hydrothermal evolution in the maher abad porphyry cu au deposit sw birjand eastern iran evidence from fluid inclusions abstract copper and gold mineralization in the maher abad deposit eastern iran is closely related to the multiple emplacement episodes of upper eocene granodiorite porphyries within andesitic volcaniclastic and coeval quartz monzonite stocks the magmatic hydrothermal fluids thereafter hydrofracturing provided appropriate conduits formed a stockwork of quartz and quartz sulfide veinlets within the porphyritic host rocks which were extensively altered into potassic propylitic phyllic and argillic assemblages four main vein veinlet groups have been identified a quartz k feldspar biotite anhydrite with pyrite chalcopyrite sporadic magnetite and pyrrhotite b quartz pyrite and minor chalcopyrite c chalcopyrite quartz and or minor bornite pyrite digenite and sporadic pyrrhotite and d quartz calcite and or clay minerals pyrite hematite galena the cu au mineralization is mainly associated with the early potassic biotite alteration zone in the deep central part of the madanha stock based on the phase contents at room temperature three types of fluid inclusions are recognized at maher abad 1 liquid rich two phase lv 2 vapor rich vl h and 3 halite bearing multiphase lvh homogenization experiments revealed a temperature range of 150 488 c for the studied inclusions ice melting of aqueous two phase inclusions and melting of halite in the aqueous multiphase inclusions provide salinity of 9 5 to 47 9 wt nacl equivalent fluid inclusion studies reveal that the single phase low salinity magmatic fluid exsolved from a granodioritic magma was separated into vapor and hypersaline brine 45 wt nacl eq phases the coexisting phases were trapped at temperature 460 c and lithostatic pressure of 350 bars corresponding to a depth of 1 3 km as vl h and lvh fluid inclusions respectively such magmatic derived fluids underwent phase separation episodically under lithostatic pressure conditions and formed the early copper sulfide bearing quartz veinlets intimately related to the potassic alteration zone copper iron sulfide precipitation and phase separation concomitant of boiling in this zone led to rapid depletion of the fluid in reduced sulfur as a result au hs 2 complexes are destabilized forcing most of the gold to precipitate above 400 c a positive trend of the homogenization temperature and salinity during the formation of the phyllic alteration zone is attributed to the cooling of a moderately saline fluid produced dominantly by magmatic vapor condensation and its subsequent boiling and mixing with meteoric waters at a hydrostatic pressure of 100 125 bars corresponding to a depth of 1 1 2 km the argillic alteration zone formed at temperature of 210 230 c from fluids with salinity of 16 18 nacl wt eq at a hydrostatic pressure of 80 bars and a depth of 800 m from paleo surface the fluid density is typically lower 3 than that of the potassic zone 1 g cm 3 indicating that the late trapped fluid was more dilute

compositional variation and the origin of deep crustal reflections abstract identifying the sources of crustal reflections is essential for deriving more geological information from deep crustal reflection profiles theoretical and model studies help place constraints on the role of compositional variation in producing deep crustal reflections analysis of laboratory derived velocities and densities of rock types typical for the continental crust indicates that reflection coefficients are generally small but significantly 17 of the possible reflection coefficients have magnitudes between 0 1 and 0 2 comparison between reflection coefficients derived from well logs and reflections observed in associated seismic profiles indicates that constructive interference associated with geological layering is at least as important as the magnitude of the reflection coefficients for producing detectable reflections constructive interference can increase reflection amplitude by two to three times but is limited to a relatively narrow range of layer thickness for a typical 10 40 hz seismic wavelet and typical crustal velocities of about 6 km s constructive interference occurs for layer thickness ranging between about 35 and 80 m layers thinner than 35 m interfere destructively if reflections result from compositional variation seismic models of hypothetical and observed geologic relations provide analogs for interpreting complex reflection patterns observed in deep crustal reflection profiles such models show reflection patterns similar to those observed in the reflection profiles the models indicate that the reflections could originate in the complexly deformed and intruded terranes that are common in the crystalline crust and it may not be necessary to appeal to unobserved phenomena such as special lamellae or fluid filled fractures to explain the reflections

synthetic fluid inclusions in natural quartz iii determination of phase equilibrium properties in the system h2o nacl to 1000 c and 1500 bars phase equilibria in the system h2o nacl have been determined to 1000 c and 1500 bars using synthetic fluid inclusions formed by healing fractures in inclusion free brazilian quartz in the presence of the two coexisting immiscible h2o nacl fluids at various temperatures and pressures petrographic and microthermometric analyses indicate that the inclusions trapped one or the other of the two fluids present or mixtures of the two salinities of the two coexisting phases were obtained from heating and freezing studies on those inclusions which trapped only a single homogeneous fluid phase results of the present study are consistent with previously published data on the h2o nacl system at lower temperatures and pressures and indicate that the two phase field extends well into the p t range of most shallow magmatic hydrothermal activity as a consequence chloride brines exsolved from many epizonal plutons during the process of second boiling should immediately separate into a high salinity liquid phase and a lower salinity vapor phase and produce coexisting halite bearing and vapor rich fluid inclusions this observation is consistent with results of numerous fluid inclusion studies of ore deposits associated with shallow intrusions particularly the porphyry copper deposits in which halite bearing and coexisting vapor rich inclusions are commonly associated with the earliest stages of magmatic hydrothermal activity

a sensor array system for profiling moisture in unsaturated rock and soil as the scope of hydrologic investigations extend deeper into the subsurface profile and increasingly include fractured rock there is a growing need for techniques that can accurately monitor saturation changes at a high spatial and temporal resolution in this environment we have developed a technique the electrical resistance sensor array system ersas to track moisture dynamics in vadose zone regions that include both fractured rock and soil the performance of ersas was compared with the time domain reflectometry tdr technique under controlled and field conditions we found that ersas was effective in determining patterns of saturation changes along vertical soil rock profiles because of the small size of individual sensors it was able to resolve travel times associated with a wetting front and peak saturation better than tdr in addition ersas is significantly cheaper than the tdr system and the sensor arrays are relatively easier to install in the subsurface profile published in 2011 by john wiley sons ltd

observations of preferential flow during a liquid release experiment in fractured welded tuffs author s salve rohit abstract to better understand preferential flow in fractured rock we carried out an in situ field experiment in the exploratory studies facility at yucca mountain nevada this experiment involved the release of 22 m3 of ponded water at a pressure head of 0 04 m over a period of 7 months directly onto a 12 m2 infiltration plot located on a fractured welded tuff surface as water was released changes in moisture content were monitored along horizontal boreholes located in the formation 19 22 m below distinct flow zones varying in flow velocity wetted cross sectional area and extent of lateral movement intercepted the monitoring boreholes there was also evidence of water being diverted above the ceiling of a cavity in the immediate vicinity of the monitoring boreholes observations from this field experiment suggest that isolated conduits each encompassing a large number of fractures develop within the fractured rock formation to form preferential flow paths that persist if there is a continuous supply of water in addition in fractured welded tuffs the propensity for fracture matrix interactions is significantly greater than that suggested by existing conceptual models in which flow occurs along a section of fracture surfaces an overriding conclusion is that field investigations at spatial scales of tens of meters provide data critical to the fundamental understanding of flow in fractured rock

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

early eocene longmala skarn pb zn cu deposit in tibet china geochemistry fluid inclusions and h o s pb isotopic compositions abstract the longmala deposit is a representative of the skarn pb zn cu deposits found in the nyainqentanglha area of tibet china the mineralization is hosted by skarn and marble of the permian wululong formation intruded by an early eocene biotite monzogranite which is associated with the pb zn cu mineralization the genesis of the deposit is related to a four stage progression involving stage i involves the development of prograde skarn stage ii is a pre ore retrograde skarn stage iii is the emplacement of quartz sulfides ore and stage iv is the emplacement of post ore carbonate the biotite monzogranite is a high k calc alkaline highly fractionated i type granite characterized by its elevated sio2 68 38 72 62 wt fet 4 09 6 19 wt and k2o na2o 7 82 8 33 wt contents its aluminum saturation index of 0 97 0 99 and a high differentiation index of 79 86 are indicative of a last stage fractionation of the magma the monzogranite is relatively enriched in light rare earth elements th u and rb depleted in sr ba k nb p and ti and has a negative eu anomaly the ehf t values 6 2 to 1 5 two stage hf model ages average tdm2 1224 ma for zircons and whole rock pb isotopic compositions 206pb 204pb 18 806 18 938 207pb 204pb 15 676 15 697 and 208pb 204pb 39 234 39 376 indicate that the source of the magma is the crust of lhasa terrane the study of fluid inclusions from each of the four stages mentioned above show that garnet and diopside from the prograde skarn stage i are characterized by high temperatures and high oxygen fugacity indicative of magmatic fluids the succeeding mineralization stage iii is characterized by moderate to high temperature and a reducing fluid and final carbonate veining stage iv with a decreased fluid temperature and salinity the 18ow values range from 1 3 to 10 8 and the dw values are 123 5 to 93 4 indicating that the ore forming fluids were derived from mixture magmatic and meteoric fluids and the 34s values of sulfides have a relatively narrow range of 0 3 3 6 suggestive of a magmatic source the 206pb 204pb 18 571 18 722 207pb 204pb 15 707 15 796 and 208pb 204pb 39 116 39 448 values of sulfides show that ore forming metals were derived from the crust in the lhasa terrane major and trace elements characteristics of the ore associated biotite monzogranite combined with the dating results suggest that the longmala deposit were formed within the india asia continental collision tectonic setting

fluid inclusion and stable isotope study of the lubin zardeh epithermal cu au deposit in zanjan province nw iran implications for ore genesis abstract the lubin zardeh deposit is located in the western alborz magmatic belt 45 km ne of zanjan iran this deposit contains polymetallic cu au pb zn mineralization which is hosted by the cenozoic volcanic intrusive rocks of mainly intermediate and acidic composition pyrite chalcopyrite galena sphalerite bornite and tennantite tetrahedrite with native gold and silver are present in the ores quartz adularia and clay minerals illite montmorillonite with minor calcite are the most abundant gangue minerals and generally occur as fine grained assemblages some are however medium and coarse grained assemblages the ore minerals show disseminated vein veinlet replacement and brecciated textures while the gangue minerals represent replacement cockade crustiform colloform comb vein veinlet and plumose textures alteration haloes along the main vein are silicic argillic illite montmorillonite sericitic and pyritic gold contents of the quartz chalcopyrite gold veins range from 0 002 to 10 ppm with an average of 0 52 ppm the average values for total reserve of 0 5 mt of lubin zardeh deposit has been determined 1 3 0 7 and 0 4 for cu pb and zn respectively most of fluid inclusions in the quartz gold sulfide veins consist of two vapor and liquid phases at room temperature the primary fluid inclusions have a low to intermediate homogenization temperature between 127 and 327 c and salinity between 4 07 and 13 98 wt nacl equivalent stable isotope and fluid inclusion studies indicate that mineralization occurred in two stages at lubin zardeh deposit i e stage i along which base metal deposited and stage ii which is associated with copper and gold mineralization the 18oquartz values from stage i and stage ii range from 9 56 to 12 77 and from 7 23 to 9 24 respectively while their 34s values of sulfide minerals range from 0 9 to 6 2 and form 6 6 to 1 9 the isotopic and microthermometric data indicate that the hydrothermal solution evolved through mixing of magmatic fluids with meteoric waters boiling of magmatic fluid and mixing with meteoric waters were the main mechanisms of ore deposition in the lubin zardeh low sulfidation epithermal deposit

liquid release tests in unsaturated fractured welded tuffs i field investigations wetting front movement flow field evolution and drainage of fracture flow paths were evaluated within the topopah spring welded tuff at yucca mountain nevada equipment and techniques were developed for in situ quantification of formation intake rates flow velocities seepage rates and volumes of fracture flow paths localized injections of liquid into a low permeability zone lpz and a high permeability zone hpz along a borehole were detected in two boreholes below the point of injection for the lpz tests water did not seep into an excavated slot that defined the lower boundary of the test bed and the liquid intake rate under constant head conditions was observed to steadily decrease by two orders of magnitude in the hpz liquid intake rates under constant head conditions were significantly higher and did not exhibit a strong systematic decline hpz tests were also conducted under a range of constant flow conditions slot seepage rates showed intermittent responses and the percentage of injected water recovered in the slot increased as each test progressed a maximum of 80 of the injected water was recovered during high rate injection tests the flow path volumes were found to increase during the course of each hpz test the data collected during these field tests has provided useful information for developing an understanding of liquid flow in unsaturated fractured welded tuff it has also provided a basis for quantitative comparisons with numerical simulations of liquid release experiments as demonstrated in a companion paper j hydrol 256 2002

geochemical fluid inclusion and o h s isotope studies of the milajerd au polymetallic prospect central iran implications for ore genesis abstract the milajerd pb zn au polymetallic prospect in naein qom magmatic zone is a favorable target for exploration geological and geochemical characteristics such as setting alteration assemblages fluid inclusion microthermometry and stable isotopes are consistent with the milajerd pb zn au polymetallic prospect being a typical low sulfidation ls epithermal deposits the au polymetallic mineralization occurs mainly as structurally controlled veins and brecciated dikes hosted by calc alkaline volcanic rocks mineralization at the milajerd prospect is controlled by an annular fault system the sulfide mineralogy of the deposit includes sphalerite galena pyrite arsenopyrite and marcasite the principal gangue minerals are quartz calcite sericite and adularia the alteration assemblages include quartz pyrite quartz sericite pyrite and chlorite calcite epidote fluid inclusions in quartz sulfide veins have homogenization temperatures th of 158 255 c and salinities of 4 7 7 7 wt nacl equiv whereas those in barren quartz carbonate veins yield th values of 135 176 c and salinities of 1 1 4 3 wt nacl equiv the h and o isotopic composition dwater 120 to 92 inferred 18owater 6 2 to 3 5 of fluid inclusions in quartz veins imply that cooling a mixed magmatic and meteoric waters was the main mechanisms of ore deposition at milajerd deposit the 34s values of ore sulfides are mostly close to zero avg 0 1 indicating a magmatic source of sulfur which could have emanated directly from magmatic activity or have been leached from the surrounding volcanic rocks

geochronological framework of mesozoic volcanic rocks in the great xing an range ne china and their geodynamic implications abstract mesozoic volcanic rocks are widespread throughout the great xing an range ne china however precise data constraining the exact eruption ages are limited especially for those from the southern great xing an range which severely hampers our understanding of the petrogenesis and geodynamics of these rocks in this paper we report precise in situ la icpms zircon u pb age measurements for these volcanic rocks volcanic rocks in the southern great xing an range were divided into four units from bottom to top namely the manketouebo manitu baiyingaolao and meiletu formations the previous studies suggested that these volcanic rocks were mainly formed in the late jurassic our data demonstrate that the manketouebo formation erupted during late jurassic to early cretaceous time whereas the other formations are all of cretaceous age the southern great xing an range age dataset along with recently obtained precise ages for volcanic rocks from the northern great xing an range indicate that mesozoic volcanism throughout the great xing an range commenced in late jurassic but peaked during the cretaceous they formed under an extensional tectonic setting which resulted from closure of the mongol okhotsk ocean and subsequent orogenic collapse the globally elevated mantle temperature in cretaceous may provided thermal contributions to the generation of the volcanisms

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

the nature and timing of ore formation in the budunhua copper deposit southern great xing an range evidence from geology fluid inclusions and u pb and re os geochronology abstract the budunhua copper deposit is located in the southern great xing an range where the stockwork ore bodies are mainly hosted in the lower permian dashizhai formation the mineralization occurs in two blocks the jinjiling and kongqueshan and both are characterized by four main stages arsenopyrite pyrite molybdenite quartz chalcopyrite pyrrhotite quartz galena sphalerite chalcopyrite quartz and calcite fluorite quartz wall rock alteration which is related to mineralization is dominated by silicification sericitization and chloritization fluid inclusion studies show that the ore forming fluids from cu stages in both blocks are broadly identical with trapping temperatures of 280 to 400 c for the kongqueshan and 300 to 420 c for the jinjiling estimated trapping pressures for the kongqueshan are 15 0 to 26 6 mpa and for the jinjiling are 14 9 to 29 4 mpa corresponding to entrapment depth of 1 5 to 2 7 km and 1 5 to 2 9 km below the paleowater table respectively zircon grains from the tonalite porphyry in the deposit yielded a weighted 206 pb 238 u mean age of 152 0 7 ma which is consistent with a molybdenite re os model age of 150 2 2 ma indicating that both the porphyry intrusion and the copper deposit are of late jurassic age our data suggest that the budunhua deposit is an atypical porphyry deposit related to a late jurassic magmatic hydrothermal system

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

cocorp and the continental crust this is a speculative paper on the continental crust a major frontier of modern earth science seismic reflection profiling data from the cocorp project coupled with other kinds of geophysical and geological observations suggest some fresh perspectives on the crust for example there is evidence for great differences within the basement at a single site and from one cocorp site to another a simple layered model is surely not an adequate representation of the crust in most areas there is however the puzzling and rather common occurrence of limited zones of parallel though not always flat layered features at various depths in certain parts of the crust are the corresponding rocks metasedimentary or igneous or both there are transparent zones from which little or no coherent reflected seismic energy is detected are the corresponding rocks intrusions or highly deformed metasediments can degree of deformation suggest whether rocks were deformed in the hanging wall or footwall of a thrust there is evidence for large scale thrusting and related features that emphasizes the great importance of the wilson cycle to continental tectonics and that raises the possibility that water and rocks of sedimentary origin are trapped deep in the crust by the thrusting process and remain there for long periods with a variety of possible rheological and petrological consequences in some places the modern moho and adjacent rocks may correspond to parts of former oceanic or continental margin sections that have been emplaced at depth as a result of thrusting the widely held concept of the moho as a consistent boundary that is everywhere similar and that always separates the same kinds of rocks may be a major barrier to further progress in understanding the continental crust

petrogenesis and metallogenesis of the early cretaceous naoniushan cu dominated polymetallic deposit in the central great xing an range ne china abstract the naoniushan cu dominated polymetallic deposit in the central great xing an range is associated locally with pb zn ag or mo mineralization mineralization mainly occurs in the lower cretaceous continental volcanic rocks here we present new la icp ms zircon u pb ages whole rock geochemical data sr nd hf isotopic data and re os ages for the naoniushan deposit the emplacement of the porphyry occurred at 137 8 1 4 ma and the mineralization at 134 3 0 8 ma the granodiorite porphyry has high sio2 67 84 73 70 wt and k2o na2o 7 67 8 30 wt contents and low contents of mgo 0 60 1 04 wt mg 0 44 0 51 tfeo 1 29 2 16 wt cao 1 67 3 66 wt and k2o na2o 0 75 0 87 the porphyry is rich in large ion lithophile elements liles e g rb sr ba and k and light rare earth elements lrees without significant eu anomalies eu 0 84 1 01 and depleted in heavy ree hrees with lree hree 12 78 16 57 and la yb n 15 37 20 68 high field strength elements hfses e g nb ta and ti and siderophile elements e g cr co and ni these features are similar to those of adakitic rocks derived from thickened lower crust the naoniushan porphyry exhibits positive end t values ranging from 1 9 to 2 8 and relatively low initial 87sr 86sr ratios ranging from 0 70458 to 0 70497 most in situ zircon hf isotopic analyses show variable positive ehf t values ranging from 3 1 to 9 4 corresponding to relatively young two stage hf model ages ranging from 994 to 591 ma excluding one spot these isotopic features suggest that the primary magma of the naoniushan granodiorite porphyry was mainly derived from the partial melting of neoproterozoic juvenile lower crust comprising a mixture of 80 juvenile basalt and 20 ancient lower crust these elemental isotopic and geochronologic data combined with the regional geology deposit geology and fluid characteristics suggest that the naoniushan cu dominated polymetallic deposit formed in an evolving environment that decreased in compression over time due to slowing of the subduction of the paleo pacific plate beneath the eurasian plate and the transition from a compressional to an extensional tectonic regime following the closure of the mongol okhotsk ocean

petrogenesis of the linxi granitoids northern inner mongolia of china constraints on basaltic underplating five representative granitoid plutons in the linxi area northern inner mongolia of china divided into two suites are mainly granodiorite and syenogranite and correspond to i and a type granites respectively zircon u pb dating yields an age of 230 ma but most ages range from 149 ma to 111 ma for intrusion of the five plutons suite 1 granitoids show lower sio2 66 1 72 51 and k2o higher al2o3 cao mgo feo and tio2 higher sr ba and eu and lower sm gd nb y and yb than suite 2 granitoids 71 73 78 14 sio2 modeling of major and trace elements shows that fractional crystallization of hornblende and lesser amounts of feldspars for suite 1 and plagioclase and alkali feldspar for suite 2 with overprint of magmatic hydrothermal fluids can explain the geochemical variations the linxi granitoids have initial end t values varying between 5 60 and 2 89 and initial 87 sr 86 sr t ratios ranging from 0 701764 to 0 707654 geochronology of inherited zircons coupled with the nd sr isotopic comparison between granitoids late jurassic basalts and proterozoic gneisses indicates that the linxi granitoids derive from a mixed source of dominantly underplated material or mafic magma with various amounts of the proterozoic gneiss basaltic underplating provides both material and heat to produce the late jurassic to early cretaceous granitoids variation of end t and 87 sr 86 sr t with age suggests involvement in the melting of increasingly greater amounts of the old lower crustal rock our refined equation yields less scattered nd isotope depleted mantle model ages the least fractionated granitoids from each suite have low ca sr rb sr rb ba and k ba ratios and hence represent parental magmas suite 1 parent magma is produced by dehydration melting or derives principally from the fluid metasomatized mantle melting of the underplated tholeiites and their differentiated products generates suite 2 parent magma d 2005 elsevier b v all rights reserved

the theoretical seismic reflection response of sedimentary sequences a sedimentary sequence can quite often be considered very fruitfully as a discrete markov chain and thus can be described by a stochastic matrix knowing this matrix and the thickness probability distributions of the layers of the various participating lithologies while assuming that their densities and velocities are normally distributed an expression is derived for the autocorrelation or power spectrum of the seismic reflection response this expression can bring out essential characteristics of the power spectra i e the low frequency droop and its slope this then leads to the possible estimation of some physical and sedimentary parameters of the sequence such as the scatter of the reflection coefficients and the sand shale ratio or sedimentary cycle thickness the case of a binary sequence as the predominant sequence of the sediments of the gulf coast area and nigeria is analyzed in detail the theoretical results conform well with field data and lead to the interesting conclusion that indee

near surface wetting of a ponded basalt surface observations using time domain reflectometry abstract the changes in dielectric constant k a during an infiltration test on a fractured basalt surface in south eastern idaho were monitored using time domain reflectometry tdr because changes in k a were caused largely by changing amounts of water in the formation and to a small extent by diurnal and seasonal temperature fluctuations tdr served as a useful indicator of the moisture status in the formation our results indicate that wetting and drying were spatially variable within and immediately beyond a 7 8 m 2 pond various locations close to the surface responded to fast flow whereas others showed evidence of poor hydraulic communication with the surface data collected during a rainfall event which occurred a few days after ponding ceased indicated that this boundary condition evoked a similar hydrologic response to ponding this effort suggests that tdr is a useful tool for detecting moisture changes in fractured media

the western central asian orogenic belt a window to accretionary orogenesis and continental growth abstract the architecture of accretionary orogens is a key to understand continental growth here we present an overview of the orogenic components and their amalgamation in the western central asian orogenic belt caob the caob records the convergence and interactions among various types of orogenic components including the japan type mariana type and alaska aleutian type arc systems as well as the active marginal sequences of the siberia craton which incorporated wide accretionary complexes and accreted arcs and terranes during construction of the caob the kazakhstan arc chain was characterized by multiple subduction whereas the northern fringe of the tarim craton remained mostly as a passive margin the multiple convergence and accretions among these various orogenic components generated huge orogenic collages in the late paleozoic and even in the early triassic involving parallel amalgamation circum microcontinent amalgamation and oroclinal bending the preservation of trapped basins played a significant role in orogenesis with some parts of the oceanic plate being subducted and others behaving as rigid units the orogenesis in the caob was long lived lasting for more than 800 m y involving multiple subduction and long continuous accretion and featuring the complexity of accretionary orogenesis and continent growth

fluid inclusions and h o s pb isotope systematics of the chalukou giant porphyry mo deposit heilongjiang province china abstract the chalukou giant porphyry mo deposit located in the northern great xing an range is the largest mo deposit in the xing an mongolia orogenic belt this deposit s ore bodies are mainly hosted in an intermediate felsic complex and jurassic volcanic sedimentary rocks of which late jurassic granite porphyry quartz porphyry and fine grained granite are closely associated with the mo mineralization three types of fluid inclusions fis are present in the quartz associated with oxide and sulphide minerals i e liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis the fis in the quartz phenocrysts of the granite porphyry contain liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis the homogenization temperatures vary from 230 c to 440 c and 470 c to 510 c and their salinities vary from 0 7 to 53 7 nacl eq and 6 2 to 61 3 nacl eq respectively the fis of k feldspar quartz magnetite veins of the early stage are composed of liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis with homogenization temperatures and salinities of 320 c to 440 c and 4 2 to 52 3 nacl eq respectively the fis of quartz molybdenite veins and breccia of the middle stage are composed of liquid rich two phase gas rich two phase and daughter mineral bearing multiphase fis with homogenization temperatures and salinities of 260 c to 410 c and 0 4 to 52 3 nacl eq respectively fis of quartz fluorite galena sphalerite veins of the late stage are liquid rich two phase fis with homogenization temperatures and salinities of 170 c to 320 c and 0 5 to 11 1 nacl eq respectively the ore forming fluids of the chalukou deposit are characterised by high temperature high salinity and high oxygen fugacity belonging to an f rich h 2 o nacl co 2 system the 18 o w values vary from 4 5 to 3 2 and the d w values vary from 138 to 122 indicating that the ore forming fluids were a mixture of magmatic and meteoric water the 34 s values range from 1 9 to 3 6 with an average of 1 6 the 206 pb 204 pb 207 pb 204 pb and 208 pb 204 pb values of the metallic minerals are in the ranges of 18 269 18 501 15 524 15 567 and 38 079 38 264 respectively both the s and pb isotopic systems indicate that the ore metals and fluids came primarily from a deep seated magma source from the juvenile lower crust the mo mineralization in the chalukou deposit occurred at a depth of 0 5 to 1 3 km and multiple stages of phase separation or immiscibility of ore forming fluid was critical for the formation of the chalukou deposit

genesis of the changlingzi zn pb deposit in the southern great xing an range northeastern china constraints from fluid inclusions and h o s pb isotope systematics the changlingzi pb zn deposit is located in the southern great xing an range metallogenic belt of northeast china this deposit experienced two types of mineralization including skarn ore block i

fluid immiscibility in natural processes use and misuse of fluid inclusion data ii interpretation of fluid inclusion data in terms of immiscibility abstract phase equilibrium analysis of the relevant systems together with the application of the principles of chemical equilibrium put severe constraints on the interpretation of fluid inclusion data in terms of immiscibility in part i following from that point the major limits on the accuracy and even the validity of fluid inclusion quantitative data and their interpretation in terms of fluid composition and density are briefly discussed the practical implications of the general constraints temperature pressure topology of the fluid systems are envisaged emphasis is laid on some important consequences such as the use of isochore intercepts and the possible resulting interpretation of fluid mixing rather than unmixing the case of highly saline inclusions the identification and interpretation of heterogeneous trapping the composition and density constraints on coexisting fluids are presented and illustrated by natural examples taking into account all the measurable parameters in fluid inclusions volume temperature and nature of phase transitions more or less complete individual spectroscopic analyses all the available experimental data and all the theoretical constraints may be long and difficult however it is most generally very informative and productive although part of these data is often sufficient to deny unmixing nevertheless a final example on metamorphic fluids demonstrates how such an approach can prove and also characterize a fluid unmixing during a geologic process

seismic reflectivity of a finely layered granulite facies ductile shear zone in the southern grenville province quebec abstract lithoprobe reflection profile 54 across the granulite facies morin shear zone msz in the grenville tectonic province quebec canada reveals a west dipping zone of strong reflections the origin of these reflections has been investigated by detailed field mapping laboratory measurements of p wave velocities and densities of representative rock samples from the main lithological units and forward synthetic modeling petrofabric and microstructural analyses were performed in order to interpret the measured seismic properties synthetic seismograms generated from the velocity and density data demonstrate that reflections originate from lithologic thin layers and thin layer clusters likely resulted from intensive tectonic transposition and metamorphic differentiation lattice preferred orientation lpo induced anisotropy of granulite facies mylonites except for those containing abundant sillimanite biotite or amphibole is very low and hence unlikely to be the primary cause for reflections confining pressure does not significantly affect the reflectivity of the shear zone because the reflection coefficients are not sensitive to pressure up to at least 600 mpa since composite reflections of thin layer clusters can cause high reflectivity the strong reflectivity from some deep crustal sections with low refraction velocities may be interpreted to be due to the presence of thin layer mafic clusters within dominantly felsic rocks

pyrite re os and zircon u pb dating of the tugurige gold deposit in the western part of the xing an mongolia orogenic belt china and its geological significance abstract the tugurige gold deposit in the northeastern margin of the north china craton ncc and western part of the xing an mongolia orogenic belt xmob is a large tonnage quartz vein type deposit with a resource of 24 t at about 4 g t au gold mineralization is hosted by porphyritic syenogranite and controlled by nw trending faults our study provides the first precise age for the tugurige gold mineralization and host porphyritic syenogranite the u pb age of zircons from the syenogranite is 276 2 ma and re os dating of six pyrite separates from the deposit yields an isochron age of 268 15 ma the results show that the ages of syenogranite and gold mineralization are the same within error furthermore geological and geochronological evidence indicate that the syenogranite and gold mineralization have very close genetic relationships and that they are products of permian magmatism related to post collisional extension of the central asian orogenic belt caob the initial os isotopic compositions 187 os 188 os 1 26 0 69 of pyrite indicate that the source of os and by inference other ore related materials are derived from the crust the late paleozoic is an important period in which economic gold mineralization was deposited in the caob

a paleomagnetic study from the late jurassic volcanics 155 ma north china implications for the width of mongol okhotsk ocean abstract a new paleomagnetic study has been carried out on the tiaojishan formation effusives in the chengde area north china block ncb the age of the tiaojishan formation volcanics was recently dated from 153 ma to 161 ma by u pb and 40 ar 39 ar a total of 154 samples from 16 sites within the tiaojishan formation were collected detailed stepwise thermal demagnetization allows us to isolate two components from 77 oriented drill core samples a low temperature component identified in most samples falls close to the present local earth field direction characteristic remanent directions obtained from high temperature pass reversal test yield a pole position at 240 3 e 59 9 n with 95 6 8 combined with coeval paleopoles obtained from the siberia block sib these results show a significant paleolatitude displacement between the ncb and sib which indicates that the mongol okhotsk ocean was still open with 3000 km width in its eastern part at ca 155 ma

metallogenic age and hydrothermal evolution of the jidetun mo deposit in central jilin province northeast china evidence from fluid inclusions isotope systematics and geochronology abstract the jidetun deposit is a large porphyry mo deposit that is located in central jilin province northeast china the mo mineralization occurs mainly at the edge of porphyritic granodiorite as well as the adjacent monzogranite field investigations cross cutting relationships and mineral paragenetic associations indicate four stages of hydrothermal activity to determine the relationships between mineralization and associated magmatism and better understand the metallogenic processes in ore district we have undertaken a series of studies incluiding molybdenite re os and zircon u pb geochronology fluid inclusions microthermometry and c h o s pb isotope compositions the molybdenite re os dating yielded a well defined isochron age of 168 9 1 9 ma mswd 0 34 that is similar to the weighted mean 206 pb 238 u age of 173 5 1 5 ma mswd 1 8 obtained from zircons from the porphyritic granodiorite the results lead to the conclusion that mo mineralization occurred in the middle jurassic 168 9 1 9 ma was spatially temporally and genetically related to the porphyritic granodiorite 173 5 1 5 ma rather than the older monzogranite 180 1 0 6 ma fluid inclusion and stable c h o isotope data indicate that the initial h 2 o nacl fluids of mineralization stage i were of high temperature and high salinity affinity and exsolved from the granodiorite magma as a result of cooling and fractional crystallization the fluids then evolved during mineralization stage ii into immiscible h 2 o co 2 nacl fluids that facilitated the transport of metals mo cu and fe and their separation from the ore bearing magmas due to the influx of abundant external co 2 and heated meteoric water subsequently during mineralization stage iii and iv increase of ph in residual ore forming fluids on account of co 2 escape and continuous decrease of ore forming temperatures caused by the large accession of the meteoric water into the fluid system reduced solubility and stability of metal clathrates thus facilitating the deposition of polymetallic sulfides

fluid inclusion and stable isotope constraints on ore genesis of the zajkan epithermal base metal deposit tarom hashtjin metallogenic belt nw iran in the zajkan pb zn cu au ag deposit of the tarom hashtjin metallogenic belt thmb northwest iran mineralization occurs as quartz base metal sulfide veins hosted by eocene volcanic and volcaniclastic rocks of the karaj formation four stages of ore formation are identified at zajkan 1 quartz chalcopyrite pyrite veins 2 quartz galena sphalerite chalcopyrite pyrite veins and breccias 3 quartz hematite veins and breccias and 4 barren quartz carbonate veinlets the primary metallic minerals are pyrite chalcopyrite sphalerite galena and trace amounts of hematite gangue minerals are mainly quartz sericite chlorite and calcite the main wall rock alteration is silicification and intermediate argillic and propylitic alteration the coexistence of different types of fluid inclusions lv vl and v in individual fluid inclusion assemblages in quartz and sphalerite suggests boiling and heterogeneous trapping excluding the heterogeneously entrapped fluid inclusions the microthermometric measurements of primary lv fluid inclusion assemblages in quartz and sphalerite indicate that the veins were formed at temperatures between 217 and 273 degrees c from fluids with salinities between 1 7 and 6 4 wt nacl equiv the oxygen isotopic compositions delta o 18 water vsmow of 3 7 to 1 1 parts per thousand indicate that the ore forming fluids were mainly derived from magmatic water with the input of meteoric water in the later ore stages sulfur isotopic values of sulfide minerals vary over a narrow range from 5 0 to 0 9 parts per thousand vcdt averaging 2 2 parts per thousand vcdt suggesting that sulfur was derived from a homogeneous magmatic source the fluid inclusion and stable isotope data indicate that fluid boiling and mixing facilitated hydrothermal alteration and mineralization at zajkan our data suggest that the zajkan deposit is an intermediate sulficiation style epithermal mineralization the estimated ore formation depth of zajkan indicates minor denudation in the region and may imply a great prospecting potential for other epithermal mineralization in the thmb

the crustal accretion history and tectonic evolution of the ne china segment of the central asian orogenic belt abstract the basement rocks in parts of ne china constitute a khondalitic sequence of sillimanite and garnet bearing gneisses hornblende plagioclase gneiss and various felsic paragneisses zircon u pb dating of garnet sillimanite gneiss samples from the erguna xing an jiamusi and khanka blocks indicates that high grade metamorphism occurred at 500 ma evidence from detrital zircons in paleozoic sediments from the songliao block also indicates the former presence of a 500 ma component this uniformity of u pb ages across all crustal blocks in ne china establishes a 1300 km long late pan african khondalite belt which we have named the ne china khondalite belt this indicates the blocks of ne china were amalgamated prior to 500 ma contrary to current belief one scenario is that this amalgamated terrane had a tectonic affinity to the siberia craton once forming part of the late pan african 500 ma sayang baikal orogenic belt extensively developed around the southern margin of the siberia craton this belt was the result of collision between currently unidentified terranes with the southeastern angara anabar province at about 500 ma where the rocks were deformed and metamorphosed to granulite facies it appears likely that at sometime after 450 ma the combined ne china blocks rifted away from siberia and moved southward to form what is now ne china the combined block collided with the north china craton along the solonker xar moron changchun suture zone at 230 ma rather than in the end permian as previously thought local rifting at the eastern extremity of the developing central asian orogenic belt caob resulted in the splitting away of the jiamusi khanka bureya blocks however this was only transient and sometime between 210 and 180 ma these were re united with the caob by the onset of pacific plate subduction which has dominated the tectonic evolution of the region since that time

on the use of dispersive apvo gpr curves for thin bed properties estimation theory and application to fracture characterization the presence of a thin layer embedded in any formation creates complex reflection patterns caused by interferences within the thin bed the generated reflectivity amplitude variations with offset have been increasingly used in seismic interpretation and more recently tested on ground penetrating radar gpr data to characterize nonaqueous phase liquid contaminants phase and frequency sensitivities of the reflected signals are generally not used although they contain useful information the present study aims to evaluate the potential of these combined properties to characterize a thin bed using gpr data acquired along a common midpoint cmp survey carried out to assess velocity variations in the ground it has been restricted to the simple case of a thin bed embedded within a homogeneous formation a situation often encountered in fractured media dispersive properties ofthe dielectric permittivity of investigated materials homogeneous formation thin bed are described using a jonscher parameterization which permitted study of the dependency of amplitude and phase variation with offset apvo curves on frequency and thin bed properties filling nature aperture in the second part we discuss and illustrate the validity of the thin bed approximation as well as simplify assumptions and make necessary careful corrections to convert raw cmp data into dispersive apvo curves two different strategies are discussed to correct the data from propagation effects a classical normal moveout approach and an inverse method finally the proposed methodology is applied to a cmp gpr data set acquired along a vertical cliff it allowed us to extract the characteristics of a subvertical fracture with satisfying resolution and confidence the study motivates interest to use dispersion dependency of the reflection coefficient variations for thin bed characterization

paleozoic multiple accretionary and collisional tectonics of the chinese tianshan orogenic collage abstract subduction related accretion in the junggar balkash and south tianshan oceans paleo asian ocean mainly in the paleozoic gave rise to the present 2400 km long tianshan orogenic collage that extends from the aral sea eastwards through uzbekistan tajikistan kyrgyzstan to xinjiang in china this paper provides an up to date along strike synthesis of this orogenic collage and a new tectonic model to explain its accretionary evolution the northern part of the orogenic collage developed by consumption of the junggar balkash ocean together with paleozoic island arcs northern ili issyk kul and chatkal located in the west which may have amalgamated into a composite arc in the paleozoic in the west and by addition of another two roughly parallel arcs dananhu and central tianshan in the east the western composite arc and the eastern dananhu and central tianshan arcs formed a late paleozoic archipelago with multiple subduction zones the southern part of the orogenic collage developed by the consumption of the south tianshan ocean which gave rise to a continuous accretionary complex kokshaal kumishi which separated the central tianshan in the east and other paleozoic arcs in the west from cratons tarim and karakum to the south cross border correlations of this accretionary complex indicate a general southward and oceanward accretion by northward subduction in the early paleozoic to permian as recorded by successive southward juxtaposition of ophiolites slices of ophiolitic melanges cherts island arcs olistostromes blueschists and turbidites which are mainly paleozoic in age with the youngest main phase being late carboniferous permian the initial docking of the southerly tarim and karakum cratons to this complicated late paleozoic archipelago and accretionary complexes occurred in the late carboniferous early permian in the eastern part of the tianshan and in the late permian in the western part which might have terminated collisional deformation on this suture zone the final stages of closure of the junggar balkash ocean resembled the small ocean basin scenario of the mediterranean sea in the cenozoic in summary the history of the altaids is characterized by complicated multiple accretionary and collisional tectonics

intermediate sulfidation type base metal mineralization at aliabad khanchy tarom hashtjin metallogenic belt nw iran abstract the aliabad khanchy epithermal base metal deposit is located in the tarom hashtjin metallogenic belt thmb of northwest iran the mineralization occurs as cu bearing brecciated quartz veins hosted by eocene volcanic and volcaniclastic rocks of the karaj formation ore formation can be divided into five stages with most ore minerals such as pyrite and chalcopyrite being formed in the early stages the main wall rock alteration is silicification and chlorite argillic and propylitic alteration microthermometric measurements of fluid inclusion assemblages show that the ore forming fluids have eutectic temperatures between 30 and 52 c trapping temperatures of 150 290 c and salinities of 6 6 12 4 wt nacl equiv these data demonstrate that the ore forming fluids were medium to high temperature medium to low salinity and low density h2o nacl cacl2 fluids calculated 18o values indicate that ore forming hydrothermal fluids had 18owater ranging from 3 6 to 0 8 confirming that the ore fluid system evolved from dominantly magmatic to dominantly meteoric the calculated 34sh2s values range from 8 1 to 5 0 consistent with derivation of the sulfur from either magma or possibly from local volcanic wall rock combined the fluid inclusion and stable isotope data indicate that the aliabad khanchy deposit formed from magmatic hydrothermal fluids after rising to a depth of between 790 and 500 m the fluid boiled and subsequent hydraulic fracturing may have led to inflow and or mixing of early magmatic fluids with circulating groundwater causing deposition of base metals due to dilution and or cooling the aliabad khanchy deposit is interpreted as an intermediate sulfidation style of epithermal mineralization our data suggest that the mineralization at aliabad khanchy and other epithermal deposits of the thmb formed by hydrothermal activity related to shallow late eocene magmatism the altered eocene volcanic and volcaniclastic rocks especially at the intersection of subvolcanic stocks with faults were the most favorable sites for epithermal ore bodies in the thmb

exploration tools for linked porphyry and epithermal deposits example from the mankayan intrusion centered cu au district luzon philippines the mankayan mineral district of northern luzon philippines hosts several significant ore deposits and prospects of various types within an area of similar to 25 km 2 including the far southeast porphyry cu au deposit the lepanto high sulfidation epithermal cu au deposit the victoria intermediate sulfidation epithermal au ag vein deposit the teresa epithermal au ag vein deposit the guinaoang porphyry cu au deposit and the buaki old palidan porphyry cu au prospects all having formed in a period of about 2 m y from similar to 3 ma the geologic units include 1 a basement composed of late cretaceous to middle miocene metavolcanic rocks volcaniclastic rocks 2 the miocene 12 to 13 ma tonalitic bagon intrusive complex 3 the pliocene similar to 2 2 to 1 8 ma imbanguila dacite porphyry and pyroclastic rocks and 4 postmineralization cover rocks including die similar to 1 2 to 1 0 ma bato dacite porphyry and pyroclastic rocks and the similar to 0 02 ma lapangan tuff extensive advanced argillic alteration crops out for similar to 7 kin along the inconformity between the basement rocks and the imbanguila dacite formation consists of quartz alunite pyrophyllite or diaspore with local zones of silicic alteration and a halo of dickite kaolinite the alteration and its subhorizontal geometry indicate that it is a lithocap or coalesced lithocaps the northwest striking portion is similar to 4 km long and hosts the lepanto enargite au ore deposit also controlled by the lepanto fault the lepanto epithermal deposit is related to the underlying far southeast porphyry the quartz alunite alteration halo of lepanto is contemporaneous with the similar to 1 4 ma potassic alteration of the porphyry there are also silicic advanced argillic alteration patches similar to 600 m above the far southeast orebody at the present surface these are interpreted to be perched alteration there is no systematic mineralogical or textural zoning in the lepanto lithocap that indicates direction to the intrusive source most surface samples of the lithocap contain less than 50 ppb au despite many being less than a few hundred meters from underground cu au ore this study found that several characteristics of the lepanto lithocap change systematically with distance from the causative intrusion the alunite absorption peak at similar to 1 480 nm in the short wavelength infrared swir spectrum shifts to higher wavelengths where the sample is closer to the intrusive center due to higher na and lower k content in the alunite published experimental studies indicate that high na na k is related to higher formation temperature high ca alunite including huangite also occurs at locations proximal to the intrusive center alunite mineral composition analyzed by laser ablation inductively coupled plasma mass spectrometry la icp ms indicates that the pb content decreases toward the intrusive center whereas sr la sr ph and la pb increase markedly whole rock compositions using only nonmineralized taken as cu similar to 350 m above the upper extent of the veins an airborne geophysics survey indicates that the far southeast orebody is associated with a wide zone of demagnetization due to extensive magnetite destructive phyllic alteration such low magnetic anomalies on the margin of a large lithocap elsewhere may deserve attention the directional indicators and mineralization signatures found in this study have the potential to indicate direction to the intrusive center during exploration of similar porphyry epithermal districts

acoustic reflections from complex strata rock strata may contain fine scale structures which are too small to be identified directly but which can give rise to anomalous seismic reflection amplitudes the variance caused by such anomalies severely hampers the use of reflection amplitudes for layer identification and techniques are required which can identify or correct for the effects of such fine structure we have done calculations which explore the consequences of two general structure types wavy interfaces and very thin layers in each case a formalism is set up which enables us to identify systematically all of their effects computer modeling of realistic formations verified our calculations we suggest that the strongly wavelength dependent response of such layers and their characteristic response waveforms may provide convenient tools for identifying fine scale features in strata

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

a probe for measuring wetting front migration in rocks to facilitate investigations of flow dynamics in unsaturated fractured rocks we have designed a probe to qualitatively monitor saturation changes in borehole environments this flexible probe is able to fit the cylindrical shape of boreholes and requires no backfill field results suggest that the design of this electrical resistivity probe erp is suitable for determining changes in relative wetness along boreholes in unsaturated fractured rock environments the performance of these probes was compared with that of psychrometers under a variety of tests these probes were found to be significantly cheaper in addition to providing data that had a greater spatial and temporal resolution

distribution of porphyry copper deposits along the western tethyan and andean subduction zones insights from a paleotectonic approach abstract along the western tethyan and andean subduction zones the distribution of cretaceous and cenozoic porphyry cu deposits is not random and shows that they were emplaced in distinct regional clusters to understand the appearance of these clusters within their geodynamical contexts and identify kinematic features which would favor the genesis of porphyry type ore bodies we use a paleotectonic approach two clusters in the aegean balkan carpathian area which were emplaced in upper cretaceous and oligo miocene and two others in the andes which were emplaced in late eocene and miocene are sufficiently well constrained to be studied in detail it appears that they are associated with a specific polyphased kinematic context related to the convergence of tectonic plates this context is characterized by 1 a relatively fast convergence rate shortly followed by 2 a drastic decrease of this rate from these observations and assuming that the major part of plate convergence is accommodated along subduction zones we propose a two phase geodynamic model favoring emplacement of porphyry cu deposits 1 a high melt production in the mantle wedge followed by 2 an extensional regime or at least relaxation of the compressional stress in the upper plate promoting ascension of fertile magmas to the upper crust melt production at depth and the following extensional regime which would be related to variations in convergence rate are thus associated with variations in plate and trench velocities themselves being controlled by both plate kinematics at the surface and slab dynamics in the upper mantle in particular along strike folding behavior of the subducting slab may strongly influence trench velocity changes and the location of porphyry cu deposits metallogenic data suggest that periods of slab retreat which would favor mineralization processes during 40 myrs would be separated by barren periods lasting 10 to 20 myrs corresponding to shorter episodes of trench advance as observed in laboratory experiments these results confirm the control of the geodynamic context and especially subduction dynamics on the genesis of porphyry cu deposits this study also shows that the paleotectonic approach is a promising tool that could help identify geodynamic and tectonic criteria favoring the genesis of various ore deposits

origin and evolution of hydrothermal fluids in the marshoun epithermal pb zn cu ag deposit tarom hashtjin metallogenic belt nw iran abstract the marshoun epithermal pb zn cu ag deposit is located in the tarom hashtjin metallogenic belt thmb northwest iran the epithermal base metal veins are mainly hosted in eocene volcanic and volcaniclastic rocks of the karaj formation and late eocene pyroxene quartz monzodiorite the mineralization process can be divided into five stages 1 quartz chalcopyrite pyrite veins and breccias 2 quartz calcite sphalerite galena chalcopyrite pyrite veins and breccias 3 barren post ore quartz veinlets 4 barren post ore calcite veinlets and 5 supergene mineral assemblages the primary metallic minerals are pyrite chalcopyrite sphalerite and galena gangue minerals are mainly quartz calcite sericite and chlorite the main wall rock alteration is silicification intermediate argillic carbonate and propylitic alteration microthermometric measurements of primary lv fluid inclusion assemblages in quartz and sphalerite indicate that the veins were mainly formed at temperatures between 173 and 285 c from fluids with salinities between 3 4 and 6 3 wt nacl equiv coexisting lv vl and v inclusions in quartz and sphalerite provide evidence for boiling in ore stage breccia and veins additionally the occurrence of bladed calcite as well as plumose and colloform crustiform banded quartz in the ore zones and the presence of hydrothermal breccias are consistent with boiling obtained oxygen and sulfur isotope compositions 18owater 9 2 to 1 5 34sh2s 10 0 to 5 7 indicate there was a major contribution from a magmatic component to metallogenesis the fluid inclusion and stable isotope data indicate that fluid boiling and mixing facilitated hydrothermal alteration and mineralization at marshoun the marshoun deposit is interpreted as an intermediate sulfidation style of epithermal mineralization our data suggest that the epithermal mineralization in the thmb are related to late eocene ca 36 37 ma shallow magmatic hydrothermal activity the altered eocene volcanic subvolcanic rocks particularly at the intersection of subvolcanic rocks with faults were the most favorable locus for exploration targeting of epithermal ores at thmb

re os dating and sulfur isotope composition of molybdenite from tungsten deposits in western namaqualand south africa implications for ore genesis and the timing of metamorphism both stratiform stratabound and granite related models have been used to explain the genesis of w mo deposits in the okiep copper district in western namaqualand south africa apparently stratabound mineralization fe rich wolframite with accessory molybdenite occurs in foliation parallel quartz veins in high grade 750 c 5 6 kbar metapelites of the wolfram formation and less commonly in small bodies of silicified leucogranites and pegmatites six re os ages for molybdenites from four deposits nababeep tungsten far west kliphoog narrap tweedam range between 1000 4 and 1026 5 ma these molybdenites define a well constrained 187re 187os isochron with an age of 1019 6 ma which is interpreted as the age of w mo mineralization this age is significantly younger than proterozoic protolith ages for supracrustal rocks and the emplacement ages for the main intrusive suites but geologic evidence requires overlap with a period of high grade metamorphism we suggest that w mo mineralization is genetically linked to intra crustal magmatic processes at 1020 ma thereby precluding the 1060 ma concordia granite as the source for mineralizing fluids a narrow range of positive 34s compositions 3 6 to 4 5 for eight molybdenites from five w mo mines is consistent with a so2 rich fluid and a granite related genetic model post peak metamorphic deformation and metamorphism of w mo ores is most likely related to the retrograde stage of the namaquan orogeny which overlaps emplacement of late orogenic evolved granites and pegmatites and the formation of w mo deposits in western namaqualand therefore the effects of retrograde namaquan metamorphism extend at least to 1020 ma or alternatively these w mo veins were affected by a poorly constrained later event e g early pan african

early jurassic porphyry copper mineralization in ne china a case study of the yanghuidongzi deposit abstract the yanghuidongzi cu deposit is located in the southeastern part of heilongjiang province in ne china and represents one of the few known early jurassic porphyry cu deposits within the eastern edge of the xing an mongolia orogenic belt here we present new whole rock major and trace element and sr nd isotopic data zircon u pb and hf isotopic data and molybdenite re os data for units associated with the deposit laser ablation inductively coupled plasma mass spectrometry la icp ms dating of zircons from the granodiorite porphyry in the study area yielded ages of 191 0 1 1 and 191 2 1 0 ma that are interpreted to be the emplacement age of this intrusion the molybdenite re os dating undertaken during this study yielded model ages of 192 7 187 0 ma an isochron age of 188 2 3 8 ma and a weighted mean model age of 190 2 2 6 ma representing the timing of formation of the cu mineralization in this area the yanghuidongzi granodiorite porphyry contains relatively high concentrations of sio 2 68 88 72 49 wt al 2 o 3 15 37 16 31 wt and sr 230 479 ppm but relatively low concentrations of y 7 97 9 87 ppm and yb 0 72 0 85 ppm suggesting that this intrusion has an adakitic affinity combining this with the positive end t 0 7 1 1 and ehf t values 4 0 6 9 low mg values 41 50 and the low concentrations of mgo 0 86 1 22 wt cr 3 17 4 37 ppm and ni 2 11 4 20 ppm within this intrusion suggests it formed from a magma generated by the partial melting of juvenile lower crustal material during the early jurassic subduction of the paleo pacific plate

what drove late mesozoic extension of the northern china mongolia tract the northern china mongolia tract exhibited a tectonic transition from contractional to extensional deformation in late mesozoic time late middle to early late jurassic crustal shortening is widely thought to have resulted from collision of an amalgamated north china mongolia block and the siberian plate but widespread late late jurassic early cretaceous extension has not been satisfactorily explained by existing models some prominent features of the extensional tectonics of the northern china mongolia tract are 1 late jurassic voluminous volcanism prior to early cretaceous large magnitude rapid extension 2 overlapping in time of contractional deformation in the yinshan yanshan belt with development of extensionrelated basins in the interior of the northern china mongolia tract and 3 widespread occurrence of alkali granitic plutonism extensional basins and metamorphic core complexes in the early cretaceous a new explanation is advanced in this study for this sequence of events the collision of amalgamated north china mongolia with siberia led to crustal overthickening of the northern china mongolia tract and formation of a high standing plateau subsequent breakoff at depth of the north dipping mongol okhotsk oceanic slab is suggested as the main trigger for late mesozoic lithospheric extension of that tract slab breakoff resulted in mantle lithospheric stretching of the adjacent northern china mongolia tract with subsequent ascent of hot asthenosphere and magmatic underplating at the base of the crust collectively these phenomena triggered gravitational collapse of the previously thickened crust leading to late late jurassic early cretaceous crustal extension and importantly coeval contraction along the southern margin of the plateau in the yinshan yanshan belt the proposed model provides a framework for interpreting the spatial and temporal relationships of distinct processes and reconciling some seemingly contradictory phenomena such as the synchronous extension of northerly terranes during major contraction in the neighboring yanshan yinshan belt d 2003 elsevier b v all rights reserved

geodynamics and metallogeny of the central eurasian porphyry and related epithermal mineral systems a review abstract major porphyry cu au and cu mo deposits are distributed across almost 5000 km across central eurasia from the urals mountains in russia in the west to inner mongolia in north eastern china these deposits were formed during multiple magmatic episodes from the ordovician to the jurassic they are associated with magmatic arcs within the extensive subduction accretion complex of the altaid and transbaikal mongolian orogenic collages that developed from the late neoproterozoic through the palaeozoic to the jurassic intracratonic extension the arcs formed predominantly on the palaeo tethys ocean margin of the proto asian continent but also within two back arc basins the development of the collages commenced when slivers of an older proterozoic subduction complex were rifted from an existing cratonic mass and accreted to the palaeo tethys ocean margin of the combined eastern europe and siberian cratons subduction of the palaeo tethys ocean beneath the karakum and altai tarim microcontinents and the associated back arc basin produced the overlapping late neoproterozoic to early palaeozoic tuva mongol and kipchak magmatic arcs contemporaneous intra oceanic subduction within the back arc basin from the late ordovician produced the parallel urals zharma magmatic arc and separated the main khanty mansi back arc basin from the inboard sakmara marginal sea by the late devonian the tuva mongol and kipchak arcs had amalgamated to form the kazakh mongol arc by the mid palaeozoic the two principal cratonic elements the siberian and eastern european cratons had begun to rotate relative to each other drawing in the two sets of parallel arcs to form the kazakh orocline between the two cratons during the late devonian to early carboniferous the palaeo pacific ocean began subducting below the siberian craton to form the sayan transbaikal arc which expanded by the permian to become the selanga gobi khanka arc by the middle to late permian as the kazakh orocline continued to develop both the sakmara and khanty mansi back arc basins were closed and the collage of cratons and arcs were sutured by accretionary complexes during the permian and triassic the north china craton approached and docked with the continent closing the mongol okhotsk sea an embayment on the palaeo pacific margin to form the mongolian orocline subduction and arc building activity on the palaeo pacific ocean margin continued to the mid mesozoic as the indosinian and yanshanian orogens significant porphyry cu au mo and au cu deposits were formed during the ordovician in the kipchak arc e g bozshakol cu au in kazakhstan and taldy bulak porphyry cu au in kyrgyzstan silurian to devonian in the kazakh mongol arc e g nurkazgan cu au in kazakhstan and taldy bulak levoberezhny au in kyrgyzstan devonian in the urals zharma arc e g yubileinoe au cu in russia devonian in the kazakh mongol arc e g oyu tolgoi cu au and tsagaan suvarga cu au in mongolia carboniferous in the kazakh mongol arc e g kharmagtai au cu in mongolia tuwu yandong cu au in xinjiang china koksai cu au kounrad cu au and the aktogai group of cu au deposits in kazakhstan carboniferous in the valerianov beltau kurama arc e g kal makyr dalnee cu au in uzbekistan benqala cu au in kazakhstan late carboniferous to permian in the selanga gobi khanka arc e g duobaoshan cu au in inner mongolia china triassic in the selanga gobi khanka arc and jurassic in the selanga gobi khanka arc e g wunugetushan cu mo and jiguanshan mo in inner mongolia china in addition to the tectonic geologic and metallogenic setting and distribution of porphyry cu au mo mineralisation within central eurasia the setting geology alteration and mineralisation at each of the deposits listed above is described and summarised in table 1

spatial temporal relationships of mesozoic volcanic rocks in ne china constraints on tectonic overprinting and transformations between multiple tectonic regimes abstract la icp ms zircon u pb ages and geochemical data are presented for the mesozoic volcanic rocks in northeast china with the aim of determining the tectonic settings of the volcanism and constraining the timing of the overprinting and transformations between the paleo asian ocean mongol okhotsk and circum pacific tectonic regimes the new ages together with other available age data from the literature indicate that mesozoic volcanism in ne china can be subdivided into six episodes late triassic 228 201 ma early middle jurassic 190 173 ma middle late jurassic 166 155 ma early early cretaceous 145 138 ma late early cretaceous 133 106 ma and late cretaceous 97 88 ma the late triassic volcanic rocks occur in the lesser xing an zhangguangcai ranges where the volcanic rocks are bimodal and in the eastern heilongjiang jilin provinces where the volcanics are a type rhyolites implying that they formed in an extensional environment after the final closure of the paleo asian ocean the early middle jurassic 190 173 ma volcanic rocks both in the erguna massif and the eastern heilongjiang jilin provinces belong chemically to the calc alkaline series implying an active continental margin setting the volcanics in the erguna massif are related to the subduction of the mongol okhotsk oceanic plate beneath the massif and those in the eastern jilin heilongjiang provinces are related to the subduction of the paleo pacific plate beneath the eurasian continent the coeval bimodal volcanic rocks in the lesser xing an zhangguangcai ranges were probably formed under an extensional environment similar to a backarc setting of double direction subduction volcanic rocks of middle late jurassic 155 166 ma and early early cretaceous 145 138 ma age only occur in the great xing an range and the northern hebei and western liaoning provinces limited to the west of the songliao basin and they belong chemically to high k calc alkaline series and a type rhyolites respectively combined with the regional unconformity and thrust structures in the northern hebei and western liaoning provinces we conclude that these volcanics formed during a collapse or delamination of a thickened continental crust related to the evolution of the mongol okhotsk suture belt the late early cretaceous volcanic rocks widely distributed in ne china belong chemically to a low to medium k calc alkaline series in the eastern heilongjiang jilin provinces i e the eurasian continental margin and to a bimodal volcanic rock association within both the songliao basin and the great xing an range the volcanics in the eastern heilongjiang jilin provinces formed in an active continental margin setting related to the subduction of the paleo pacific plate beneath the eurasian continent and the bimodal volcanics formed under an extensional environment related either to a backarc setting or to delamination of a thickened crust or both late cretaceous volcanics limited to the eastern heilongjiang jilin provinces and the eastern north china craton ncc consist of calc alkaline rocks in the eastern heilongjiang jilin provinces and alkaline basalts in the eastern ncc suggesting that the former originated during subduction of the paleo pacific plate beneath the eurasian continent whereas the latter formed in an extensional environment similar to a backarc setting taking all this into account we conclude that 1 the transformation from the paleo asian ocean regime to the circum pacific tectonic regime happened during the late triassic to early jurassic 2 the effect of the mongol okhotsk suture belt on ne china was mainly in the early jurassic middle late jurassic and early early cretaceous and 3 the late early cretaceous and late cretaceous volcanics can be attributed to the subduction of the paleo pacific plate beneath the eurasian continent

genesis of the tianbaoshan pb zn cu mo polymetallic deposit in eastern jilin ne china constraints from fluid inclusions and c h o s pb isotope systematics abstract the tianbaoshan pb zn cu mo deposit is located in the eastern part of jilin heilongjiang region ne china which is considered to be the eastern segment of the central asian orogenic belt field and geochronological evidences indicate that this deposit experienced three types of mineralization including hercynian skarn cryptoexplosion breccia pipe and yanshanian quartz vein the early stages of the pb zn cu mineral systems in skarn and cryptoexplosion breccia pipe are characterized by a high temperature high salinity h 2 o co 2 nacl system of hydrothermal fluids that were possibly exsolved from the hercynian wall rock granodiorite these fluids show h o isotopic compositions similar to those of typical magmatic fluids by contrast the low temperature hydrothermal fluids of the later stages are represented by low salinity nacl h 2 o systems with low h o isotopic values the skarn and cryptoexplosive breccia pipe types of pb zn cu mineralization tend to have weakly negative 34 s values of 4 0 to 0 8 mean values of 2 31 and 2 16 respectively indicating that the sulfur was sourced from the hercynian magma therefore the early stage ore forming fluids of the skarn and cryptoexplosive breccia pipe were most likely sourced from high temperature and high salinity fluids closely related to the cooling and fractional crystallization of the hercynian granodiorite while the later stages changed to nacl h 2 o meteoric water influx whereas the ore forming fluids of the quartz vein type of mo mineralization were high temperature high salinity nacl h 2 o systems that differed from those of the skarn and cryptoexplosion breccia pipe but their h o isotopic compositions also indicate a magmatic fluid the weakly enriched 34 s values of molybdenite from the quartz vein type mo mineralization 34 s 0 2 2 8 average of 1 65 are comparable with those of other mesozoic yanshanian mo deposits 34 s 0 4 4 1 with an average of 1 39 3 15 but differ significantly from those of the hercynian pb zn cu skarn and cryptoexplosion breccia pipe this indicates that the sulfur of quartz vein type of mo originated from mesozoic yanshanian magmatism and that the ore forming fluids were derived from yanshanian magmatic rocks rather than being a product of the hercynian activity the 13 c values of the fluid inclusions in quartz from the skarn cryptoexplosion breccia pipe and quartz vein types are in a narrow range of 19 5 to 9 3 similar to those of the shanxiuling group which indicates that the carbon of the three types of mineralization had the same primary origin in the shanxiuling group the lead isotope compositions of ores from the skarn and cryptoexplosion breccia pipe types of mineralization 206 pb 204 pb 18 0725 18 3627 207 pb 204 pb 15 3721 15 5694 and 208 pb 204 pb 37 5542 38 8208 overlap with those of the hercynian granodiorite and shanxiuling group marble suggesting that the lead was probably derived from a mix of two different sources the shanxiuling group and the hercynian granodiorite whereas the lead isotope compositions of ores from the quartz vein type of mo mineralization 206 pb 204 pb 18 3837 18 6949 207 pb 204 pb 15 6824 15 7293 and 208 pb 204 pb 39 1009 39 1889 are significantly higher than those of the shanxiuling group marble and the hercynian granodiorite this indicates that the lead may be a product of yanshanian magmatic activity instead of the nearby hercynian granodiorite

melting behavior of fluid inclusions in laboratory grown halite crystals in the systems naclh2o naclkclh2o naclmgcl2h2o and naclcacl2h2o abstract the chemical composition of aqueous fluid inclusions in crystals of halite can be accurately determined from observed melting behaviors of ice hydrohalite and sylvite some fluid inclusion melting behaviors observed in laboratory grown halite crystals systems nacl h 2 o nacl kcl h 2 o nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o differ from predicted stable equilibrium relations in the nacl h 2 o and nacl kcl h 2 o systems observed first melt temperatures are up to 15 c below the equilibrium eutectic temperatures of 21 2 and 22 9 c respectively the final melting temperature of ice in the presence of hydrohalite and the final melting temperature of hydrohalite are reproducible and match predicted melting temperatures the limit of detection of sylvite daughter crystals in the nacl kcl h 2 o system is approximately 5 wt 1 molal kcl final melting temperatures of sylvite match published equilibrium data to within 0 3 c in the nacl kcl h 2 o system at halite saturation m kcl can be determined from the final sylvite dissolution temperature or from the final melting temperature of hydrohalite fluid inclusions in the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems that form stable salt hydrates mgcl 2 12h 2 o and cacl 2 6h 2 o during freezing first melt within 3 c of predicted eutectic temperatures 37 and 52 c however fluid inclusions with mgcl 2 or cacl 2 may also start melting at temperatures as low as 80 c such low first melt temperatures indicate the presence of metastable salt hydrates presumably mgcl 2 8h 2 o mgcl 2 6h 2 o or cacl 2 4h 2 o the formation of metastable phases during freezing of fluid inclusions can lead to misinterpretation of the chemical composition of fluid inclusions in natural samples this is especially true for fluid inclusions with first melt temperatures below 37 c which may be erroneously interpreted as being rich in cacl 2 the final melting of ice in the presence of hydrohalite may vary by more than 15 c in fluid inclusions of different size but identical bulk composition and occurs at lower temperatures than predicted in fluid inclusions from the nacl mgcl 2 h 2 o and nacl cacl 2 h 2 o systems however the final melting temperature of ice in inclusions which fail to nucleate hydrohalite and the final melting temperature of hydrohalite are reproducible to within 0 1 c and can be used to determine mgcl 2 and cacl 2 molalities

timing and genesis of ore formation in the qarachilar cu mo au deposit ahar arasbaran metallogenic zone nw iran evidence from geology fluid inclusions o s isotopes and re os geochronology in the qarachilar cu mo au deposit of the ahar arasbaran metallogenic zone aamz northwest iran mineralization occurs as three quartz sulfide veins that cut granodiorite quartz monzodiorite rocks of the qaradagh batholith qdb ore formation can be divided into three stages with chalcopyrite molybdenite and gold bearing pyrite appearing mainly in the first two stages the main wall rock alteration is silicification and intermediate argillic carbonate and propylitic alteration fluid inclusion microthermometry indicates trapping of medium to high salinity 9 2 55 wt nacl equiv fluids at qarachilar fluid inclusion trapping conditions are estimated to be 190 degrees c 530 degrees c and 0 1 3 kbar the variable phase ratios as well as spatial coexisting of liquid and vapor rich two phase and halite bearing multiphase fluid inclusions homogenizing over the same temperatures are consistent with fluid boiling during ore formation obtained delta o 18 h2o values of quartz from ore stage veins are 5 7 parts per thousand to 9 7 parts per thousand signifying that the ore fluid system was predominantly magmatic water the average calculated delta s 34 h2s values are 1 1 parts per thousand for pyrite chalcopyrite and molybdenite consistent with a magmatic source for sulfur combined the fluid inclusion and stable isotope data indicate that the ore forming fluids at qarachilar were magmatic in origin and were subsequently cooled and diluted by meteoric water fluid boiling and mixing facilitated hydrothermal alteration and mineralization molybdenite re os dating shows that mineralization occurred at 42 35 0 16 ma coincident with formation of porphyry cu mo mineralization at agarak deposit and hanqasar aygedzor and dastakert prospects in the lesser caucasus however qarachilar is older than all porphyry cu mo mineralization in the aamz and urumieh dokhtar magmatic arc udma which suggests that collision between arabia and eurasia were oblique and thus diachronous our data suggest that mineralization at qarachilar is related to collisional eocene magmatic hydrothermal activity related to neo tethys subduction and shares a number of similarities with the vein type cu mo au mineralization related to cu mo porphyries

a type granites in northeastern china age and geochemical constraints on their petrogenesis abstract a type granites are widely distributed in northeastern china ne china they were emplaced during three major episodes the permian late triassic to early jurassic and early cretaceous and evolved in different tectonic regimes according to their mineralogical and geochemical characteristics two subgroups of a type granites aluminous and peralkaline can be recognized the peralkaline subgroup contains alkali mafic minerals such as riebeckite arfvedsonite and sodic pyroxene while the aluminous subgroup contains annite and fe rich calcic or sodic calcic amphibole with respect to the aluminous subgroup the peralkaline granites contain higher rb ga and total rare earth elements ree but lower mgo cao al 2 o 3 ba and sr based on the discrimination criteria of eby geology 20 1992 641 the permian and late triassic to early jurassic a type granites belong to the a 2 post orogenic type whereas the early cretaceous granites are of the a 1 anorogenic type nd isotopic compositions of these a type granites indicate their derivation from a dominantly juvenile crustal source their origin is thought to have involved partial melting of an underplated lower crustal source because the generation of a type granites requires high melting temperature we propose models involving slab break off lithospheric delamination and extension the permian a type granites have the same age range as those in eastern junggar southern mongolia and central inner mongolia they occur along a major suture and form a narrow belt between the north china and siberian cratons we suggest that their formation was associated with post collisional slab break off the late triassic to early jurassic a type granites are likely to be the product of lithospheric delamination after the final collision of the major crustal blocks in the late paleozoic to early triassic the early cretaceous a type granites have an anorogenic affinity and were possibly associated with rifting in eastern china at this time associated with the onset of paleo pacific subduction consequently we conclude that the a type granites in ne china were generated at three different times involving multiple processes operative in different tectonic environments

late mesozoic metallogeny and intracontinental magmatism southern great xing an range northeastern china abstract mineral deposits are typically tied to plate margin processes such as accretion or rifting however some major deposits occur in plate interiors e g deposits in the southern great xing an range lacking a clear association with the supercontinent cycle intrusive activity in the southern great xing an range peaked in late mesozoic i e 155 120 ma simultaneously with large scale mineralization in this area in addition the late mesozoic granitoids show initial nd and hf isotopic signatures of depleted mantle possibly newly underplated basaltic materials with variable contamination from older crust and with model ages younger than 1 0 ga fluid inclusion waters extracted from ore minerals pyrite galena sphalerite and chalcopyrite associated with the late mesozoic mineralization have elevated 3he 4he ratios indicating a contribution of mantle derived helium stable isotopes of fluid inclusion waters hydrogen and oxygen and of sulfide minerals sulfur confirm a magmatic source for these components lead isotope data of ore minerals indicate a significant mantle lead contribution from the newly underplated material thus the southern great xing an range is best described as a typical late mesozoic intracontinental metallogenic belt related to magmatism with a significant mantle contribution the magmatism and mineralization took place in a setting of lithospheric extension and resulted because of the break off of the southerly dipping mongol okhotsk oceanic slab at depth during closure of the mongol okhotsk ocean which also restricted the westward movement of the paleo pacific oceanic plate this interplay between plate tectonic events and mantle dynamics provides a good example of the evolution of magmatism and hydrothermal activity in intracontinental settings

in situ u pb zircon dating using laser ablation multi ion counting icp ms high resolution in situ u pb zircon geochronology on zoned grains can obtain isotope signatures from multiple growth or thermal events we present a method using laser ablation multicollector inductively coupled plasma mass spectrometry la mc icp ms to overcome complications associated with intricately zoned zircon crystals through in situ sampling of zircon volumes as small as 12 m 25 m and 40 m in diameter by about 10 m in depth high precision u pb age of a series of zircon standard covering a wide age range of 30 to 1 065 ma was acquired using la mc icp ms the precision of measured pb u ratios in homogeneous zircon is about 2 2 resulting in routinely achieved precision of u pb ages obtained by external calibration of 1 2 or better all masses of interest can be simultaneously recorded with a multi ion counting system mic operating in static mode and the short ablation required to achieve such precision results in spatial resolution that is superior to comparable u pb zircon analyses by single collector icp ms the resulting present u pb age for five zircon reference samples and two geological samples show an excellent agreement with the previously reported id tims or shrimp data

geodynamic setting of mesozoic magmatism in ne china and surrounding regions perspectives from spatio temporal distribution patterns of ore deposits abstract north eastern china and surrounding regions host some of the best examples of phanerozoic juvenile crust on the globe however the mesozoic tectonic setting and geodynamic processes in this region remain debated here we attempt a systematic analysis of the spatio temporal distribution patterns of ore deposits in ne china and surrounding regions to constrain the geodynamic milieu from an evaluation of the available geochronological data we identify five distinct stages of ore formation 240 205 ma 190 165 ma 155 145 ma 140 120 ma and 115 100 ma the triassic 240 205 ma magmatism and associated mineralisation occurred during in a post collisional tectonic setting involving the closure of the paleo asian ocean the early mid jurassic 190 165 ma events are related to the subduction of the paleo pacific ocean in the eastern asian continental margin whereas in the erguna block these are associated with the subduction of the mongol okhotsk ocean from 155 to 120 ma large scale continental extension occurred in ne china and surrounding regions however the late jurassic magmatism and mineralisation events in these areas evolved in a post orogenic extensional environment of the mongol okhotsk ocean subduction system the early stage of the early cretaceous events occurred under the combined effects of the closure of the mongol okhotsk ocean and the subduction of the paleo pacific ocean the widespread extension ceased during the late phase of early cretaceous 115 100 ma following the rapid tectonic changes resulting from the paleo pacific oceanic plate reconfiguration