batch of magma was also highly fractionated and depleted in ni crystallizing fe rich and ni depleted olivine fo72 600 ppm ni the final batch of magma became more primitive again crystallizing the most primitive olivine fo81 86 the occurrence of rounded sulfide inclusions in olivine primocrysts in the huangshandong ultramafic rocks indicates that immiscible sulfide liquid droplets were present during olivine crystallization the ni tenors of disseminated sulfide ores in the gabbronorite dyke vary mainly between 5 and 8 wt which are too high to have been produced by the parental magma of the dyke the ni cu and platinum group elements pge tenors of disseminated sulfide ores in the dyke phase iii and the ultramafic sheet phase ii are remarkably similar these observations together with the sequence of magma emplacement suggest that the sulfide liquids entrapped in the magma of the dyke formed at depth by a previous pulse of more primitive magma the estimated parental magma for the most primitive lherzolites in the huangshandong intrusion contains 10 wt mgo modeling shows that sulfide saturation in the parental magma of the huangshandong lherzolites could have resulted from fractional crystallization significant pge depletions relative to ni and cu in the disseminated sulfide ores of the huangshandong deposit may be due to sulfide retention in the source mantle

the genesis of the ores and granitic rocks at the hongshi au deposit in eastern tianshan china constraints from zircon u pb geochronology geochemistry and isotope systematics abstract the hongshi gold deposit is located in the southwestern margin of the kanggur huangshan ductile shear zone in eastern tianshan northwest china the gold ore bodies are predominantly hosted in the volcanogenic metasedimentary rocks of the lower carboniferous gandun formation and the carboniferous syenogranite and alkali feldspar granite the syenogranite and the alkali feldspar granite yield shrimp zircon u pb ages of 337 6 4 5 ma 2 mswd 1 3 and 334 0 3 7 ma 2 mswd 1 1 respectively indicating that the hongshi gold deposit is younger than 334 ma the granitoids belong to shoshonitic series and are relatively enriched in large ion lithophile elements rb k ba and pb and depleted in high field strength elements nb ta p and ti moreover these granitoids have high sio 2 al 2 o 3 and k 2 o contents low na 2 o mgo and tio 2 contents low nb ta ratios and slightly positive eu anomalies the e hf t values of the zircons from a syenogranite sample vary from 1 5 to 8 8 with an average of 5 6 the e hf t values of the zircons from an alkali feldspar granite sample vary from 5 0 and 10 1 with an average of 7 9 the 34 s values of 10 sulfide samples ranged from 11 5 to 4 2 with peaks in the range of 1 to 4 the above mentioned data suggest that the hongshi granitoids were derived from the melting of juvenile lower crust mixed with mantle components formed by the southward subduction of the paleo tianshan ocean plate beneath the aqishan yamansu island arc during the early carboniferous the hongshi gold deposit was formed by post collisional tectonism during the permian the granitoids most likely acted as impermeable barriers that prevented the leakage and runoff of ore bearing fluids thus the granitoids probably played an important role in controlling gold mineralization

in situ la mc icp ms u pb geochronology of igneous rocks in the ashele basin altay orogenic belt northwest china constraints on the timing of polymetallic copper mineralization abstract the altay orogenic belt of kazakhstan hosts a world class polymetallic copper volcanogenic massive sulfide vms metallogenic belt and the eastern margin of this belt extends into the southern chinese altay the ashele basin is located at the western end of the chinese altay and borders kazakhstan the basin hosts the large ashele copper zinc deposit which is a typical vms deposit and the largest deposit in the ashele basin and it hosts the subvolcanic hosted medium sized sarsuk polymetallic gold deposit both of these deposits are hosted in the ashele formation volcanic sequence the ashele copper zinc orebodies are stratabound orebodies located between basalt and tuff units and were formed during exhalative sediment deposition in comparison the sarsuk gold copper lead zinc orebodies are hosted by rhyolite porphyry that contains disseminated veinlet and veinlet stockwork ore that formed during intrusion of the rhyolite porphyry this study presents new zircon la mc icp ms u pb analyses of six volcanic and subvolcanic units and dikes associated with the sarsuk and ashele deposits the ore bearing rhyolite porphyry diabase dike basalt tuff and dacite porphyry samples analyzed during this study yielded ages of 382 0 382 8 381 7 388 2 387 0 and 379 4 ma respectively these data indicate that the ashele formation formed during the early mid devonian 375 402 ma whereas the ashele copper zinc deposit formed during the middle devonian 388 387 ma and the sarsuk polymetallic copper gold deposit formed during the latest middle devonian 382 ma inherited zircons within the six samples analyzed during this study yielded u pb ages of 618 2294 ma suggesting the presence of precambrian crystalline basement within the altay orogenic belt

europa initial galileo geological observations abstract images of europa from the galileo spacecraft show a surface with a complex history involving tectonic deformation impact cratering and possible emplacement of ice rich materials and perhaps liquids on the surface differences in impact crater distributions suggest that some areas have been resurfaced more recently than others europa could experience current cryovolcanic and tectonic activity global scale patterns of tectonic features suggest deformation resulting from non synchronous rotation of europa around jupiter some regions of the lithosphere have been fractured with icy plates separated and rotated into new positions the dimensions of these plates suggest that the depth to liquid or mobile ice was only a few kilometers at the time of disruption some surfaces have also been upwarped possibly by diapirs cryomagmatic intrusions or convective upwelling in some places this deformation has led to the development of chaotic terrain in which surface material has collapsed and or been eroded

geochemical characteristics of late carboniferous mineralization in the east tianshan a case study of the meiling deposit in the kalatage area abstract the meiling deposit in the kalatage area of the east tianshan which is the most recently identified late carboniferous hydrothermal vein deposit is located in a series of basic intermediate acidic volcanic pyroclastic rocks and contains ore bodies composed of single quartz sulfide veins and quartz sulfide vein groups in a stockwork en echelon arrangement with cu as the primary ore forming element and zn au and ag as secondary ore forming elements this study examines the geochemical characteristics of sub volcanic rocks and analyses fluid inclusions and stable isotopes h o and s to determine the metallogenic characteristics of the meiling deposit and discusses the pattern and geological significance of the mineralization in the kalatage area the quartz porphyry dacite porphyry and granite porphyry from the meiling deposit which are closely related to the mineralization are calc alkaline magmatic rocks that formed in an island arc setting most of the primary quartz fluid inclusions are liquid rich two phase fis with homogenization temperatures mainly of 154 251 c and salinities of 3 1 5 6 nacl equivalent and the sphalerite fluid inclusions are liquid rich two phase fis characterized by omogenization temperatures mainly of 156 263 c and salinities of 2 4 5 3 nacl equivalent which are low temperature and low salinity h and o isotope analysis show that in the polymetallic sulfide quartz stage the d values ranged from 79 3 to 54 0 the 18oh2o values ranged from 8 99 to 2 57 and the primary ore forming fluids were mixtures of a dominant meteoric water phase with minor amounts of magmatic fluid s isotope analysis shows that in the polymetallic sulfide quartz stage the 34s values of the main sulfides were distributed between 1 6 and 5 2 similar to the range of a homogenous sulfur source these results together with the s isotopic characteristics of the wall rocks from the meiling deposit demonstrate that the ore forming metals might have originated from the volcanic subvolcanic wall rocks these results show that the metallogenic characteristics of the meiling deposit are consistent with those of low temperature epithermal deposits and clearly demonstrate that the meiling deposit is a low temperature epithermal deposit that formed in an island arc setting the kalatage area provides a natural laboratory for studying the characteristics of geological mineralization during the arc basin system transformation process

metamorphosed pb zn ag ores of the keketale vms deposit nw china evidence from ore textures fluid inclusions geochronology and pyrite compositions abstract the keketale pb zn deposit is located in the devonian volcanic sedimentary maizi basin of the altay orogenic belt the mineralization at keketale is hosted in marbles and deformed volcanic tuffs and biotite garnet chlorite schists folded into a series of overturned synclines formed in multiple deformation events keketale contains economic amounts of pb 0 89 mt 1 51 wt zn 1 94 mt 3 16 wt and ag 650 t 40 g t detailed petrographic studies have defined two main generations of sulfide development the banded pyrite of the early stage a is commonly stratiform with minor galena sphalerite and chalcopyrite stage b is characterized by a large amount of polymetallic sulfides including pyrrhotite chalcopyrite sphalerite and galena with minor pyrite hosted in quartz veins three types of fluid inclusions fis including mixed carbonic aqueous c type pure carbonic pc type and aqueous w type have been recognized in quartz of stage b the c type fis have homogenization temperatures of 150 326 c and salinities of 0 2 16 6 wt nacl equivalent the pc type fis are dominated by co2 with minor ch4 and n2 and have initial ice melting temperatures of 57 5 to 56 7 c co2 homogenization temperatures of 11 14 1 c the w type primary fis were completely homogenized at temperatures of 124 359 c with salinities of 5 0 14 6 wt nacl equivalent such co2 rich fluid inclusions are consistent with those discovered in orogenic type deposits in the altay area and elsewhere muscovite separates from the polymetallic quartz veinlets of stage b yield a well defined 40ar 39ar isotopic plateau age of 259 33 2 56 ma with an isochron age of 259 62 2 65 ma this age is coeval with the closure of the paleo asia ocean and reactivation of the ertix fault system la icp ms analyses of two generations of pyrite indicate that the banded pyrite of stage a is relatively depleted in metallic elements and contains low contents of cu 0 39 ppm ag 0 20 ppm au below the detection limits pb 17 43 ppm and zn 14 38 ppm whereas the pyrite in quartz polymetallic sulfide veinlets of the stage b is relatively rich in metallic elements e g cu 2 56 ppm ag 3 07 ppm au 0 01 ppm pb 1047 ppm and zn 1136 ppm the trace amounts of cu pb zn au and ag are interpreted to have been initially locked in the lattice of type a pyrite and then liberated and precipitated as micromineral inclusions with type b pyrite during subsequent metamorphism and deformation two key factors are considered vital to the formation of economic ores of the keketale pb zn deposit namely the original devonian banded pyrite formed in a vms system and subsequent permian deformation and metamorphic processes that liberated cu pb zn au and ag from the lattice of type a pyrite to form galena sphalerite and chalcopyrite with minor muscovite in quartz veinlets the model provides a new interpretation of vms pb zn deposit occurring in back arc basin environments followed by collision and new insights into the unique regional fe cu pb zn au mineralization in the altay orogenic belt

laramide porphyry cu mo mineralization in northern mexico age constraints from re os geochronology in molybdenite twenty five new re os molybdenite ages for nine porphyry copper molybdenum deposits from northern mexico constrain the timing of mineralization and the longevity of porphyry systems in this region the ages of all the deposits are between 50 and 61 ma i e paleocene to early eocene and are associated with the laramide orogeny the oldest deposits are those from the cananea district and include the el alacran prospect 61 ma the maria deposit 60 ma the current cananea mine and la colorada breccia 59 ma the age of mineralization at cumobabi also is 59 ma and it was followed by the emplacement of deposits at suaqui verde and cuatro hermanos at about 57 to 56 ma the malpica prospect the southernmost porphyry copper prospect in western mexico was emplaced at 54 ma the la caridad deposit in nacozari and the el creston prospect both have re os molybdenite ages of 54 ma the tameapa prospect has a protracted hydrothermal mineralization history with multiple molybdenite mineralization events at 57 52 to 53 and 50 ma total re and 187 os concentrations for molybdenites range from 10 424 to 26 ppm and from 6 641 to 14 ppb respectively the deposit with the highest re and os concentrations is el alacran and the lowest concentrations are found in el creston the ages determined support the formation of porphyry copper deposits in northern mexico during the laramide orogeny in general the ages of porphyry copper deposits in the north american province range from 76 ma at bagdad arizona to 50 ma at tameapa sinaloa the ages also show that porphyry copper mineralization occurred continuously between these two dates with two main episodes at 60 ma cananea district mexico and sierrita and copper creek united states and at 54 ma la caridad el creston malpica in mexico and morenci united states

paleozoic accretionary and collisional tectonics of the eastern tianshan china implications for the continental growth of central asia this paper deals with the various tectonic units in the chinese eastern tianshan orogenic collage in the central asian orogenic belt and discusses the paleozoic geological history of the several periods of accretion and collision of archipelago systems lying between the tarim and southern angaran continental margins the late ordovician silurian to early devonian eastern tianshan archipelago was characterized by a the harlik dananhu subduction system with a s dipping polarity in the north b a southerly n dipping subduction system beneath the central tianshan arc in the middle and c the south tianshan ocean against tarim in the south during the devonian to early carboniferous n dipping subduction led to the harlik dananhu arc and the kanggurtag forearc basin accretionary complex in the early to mid carboniferous the magmatic front associated with the n dipping subduction beneath the dananhu harlik arc migrated southwards forming the yamansu arc constructed upon the kanggurtag accretionary forearc by the late carboniferous the dananhu harlik arc was attached northwards to the angaran margin resulting in lateral enlargement of the angaran continent in the latest carboniferous to early permian a multiple soft collision left wide suture zones in the south that include the ophiolite strewn aqikkuduk shaquanzi and kumishi accretion collision complexes which were stitched by early permian post collisional plutons by re defining and re interpreting the various tectonic terranes this paper presents a new improved model for the paleozoic evolution of this part of central asia

brines exposed to europa surface conditions 1 evidence for an ocean beneath the icy crust of europa includes reflectance spectra of disrupted surface regions indicating hydrated materials such as salts we simulated exposure of salty brine on the cold surface of europa by flash freezing sulfate and carbonate solutions this produces materials that have near infrared reflectance spectra distinct from those for crystalline minerals and more similar to those for europa s non ice regions these new spectroscopic data along with geophysical evidence geochemical models and meteorite studies strongly suggest that the non ice materials in the disrupted regions on europa s surface contain large amounts of disordered and heavily hydrated mgso4 and perhaps na2so4 that are endogenic in origin

europa s rate of rotation derived from the tectonic sequence in the astypalaea region abstract the most recent visible tectonic features in the astypalaea region in the southern hemisphere of europa are a set of cycloidal ridges three of which have cross cutting relationships that define a time sequence for their formation the longitudes at which each of these features formed which may be different from the current location due to rotation of europa are constrained by models of their formation reconciling the time sequence with the inferred longitudes of formation appears to require that

the tidal response of europa the tidal response of europa to a time varying potential is determined by solving the quasi static equilibrium equations for a body composed of several uniform maxwell viscoelastic layers models in which europa s surface ice extends all the way to the silicate mantle have weak tidal responses 1 m vertical deflection while models in which a liquid ocean underlies the ice have about 30 m peak vertical deflection the phase lag of the tidal response is very small 2 in the case of an ocean but may be large if there is no ocean and the ice has a viscosity around 1013 pa s for models with an ocean the product of the thickness and strength of the ice determines the tidal response making it difficult to determine the thickness of the ice by observing the tidal deflection of europa

metallogenesis and fluid evolution of the huangtupo cu zn deposit east tianshan xinjiang nw china constraints from ore geology fluid inclusion geochemistry h o s isotopes and u pb zircon re os chalcopyrite geochronology abstract the recently discovered huangtupo cu zn deposit is located in the dananhu tousuquan arc east tianshan nw china orebodies are hosted in volcano sedimentary rocks of the late ordovician early silurian daliugou formation the metallogenic physicochemistry ore forming fluids and metallogenesis of the deposit were investigated through orebody features fluid inclusion microthermometry laser raman spectroscopy and synchrotron radiation x ray fluorescence srxrf the results indicate that the deposit includes an upper sedimentary exhalative ore belt stage i as well as a lower vein stockwork ore belt in a hydrothermal fluid supply channel stage ii associated with silicification chloritization epidotization pyrophyllitization and beresitization alteration the re os isochron age of 429 5 10 ma obtained from primary chalcopyrite the la icp ms zircon u pb age of 423 3 2 9 ma for the host hangingwall tuff fluid inclusion fi microthermometry and geological characteristics were applied to constrain hydrothermal processes and ore genesis quartz and barite were collected from the massive sulfide and vein ores for fi study four types of fi were identified liquid rich l type vapor rich v type daughter mineral bearing s type and c type containing co2 h2o stage i barite fis yield homogenization temperatures of 232 364 c peak value 265 c with salinities of 4 85 10 94 wt nacl equiv whereas stage ii quartz fis yield temperatures of 270 400 c peak value 350 c with salinities of 2 41 13 72 wt nacl equiv peak value 6 28 wt laser raman spectroscopy analyses of fi gas compositions indicate that the fis contain mainly h2o with minor co2 and n2 initial ore forming fluids comprise a medium high temperature low salinity system of hot evolved seawater that was cooled and diluted by mixing with cold seawater fluid mixing and local boiling would have facilitated mineralization srxrf analyses indicate that the liquid phase is enriched in cu and zn the 34s values of sulfide indicate that the sulfur was derived from the magma host volcanic rocks oxygen and hydrogen isotopic data also imply that the ore forming fluids were mainly derived from deep circulation of seawater and mixed with minor magmatic fluids the estimated trapping pressures for vein stockwork mineralization fluids range from 20 to 60 bar average 40 bar at a depth of 0 4 km the ore fluids ascenting along faults and fracture networks at or near the seafloor played important roles in oreforming processes of the huangtupo vms cu zn deposit

geology tectonic settings and iron ore metallogenesis associated with submarine volcanism in china an overview abstract submarine volcanogenic iron oxide svio deposits are one of the most important sources of high grade iron ores in china the spatial distribution of the deposits is controlled by the tectonic settings including arc back arc and rift environments with the svio deposits mostly concentrated in the western part of china namely the southwestern yangtze craton western and eastern tianshan and altay orogens and the kaladawan iron ore district in the eastern part of the altyn tagh region the chinese svio deposits range in age from paleoproterozoic to mesozoic and were formed during two main metallogenic epochs in the proterozoic and paleozoic more than 70 of the svio deposits formed in the paleozoic with three important svio metallogenic provinces recognized in the altay eastern and western tianshan orogens these svio deposits are hosted in lithofacies that are related to submarine magmatism such as lavas and associated pyroclastic and volcaniclastic sedimentary rocks the iron orebodies are hosted in different volcanic lithofacies with different features moreover the different volcanic lithofacies in which the fe ores are hosted also provide information as to their spatial relationship ranging from distal to proximal to the eruption center or vent many of these deposits are characterized by well developed skarns and could be interpreted either by a distal position of the ore system in question and or exposed igneous rocks or active magma chamber or a relationship to early metamorphism and continuous alteration at relatively high temperature followed by retrograde alteration as temperatures decline geological and geochemical evidence suggests that these deposits were formed as a result of submarine magmatic activity including subaqueous volcanic eruptions associated volcano sedimentary lithofacies and related post magmatic hydrothermal activity iron oxide ore probably formed the hydrothermal fluids which generated the skarns could be a mixture of evolved magma derived water and convecting sea water driven by the heat from the shallow active magma chamber whereas volcano sedimentary deposits could be formed by the fallout of the ore bearing materials to the sea floor emanating from submarine eruption columns or fractional precipitation of iron which had been introduced locally into the bottom water by volcanic origin hydrothermal solutions and by leaching from the relatively iron rich volcanic rocks the formation of these various styles of fe ore deposits is controlled by several key factors such as magma differentiation lithofacies of host rocks temperature and chemical compositions of hydrothermal fluids as well as the depth of sea water in combination with their geological characteristics geodynamic mechanisms and metallogenesis we propose a genetic model in which the origin of these deposits can be related to the space time evolution of the submarine volcanism and their relationship to volcanic lithofacies variation such as central proximal and distal environments of ore formation

skarn mineralized porphyry adakites in the harlik arc at kalatage e tianshan nw china slab melting in the devonian early carboniferous in the southern central asian orogenic belt abstract the geodynamic control of mineralization in the accretionary evolution of the central asian orogenic belt caob has long been controversial here we report new field geochemical and geochronological data on recently defined porphyry and skarn type ore deposits devonian early carboniferous in the kalatage area in the middle of the harlik dananhu arc eastern tianshan nw china in the southern caob with the aim of better understanding the accretionary tectonics and genesis of porphyry and skarn type mineralization the yudai porphyry cu au deposits and the xierqu skarn cu fe au deposits are closely associated with middle devonian adakitic diorite porphyries 382 390 ma which are calc alkaline and characterized by high na2o k2o ratios and sr contents 310 1020 ppm strong depletion of hree e g yb 0 80 1 44 ppm and y 7 68 14 50 ppm and all enriched in rb sr ba k and depleted in nb and ti they are characterized by distinctive eu positive anomalies high na2o contents and morb like sr and nd isotope signatures high end t 6 1 to 7 0 and low 87sr 86sr i 0 70412 0 70462 these adakites most likely formed by melting of a young hot subducted oceanic slab and adakites in general are important carriers of porphyry cu au deposits early carboniferous adakites in the tuwu area south of kalatage are known to have similar features therefore skarn mineralized porphyry adakites get younger from north to south suggesting southward migration of the harlik dananhu arc from 390 ma to 322 ma these data indicate that partial melting of hot and or young oceanic crustal slabs were an important mechanism of accretionary crustal growth and mineralization in the southern caob

geology geochronology and fluid inclusion studies of the xiaorequanzi volcanogenic massive sulphide cu zn deposit in the east tianshan terrane china the xiaorequanzi cu zn deposit is in the westernmost part of east tianshan terrane in northwestern china the deposit is unique in the region being a volcanogenic massive sulphide vms deposit loc

tectonic processes on europa tidal stresses mechanical response and visible features abstract europa s orbital eccentricity driven by the resonance with io and ganymede results in diurnal tides 3 5 day period and possibly in nonsynchronous rotation both diurnal variation and nonsynchronous rotation can create significant stress fields on europa s surface and both effects may produce cracking patterns and time sequences of apparent tectonic features on europa include lineaments that correlate with both sources of stress if we take into account nonsynchronous rotation after initial crack formation by amounts ranging up to several tens of degrees for example the crosscutting time sequence of features in the cadmus and minos linea region is consistent with a combined diurnal and nonsynchronous tensile stress field as it evolves during tens of degrees of nonsynchronous rotation constraints on the rotation rate from comparing voyager and galileo images show that significant rotation requires 104yr but could be fast enough to have allowed significant rotation since the last global resurfacing even if such resurfacing was as recent as a few million years ago once cracking is initiated diurnal tides work cracks so that they open and close daily although the daily effect is small over 105yr double ridges could plausibly be built along the cracks with sizes and morphologies consistent with observed structures according to a model in which underlying liquid water fills the open cracks partially freezes and is extruded during the daily closing of the cracks thus several lines of observational and theoretical evidence can be integrated if we assume nonsynchronous rotation and the existence of a liquid water layer

fluid inclusion and isotope evidence for magmatic hydrothermal fluid evolution in the tuwu porphyry copper deposit xinjiang nw china abstract the tuwu deposit 557 mt at 0 58 cu is the most typical and economically significant one of several porphyry copper deposits in the dananhu tousuquan arc belt near the turpan hami basin northwest china the mineralization occurs as chalcopyrite and minor bornite in quartz bearing veins and host porphyries i e diorite porphyry and tonalite porphyry and is closely associated with potassic e g k feldspar magnetite and hematite and phyllic e g sericite pyrite albite and chlorite alterations fluid inclusions were studied in different generations of quartz defined as qzia ib qzii qziii and qziv four types of fluid inclusions were recognized namely liquid rich biphase l0 vapor rich biphase v0 and triphase v1 with one opaque mineral as well as brine rich b0 with or without an opaque mineral inclusions based on fluid inclusion microthermometry using fia method the fluids associated with qzib early ore stage are characterized by relatively high temperatures 306 458 c and salinities 50 3 62 1 and 6 5 22 6 wt nacl cacl2 equiv for b0 and l0 inclusions respectively under lithostatic pressure of 167 to 444 bars depth of 0 6 1 6 km and the fluids associated with qzii and qziii main ore stage have progressively decreasing temperatures from 201 to 345 c under hydrostatic pressure of about 90 bars depth of 0 9 km which induced to large scale mineralization at tuwu mineralogy and physicochemical calculations suggest that the early stage occurred at alkaline and high oxidized fluid environment ph 9 6 to 11 5 logfo2 26 4 to 24 3 whereas the main ore stage took place at acidic and low oxidized conditions ph 4 0 to 5 0 logfo2 30 8 the fluids associated with qziv late ore stage show low homogenization temperatures

the sr and nd isotopic variations of the chinese loess plateau during the past 7 ma implications for the east asian winter monsoon and source areas of loess abstract 143 nd 144 nd and 87 sr 86 sr ratios of the acid insoluble residues of the red clay and overlying loess paleosols from the lingtai profile of the loess plateau china were investigated the results show that variations of the 87 sr 86 sr ratios of the lingtai profile can be divided into two stages from 7 ma b p to 2 5 ma b p the acid insoluble residues in the red clay rc formation are characterized by higher 87 sr 86 sr ratios with an average of 0 7230 from 2 5 ma b p to the present the acid insoluble residues in the wuchen loess wl4 ws1 lishi loess l15 s1 malan loess l1 and holocene loess s0 have relatively lower 87 sr 86 sr ratios and display an overall descending trend from 0 7223 at 2 5 ma b p to 0 7182 at the present among three possible interpretations for the variations of 87 sr 86 sr ratios of acid insoluble residues of the loess provenance change chemical weathering change or grain size distribution change only grain size distribution change provides a satisfactory interpretation this implies that the east asian winter monsoon strength was weak and relatively stable from 7 ma b p to 2 5 ma b p but became continuously enhanced from 2 5 ma b p to the present all the red clay and the overlying loess paleosols in the lingtai profile have generally identical e nd 0 implying that the source regions of these eolian deposits of the chinese loess plateau may be relatively stable and has not changed since 7 ma b p

microthermometry and chemical composition of fluid inclusions from the mt chalmers volcanic hosted massive sulfide deposits central queensland australia implications for ore genesis mt chalmers is a mound style volcanic hosted massive sulfide vhms deposit in central queensland australia the ore lenses are hosted by rhyolitic volcanics and sedimentary rocks of early permian age the two ore lenses main lode and west lode consist of cu zn pb massive sulfide underlain by cu rich stringer mineralization textural and petrographic investigations of fluid inclusions indicate that primary type i inclusions up to 25 microns are found in quartz from the stringer mineralized zone and microthermometric studies of these inclusions yielded homogenization temperatures of 160 285 degrees c and salinities of 5 10 5 nacl equiv wt laser raman spectroscopic lrs analysis indicates the presence of co2 0 1 1 mol in the mt chalmers vhms systems semiquantitative sem wds microprobe analyses of fluid inclusion decrepitates indicate that the mt chalmers ore fluids were enriched in potassium and calcium but depleted in magnesium relative to seawater pixe microanalysis of fluid inclusions in quartz from the stringer zone also indicates a significant base metal concentration in these fluids cation composition and higher salinities relative to seawater suggest that recycled seawater cannot be the sole source of the ore fluids high base metal content and the presence of co2 in the fluid inclusions imply that magmatic input of ore metals copper in particular accompanying seawater leaching of the footwall volcanic pile is a distinct possibility in terms of fluid composition the k ca fe variation of the mt chalmers ore fluid is comparable with those of typical epithermal deposits e g thames new zealand and porphyry copper deposits bingham ut the cu zn fe 10 plot of the mt chalmers ore fluids indicates that there is significant copper in the system comparable to copper enrichment in a porphyry copper system the mt chalmers ore fluids also show similar copper content with the cu rich end member ore fluid composition of the mineralized stage 2b veins of the hellyer vhms deposit whereas the stage 2a veins of hellyer are more enriched in lead and zinc overall the ore fluids have a variable chemistry with a continuum of compositional data from vhms to epithermal porphyry style ore fluids shallow water emplacement 300 m for the vhms mineralization has been postulated for the mt chalmers deposit based on the presence of trace fossils in the footwall and hanging wall sedimentary rocks and volcanic facies studies however fluid inclusion studies do not rule out a moderate to deeper submarine environment as there is no fluid inclusion evidence of boiling at mt chalmers boiling of ore fluids would probably have occurred as in most epithermal systems if the ore fluid exhaled onto the seafloor under a shallow environment

a combined fluid inclusion and s pb isotope study of the neoproterozoic pingshui volcanogenic massive sulfide cu zn deposit southeast china abstract the pingshui cu zn deposit is located in the jiangshan shaoxing fault zone which marks the neoproterozoic suture zone between the yangtze block and cathaysia block in south china it contains 0 45 million tons of proven ore reserves with grades of 1 03 wt cu and 1 83 wt zn this deposit is composed of stratiform massive sulfide ore bodies which contain more than 60 vol sulfide minerals these ore bodies are hosted in altered mafic and felsic rocks spilites and keratophyres of the bimodal volcanic suite that makes up the neoproterozoic pingshui formation metallic minerals include pyrite chalcopyrite sphalerite tennantite tetrahedrite and magnetite with minor galena gangue minerals are quartz sericite chlorite calcite gypsum barite and jasper three distinct mineralogical zones are recognized in these massive sulfide ore bodies a distal zone composed of sphalerite pyrite barite zone i an intermediate zone characterized by a pyrite sphalerite chalcopyrite assemblages zone ii and a proximal zone containing chalcopyrite pyrite magnetite zone iii a thin layer of exhalative jaspilite overlies the sulfide ore bodies except in the proximal zone the volcanic rocks of the pingshui formation are all highly altered spilites and keratophyres but their trace element geochemistry suggests that they were generated by partial melting of the depleted mantle in an island arc setting homogenization temperatures of the primary fluid inclusions in quartz from massive sulfide ores are between 217 and 328 c and their salinities range from 3 2 to 5 7 wt nacl equivalent raman spectroscopy of the fluid inclusions showed that water is the dominant component with no other volatile components fluid inclusion data suggest that the ore forming fluids were derived from circulating seawater the 34 s values of pyrite from the massive sulfide ores range from 3 6 to 3 4 indicating that the sulfur was primarily leached from the arc volcanic rocks of the pingshui formation both pyrite from the massive sulfide ores and plagioclase from the spilites have similar lead isotope compositions implying that the lead was also derived from the pingshui formation the low lead contents of the massive sulfide ores and the geochemistry of their host rocks are similar to many vms cu zn deposits in canada e g noranda and thus can be classified as belonging to the bimodal mafic subtype the presence of magnetite and the absence of jaspilite and barite at the 505 m level in the pingshui deposit suggest that this level is most likely the central zone of the original lateral massive sulfide ore bodies if this interpretation is correct the deep part of the pingshui cu zn deposit may have significant exploration potential

a review of cu dominant mineral systems in the kalatag district east tianshan china abstract the chinese east tianshan is the easternmost sector of the tianshan mountain range in the central asian orogenic belt caob and accommodates several events of magmatism crustal growth and mineralization the kalatag arc is unique in the east tianshan due to its widespread early paleozoic volcanic rocks which offers a special opportunity to study the early paleozoic cu dominant mineral systems in island arc setting in this region nine deposits have been discovered in recent years these deposits occur in paleozoic volcanic rocks between the kalatag fault and kabei fault and can be divided into six mineral systems i e vms cu zn epithermal cu porphyry cu au skarn fe cu magmatic cu ni sulfide and hydrothermally overprinted deposits among them vms epithermal porphyry skarn and magmatic cu ni sulfide mineralization are distributed in the southeastern central northwestern and westernmost kalatag respectively the mineralization and associated intrusive rock ages can be clustered into four episodes in the kalatag arc i e late ordovician silurian ca 450 430 ma middle devonian ca 390 380 ma late carboniferous ca 320 300 ma and permian ca 280 ma here paleozoic granitoids show similar geochemistry and isotopic features all paleozoic granitoids plot in the subalkaline field and predominantly tholeiitic to calc alkaline series with enrichment of large ion lithophile elements and depletion of high field strength elements these granitoids plot in a volcanic arc fields in tectonic discrimination diagrams which are characteristic of an island arc setting the fluid inclusions in porphyry and skarn system are characterized by high temperature high salinity low content of co2 whereas epithermal system represented by low temperature low salinity low content of co2 and the vms system can be described as medium temperature medium low salinity co2 bearing fluid h o isotopic data suggest that ore fluids were sourced from a mixing fluid between magmatic and meteoric water s pb isotopic data show that the sulfur mainly came from magma or ore hosting igneous rocks the yudai porphyry cu au deposit the hongshi epithermal cu deposit and the honghai au rich vms cu zn deposit formed at the same time related to a subduction environment the early paleozoic vms mineralization is generally overprinted by late magmatic hydrothermal fluids which may be due to multiple accretionary orogeny in kalatag island arc we propose that the north dipping subduction of the paleo tianshan ocean or south dipping subduction of the junggar ocean during late ordovician silurian which may led to the development of yudai porphyry copper hongshi epithermal copper and honghai vms copper zinc deposits in the kalatag arc after that north dipping subduction of the paleo tianshan ocean resulted to the formation of the middle devonian ca 390 380 ma and late carboniferous ca 320 300 ma cu mineralization finally the permian ca 280 ma magmatic copper nickel sulfide deposits associated with ultramafic mafic complexes developed in post collisional extension setting part of a large igneous province lip event associated with mantle plume upwelling

effect of non synchronous rotation on surface stress upon europa constraints on surface rheology 1 in this study visco elastic tidal deformation on europa associated with its non synchronous rotation is calculated the induced surface stress is largely dependent on the rotation period and surface viscosity on the basis of the relationship between the geological setting rotation period and surface rheology the surface viscosity is inferred to be in the range between 1019 and 1020 pa s the approach presented herein raises the possibility of estimating the surface viscosity on the satellite from not only the rheological law of ice but also the tectonic setting

viscous gravitational relaxation summary this paper is concerned with a detailed examination of the response of maxwell models of the planet to surface mass loads particular attention is devoted to an examination of the factors which determine the isostatic response since the understanding of this response is crucial in a number of different geodynamic problems one particular example which we discuss in detail is concerned with the prediction of free air gravity anomalies produced by large scale deglaciation events using the methods developed here we are able to provide the first direct assessment of the importance of initial isostatic disequilibrium on the observed relative sea level variations and free air gravity anomalies forced by the melting of the laurentide ice sheet we are therefore able to estimate the extent to which such initial disequilibrium might influence the inference of mantle viscosity from isostatic adjustment data our calculations establish that free air gravity data although they are sensitive to the degree of initial disequilibrium provide an extremely high quality constraint upon the viscosity of the lower mantle

a coupled mode solution for acoustic propagation in a waveguide with stepwise depth variations of a penetrable bottom a coupled mode solution is formulated for the problem of acoustic propagation in a cylindrically symmetric ocean divided in range into a finite number of adjoining pekeris waveguides of differing water depths attenuation is included in the bottom and the problem is discretized by assigning a pressure release boundary condition at a depth which is sufficiently far removed to prevent significant energy from returning to the water this formulation includes backscatter from the depth variations of the water column and full coupling between a finite number of modes propagating in the water column and in the bottom numerical results based on an implementation of this solution are presented

petrological and geochemical features of the early paleozoic granitic gneisses and iron ores in the tianhu iron deposit eastern tianshan nw china implications for ore genesis abstract this paper reports whole rock geochemical zircon u pb and hf isotopic data for ore hosted granitic gneisses mineral compositions of oxides and sulfur isotopic data for sulfides in iron ores from the tianhu deposit central part of the eastern tianshan our results can provide crucial constraints on the genesis of granitic gneisses and early paleozoic tectonic setting of the eastern tianshan la icp ms u pb dating on magmatic zircons yielded weighted mean 206pb 238u ages of 463 to 438 ma interpreted as the crystallization ages of the granitic protoliths and the formation ages of the tianhu group zircon u pb age of ore hosted granitic gneiss ca 459 ma can provide reliable constrains on upper limit for iron mineralization age in the tianhu deposit geochemical characteristics suggest that the protoliths of the tianhu granitic gneisses are metaluminous to weakly peraluminous high k calc alkaline granitic rocks exhibiting typical subduction related features such as strong enrichment in lree and lile and depletion in hfse zircon hf isotopic compositions show a positive trend from 463 to 438 ma indicating that 460 ma magmas came from both ancient and juvenile sources whereas 438 ma magmas involved more juvenile material some early paleozoic granitoids were recently identified in the eastern tianshan with the ages between ca 475 and ca 425 ma the formation of these early paleozoic granitoids was in response to subduction processes suggesting that subduction of junggar ocean probably began in the early ordovician and lasted until late silurian pyrite and pyrrhotite in iron ores have 34scdt values from 4 6 to 15 7 which are consistent with the marine source but inconsistent with the magmatic source or those involved evaporites in skarn iron deposit geological geochemical and isotopic data suggest that the tianhu iron ores were formed by volcano sedimentary processes in a subduction environment during the early paleozoic time and tianhu is a metamorphosed volcano sedimentary iron deposit rather than a skarn iron deposit as previously proposed

geological and fluid inclusion characteristics of meiling cu au deposit in kalatage ore belt eastern xinjiang in comparison with typical zijinshan style hs epithermal deposit located in the paleozoic uplift along the southern margin of tu ha basin in eastern xinjiang the newly discovered meiling cu au deposit occurs in the superimposed mesozoic volcanic basin upon the northern part of late paleozoic dananhu tousuquan accretionary arc the meiling cu au deposit is controlled by nww sn and ew trending faults and can be divided into three cu au sub zones host rocks are mainly rhyolitic dacitic ignimbrite whereas cu au mineralization is closely related to quartz porphyry rhyolitic porphyry and granitic porphyry ore forming styles are dominantly veinlet disseminations and veinlets and occasionally stockworks the mineral association consists of chalcopyrite pyrite bornite chalcocite and sphalerite typical minerals are alunite and pyrophyllite hydrothermal alterations are mainly silicfication sericitization alunitization pyrophylitization illitization hydromuscovitization and chloritization fluid inclusions are very small 3 10 m and sparse and gas to liquid ratios are 4 10 the homogenization temperatures fall in the range of 107 260 with the salinities from 0 2 to 8 4 w nacleq and the estimated pressure mainly from 3 to 16 mpa fluid inclusions and geological data suggest that the ore forming process occurred in depths of 0 4 0 8 km based on field observation volcanic sub volcanic rock composition hydrothermal alteration ore structure and ore forming characteristics this paper holds that the meiling cu au deposit belongs to the transitional type from high sulfidation epithermal deposit to porphyry cu au deposit corresponding to typical hs epithermal deposits such as the zijinshan au cu deposit in fujian and the chinkuashih au cu deposit in taiwan

formation of cycloidal features on europa cycloidal patterns are widely distributed on the surface of jupiter s moon europa tensile cracks may have developed such a pattern in response to diurnal variations in tidal stress in europa s outer ice shell when the tensile strength of the ice is reached a crack may occur propagating cracks would move across an ever changing stress field following a curving path to a place and time where the tensile stress was insufficient to continue the propagation a few hours later when the stress at the end of the crack again exceeded the strength propagation would continue in a new direction thus one arcuate segment of the cycloidal chain would be produced during each day on europa for this model to work the tensile strength of europa s ice crust must be less than 40 kilopascals and there must be a thick fluid layer below the ice to allow sufficient tidal amplitude

three dimensional acoustic scattering of a source generated field from a cylindrical island in this work an analytic solution is presented for the three dimensional 3 d problem of acoustic scattering from a nonpenetrable cylindrical island in shallow water the ocean environment around the island is considered range independent with arbitrary sound speed profile and the bottom is assumed to be rigid the total acoustic field generated by an harmonic point source is obtained as a normal mode double series expansion a systematic numerical investigation of the double series is presented results concerning the pressure field and the transmission loss around the cylindrical island are given for the case of an acoustically soft and an acoustically hard island boundary in an isovelocity environment the presented analytic solution is numerically efficient for relatively low frequencies and can serve as a 3 d benchmark solution in the appropriate frequency range

europa s differentiated internal structure inferences from four galileo encounters radio doppler data from four encounters of the galileo spacecraft with the jovian moon europa have been used to refine models of europa s interior europa is most likely differentiated into a metallic core surrounded by a rock mantle and a water ice liquid outer shell but the data cannot eliminate the possibility of a uniform mixture of dense silicate and metal beneath the water ice liquid shell the size of a metallic core is uncertain because of its unknown composition but it could be as large as about 50 percent of europa s radius the thickness of europa s outer shell of water ice liquid must lie in the range of about 80 to 170 kilometers

crack azimuths on europa the g1 lineament sequence revisited abstract the tectonic sequence in the anti jovian area covered by regional mapping images from galileo s orbit e15 is determined from a study of cross cutting relationships among lineament features the sequence is used to test earlier results from orbit g1 based on lower resolution images which appeared to display a progressive change in azimuthal orientation over about 90 in a clockwise sense such a progression is consistent with expected stress variations that would accompany plausible non synchronous rotation the more recent data provide a more complete record than the g1 data did we find that to fit the sequence into a continual clockwise change of orientation would require at least 1000 5 cycles of azimuthal rotation if due to non synchronous rotation of europa this result implies that we are seeing back further into the tectonic record than the g1 results had suggested the three sets of orientations found by geissler et al now appear to have been spaced out over several cycles not during a fraction of one cycle while our more complete sequence of lineament formation is consistent with non synchronous rotation a statistical test shows that it cannot be construed as independent evidence other lines of evidence do support non synchronous rotation but azimuths of crack sequences do not show it probably because only a couple of cracks form in a given region in any given non synchronous rotation period

three dimensional acoustic scattering from a penetrable layered cylindrical obstacle in a horizontally stratified ocean waveguide in this work a normal mode solution is presented for the three dimensional problem of acoustic scattering from a penetrable horizontally layered cylindrical obstacle in a shallow water waveguide the ocean environment around the obstacle is considered horizontally stratified and the bottom is assumed to be rigid in the general case of depth dependent sound speed and density profiles ssdp the total acoustic field is calculated numerically while an analytic solution is obtained in the special case of depth independent ssdp numerical results concerning the transmission loss outside and inside single or double layered cylindrical structures made of acoustic materials are given for a typical depth dependent ocean environment comparisons with the cases of ideally soft and ideally hard cylindrical obstacles j acoust soc am 100 206 218 1996 are also made illustrating the effect of acoustic properties of the obstacle an important feature which clearly emerges from the theoretical analysis and th

dating the xiaobaishitou skarn w mo deposit eastern tianshan nw china constraints from zircon u pb muscovite 40ar 39ar and molybdenite re os system abstract the xiaobaishitou deposit 36 264 tonnes 0 78 wt wo3 in the eastern tianshan orogenic belt is a medium sized skarn deposit characterized by w mo ore bodies that developed along contacts between triassic biotite granite and mesoproterozoic carbonaceous rocks scheelite and molybdenite are the dominant metallic minerals in this deposit and mostly precipitated during the retrograde stage and or quartz sulfide stage respectively laser ablation multi collector inductively coupled plasma mass spectrometry la mc icp ms zircon u pb dating of the mineralization related biotite granites from underground openings and outcrops yields ages of 247 9 1 7 ma 1 n 22 mswd 0 69 and 252 2 3 0 ma 1 n 12 mswd 1 60 implying they were emplaced in the early triassic a muscovite 40ar 39ar weighted plateau age of 247 6 2 3 ma 2 mswd 2 03 and molybdenite re os model ages ranging from 235 8 5 7 ma to 249 6 3 6 ma weighted mean age 251 1 1 6 ma 2 mswd 0 70 are interpreted as the time of the hydrothermal activity mineralization the excellent agreement among the u pb 40ar 39ar and re os chronometers confirms that the xiaobaishitou deposit formed in the early triassic the re contents of the molybdenites range from 18 477 to 130 447 ng g suggesting that the ore forming materials were derived from continental crust together with the involvement of abundant mantle components as one of the representative triassic deposit in eastern tianshan the xiaobaishitou provides important chronological evidence for metallogenic regularity in the eastern tianshan and the central asian orogenic belt the new ages reported here confirm that the xiaobaishitou deposit represents one of the magmatic hydrothermal mineralization events that occurred in the eastern tianshan orogenic belt in lithospheric extension during the triassic it is suggested that mantle material played a role in producing the triassic mineralization and associated magmatism

temperatures on europa from galileo photopolarimeter radiometer nighttime thermal anomalies galileo observations of europa s thermal emission show low latitude diurnal brightness temperatures in the range of 86 to 132 kelvin nighttime temperatures form an unexpected pattern with high temperatures on the bright ejecta blanket of the crater pwyll and an equatorial minimum in temperatures after sunset uncorrelated with surface albedo or geology the nighttime anomalies may be due to regional thermal inertia variations of an unknown origin which are equivalent to a two to threefold variation in thermal conductivity or to endogenic heat fluxes locally reaching 1 watt per square meter endogenic heat flow at this high level although consistent with some geological evidence is theoretically unlikely