u pb trace element and lu hf properties of unique dissolution reprecipitation zircon from uhp eclogite in sw sulu terrane eastern china abstract a unique dissolution reprecipitation zircon has been identified for the first time in a qtz and phe bearing eclogite from the drill hole ccsd mh southwestern sulu uhp terrane by using laser raman and cathodoluminescence cl imaging combined with trace element analyses and u pb and lu hf isotope data relic inherited domains of partially dissolved zircon show magmatic features and preserve mineral inclusions of cpx pl qtz ap whereas newly formed zircons crystallized around or along cracks of the inherited magmatic domains and contain mineral inclusions of coe grt omp phe ap typical for uhp metamorphism in addition primary fluid inclusions were identified in the coesite bearing zircon domains characterized by a single h2o phase or co2 h2o phase indicating the presence of fluids during uhp conditions strongly dissolved inherited magmatic zircons yielded shrimp 206pb 238u ages of 782 588 ma with an upper intercept age of 780 14 ma new recrystallized or metamorphic zircons yielded consistent triassic uhp ages around 238 225 ma with a weighted mean of 229 2 2 3 ma zircon trace element and hf isotope compositions and mineral inclusions classify the protolith of the sulu eclogite as an intermediate to mafic neoproterozoic igneous rock which was subducted to mantle depth and experienced uhp metamorphism in middle triassic times the juvenile ehf 780 ma value of 7 4 2 9 in inherited magmatic zircon points to a significant input from the depleted mantle to the dabie sulu uhp terrane during middle neoproterozoic new uhp zircon domains have low lu hf th u and significantly higher 176hf 177hf ratios than the inherited magmatic zircons consistent with formation during recrystallization and fractionation of the lu hf system during uhp metamorphism

mesozoic orogenic gold mineralization in the jiaodong peninsula china a focused event at 120 2 ma during cooling of pregold granite intrusions

fluvial changes of the guadalquivir river during the holocene in cordoba southern spain this research was funded by a grant from proyectos de cordoba siglo xxi coordinated by prof r jose roldan canas universidad de cordoba

a model of channel response in disturbed alluvial channels dredging and straightening of alluvial channels between 1959 and 1978 in west tennessee caused a series of morphologic changes along modified reaches and tributary streams degradation occurred for 10 to 15 years at sites upstream of the area of maximum disturbance and lowered bed levels by as much as 6 1 m following degradation reaches upstream of the area of maximum disturbance experienced a secondary aggradation phase in response to excessive incision and gradient reduction aggradation downstream of the area of maximum disturbance reached 0 12 m per year with the greatest rates occurring near the stream mouths the adjustment of channel geometry and phases of channel evolution are characterized by six process oriented stages of morphologic development premodified constructed degradation threshold aggradation and restabilization down cutting and toe removal during the degradation stage causes bank failure by mass wasting when the critical height and angle of the bank material is exceeded threshold stage channel widening continues through the aggradation stage as the slough line develops as an initial site of lower bank stability the bank profile develops three dynamic elements 1 vertical face 70 to 90 2 upper bank 25 to 50 and 3 slough line 20 to 25 alternate channel bars form during the restabilization stage and represent incipient meandering of the channel

relationships between gold and pyrite at the xincheng gold deposit jiaodong peninsula china implications for gold source and deposition in a brittle epizonal environment the xincheng gold deposit hosted by the early cretaceous 132 to 123 ma guojialing type granitoids in northwest jiaodong peninsula southeast north china craton formed about 2 billion years later than regional metamorphism of the archean jiaodong basement rocks the xincheng deposit comprises mineralized zones with three types of hydrothermal pyrite associated with gold tellurides and a variety of sulfides py1 as disseminated euhedral to subhedral grains in altered granitoids around quartz veins py2 as subhedral grains with brittle cataclastic textures and fractures in quartz pyrite veins and py3 as subhedral partially corroded crystals in sulfide rich veins or veinlets all three generations of pyrite are unzoned and have low trace element contents including very low lattice bound gold contents py1 0 180 ppm py2 0 053 ppm py3 0 060 ppm given that there is 10 to 15 pyrite in the ore zone at xincheng its very low gold content indicates that it contributes 0 2 of gold to the 7 75 g t gold in the orebody instead over 99 of the gold is present as discrete electrum and or gold total range 0 02 59 silver grains which are largely sited in fractures at all scales in pyrite other ore minerals and quartz importantly visible gold in py3 is also sited on solution corroded pyrite grains the pyrite textural and geochemical data indicate that it is impossible to derive the high gold grade orebodies through local remobilization of originally lattice bound gold in pyrite instead the gold is interpreted to have been deposited through sulfidation reactions and phase separation of a h2o co2 ore fluid during progressive brittle cataclastic deformation associated with seismic activity and regional sinistral transtensional shear movement this concomitant fluid infiltration and deformation caused episodic deposition and fracturing and corrosion of earlier formed pyrite and deposited visible gold in dilational cracks the coupled development of the transtensional rather than normal transpressional setting and precipitation of gold within dilational veins and wall rock alteration facilitated the deposition of visible gold and an exceptionally high gold tenor all deposit characteristics indicate that the xincheng gold deposit is a member of the epizonal orogenic deposit class

geochemistry and geochronology of zircons from granite hosted gold mineralization in the jiaodong peninsula north china implications for ore genesis abstract large scale quart vein and structurally controlled gold mineralization is intensely developed in the jiaodong peninsula north china craton and is typified by the linglong and jiaojia deposits respectively in this work zircons from typical gold bearing ores of the sanshandao northern sea sns jiuqu jq and canzhuang cz gold deposits were compared in terms of texture u pb age trace element content and hf isotopic signatures in order to discern whether zircon from ore samples can be used as an indicator of ore genesis and grade most studied zircons are magmatic in origin with a hydrothermal overprint i e zircons with core rim assemblages fractured dissolution textures and hydrothermal activity related fluid mineral inclusions three zircon age clusters were differentiated 120 ma 150 ma and 2000 ma the 120 ma zircons show evidence of hydrothermal alteration dark in cathodoluminescent images with hydrothermal rim textures and are characterized by high lree p ti and ehf t 21 to 15 and young tdmc 2100 2500 ma this suggests an interaction between the mantle and crust at the magma source and that a p ti rich al poor high temperature high fo2 wet late stage residual granitic melt and intense hydrothermal alteration played an important role in the formation of gold mineralization the 150 ma zircons have high y nb ta and u contents low ehf t 26 to 20 and old tdmc 2300 3000 ma ages and hree enriched patterns with pronounced ce and eu anomalies these features indicate a reduced cool and al rich magma which did not favor gold mineralization even though it was highly evolved this also implies that the degree of magma differentiation is not the key factor that led to gold mineralization in the jiaodong gold province the 2000 ma zircons are primarily limited to gold ores with high pb contents hree enriched patterns and variable ce and eu anomalies indicating that they were inherited from the paleoproterozoic 2000 2200 ma basement in addition the sns high grade ores yielded zircon with the greatest u pb age range mainly 110 180 ma and the most pronounced hydrothermal overprinting indicating that large scale mineralization resulted from multi stage granitic intrusion with intense fluid dissolution and metasomatism this research highlights that correlations between zircon age populations hf isotope signatures internal structures and trace element patterns can provide insights into ore genesis and fluid evolution in gold mineralization systems

geochronology and geochemistry of mesoproterozoic granitoids in the lhasa terrane south tibet implications for the early evolution of lhasa terrane abstract the early history of the lhasa terrane remains poorly constrained due to the poor exposure of the proterozoic rocks we report here u pb zircon ages geochemical and hf isotopic data for granite gneisses and biotite gneisses from the bomi complex in the eastern part of the lhasa terrane south tibet petrological and geochemical data suggest that the protoliths of the granite gneisses and the biotite gneisses could be granites and tonalites respectively la icpms u pb zircon analyses yielded ages of 1343 27 ma mswd 0 3 and 1276 22 ma mswd 0 4 for two granite gneisses and a consistent age of ca 1250 ma for two biotite gneisses these ages are interpreted as the magma crystallization time of both the gneisses protoliths and thus the bomi complex represents the oldest rocks found in the lhasa terrane our data indicate that the mesoproterozoic detrital zircons from the paleozoic metasedimentary rocks in the lhasa terrane could be derived from the lhasa terrane itself or the tethyan himalaya rather than necessarily from the albany fraser belt in the australia geochemical characteristics show that the granite gneisses have an aluminous a type granite affinity the two granite gneisses dated in this study have zircon hf t values between 4 0 and 1 8 and between 2 6 and 0 2 respectively they have identical two stage hf model ages of 2 0 ga we suggest that the protoliths of the granite gneisses were produced by protracted high temperature partial melting of a felsic intracrustal source in an extensional setting in contrast the biotite gneisses have similar geochemical characteristics to those of calc alkaline granitoids that probably formed in a subduction related environment zircons from the two dated biotite gneisses have relatively higher hf t values of 8 1 to 3 6 and 10 5 to 5 7 respectively indicating a juvenile mantle contribution to their magma source earlier magmatism at 1343 1276 ma may formed in a continental rift setting related to the final breakup of supercontinent columbia while subsequent magmatism of 1250 ma resulted from subduction of ocean slab during the assemblage of rodinia we thus infer that the bomi complex was related to the contact zone between the eastern ghats belt and the archean cratons in southeastern india during the mesoproterozoic

thermochronologic constraints on evolution of the linglong metamorphic core complex and implications for gold mineralization a case study from the xiadian gold deposit jiaodong peninsula eastern china abstract the nne trending linglong metamorphic core complex hosts the majority of the gold deposits in the jiaodong peninsula of eastern china many of the deposits are hosted by the 163 155 ma linglong granite in the footwall of the linglong detachment fault argon thermochronology suggests that the granite had cooled to 400 c by 143 1 5 ma possibly as a result of normal movement on the detachment nine zircon fission track zft ages from samples collected along a nw se transect perpendicular to the central part of the linglong detachment fault at the 652 m level in the xiadian deposit constrain the subsequent thermal evolution of linglong metamorphic core complex which overlapped the period of major gold deposition the zft ages vary from 136 9 3 3 ma 1 to 130 1 2 2 ma 1 the unaltered linglong granite in the footwall and amphibolite in the hangingwall have similar ages at 136 9 3 3 ma 1 and 135 0 3 0 ma 1 whereas ages for the disseminated and stockwork style ores appear to be younger at ca 131 130 ma although there is an overlap of ages when considering the 1 precision interestingly zft ages show no marked differences between the hangingwall and footwall of the linglong detachment fault although significant movement along the fault occurred the results are best interpreted to indicate that the linglong granite was emplaced at 160 ma and cooled to 240 50 c at 135 ma as recorded by unaltered rocks in the footwall hydrothermal alteration along the linglong detachment fault led to annealing of zircon fission tracks and the consistent younger ages of 131 ma quartz aggregates associated with gold mineralization show evidence of recrystallization suggesting that the hydrothermal event was initiated at temperatures of at least 300 350 c near the brittle ductile transition but cooled rapidly to zft closure temperatures within a country rock environment that was already relatively cool therefore these zft ages suggest that the timing of mineralization at the xiadian deposit was post 135 ma and likely very close to 131 ma the mineralization and cooling occurred in the footwall of a major detachment fault under an extensional regime possibly related to the progressive slab rollback of the paleo pacific plate and controlled by the linglong metamorphic core complex

the age isotopic signature and significance of the youngest mesozoic granitoids in the jiaodong terrane shandong province north china craton abstract most cretaceous granitoids in the jiaodong terrane of shandong province north china craton were intruded between 130 and 122 ma however four granitoid batholiths are significantly younger with an average zircon u pb shrimp emplacement age of 116 2 ma these are the sanfoshan batholith 118 1 ma the aishan batholith 116 1 ma the yashan pluton 113 2 ma and the laoshan batholith 115 2 ma these granitoids post date proposed delamination that occurred prior to 125 ma in the eastern ncc and their geochemistry thus provides information about the nature of the continental crust at this time the rocks are mostly monzogranites and syenogranites of i type affinity with local alkali feldspar granite of a type affinity in addition a monzogranite sample from the aishan batholith records an age of 125 3 ma indicating a direct association with the slightly older granitoids in the area indeed they all contain inherited zircons with ages of 125 120 ma indicating interaction with these earlier granitoids most samples are metaluminous enriched in light rare earth elements and depleted in high field strength elements paleo to neoarchean t dm2 model ages ranging from 3900 ma to 2491 ma and negative e hf t values imply the involvement of archean basement and older recycled continental crustal material in the magma source region they were likely derived from partial melting of the lower or middle crust due to mafic magma underplating followed by various degrees of interaction between mantle derived mafic magma and felsic crustal magma accompanied by fractional crystallization we propose that lithospheric thinning and extension in the early cretaceous due to roll back of the pacific plate beneath the eastern north china craton led to asthenospheric upwelling and basaltic magmatism this underplating in turn led to crustal melting and evolution of the granitic intrusions described here

gold deposition and resource potential of the linglong gold deposit jiaodong peninsula geochemical comparison of ore fluids abstract the linglong gold deposit is a super large deposit in the linglong goldfield northern jiaodong peninsula the orebodies consist of hundreds of auriferous quartz veins that surrounded by relatively narrow k feldspar alteration halos four mineralization stages have been identified on the basis of cross cutting relationships and mineralogical and textural characteristics milky quartz pyrite stage 1 grey white quartz pyrite stage 2 quartz pyrite base metal sulfide stage 3 and quartz carbonate stage 4 native gold was mainly deposited in stages 2 and 3 petrographical and microthermometric studies on quartz from stages 2 and 3 ores reveal three types of fluid inclusions associated with gold mineralization type 1 h2o co2 nacl ch4 inclusion that consisting fia 1 and represent a homogeneous fluid trapped at the same pressure and temperature coexisting type 2a h2o rich h2o co2 nacl ch4 and type 2b co2 rich h2o co2 nacl ch4 inclusions that constitute fia 2 and are interpreted to be products of a heterogeneously trapped fluid the ore forming fluids belong to a h2o nacl co2 ch4 system with medium temperatures 290 340 c low salinity 4 7 wt nacl eq and are co2 rich 15 mol with minor ch4 2 5 mol the d 18o values of ore forming fluids vary from 63 to 57 and 6 0 to 9 3 respectively overlap both the magmatic and metamorphic fluid fields the 34s values of hydrothermal pyrite have a narrow range from 5 6 to 7 9 and are within the ranges of neoarchean jiaodong group and mesozoic linglong granite guojialing granitoid and intermediate basic dikes combined with h o s isotope data fluid inclusions compositions and regional geological events the ore forming fluids may have a metamorphic dominate origin but a mantle or crustal contribution cannot be excluded fluid immiscibility played a major role and fluid wallrock interaction may be a subordinate reason for gold deposition in linglong the stage 2 quartz grains contain more fias 2 and volatiles than those in stage 3 quartz indicating a more extensive fluid immiscibility process which has a positive correlated higher gold grade based on the data of fias 2 the p t conditions of gold depositions generally range from 242 to 54 mpa and 348 to 269 c with a depth of metallogenesis of 5 4 9 0 km considering the depth of regional post ore exhumation has been calculated as about 5 7 km the space with deep gold exploration is expectable at linglong

gold hosting high ba sr granitoids in the xincheng gold deposit jiaodong peninsula east china petrogenesis and tectonic setting abstract the xincheng deposit is the only large gold deposit with a proven reserve of 200 t gold hosted by the early cretaceous granitoids in northwest jiaodong peninsula east china the granitoids hosting this ore deposit comprise an inner medium to fine grained quartz monzonite and an outer medium to coarse grained monzogranite with distinctive k feldspar megacrysts la icp ms zircon dating yields u pb ages of 128 1 to 132 1 ma and 127 2 to 129 1 ma for the quartz monzonite and the monzogranite respectively the early cretaceous ages obtained in our study are comparable with the 126 130 ma age range reported for the guojialing granitic suite the monzogranites typical high ba sr granites possess high sio2 70 89 73 35 k2o 3 85 4 32 total alkalis k2o na2o 8 08 8 68 sr 634 888 ppm ba 1395 2111 ppm and lree 59 43 145 88 with low hree and hfse contents and insignificant eu anomalies the rocks display markedly high sr y 114 297 and la yb n 20 79 ratios they have low mgo 0 23 0 62 cr 0 4 8 33 ppm and ni 0 47 2 92 ppm contents the typical high ba sr signatures of the outer acidic monzogranites are also shared by the inner intermediate acidic quartz monzonites with a relatively higher abundance of these elements the plagioclases in the quartz monzonites and monzogranites are oligoclase andesine with an contents of 11 7 44 5 and oligoclase with an contents of 12 9 29 3 respectively which both show the reverse zoning texture the quartz monzonites have zircon ehf t values of 21 3 to 13 9 average 18 7 which are less negative and show larger variations than those of the monzogranites ehf t 24 7 to 18 1 average 19 5 detailed elemental mineralogical and isotopic data suggest that the high ba sr quartz monzonites and monzogranites were most likely generated by partial melting of the basement rocks of the jiaobei terrane accompanied by crustal assimilation with minor addition of the intermediate magma derived from the partial melting of juvenile mafic lower crust formed by the earlier underplating of mantle magma and the quartz monzonites may represent the path of intermediate magma inputting into felsic magma in combination with previous investigations we suggest subduction of the paleo pacific slab beneath the north china craton ncc and associated asthenosphere upwelling were most likely the mechanism associated with the generation of the high ba sr granites

channel adjustments in the lower guadalquivir river southern spain over the last 250 years abstract the lower guadalquivir river has been subjected to a series of channel adjustments over the last 250 years mainly in response to human factors and disturbances from 1778 to 1918 the results show an oscillation in the sinuosity along the upstream segment and a reduction along the downstream segment in response to artificial cut offs the first phase of incision started in approximately the 1840s 1850s following a previous phase of predominant aggradation probably related to abundant sediment supply caused by deforestation in the catchment during approximately the last 100 years notable incision and progressive channel narrowing occurred in both segments although secondary aggradation upstream of the dams and widening in a portion of the downstream segment were also observed the first phase of bed incision migrating upstream is interpreted as a consequence of artificial meander cut offs whereas most of the adjustments that occurred during the last 100 years are interpreted as a consequence of the large number of dams in the catchment and along the studied area which caused a notable deficit in bedload

impact on volcanic ash detection caused by the loss of the 12 0 μm split window band on goes imagers abstract geostationary operational environmental satellite goes imager and sounder data were evaluated to determine the potential effects of volcanic ash detection without the use of a 12 m infrared ir band on goes m 12 through q a period of at least 10 years principal component analysis pca images with and without 12 m ir data were compared subjectively for six weak to moderate eruptions using pattern recognition techniques and objectively by determining a false detection rate parameter goes sounder data were also evaluated in a few instances to assess any potential contributions from the new 13 3 m imager band results indicated that during periods of daylight there was little apparent difference in the quality of ir detection without the 12 m ir likely due to a maximum in solar reflectance of silicate ash in a shortwave ir swir band centered near 3 9 m at night when swir reflectance diminished the ash detection capability appeared to be significantly worse evidenced by increased ambiguity between volcanic ash and meteorological clouds or surface features the possible effects of this degradation on aviation operations are discussed the new 13 3 m ir band on goes has the capability to help distinguish ash from cirrus clouds but not from low level clouds consisting of water droplets multi spectral data from higher resolution polar orbiting satellites may also be used to supplement analyses from lower resolution goes for long lived ash cloud events the advanced very high resolution radiometer avhrr and moderate resolution imaging spectroradiometer modis instruments appear to be the best options in accomplishing this with additional satellite missions becoming available later in the decade in summary it will still be possible to observe and track significant volcanic ash clouds in the goes m through q era 2003 2012 without the benefit of 12 m ir data but with some degradation that will be most significant at night

nature age and tectonic setting of granitoid hosted orogenic gold deposits of the jiaodong peninsula eastern north china craton china the jiaodong gold province along the southeastern margin of the north china craton has combined production and resources of 900 tonnes of gold more than 95 of the gold in this province is hosted in mesozoic granitoids which intruded late archean metamorphic basement rocks episodically at ca 160 150 and 130 126 ma the deposits of the jiaodong peninsula form one of the largest provinces of granitoid hosted lode gold deposits in the world the jiaodong gold deposits occur as massive auriferous quartz veins hosted in subsidiary second or third order faults and as disseminated and stockwork style mineralization hosted in alteration zones along major regional scale faults mineralization took place during brittle reactivation d3 of pre existing d2 ductile shear zones wall rock alteration is dominated by k feldspar and sericite with also sulfide minerals and extensive silicification closest to the orebodies the alteration was accompanied by the introduction of volatiles fe mg k rb ag as au bi and sb enrichment of base metals in the gold lodes is generally low although locally significant gold deposition took place at temperatures of 250 to 350 c for most gold deposits and the ore fluids are co2 bearing and have calculated salinities of 6 13 wt nacl equiv deposits from the zhao ye xixia and muping rushan belts have similar if not identical structural controls alteration patterns ore mineral assemblages and stable isotope signatures lead isotope data indicate that the ore stage leads were buffered by their host rocks the granitoid hosted gold deposits in the zhao ye belt are most radiogenic the greenstone hosted deposits in the xixia belt is the least radiogenic and the granitoid hosted deposits in the muping rushan belt have intermediate compositions gold mineralization in the zhao ye xixia and muping rushan belts in the jiaodong gold province appears to be broadly contemporaneously at ca 130 120 ma as constrained by shrimp u pb zircon dating on host rocks and a post gold dike as well as by ar ar rb sr and k ar dating of hydrothermal alteration minerals and ores this early cretaceous age is about 100 million years younger than the peak of ultra high pressure metamorphism in the qinling dabie sulu orogen between the north china and yangtze cratons and about 500 km south of the gold province however it overlaps with the extension and exhumation stage of the collisional orogeny and the subduction of the pacific plate beneath the eurasian continental crust whereas the majority of the jiaodong gold deposits occur on the margin of the north china craton some also occur in the suture zone between the two cratons they are significantly landward relative to the subduction zone of the pacific plate compared with typical orogenic lode gold deposits globally lode gold deposits of ca 130 120 ma occurred on both sides of the tan lu fault zone available data favor a temporal link of gold mineralization with pacific plate subduction

how natural are alpine mountain rivers evidence from the italian alps historical human induced channel adjustments in lowland gravel bed rivers have been documented in several geographical contexts worldwide in particular it is now widely accepted that the vast majority of european rivers are far from any natural reference state prior to anthropic disturbances and a complete restoration is hardly achievable however few investigations have addressed changes that have occurred in mountain rivers of the alps and these channels are commonly reckoned quite natural by society this paper intends to describe how human pressure on italian alpine basins has been quite relevant for several centuries in terms of land use variations in channel structures timber transport splash damming and riparian vegetation management such that nowadays reference conditions cannot be found even in small mountain creeks in addition recent natural climatic variations e g the little ice age are superimposed on human disturbances thus defying the definition of any equilibrium morphological conditions even under human free states a summary of published as well as unpublished works on historical channel adjustments in rivers of the italian alps is presented in order to document the impacts deriving from human pressure at different basin scales and for different river morphologies from steep confined streams to large unconfined rivers general options for river management and restoration actions aiming to combine geomorphological functionality and flood hazard mitigation are discussed in the light of the current european legislative context copyright 2011 john wiley sons ltd

thermochronologic constrains on the processes of formation and exhumation of the xinli orogenic gold deposit jiaodong peninsula eastern china abstract the xinli orogenic gold deposit with gold resources of 40 t located in the northwestern part of the giant jiaodong gold province eastern china is controlled by the sanshandao fault and is one of a few deposits hosted by the early cretaceous 129 128 ma guojialing granitoid soon after intrusion the granitoid underwent ductile shearing at 400 500 c marked by recrystallized quartz ribbons and bending of plagioclase lamellae with rapid cooling from zircon crystallization temperature of 750 800 c at 129 128 ma u pb to closure temperature of 300 50 c for biotite 40ar 39ar method at 124 1 ma the ductile deformation lasted 4 million years mineralization was associated with subsequent brittle reactivation of normal movement on the fault indicated by a se plunging downdip lineation on the fault a hydrothermal sericite 40ar 39ar age of 121 ma inferred to date the alteration associated with gold mineralization has been previously obtained for the adjoining cangshang gold deposit also controlled by the sanshandao fault at the xinli deposit the 121 5 1 3 ma and 120 5 1 2 ma 40ar 39ar plateau ages of weakly fractured igneous k feldspar record closely the time of normal faulting and cooling within the range of mineralization temperatures 350 250 c two zircon fission track zft ages of 91 4 ma and 90 3 ma constrain the time of cooling through 240 50 c unimodal distribution of apatite fission track aft lengths with a slightly negative skew and mean fission track lengths of 12 3 0 2 m indicate relative slow continuous cooling through 125 60 c at 60 6 ma the slight acceleration of cooling around 90 ma constrained by the 40ar 39ar zft and aft data and thermal modelling may have resulted from the late normal reactivation of the sanshandao fault in summary extension and normal faulting not only created the channelways for the mineralizing fluids but also gave rise to the subdued topography and post mineralization exhumation that preserved the deposit

spatial disaggregation and aggregation procedures for characterizing fluvial features at the network scale application to the rhone basin france network scale heterogeneity in fluvial forms and processes has been analyzed for decades through the field based characterization of a reduced number of sites spatially continuous data sets are increasingly available at a national scale e g digital elevation models or aerial orthophotographs and open up new possibilities to investigate spatial structures in stream networks the paper introduces a gis methodological framework to support and automate the large scale characterization of the fluvial system based on spatial disaggregation and aggregation procedures the spatial disaggregation consists in the longitudinal discretisation of geographical objects into relatively high resolution spatial units to characterize fluvial features continuously along stream networks because rivers are heterogeneous and hierarchically organized the spatial aggregation aims to delineate statistically pattern or process based spatial units to answer questions at appropriate scales the paper develops the gis implementation of the disaggregation and aggregation procedures for characterizing stream networks in a geomorphic perspective we illustrate the approach on the rhone network focusing on the characterization of three geographical objects commonly used in classification schemes the streamline the valley bottom and the active channel the latter on a limited area the spatial aggregation is automated using the threshold test of pettitt 1979 to detect change points in univariate data series and delineate homogeneous spatial units throughout the stream network we provide three simple application examples to illustrate the potentialities of the spatial aggregation to investigate spatial heterogeneity in stream networks finally insights limitations and future challenging issues emerging from the application of the methodological framework are discussed

contrasting origins of late mesozoic adakitic granitoids from the northwestern jiaodong peninsula east china implications for crustal thickening to delamination two suites of granitoids the late jurassic 158 3 ma linglong suite and the early cretaceous 130 126 ma guojialing suite crop out in the northwestern jiaodong peninsula eastern china the linglong suite is a monzogranite comprising alkali feldspar plagioclase quartz and fe rich biotite the guojialing suite includes at least five plutonic bodies of both granodiorite and monzo granite the rocks are composed of plagioclase alkali feldspar quartz mg rich amphibole and mg rich biotite both the linglong and guojialing suites have adakitic affinity they are enriched in lree with high la yb ratios and show positive eu anomalies the rocks are also enriched in lile and depleted in hfse with high sr y ratios the linglong granite shows very uniform sr nd isotopic compositions with initial 87 sr 86 sr ratios of 0 7119 0 7126 and e nd t values of 21 3 to 21 6 which are similar to those of the local neoarchaean basement the guojialing suite has variable initial 87 sr 86 sr ratios 0 7108 0 7120 and e nd t values 10 8 to 17 2 which are distinct both from those of the neoarchaean basement and from those of the local enriched lithospheric mantle inferred from the coeval mafic dykes in the studied area detailed petrological and geochemical data indicate that the linglong suite was derived by partial melting of neoarchaean metamorphic lower crustal rocks at depth of 50 km with a eclogite residue whereas the guojialing suite was formed by the reaction of delaminated eclogitic crust derived melt with the upwelling asthenospheric mantle the petrogenesis of these two contrasting adakitic granitoids suggests intensive lower crustal delamination during early cretaceous times following a crustal thickening process from the late stage of the early jurassic to early stage of the late jurassic with crustal thickness of 50 km respectively

reach scale morphological adjustments and stages of channel evolution the case of the trebbia river northern italy abstract a multitemporal series of aerial photos and cross section topographic surveys have been used to analyze reach scale channel evolution along a segment length of about 22 km of the lower trebbia river northern italy with the aims to investigate the relations between channel width vs bed level adjustments and to identify spatio temporal patterns of stages of channel evolution dendrochronology was used to determine the age of tree establishment of riparian and island forests during channel evolution we identified a first phase of major adjustments 1954 1992 following a series of disturbances dominated by channel narrowing and bed incision during the final stage of narrowing woody vegetation establishment contributed to stabilize new floodplain or island surfaces a period of partial morphological recovery occurred from 1992 to 2010 dominated by an inversion of trend of channel width during the phase of partial recovery a stage of widening combined with a continuation of bed incision was identified and a last stage characterized by widening and initial aggradation was observed on the central portion of the study reaches suitability and differences of existing channel evolution models cems derived in other geographical contexts were discussed and a specific conceptual model comprising four stages of channel evolution was developed for the lower trebbia river

fluid immiscibility and gold deposition in the xincheng deposit jiaodong peninsula china a fluid inclusion study abstract the xincheng gold deposit located in west jiaodong peninsula in southeast north china craton is a representative mesothermal lode deposit hosted in late mesozoic granitoids in jiaodong gold mineralization occurs as disseminated and stockwork style ores within the hydrothermal breccias and cataclastic zones controlled by the jiaojia fault whereas echelon tensile auriferous veins hosted in the ne and nne trending subsidiary faults cutting the granitoids occur subordinately according to crosscutting relationships and mineral paragenesis four paragenetic stages were identified which are pyrite quartz sericite stage 1 quartz pyrite stage 2 quartz polysulfide stage 3 and quartz carbonate stage 4 gold was deposited during the quartz pyrite and quartz polysulfide stages on the basis of microthermometry and raman spectroscopy on fluid inclusions contained within the quartz veins from stages 2 and 3 three types of fluid inclusions were recognized 1 type 1 h 2 o co 2 inclusions that show high temperatures ca 260 c low salinities 2 4 8 9 wt equiv nacl and variable xco 2 0 03 to 0 20 2 type 2 aqueous inclusions with medium temperatures ca 220 c and low to moderate salinities 3 1 13 3 wt equiv nacl 3 type 3 pure co 2 inclusions with a carbonic phase density of 0 712 0 03 g cm 3 types 1 and 2 inclusions appear in the same growth phase of the quartz grains from the breccias and tensile auriferous veins these coexisting inclusions are likely formed by fluid immiscibility due to unmixing from a single homogeneous h 2 o co 2 parent fluid at trapping p t conditions of 221 to 304 c average 261 19 c and 780 to 2080 bar the fluid immiscibility is interpreted to be initiated by fluid pressure decrease at ca 300 c the ore fluid p t x conditions of the xincheng gold deposit are the same as those for mesothermal deposits gold was most probably transported as a au hs 2 complex at xincheng fluid immiscibility over the temperature interval of 221 304 c resulted in significant h 2 s loss from the hydrothermal solution thereby reducing au hs 2 solubility with concomitant deposition of gold the mineralizing process of the granitoid hosted xincheng lode gold deposit is likely related to the fluid immiscibility

timing and mechanism of gold mineralization at the wang ershan gold deposit jiaodong peninsula eastern china abstract the wang ershan gold deposit located in the southern jiaojia goldfield is currently the largest gold deposit hosted within the subsidiary faults in jiaodong peninsula with a gold reserve of 60 t gold at a grade of 4 07 g t au it is hosted in the late jurassic linglong biotite granites and controlled by the second order n to nne trending wang ershan fault and its subsidiary faults which is broadly parallel to the first order jiaojia fault in the goldfield gold mineralization occurs as both disseminated and stockwork style and quartz sulfide vein style ores mainly within altered cataclasites and breccias and sericite quartz and potassic alteration zones respectively mineralization stages can be divided into 1 the pyrite quartz sericite stage 2 the quartz pyrite stage 3 the quartz sulfide stage and 4 the quartz carbonate stage two sericite samples associated with the main ore stage pyrites from pyritic phyllic ores of the deposit with weighted mean plateau 40 ar 39 ar age of 120 7 0 6 ma and 119 2 0 5 ma respectively were selected for 40 ar 39 ar geochronology on the basis of petrography and microthermometry three types of primary fluid inclusions related to the ore forming event were identified type 1 h 2 o co 2 nacl type 2 aqueous and type 3 co 2 fluid inclusions in decreasing abundance stage 1 quartz contains all three primary fluid inclusions while stages 2 and 3 quartz contain both type 1 and 2 inclusions and stage 4 quartz contains only type 2 inclusions the contemporaneous trapping similar salinities and total homogenization temperature ranges and different homogenization phases of type 1 and type 2 inclusions indicate that fluid immiscibility did take place in stages 1 2 and 3 ores with p t conditions of 190 to 85 mpa and 334 to 300 c for stage 1 and 200 to 40 mpa and 288 to 230 c for stages 2 and 3 combined with the h o c s pb isotopic compositions ore forming fluids may have a metamorphic dominant mixed source which could be associated with the dehydration and decarbonisation of a subducting paleo pacific plate and characterized by medium high temperature 285 350 c co 2 bearing 8 mol with minor ch 4 1 4 in carbonic phase and low salinity 3 38 8 45 eq wt nacl during mineralization the fluid finally evolved into a medium low temperature nacl h 2 o system au hs 2 was the most probable gold transporting complex at wang ershan due to the low temperature 157 350 c and near neutral to weakly acidic ore fluids the reaction between gold bearing fluids and iron bearing wall rocks and fluid immiscibility processes caused via fluid pressure cycling during seismic movement along fault zones that host lode gold orebodies which led to breakdown of au hs 2 are interpreted as the two main precipitation mechanisms of gold deposition in general the wang ershan deposit and other deposits in the jiaojia camp have concordant structural system and wall rock alteration assemblages nature of orebodies and gold occurrence conditions as well as the similar geochronology ore forming fluids system and stable isotope compositions thus gold mineralization in the jiaojia goldfield was a large scale unified event with consistent timing origin process and mechanism

mesozoic high ba sr granitoids from north china geochemical characteristics and geological implications mesozoic magmatism occurred extensively in the north china block ncb and the dabie sulu orogen dso post dating the north south china collision resulting in abundant intrusive and volcanic rocks ranging from basic to acidic compositions the intermediate acidic intrusive rocks can be grouped into two types namely high ba sr granitoids and low ba sr granitoids that both have distinct geochemical characteristics the high ba sr granitoids are similar in most of the incompatible trace element systematics to the associated basic rocks which probably originated from melting of subcontinental lithospheric mantle indicating significant mantle contributions to them geochemical similarities are observed between the basic rocks from the ncb and dso implying a regional scale magma generating mechanism and that mantle enrichment beneath the dso was independent from the triassic deep continental subduction in the region we therefore interpret that the mesozoic magmatism resulted from delamination of the ancient lithospheric mantle beneath the eastern part of north china

causes of 20th century channel narrowing in mountain and piedmont rivers of southeastern france extensive channel narrowing in southeastern france provides an illustration of geomorphic response to land use changes the study region comprises a range of environments from large piedmont and intramountain gravel bed rivers to small mountain streams field measurements and analysis of historical data demonstrate two distinct periods of channel change from 1850 to 1950 channel narrowing is interpreted to be the result of a recovery process in response to widespread channel destabilization induced by major floods during the second half of the 19th century at the time the largely deforested basins were highly responsive to flooding whereas the recovery process was accelerated by floodplain and basin scale land use changes afforestation and torrential control works which in turn reduced sediment delivery and enabled vegetation development in channels from 1950 to 1970 channel narrowing accelerated in most of the studied rivers this recent phenomenon is considered as a human induced fluvial adjustment directly related to forest development on river margins and human abandonment of intensive floodplain land uses at the same time long profile degradation occurred as a result of long term bedload supply decrease in small mountain streams channel narrowing is mainly explained by channel incision which seems to progress from upstream where sediment sources are progressively stabilized by afforestation copyright 2002 john wiley sons ltd

age and origin of high ba sr appinite granites at the northwestern margin of the tibet plateau implications for early paleozoic tectonic evolution of the western kunlun orogenic belt abstract the buya appinite granite is a typical high ba sr granite emplaced at the northern west kunlun orogenic belt along the northwestern margin of the tibetan plateau the granite is dated at ca 430 ma using the shrimp u pb zircon method it consists of alkaline feldspar granites with coeval appinite enclaves the granite possesses high sio2 69 77 72 69 k2o 4 44 5 10 and total alkalinity k2o na2o 8 80 9 92 sr 655 1100 ppm ba 1036 1433 ppm and lree and low hree and hfse contents and insignificant negative eu anomalies consequently the samples have very high sr y 74 141 and la yb n 37 96 ratios on the other hand they have low mgo or mg cr and ni contents and low radiogenic nd isotopes nd t 8 4 to 10 4 the high ba sr and other geochemical signatures of the granite also appear in the appinite enclaves except that the appinite enclaves have relatively higher abundances in these elements and higher nd t values 5 7 to 6 7 elemental and isotope compositions suggest that the appinites were derived from partial melting of an enriched lithospheric mantle source probably induced by upwelling of the asthenosphere due to the delamination of a subducted slab the granite was likely derived from partial melting of the mafic lower crust with residual garnet associated with involvement of minor lile enriched appinitic magma followed by crystal fractionation of hornblende biotite apatite and allanite in combination with previous investigations on the evolution of the western kunlun we suggest that the buya high ba sr plutons represent the end of an early paleozoic crust thickening event after a terrane accretion on southern tarim craton and the beginning of a post orogenic collapse phase in the paleozoic west kunlun orogenic belt

assembling north china craton within the columbia supercontinent the role of double sided subduction abstract an evaluation of recent s wave receiver functions s wave velocities and two versions of p wave tomographic images along various transects in the north china craton provides some clues on the subduction collision history of the different crustal blocks and their final amalgamation within the paleoproterozoic columbia supercontinent interpretation of a n s seismic section of the craton suggests thick slab debris sinking to various depths in the mantle the w e seismic corridors show the preservation of a thick 200 km lithospheric root tectosphere beneath the ordos block and its variable and extensive erosion towards the yanliao block eastern block this zone is characterized by layers with marked velocity contrast and suggests repeated stacking of the remnants of underplated and accreted paleoproterozoic oceanic lithosphere the present day lithosphere asthenosphere boundary beneath this region probably marks the erosional plane along which decratonization occurred through subduction erosion from the east and thermal and material erosion by upwelling asthenosphere from below resulting in the partial destruction of the tectosphere and its thinning towards the east within the asthenosphere below the yanliao block younger and thinner slabs predominate in the absence of any prominent thick high velocity layers these younger slabs define a westward polarity and constitute a mega scale duplex formed by underplating through phanerozoic subduction process particularly the pacific plate subduction from the east the lithologic associations within the inner mongolia suture zone dividing the yinshan block to the north and ordos block to the south correspond to an accreted ocean plate stratigraphic sequence with the tonalite trondhjemite granodiorite ttg gneisses charnockites and calc alkaline granites representing a continental arc built up through subduction from the north the seismic transects bring out a contrasting polarity in the subduction regime with an oblique east to southward subduction of the yinshan block and a westward subduction of the yanliao block here i propose a double sided subduction history for the ncc similar to the ongoing subduction process in the western pacific such double sided subduction is considered to promote rapid amalgamation of continental fragments within supercontinents and the subduction polarities and mantle dynamics of ncc are therefore considered to be critical in evaluating the final assembly of the paleoproterozoic supercontinent columbia

experimental simulation of element mass transfer and primary halo zone on water rock interaction abstract primary halo zone is an important theory for prospecting the deep blind ore body and predicting resource potential the common description of primary halo zone of multiple elements is based on their behaviors during hydrothermal alteration or mineralization a geofluid with multiple elements which are bi cu pb zn cd ag and as bearing ni and mo is prepared to simulate the dispersive transfer of elements in a hydrothermal fluid granite reaction at 15 mpa 100 c using a new constructed core flow through pressure vessel reactor core granite samples with 5 cm long after water rock reaction are cut into ten sections to analyze their major oxides and trace elements according to experiment results and the method of immobile plateau we determine that al and ti are immobile elements during the water rock reaction and the hydrothermal alteration of granite is a mass gained process the mobility index mi of each of experimental elements is calculated based on the immobile component al 2 o 3 the sequence of experimental elements is from as to ag pb zn cu bi ni cd and mo which are sorted on their values of mi in these reacted granite cores from near to far end respecting to the reaction fluid this result is consistent with the empirical sequence of zonation of primary halo elements which is derived from the statistical results from 58 gold deposits in china the denudation coefficient of primary halo zone zf or zfe is proposed to assess the degree of approaching to ore body on these experiments which is the averaged mi ratio of front halo elements to ore body halo elements the denudation coefficient of primary halo zone is applied on the cross section of gold ore body hosted in the granite of the linglong gold deposit located in the jiaodong peninsula of eastern china the degree of approaching to the gold ore body is clearly illustrated by the denudation coefficient of primary halo zone

geochronology of the pengjiakuang and rushan gold deposits eastern jiaodong gold province northeastern china implications for regional mineralization and geodynamic setting the jiaodong gold province the largest gold producing district in china is located in the jiaodong peninsula at the eastern margin of the north china craton and bounded by the continental scale tan lu fault 40 kin to the west previous geochronological studies suggest that pervasive gold deposition took place in the western part of the province between 122 and 119 ma here we report high quality ar 40 ar 39 ages of the pengjiakuang and rushan deposits from the eastern part of the jiaodong gold province placing additional chronological constraints on the timing of regional mineralization seven sericite grains extracted from auriferous alteration assemblages at the pengiiakuang deposit yielded well defined plateau ages between 120 9 0 4 and 119 1 0 2 ma 2 sigma three separates of igneous biotite from a sample of the queshan gneissic granite adjacent to the pengjiakuang deposit gave reproducible plateau ages of 124 6 0 6 to 123 9 0 4 ma 2 sigma six sericite separates front two samples in the rushan deposit yielded ar 40 ar 39 plateau ages at 109 3 0 3 to 107 7 0 5 ma 2 sigma whereas biotite from the kunyushan monzogranite that hosts the rushan deposit had plateau ages ranging from 129 0 0 6 to 126 9 0 6 ma 3 separates front one sample the apparent age gap between hydrothermal sericite and magmtic biotite from both deposits together with the similar argon closure temperatures for these mica minerals suggest that gold mineralization had no direct relationship to the granitoid magmatism instead gold deposition coincided with the emplacement of mafic to intermediate dikes widespread in the jiaodong gold province which have been dated at ca 122 to 119 ma and less commonly at 110 to 102 ma the new ar 40 ar 39 ages from the eastern jiaodong peninsula when combined with published data from the western part suggest that gold mineralization was broadly contemporaneous throughout the district the early cretaceous gold mineralization also is widely developed in four other major gold districts along the tan lu fault the temporal and spatial correlation of these gold deposits with mafic to intermediate dikes commonly found in most mineralized areas the presence of well documented metamorphic core complexes and half graben basins along the tan lu fault and voluminous basalts therein suggest that the early cretaceous was an important period of lithospheric extension possibly caused by the late mesozoic lithospheric thinning beneath the eastern block of the north china craton lithospheric thinning and extension could have resulted in abnormally high heat and fluid fluxes necessary for large scaled gold mineralization

titanite scale insights into multi stage magma mixing in early cretaceous of nw jiaodong terrane north china craton abstract the early cretaceous guojialing type granodiorites in northwestern jiaodong terrane carry significant records for strong mantle crust interaction during the destruction of north china craton ncc however the definite petrogenetic mechanism and detailed magmatic process remain an enigma titanite in igneous rocks can serve as an effective petrogenetic indicator here we present integrated geochronological and geochemical studies on titanites from guojialing type granodiorites and their dioritic enclaves to constrain their petrogenesis titanites from granodiorites g type and plagioclase rich dioritic enclaves e type i present an identical u pb age 130 ma and an indistinguishable wide range of zr and total rees contents and th u ratios however these two types of titanites exhibit distinct micro scale textures and geochemical compositions g type titanites are characterized by oscillatory zonings with two light bse zones lbz and two or three dark bse zones whereas e type i titanites are marked by core mantle rim zonings drastic increase of lrees zr hf and fe and decrease of nb ta al and f contents are observed in lbz of g type titanites whereas remarkable reduction of lrees zr and hf and elevation of f contents are observed from the cores to the mantles of e type i titanites based on zr in titanite thermometry g type titanites are interpreted to have experienced twice notable temperature increase while e type i titanites are inferred to have undergone a rapid cooling process furthermore we suggest that the drastic chemical changes in g type and e type i titanites are ascribed to early stage magma mixing between a colder felsic magma and a fe ree rich hotter dioritic magma compared to g type and e type i titanites titanites from plagioclase poor dioritic enclaves e type ii are characterized by their occurrence in interstitial space and present a relatively younger u pb age 128 ma and much narrower and lower range of zr total rees contents and th u ratios but reveal high f contents 0 35 0 76 wt and extreme high nb ta ratios up to 65 6 such titanites are perceived to record late stage mingling during which f rich and ree poor hybrid granodioritic magma squeezed into the incompletely consolidated dioritic enclaves with accompanying fluid rock interaction combining our results with previous isotopic studies a new genetic model for guojialing type granodiorites is envisaged which involves multi stage magma mixing between archean lower crust derived felsic magma and mafic lower crust derived dioritic magma triggered by mantle derived mafic magma underplating during the course of asthenospheric upwelling in early cretaceous such process further implicates the reactivation of jiaodong lower crust during the destruction of ncc

effects of check dams reforestation and land use changes on river channel morphology case study of the rogativa catchment murcia spain this work has been financially supported by the project respuesta hidrologica y geomorfologica de los sistemas fluvio torrenciales afectados por proyectos de restauracion hidrologico forestal en cuencas semiaridas del sureste peninsular of the fundacion instituto euromediterraneo de hidrotecnia ce the first author was financially supported by an i3p postdoc contract csic ce and a ramon y cajal contract from the education and science ministry spain gonzalo g barbera also was supported by i3p postdoc contract

cretaceous cenozoic tectonic history of the jiaojia fault and gold mineralization in the jiaodong peninsula china constraints from zircon u pb illite k ar and apatite fission track thermochronometry the jiaojia fault jjf in the jiaodong area of eastern china is an important nne trending structure that is subsidiary to the regional tancheng lujiang tan lu fault zone and hosts 1200 t of gold reserves contained in disseminated and stockwork ore dominantly in the footwall of the fault we present new zircon u pb apatite fission track and illite k ar data along the jjf and have delineated its tectonic history focusing on its formation and reactivation zircon u pb dating shows that the shangzhuang granite is a composite body with ages between 132 1 and 127 1 ma illite k ar ages for the fault s gouge range from 83 2 to 68 2 ma and the measured apatite fission track ages for ores are between 55 and 21 ma previous zircon u pb geochronology and structural studies suggest that the jjf was originally activated in the jurassic during 160 150 ma as a sinistral fault the jjf was a normal fault in the early cretaceous due to nw se orientated tension and ne sw compression which lasted from 135 to 120 ma this was followed by sinistral strike slip faulting due to nw se compression and ne sw tension during 120 110 ma and it changed to normal displacement at ca 110 ma our apatite fission track data analysis and thermal modeling of representative samples suggest that there was a subsequent dextral reactivation of the fault at ca 55 ma previous age data of ca 130 110 ma for gold mineralization along the jjf coincides with the early cretaceous magmatism and is coeval with the transition from normal faulting to sinistral strike slip faulting of the jjf in early cretaceous which is interpreted to be due to changing direction of the subducting pacific plate

geology and timing of mineralization at the cangshang gold deposit north western jiaodong peninsula china the cangshang gold deposit of the north western jiaodong peninsula contains reserves of greater than 50 tonnes t and is developed by the largest open pit gold mine in china this deposit is a jiaojia style i e disseminated and veinlet deposit it is controlled by the san cang fault zone which trends 040 and dips 40 75 se at the mine site the main no 1 orebody lies between a hanging wall of precambrian metamorphic rocks mainly amphibolite of the fenzishan group and a footwall composed of the mesozoic linglong granitoid the ore zone is mainly composed of pyritized sericitized and silicified granitoid which has undergone variable degrees of cataclasis shrimp u pb dating of zircon indicates that the protolith of the hanging wall amphibolite was formed at 2530 17 ma and underwent metamorphism at 1852 37 ma the footwall granodiorite has been dated at 166 4 ma whereas zircons from the ore zone yield a younger age of 154 5 ma cathodoluminescence images of zircons from the granodiorite and ore zone show oscillatory zonation indicative of an igneous origin for both and the ages of these zircons therefore are all interpreted to be representative of magmatic crystallization dating of sericite by 40ar 39ar has been used to directly determine the timing of formation of the cangshang deposit providing the first time absolute age on formation of the jiaojia style gold deposits the well defined age of 121 3 0 2 ma provides the precise timing of gold mineralization at the cangshang deposit this age is consistent with those of linglong style vein type gold mineralization also from the north western jiaodong peninsula at between 126 and 120 ma therefore our work indicates that both styles of gold deposits in the jiaodong peninsula were formed during the same mineralization event

geochronology and geochemistry of metamorphic rocks in the jiaobei terrane constraints on its tectonic affinity in the sulu orogen abstract tectonic affinity of tectono lithological units close to ultrahigh pressure metamorphic belt is a key issue for understanding the geodynamics of continental collision this is particularly so for the jiaobei terrane northeast of the dabie sulu orogenic belt in china new data from la icpms zircon u pb dating whole rock elements and nd sr isotopes and mineral o isotopes are presented for metamorphic rocks from this terrane the results place geochronological and geochemical constraints on their protolith nature and metamorphic timing and thus on its tectonic affinity to one of the two triassic collided continents the north and the south china blocks protolith ages for ttg gneiss amphibolite and mafic granulite are 2 7 2 5 and 2 4 ga respectively regional metamorphism took place extensively at 1 76 ga protolith of the ttg gneiss was generated by partial melting of mantle derived rocks at the root of a thickened crust protolith of the amphibolite was probably a product of arc like magmatism protolith of the mafic granulite was derived from a depleted mantle source both of them were locally contaminated by supracrustal materials protoliths of paragneiss and schist in the fenzishan group were mostly derived from supracrustal sources but protolith of amphibolite in the fenzishan group is of mantle derived signature unlike the uhp metaigneous rocks in the dabie sulu orogenic belt that show unusual 18 o depletion the jiaobei metamorphic rocks have basically preserved their original mantle like o isotope compositions in general the nature and timing of geological events recorded in the metamorphic rocks from the jiaobei terrane are comparable with those from the north china block rather than the south china block thus the jiaobei terrane is concluded to have tectonic affinity to the former but behave like a micro continent during the triassic continental collision the 1 76 ga regional metamorphism in the jiaobei terrane is likely related to reworking of the arc continent collisional orogen in the periphery of the north china block rather than the 1 85 ga collision event between the eastern and western north china blocks the present study lends support to the common assumption that the suture boundary between the north and south china blocks in the sulu orogen is located along the wulian yantai fault tectonic mingling along the wulian yantai fault is probably related to subduction erosion during the continental collision

reactivation of the archean lower crust implications for zircon geochronology elemental and sr nd hf isotopic geochemistry of late mesozoic granitoids from northwestern jiaodong terrane the north china craton the late mesozoic granitoids widely distributed in the northwestern jiaodong terrane are important markers of cratonic destruction and lithospheric thinning of the eastern north china craton ncc here we investigate the late jurassic linglong and luanjiahe granites and report zircon u pb emplacement ages of 157 159 ma these rocks also contain abundant late archean paleoproterozoic neoproterozoic early paleozoic and triassic inherited zircons suggesting the involvement of continental crustal materials from both the ncc and yangtze craton in magma tectonics the rocks investigated in this study show high na2o k2o and low mgo and are peraluminous with enrichment in lrees and liles rb ba u and sr and depletion in hfses nb ta p and ti they also display low ehf t values and high sr y ratios comparable to adakitic rocks suggesting that the linglong and luanjiahe granitoids formed under relatively high pressure conditions and were likely derived from the partial melting of the thickened lower crust of the ncc the guojialing granodiorites were emplaced in the early cretaceous 129 ma and also contain abundant late archean and paleoproterozoic inherited zircons the rocks possess high cao tfe2o3 and mgo and are metaluminous with enrichment in lrees and liles and depletion in hfses they are also characterized by high sr y ratios and have higher end t and ehf t values than the late jurassic granitoids suggesting the involvement of mantle components in the magmatic source we correlate the magma tectonics with the processes accompanying the subduction of the pacific plate beneath the ncc and the associated asthenospheric upwelling

40ar 39ar geochronological constraints on the formation of the dayingezhuang gold deposit new implications for timing and duration of hydrothermal activity in the jiaodong gold province china abstract china s largest gold resource is located in the highly endowed northwestern part of the jiaodong gold province most gold deposits in this area are associated with the ne to nne trending shear zones on the margins of the 130 126 ma guojialing granite these deposits collectively formed at ca 120 5 ma during rapid uplift of the granite the dayingezhuang deposit is a large 120 t au orogenic gold deposit in the same area but located along the eastern margin of the late jurassic linglong metamorphic core complex new 40ar 39ar geochronology on hydrothermal sericite and muscovite from the dayingezhuang deposit indicate the gold event is related to evolution of the core complex at 130 4 ma and is the earliest important gold event that is well documented in the province the dayingezhuang deposit occurs along the linglong detachment fault which defines the eastern edge of the ca 160 150 ma linglong granite granodiorite massif the anatectic rocks of the massif were rapidly uplifted at rates of at least 1 km m y from depths of 25 30 km to form the metamorphic core complex the detachment fault with precambrian metamorphic basement rocks in the hangingwall and the linglong granitoids and migmatites in the footwall is characterized by early mylonitization and a local brittle overprinting in the footwall gold is associated with quartz sericite pyrite k feldspar altered footwall cataclasites at the southernmost area of the brittle deformation along the detachment fault our results indicate that there were two successive yet distinct gold forming tectonic episodes in northwestern jiaodong one event first reactivated the detachment fault along the edge of the linglong massif between 134 and 126 ma and then a second reactivated the shears along the margins of the guojialing granite both events may relate to a component of northwest compression after a middle early cretaceous shift from regional nw se extension to a ne sw extensional regime

u pb zircon ages constrain the architecture of the ultrahigh pressure qinling dabie orogen china new shrimp and tims zircon ages 40ar 39ar ages and eclogite locations contribute significantly to our understanding of the ultrahigh pressure dabie shan 1 the geographic extent of the yangtze craton that was subducted to ultrahigh pressure extends to the northern edge of the dabie shan 2 the northern half of the dabie shan is a magmatic complex intruded over a 10 myr interval between 137 and 126 ma that accommodated 100 n s stretching of the pre existing collisional architecture 3 granitic orthogneisses and enclosing ultrahigh pressure paragneisses have indistinguishable zircon populations the population of triassic zircon ages ranges from 219 to 245 ma leading us to question the prevailing assumption that 219 ma zircons formed at ultrahigh pressure and to propose instead that they reflect late retrogression at crustal pressures following the bulk of exhumation

in situ zircon u pb oxygen and hafnium isotopic compositions of jurassic granites from the north china craton evidence for triassic subduction of continental crust and subsequent metamorphism related 18o depletion abstract six samples of the linglong granitic pluton from the southeastern margin of the north china craton yield similar jurassic magmatic zircon u pb ages and evolved whole rock sr nd isotopic compositions they are weakly peraluminous to strongly peraluminous with a cnk molar al 2 o 3 cao na 2 o k 2 o ratios of 1 05 to 1 3 except one sample with an a cnk of 0 98 however they have contrasting inherited zircon ages and magmatic zircon hf and o isotopic compositions two samples have 2 5 ga inherited zircons and high 18 o magmatic zircons and are interpreted to be derived dominantly from the lower crust of the north china craton another two samples with dominantly triassic inherited zircons and low 18 o magmatic zircons are considered to be derived mainly from the subducted continental crust of the south china craton and the source was considered to be significantly depleted in 18 o during triassic metamorphism the rest two samples have dominantly neoproterozoic inherited zircons and intermediate 18 o magmatic zircons and are also considered to be derived mainly from the subducted continental crust of the south china craton but the source was not significantly depleted in 18 o during triassic metamorphism the different lithologies whole rock e nd t and zircon e hf t between the samples also strongly support that they are derived from different sources although magmatic zircons from the six samples have variable 18 o from 0 7 to 8 5 and e hf t from 27 6 to 11 8 individual samples have more limited e hf t and 18 o the 18 o and e hf t of magmatic zircons from the samples indicate no contribution of mantle derived magmas to the linglong granites this is supported by the fact of no coeval mantle derived rocks in the region the results suggest that large variations of e hf t and 18 o do not necessarily indicate mixing between mantle and crustal derived magmas instead they may reflect heterogeneity in the source the granites are interpreted to result from partial melting of the thickened crust caused by triassic subduction of the south china craton continental crust beneath the north china craton subsequent lithospheric extension and orogenic collapse are the most likely mechanism for the granites

juvenile vs recycled crust in ne china zircon u pb geochronology hf isotope and an integrated model for mesozoic gold mineralization in the jiaodong peninsula abstract the continental crust of the north china craton ncc is a major reservoir of mineral resources with imprints of secular changes in tectonics and metallogeny the jiaodong peninsula located in the eastern margin of the north china craton ncc is currently one of the largest gold producers over the globe and preserves the records of multiple magmatic and metamorphic events here we characterize the timing and tectonics of the major mesozoic magmatism and the associated gold metallogeny in this region through a comprehensive u pb geochronological and hf isotope investigation of zircons in a suite of granitoids mafic magmatic enclaves melanocratic dikes and melted basement rocks the linglong granite hosting one of the major gold deposits in jiaodong shows emplacement ages between 150 and 160 ma and the dominantly negative e hf t values 34 0 to 23 8 of zircons from this intrusion suggest magma derivation from recycled components in the archean basement the guojialing granodiorite and its mafic magmatic enclaves show similar ages between 123 and 127 ma with negative e hf t values 19 3 to 16 8 corresponding to crustal magma source the melanocratic dikes belonging to pre and syn mineralization stages with u pb age range of 126 to 166 ma display large variation in their zircon e hf t values 25 7 and 2 3 suggesting the involvement of both recycled crustal and juvenile mantle components zircons in the melted basement rocks with ages in the range of ca 127 132 ma also display both positive and negative e hf t values 44 6 and 9 8 indicating a mixture of recycled ancient crust and juvenile magmas our study shows that although the peak of gold metallogeny coincided with the tectonics associated with pacific plate subduction which mobilized and concentrated the ores the source materials of gold mineralization and magmatism had multiple origins including from the precambrian basement rocks mesozoic granitoids and mantle derived mafic magmas with extensive mixing of crustal lithosphere mantle and asthenospheric components a combination of delamination mantle upwelling subduction related metasomatic enrichment and recycling of ancient components facilitated the gold metallogeny in this region our study provides a typical case of juvenile and recycled components in the formation and evolution of continental crust and associated mineral resources

timing of metamorphism in the paleoproterozoic jiao liao ji belt new shrimp u pb zircon dating of granulites gneisses and marbles of the jiaobei massif in the north china craton abstract the paleoproterozoic jiao liao ji belt lies in the eastern block of the north china craton with its southern segment extending across the bohai sea into the jiaobei massif high pressure pelitic and mafic granulites have been recently recognized in the paleoproterozoic jingshan group jiaobei massif new shrimp u th pb geochronology combined with cathodoluminescence cl imaging of zircon has been applied to the determination of the timing of the metamorphism of the high temperature and high pressure granulites and associated gneisses and marbles metamorphic zircons in these high pressure granulites gneisses and marbles occur as either single grains or overgrowth or recrystallization rims surrounding and truncating oscillatory zoned magmatic zircon cores metamorphic zircons are all characterized by nebulous zoning or being structureless with high luminescence and relatively low th u values metamorphic zircons from two high pressure mafic granulites yielded 207pb 206pb ages of 1956 41 ma and 1884 24 ma one metamorphic zircon from a garnet sillimanite gneiss also gave an apparent 207pb 206pb age of 1939 15 ma these results are consistent with interval of ages of c 1 93 1 90 ga already obtained by previous studies for the north and south liaohe groups and the laoling group in the northern segment of the jiao liao ji belt metamorphic zircons from a high pressure pelitic granulite and two pelitic gneisses yielded weighted mean 207pb 206pb ages of 1837 8 ma 1821 8 ma and 1836 8 ma respectively two diopside olivine phlogopite marbles yielded weighted mean 207pb 206pb ages of 1817 9 ma and 1790 6 ma these paleoproterozoic metamorphic ages are largely in accordance with metamorphic ages of c 1 85 ga produced from the ji an group in the northern segment of the jiao liao ji belt and c 1 86 1 80 ga obtained for the high pressure pelitic granulites from the jingshan group in the southern segment as this metamorphic event was coeval with the emplacement of a type granites in the jiao liao ji belt and its adjacent areas it is interpreted as having resulted from a post orogenic or anorogenic extensional event

mineralization age and geodynamic background for the shangjiazhuang mo deposit in the jiaodong gold province china abstract the shangjiazhuang mo deposit is located on the jiaodong peninsula in eastern china which is famous for the ca 120 ma jiaodong type au deposits with total au endowment of over 3000 t in this paper we discuss the deposit geology mineralization age and geochemical features of the host granodiorite of the shangjiazhuang mo orebody using this information we aim to clarify the time and geodynamic mechanism for the mo deposit which is another constraint to understand the genesis of au deposits the mo mineralization generally occurs as quartz sulfide veins within the medium grained yashan granodiorite the alteration consists of potassic alteration silicification sericitization chloritization and carbonatization with a weak unclear zonation the ore minerals mainly include molybdenite chalcopyrite and pyrite we measured re os isotopes of molybdenite grains which yielded a weighted mean model age of 116 9 0 81 mswd 1 03 and a well constrained 187 re 187 os isochron age of 117 1 1 4 ma mswd 1 6 these ages are slightly younger than the age of au mineralization on the jiaodong peninsula rhenium contents of 5 84 29 99 ppm with an average of 16 4 ppm in molybdenites indicate a crustal source whole rock geochemical compositions show that the granodiorite is high k calc alkaline and metaluminous to peraluminous the samples show low y contents from 8 2 to 10 5 ppm and sr y ratios from 48 2 to 58 8 displaying an adakitic affinity the yashan granodiorite has high initial 87 sr 86 sr ratios of 0 7101 to 0 7104 low e nd t values of 17 6 to 16 7 and zircon e hf t values from 24 8 to 17 1 with corresponding hf model ages of 2 7 to 2 2 ga these isotopic data together with the adakitic affinity of the granodiorite indicate that the parental magma was derived from ancient crust mafic microgranular enclaves mme that are contemporaneous with the host granodiorite show sio 2 contents of 57 98 58 41 wt and depletion in nb ta the mmes show enriched initial 87 sr 86 sr ratios of 0 7102 to 0 7106 and low e nd t values of 17 3 to 16 3 the mmes are the products of mixing between the metasomatized lithospheric mantle derived mafic magma and the ancient crust derived felsic magma the early cretaceous mo mineralization 120 110 ma is slightly younger than the peak time of au mineralization 126 120 ma on the jiaodong peninsula but have a different spatial distribution which suggests different sources of au and mo the jiaodong type au deposits were probably related to the upwelling of metasomatized lithospheric mantle while the mo mineralization on the jiaodong peninsula may delineate a 120 110 ma mo metallogenic belt along the southern margin of the north china craton with the east qinling which is related to the melting of ancient crustal sources the subduction of the paleo pacific slab and accompanying asthenospheric upwelling triggered upwelling of metasomatized lithospheric mantle forming jiaodong type au deposits subsequently the ponding of mantle derived magmas resulted in partial melting of ancient crust and associated mo deposits

relative roles of formation and preservation on gold endowment along the sanshandao gold belt in the jiaodong gold province china importance for province to district scale gold exploration the 13 km long sanshandao gold belt along the nne trending sanshandao fault has highly variable orogenic gold endowment along strike new thermochronological data from the small cangshang gold deposit demonstrate similar degrees of uplift and exhumation rates as for larger deposits negating selective preservation as the prime gold endowment factor the haiyu sanshandao xiling and cangshang deposits of variable gold endowment lie adjacent to ne ene trending jogs similar to those at jiaojia and linglong so these structures cannot be the prime control on gold mineralization ore zones show a broad gentle northeast plunge with the southwestern cangshang and xinli deposits being closest to the ground surface and the northeastern haiyu deposit being the deepest thus preferential erosion of the shallower southwestern orebodies could be a factor affecting endowment another variable is the depth of drilling at haiyu sanshandao gold mineralization is better developed on more gently dipping fault segments consistent with a thrust component of oblique slip along them relative to the northeastern deposits the cangshang and xinli deposits are located in areas where relatively shallow drilling has intersected ore zones on steeply dipping fault segments indicating the potential for deeper drilling to intersect gold ore along deeper more gently dipping segments heterogeneous gold endowment is thus largely a formational factor related to the plunge of orebodies combined with the variable depth of drilling along the sanshandao fault over the entire jiaodong gold province there are equivalent age mesozonal to epizonal orebodies implicating their preservation at different crustal levels and thus increasing the province scale gold endowment potential and probability of further exploration discoveries

anatomy of a world class epizonal orogenic gold system a holistic thermochronological analysis of the xincheng gold deposit jiaodong peninsula eastern china abstract xincheng is a world class orogenic gold deposit hosted by the early cretaceous guojialing granitoid in the jiaodong peninsula eastern china a zircon u pb age of 126 1 4 ma together with previous data constrain the emplacement of the guojialing intrusion to 132 123 ma the granitoid underwent subsolidus ductile deformation at 500 c following its intrusion the small difference in age between the youngest zircon u pb age of unaltered granitoid 123 ma and the ca 120 ma 40ar 39ar ages of sericite associated with breccias and gold mineralization within it indicate initial rapid cooling from magmatic temperatures to those prevalent during brittle deformation and associated gold mineralization at 220 300 c evidence of a direct association between granitic magmatism and gold mineralization such as at least localized near magmatic depositional temperatures and metal zoning evident in undoubted intrusion related gold deposits is absent the 40ar 39ar age of 120 ma coincides with the mineralization age of many other orogenic gold deposits along the jiaojia fault sixteen zircon fission track zft ages across the ore and alteration zones range from 112 9 3 4 to 99 1 2 7 ma the long period of cooling to the 100 ma zft closure temperatures recorded here suggests that ambient temperatures for hydrothermal alteration systems lasted to 100 ma possibly because of their focus at xincheng within the young guojialing granitoid as it cooled more slowly below approximately 300 c to 220 c however the restricted number of auriferous ore stages combined with the presence of cross cutting gold free quartz carbonate veins indicate that gold itself was only deposited over a restricted time interval at 120 ma consistent with studies of orogenic gold deposits elsewhere this highlights the complex interplay between magmatism deformation and the longevity of hydrothermal systems that cause genetic controversies based on apatite fission track aft ages the xincheng gold deposit was then uplifted and exhumed to near the surface of the crust at 15 ma probably due to movement on the crustal scale tan lu fault recognition of such exhumation histories along gold belts has conceptual exploration significance in terms of the probability of discovery of additional exposed or sub surface gold ore bodies as discovery is as much a function of preservation as formation of the deposits

late mesozoic magmatism and sedimentation in the jiaodong peninsula new constraints on lithospheric thinning of the north china craton abstract intense magmatism and voluminous sedimentation occurred in the jiaodong peninsula during mesozoic in response to the lithospheric thinning in eastern north china craton ncc here we report the results from an integrated geochemical and sr nd pb hf isotopic study on granitoids and u pb and lu hf isotopes of the detrital zircons from mesozoic sediments in the jiaodong peninsula to provide new constraints on the crustal response to the lithospheric thinning geochronologic data reveal three distinct magmatic pulses at 170 140 ma 140 125 ma and 125 105 ma in this region the sr nd pb isotope data 0 7080 0 7139 for 87sr 86sr 22 3 10 8 for nd t 16 97 17 47 for 206pb 204pb 15 42 15 55 for 207pb 204pb 37 36 38 34 for 208pb 204pb and zircon hf t values 29 10 for the mesozoic plutons show more similarities with those of the lower crust of the yangtze craton yc wedged beneath the ncc than those of the ncc the sr y la yb n and nb ta ratios for the three episodes of granitic magmatism show a gradual decrease which is interpreted to reflect upward migration of the depth of partial melting from 170 ma to 105 ma the dominant detrital zircon population in the sediments deposited during ca 125 105 ma was derived from pre jurassic sources in the ncc and yc basement whereas the cretaceous population was derived from volcanic rocks in the interior of the craton the alternating sequence suggests episodic uplift of the ncc and yc basements during this period the data obtained in this study allow us to summarize the crustal evolution of this region into three phases 1 during 170 140 ma partial melting of wedged yc lower crust resulted in high magmatic flux 2 during 140 125 ma intense magmatism continued accompanied by uplift and erosion of basement and initiation of basin filling 3 during 125 105 ma the source depth of granitoid magma became shallower associated with continuing episodic basement uplift representing the peak of lithospheric thinning

evolution of the lithospheric mantle beneath the southeastern north china craton constraints from mafic dikes in the jiaobei terrain abstract two stages of mafic dikes with ages of 117 116 ma and 95 87 ma respectively are identified in the jiaobei terrain based on zircon u pb ages the early cretaceous mafic intermediate dikes ecmds and late cretaceous mafic dikes lcmds show distinct geochemical and isotopic features the ecmds are enriched in large ion lithophile elements lile rb sr ba u and th and light rare earth elements lree la ce pr nd sm and eu with a strong depletion in high field strength elements hfse nb ta ti and p they show uniformly high 87sr 86sr i 0 70841 0 71387 low end t values 18 1 to 13 2 positive 206pb 204pb i 17 07 17 90 and negative ehf t 21 0 to 6 1 values these rocks were derived from partial melting of an enriched lithospheric mantle and the enrichment of the mantle source resulted from source metasomatism imparted by the melts generated from remelting of the subducted lower crust of the yangtze craton yc in contrast the lcmds show lower sio2 41 5 50 1 wt lack of hfse depletion and are depleted in whole rock nd and zircon hf isotope they are interpreted to have sourced from a newly accreted depleted lithospheric mantle generated through continuous erosion of older enriched lithospheric mantle by asthenospheric upwelling leaving out minor remnants of the older mantle in the newly accreted lithospheric mantle the geochemical and isotopic characteristics reported in our study demonstrate that the lithospheric mantle beneath the southeastern north china craton ncc was generally enriched during the early cretaceous 120 ma and the mechanism of the enrichment may be related to source metasomatism caused by the subducted lower crust of the yc however in late cretaceous the lithospheric mantle beneath southeastern ncc was highly heterogeneous which might be related to asthenospheric non uniform erosion the 116 87 ma marks the transition from enriched lithospheric mantle to depleted asthenospheric mantle

epma u th pb monazite and shrimp u pb zircon geochronology of high pressure pelitic granulites in the jiaobei massif of the north china craton the jiaobei massif constitutes the southern segment of the paleoproterozoic jiao liao ji belt in the eastern block of the north china craton and contains high pressure hp mafic and pelitic granulites the hp pelitic granulites contain four distinct mineral assemblages garnet kyanite biotite muscovite rutile m1 garnet kyanite ternary feldspar biotite muscovite rutile m2 garnet sillimanite biotite perthite anti perthite m3 and biotite muscovite sillimanite plagioclase m4 of which m2 is a typical hp pelitic assemblage the origin of these hp granulites is important for understanding the tectonic evolution of the jiao liao ji belt but the timing of the hp event still remains unknown this study applied the epma u th pb monazite and shrimp u pb zircon dating techniques to determine the metamorphic ages of the hp pelitic granulites in the jiaobei massif cl images and th u ratios show that all monazite and zircon grains in the analyzed samples are of metamorphic origin eighty two epma analyses on 16 monazite grains from two samples yielded three age groups at 1895 to 1882 ma 1814 to 1813 ma and 1706 to 1692 ma and the ages of 16 shrimp analyses on 14 zircon grains from one sample range from 1864 to 1803 ma the oldest ages of 1895 to 1882 ma were yielded from high y monazite grains enclosed in garnet and sillimanite pseudomorph after kyanite and thus interpreted as the time of the hp m2 granulite facies metamorphism the epma monazite ages of 1814 to 1813 ma and shrimp zircon ages of 1864 to 1803 ma are interpreted as the approximate ages of the post hp granulite facies metamorphism m3 most probably resulting from the exhumation of the hp granulites to the medium pressure granulite facies levels the youngest age group of 1706 to 1692 ma obtained from low y monazite grains in the matrix can be interpreted as the age of late cooling and retrograde metamorphism m4 that occurred when the hp pelitic granulites were exhumed to the upper crust the presence of paleoproterozoic hp mafic and pelitic granulites in the southern segment of the jiao liao ji belt suggests that the evolution of the jiao liao ji belt in the eastern block of the north china craton must have been involved in subduction or collision related tectonic processes

metallogeny of the north china craton link with secular changes in the evolving earth abstract the north china craton ncc has experienced a complex geological evolution since the early precambrian and carries important records of secular changes in tectonics and metallogeny here we synthesize the salient geological and tectonic features of the evolution and destruction of the ncc vis a vis major metallogenic events and the formation of potential ore deposits we identify a close relationship between the major geological events in the ncc and those reported elsewhere on the globe we trace the records of a regular change in the pattern of metallogeny mineral deposit character spatial distribution and genetic mechanisms which closely match the timing and styles of the major geological and tectonic events in this craton the ncc went through five major tectonic cycles 1 neoarchean crustal growth and stabilization 2 paleoproterozoic rifting subduction accretion collision with imprints of the great oxidation event goe 3 late paleoproterozoic neoproterozoic multi stage rifting 4 paleozoic orogenesis at the margins of the craton and 5 mesozoic extensional tectonics associated with lithospheric thinning and decratonization coinciding with these major geological events are five major metallogenic systems identified as follows 1 an archean bif system 2 paleoproterozoic cu pb zn and mg b systems 3 a mesoproterozoic ree fe pb zn system 4 a paleozoic orogenic cu mo system and 5 mesozoic intracontinental au and ag pb zn and mo systems the ore deposit types in each of these metallogenic systems show distinct characteristics and tectonic affinities from early precambrian through late precambrian to paleozoic and mesozoic the ncc records a transition from primitive to modern style plate tectonics evidence for imbricated oceanic plate stratigraphy in a subduction accretion setting and collisional orogenesis along at least three major zones of ocean closure are documented major transitions in tectonic style and surface environmental changes recorded in other parts of the world are also reflected in the geological history and metallogenic events in the ncc large scale gold deposits formed through intraplate tectonics during the mesozoic provide important insights into mantle dynamics and crust mantle interaction associated with lithospheric thinning and craton destruction the ncc provides one of the best examples for documenting secular changes in the geological history and metallogenic epochs of an evolving earth

zircon geochronology geochemistry and stable isotopes of the wang ershan gold deposit jiaodong peninsula china abstract the early cretaceous gold deposits of the jiaodong peninsula eastern china define china s largest gold province with an overall endowment estimated more than 3000 t au the wang ershan gold deposit at the northern margin of the jiaolai basin in jiaodong peninsula of eastern china is located in the central southern segment of the wang ershan fault zone the major mesozoic intrusions exposed in this region are the linglong granite and the guojialing granodiorite to the northeast of the deposit both these intrusions show high k and alkaline signature the linglong granite displays peraluminous feature whereas the guojialing granodiorite is metaluminous zircon u pb dating of the linglong granite yields 206 pb 238 u weighted mean age of 149 0 1 3 ma the muscovite from the alteration zones associated with mineralization in the linglong granite yields a plateau age of 130 35 0 96 ma representing the initial phase of the hydrothermal activity the 34 s values of pyrite from the gold mineralized veins range from 6 to 8 3 with the mean value of 7 66 the 3 he 4 he ratios of pyrite are in the range 1 58 2 71 ra with a mean value at 2 168 ra the 40 ar 36 ar ratios show variation from 1220 3 to 1625 7 with an average of 1483 8 the 18 o values of the mineralizing fluids show a range of 2 13 to 7 5 with an average of 2 4 the 18 d w values are in the range of 97 5 to 61 4 with a mean at 82 6 detailed elemental and isotopic data suggest that the hydrothermal fluids in early stage were mainly magmatic and derived from the guojialing granodiorite and the ore forming fluids in the main ore forming stages evolved into a mixture of magmatic and meteoric water the ore forming materials were primarily derived from crust with minor input of mantle components the ore forming fluids might be related to the subduction of the paleo pacific slab beneath the north china craton and the associated asthenosphere upwelling and consequent lithospheric thinning

hydrothermal alteration associated with mesozoic granite hosted gold mineralization at the sanshandao deposit jiaodong gold province china abstract the sanshandao gold deposit reserves of more than 200 t au and average grade of 3 96 g t located at northwestern edge of the jiaodong peninsula eastern north china craton is one of the largest gold deposits in the jiaodong gold province in this deposit disseminated and stockwork style ores are hosted in mesozoic granitoids mineralization and alteration are largely controlled by the regional sanshandao cangshang fault host granitic rocks for the deposit display a complex paragenetic sequence of alteration and mineralization activities of the sanshandao cangshang fault created structurally controlled permeability allowing for infiltration of hydrothermal fluids leading to diffusive k feldspar alteration on the two fault planes later large scale diffusive sericitization symmetrically developed across the main fault and partially overprinted the earlier k feldspar alteration following the sericitization relatively small scale silicification occurred but now it is only retained in the hanging wall of the main fault subsequently the fault gouge formed as a barrier layer which is impermeable for later fluids to move upward after that strong pyrite sericite quartz alteration occurred only in the footwall of the main fault and was accompanied by gold precipitation the last stage carbonation and quartz carbonate veins marked the waning of gold related hydrothermal activity mass balance calculations indicate complex behaviors of different types of elements during fluid rock interaction most major elements were affected by intensive mineral replacement reactions as expected the fluid mobile elements lile and lree generally show moderate to high mobility it is notable that even the commonly assumed fluid immobile elements such as hree and hfse tend to be changed to various degrees in addition y ho zr hf and nb ta fractionations are observed in altered domains studies on alteration assemblages and fluid inclusions suggest that the ore forming fluids were characterized by low salinity 8 4 wt nacl equiv moderate temperature 300 400 c weakly acidic ph 3 5 and relatively reducing log fo2 28 characteristics in this type of fluids gold was most likely transported as au hs 2 complex with alteration going on log ak ah of fluids generally decreased due to significant formation of secondary k bearing minerals in addition there might be a decrease of fo2 from pre gold alteration stage to the main gold mineralization stage and decrease of fo2 was probably one of the factors controlling gold precipitation the sr and nd isotopic compositions of hydrothermal minerals combined with previous h o and he ar isotopic studies indicate that the hydrothermal fluids were mainly derived from crustal sources e g degassing of felsic magmas and meteoric water but with involvement of mantle derived components the gold mineralization event just coincided with reactivation of the north china craton as marked by asthenosphere upwelling voluminous igneous rocks and high crustal heat flow which may have provided sufficient heat energy and fluid input required for the formation of the gold deposits

an integrated mineral system model for the gold deposits of the giant jiaodong province eastern china abstract the giant jiaodong gold province with more than 5000 t of proven gold resources is unique in that its mesozoic gold deposits are hosted in a precambrian basement block there has long been debate on the source of gold the mechanism for its extreme enrichment and a holistic genetic model for these spectacular deposits in order to improve understanding of these factors a mineral system model is proposed for the jiaodong gold deposits for the first time it is based on a detailed review of the architecture and composition of the underlying mantle lithosphere the geodynamic setting at the time of gold mineralization the geological and geochemical features of the deposits themselves and mechanisms of their preservation regional geodynamic reconstructions combined with the nature of mesozoic magmatic systems show that late mesozoic breakoff of the subduction slab and rollback of the paleo pacific plate caused asthenosphere upwelling and lithosphere extension and thinning robust geochronological studies demonstrate that the jiaodong gold deposits formed at ca 120 ma during a change of subduction direction of the paleo pacific plate and the synchronous transition of tectonic regime from regional compression to transpression or transtension prior to peak extension caused by thinning of the lithosphere geophysical exploration data and hf nd isotope mapping of the jiaodong peninsula reveal a relatively simple ancient crustal structure cut by near vertical shear or fault zones including the lithosphere scale tan lu and wulian yantai faults that provided the first order architecture for emplacement of mantle magmas and sub crustal fluids in terms of fertility the significant older pre mineralization crustal metamorphism combined with sulfur lead and strontium isotope ratios indicate a dominant sub crustal source for the ore components for the jiaodong gold deposits consistent with evidence for volatile and gold fertilized metasomatized mantle lithosphere beneath the north china block helium ar and c o isotope ratios implicate mantle sources of ore fluids with contamination by crustal components en route to crustal depositional sites in terms of crustal architecture combined geophysical structural mineralogical fluid inclusion and geochemical studies show that the deeply sourced ore fluids and metals advected upwards through lithosphere scale faults to deposit gold via sulfidation and phase separation in crustal scale nne ne trending fault systems at mid to upper crustal levels preservation of disseminated to stockwork style deposits and auriferous quartz pyrite vein deposits was enhanced by deep crustal formation combined with limited uplift and exhumation of the province the jiaodong gold deposits although commonly hosted in granite intrusions clearly post date them on the basis of robust and reliable geochronology the spatial but non temporal relationships of gold deposits with granites their strong structural control and their other characteristics clearly place them in the orogenic gold group it is suggested because of their uniqueness that they be termed jiaodong type orogenic gold deposits

a comparison of jiaojia and linglong type gold deposit ore forming fluids do they differ abstract the jiaodong peninsula contains the most important concentration of gold deposits in china which can be divided into jiaojia type and linglong type deposits based on mineralization style the former is characterized by disseminated and stockwork style mineralization hosted in first order regional faults with relatively larger tonnages and lower gold grades the latter is characterized by massive auriferous quartz veins commonly hosted in subsidiary second or third order faults with smaller tonnage but higher grade orebodies despite these differences both groups of deposits have the same alteration assemblages mineral paragenesis element concentrations and ore forming ages the mainly jiaojia type luoshan gold deposit and the mainly linglong type fushan gold deposit are characterized by h o s pb isotope data that indicate the ore forming fluids have a dominantly metamorphic source the fluids were derived during the yanshanian orogenic event and were most likely associated with dehydration and decarbonization processes near the top of the subducting paleo pacific plate the linglong type ores have relatively lighter calculated 18 o compositions 3 9 to 2 3 than the jiaojia type ores 0 3 8 0 possibly because of a greater degree of mixing with meteoric water petrographic cathodoluminescence microthermometric and laser raman spectroscopic analyses of fluid inclusion assemblages in quartz from the two types of ores indicate fluids were similar in both cases characterized by medium high homogenization temperatures 211 393 c significant co 2 15 mol minor ch 4 18 in the carbonic phase and low salinity 11 2 wt nacl eq the linglong type ores however have a wider range of co 2 and ch 4 concentration and salinity than the jiaojia type ores fluid immiscibility occurred in main ore stage of both ore types with the trapping conditions of 77 185 mpa and 284 328 c although the unmixing is more intense and widespread in the linglong type ores both fluid wallrock interaction and fluid immiscibility are important gold deposition processes in the two types but immiscibility is more important in the linglong type ores and that has led to the typical higher gold grade in general there is little geochemical differences between the ore forming fluids for jiaojia and linglong type gold deposits both jiaojia and linglong type ores can exist in a single deposit and form in the same metallogenic event the linglong type ores developed as more massive veins because of their location in zones of more extensive extension and they lack significant post ore cataclastic deformation

disturbance stream incision and channel evolution the roles of excess transport capacity and boundary materials in controlling channel response abstract channel incision is part of denudation drainage network development and landscape evolution rejuvenation of fluvial networks by channel incision often leads to further network development and an increase in drainage density as gullies migrate into previously non incised surfaces large anthropogenic disturbances similar to large or catastrophic natural events greatly compress time scales for incision and related processes by creating enormous imbalances between upstream sediment delivery and available transporting power field examples of channel responses to antrhopogenic and natural disturbances are presented for fluvial systems in the mid continent and pacific northwest usa and central italy responses to different types of disturbances are shown to result in similar spatial and temporal trends of incision for vastly different fluvial systems similar disturbances are shown to result in varying relative magnitudes of vertical and lateral widening processes and different channel morphologies as a function of the type of boundary sediments comprising the bed and banks this apparent contradiction is explained through an analysis of temporal adjustments to flow energy shear stress and stream power with time numerical simulations of sand bed channels of varying bank resistance and disturbed by reducing the upstream sediment supply by half show identical adjustments in flow energy and the rate of energy dissipation the processes that dominate adjustment and the ultimate stable geometries however are vastly different depending on the cohesion of the channel banks and the supply of hydraulically controlled sediment sand provided by bank erosion the non linear asymptotic nature of fluvial adjustment to incision caused by channelization or other causes is borne out in similar temporal trends of sediment loads from disturbed systems the sediments emanating from incised channels can represent a large proportion of the total sediment yield from a landscape with erosion from the channel banks generally the dominant source disturbances that effect available force stream power or flow energy or change erosional resistance such that an excess of flow energy occurs can result in incision channel incision therefore can be considered a quintessential feature of dis equilibrated fluvial systems

shrimp zircon u pb dating and hf isotope analyses of the muniushan monzogranite guocheng jiaobei terrane china implications for the tectonic evolution of the jiao liao ji belt north china craton abstract the paleoproterozoic granitoid rocks in the jiaobei terrane which lies in the southern part of the jiao liao ji belt jljb in china provide valuable information on the tectonic and evolutionary history of the north china craton ncc shrimp u pb dating of zircons from the muniushan monzogranite in the guocheng gold deposit area as well as in situ hf isotope analyses of the zircons were used to constrain the ages of emplacement and metamorphism and to understand the petrogenesis of the granite the geochronological data show emplacement ages of ca 2 1 ga and metamorphic ages of ca 1 85 ga the magmatic cores of the zircons have ehf t values of 0 51 to 4 00 average 1 98 and depleted mantle two stage model ages tdm2 of 2444 2703 ma average 2563 ma the rocks show the same trends of crustal evolution as ca 2 5 ga tonalite trondhjemite granodiorite ttg rocks in the jiaobei terrane indicating that they were formed by the remelting of those ttg rocks the muniushan monzogranite is part of a linear belt of ca 2 2 2 0 ga paleoproterozoic granitoids within the jljb the granitoids are a types and are accompanied by coeval mafic intrusions and bimodal volcanic rocks thus indicating widespread extension along the jljb in the period 2 2 2 0 ga the ca 1 85 ga metamorphism was related to the collision of the longgang and nangrim blocks the paleoproterozoic evolution of the ncc constrains the crustal architecture and the source of mesozoic granitoids in the jiaobei sulu region inherited zircons of paleoproterozoic age are widespread in the mesozoic granitoids in addition paleoproterozoic ages have been reported from lower crustal granulite xenoliths in the sulu orogen and the southeastern margin of the ncc mirrors the evolution of the jljb it is probable therefore that ncc lower crust underlies the sulu orogen and that the ncc was the main source for the mesozoic granitoids in the jiaobei sulu region this view is consistent with the appearance of inherited zircons of archean and paleoproterozoic age on both sides of the orogen normal 18o values of magmatic zircons and paleoproterozoic to archean two stage hf model ages for the granitoids

a multifractal analysis of mineralization characteristics of the dayingezhuang disseminated veinlet gold deposit in the jiaodong gold province of china abstract the gold concentration distributions along drifts in the dayingezhuang fault controlled disseminated veinlet gold deposit in the jiaodong gold province eastern china has been analyzed using a multifractal technique with the aim of better understanding the ore forming processes some intensely mineralized areas show small gold singularities representing compact concentration distributions which is resulted from intense stress release and development of abundant microfractures with various sizes several intensely and moderately mineralized areas are characterized by isolated distributions of lower concentrations suggesting that only relatively large microfractures locally develop resulted from less intense stress release some barely and moderately mineralized areas show isolated distributions of higher concentrations due to occurrences of only a few fractures or large microfracture most barely mineralized areas are characterized by dense concentrations distributions because the widespread development of relatively small microfractures caused by weak stress release thus making the areas unsuitable for gold deposition these characteristics reflect that variable development of the structures is responsible for different gold mineralization within the deposit the ratios between the singularity a q and its fractal dimension f a q for the different drifts vary similarly as q 0 8 or q 0 8 thus from the multifractal viewpoint it is suggested that gold enrichment processes are consistent in both mineralized and barely mineralized areas despite their differing mineral intensities

rapid exhumation of the northern jiaobei terrane north china craton in the early cretaceous insights from al in hornblende barometry and u pb geochronology abstract the guojialing and aishan plutons in the northern jiaobei terrane represent the magmatic products of the lithospheric thinning of the north china craton in the early cretaceous the exhumation history of the terrane in response to the thinning process and its effect on the formation and preservation of coeval gold deposits remain poorly constrained granodiorites from the guojialing pluton and monzogranites from the aishan pluton contain zircon grains with u pb ages of ca 130 ma and ca 116 ma respectively using the al in hornblende barometry the guojialing and aishan plutons had crystallization pressures of 3 2 5 4 kbar 12 km and 1 5 2 6 kbar 5 km respectively using the hornblende plagioclase thermometry the guojialing and aishan plutons had crystallization temperatures of 628 697 c and 702 745 c respectively fluid inclusion microthermometric data show that auriferous quartz veins in the daliuhang deposit formed at temperatures between 243 and 322 c at a depth of 7 11 km which was similar to the emplacement depth of the aishan pluton these thermobarometric and geochronological data reveal 7 km uplift between 130 ma and 116 ma but negligible exhumation for the gold deposits after its formation until 116 ma combining previous results we envisage that the exhumation magnitude of the guojialing intrusions were nearly the same in the wide area with slight differences between the core and margin of a single pluton numerous gold deposits in the jiaobei terrane formed during or after the late stage of rapid exhumation of granitoids and were uplifted with similar depths to the aishan pluton since ca 116 ma the rapid exhumation of the guojialing pluton was with the regional extension and might be genetically associated with the intensive delamination of destabilized lithospheric root and dense residues

fluvialcorridor a new arcgis toolbox package for multiscale riverscape exploration abstract both for scientists and river basin managers development of automated geographic information system gis tools is essential today to characterize riverscapes and explore biogeomorphologic processes over large channel networks since the 1990s gis toolboxes and add in programs have been used to characterize catchments however there is currently no equivalent to a planimetric and longitudinal characterization of fluvial corridor networks at multiple scales this paper describes fluvialcorridor a new gis toolbox this package allows the user i to extract a large set of riverscape features such as the main components of fluvial corridors from dem and vector layers e g stream network or valley bottom and ii to aggregate spatial features into homogeneous segments and metrics characterizing each of them the methodological frameworks involved have been previously described by alber and piegay 2011 leviandier et al 2012 and bertrand et al 2013 and this contribution focuses on the gis tools allowing the user to automatically operate them a case study on the drome river france is provided to illustrate the potential of the package both for geomorphologic understanding and target management actions fluvialcorridor has been developed for arcgis with the related native python library named arcpy and tested on arcgis 10 0 and 10 1 obviously each component of the package can be used separately however it also provides a complete workflow for fluvial corridor characterization even as the toolbox is continually under development and revision case study database fluvialcorridor package and guidelines are available online at http umrevs isig fr