salt weathering simulation using a single immersion technique samples of concrete were subjected in an environmental cabinet to six different diurnal cycles of temperature and humidity change representative of desert surface conditions in the presence of a range of saturated salt solutions the samples were not subjected to repeated immersion or continuous partial immersion as has been the case in most previous experiments breakdown did occur nonetheless the two most effective cycles were one from egypt with a very high daytime maximum and one from the negev with high nocturnal humidity conditions cycles with relatively modest temperature and humidity cycles were ineffective in causing debris liberation

geological context and vents morphology of the ultramafic hosted ashadze hydrothermal areas mid atlantic ridge 13 n 1 recent rov dives and high resolution bathymetric data acquired over the ashadze fields on the mid atlantic ridge 13 n allow us to derive constraints on the regional and local geological setting of ultramafic hosted hydrothermal fields the active vent fields of ashadze hydrothermal fields are located in the western axial valley wall downslope from the termination of a prominent corrugated surface and in a transitional domain with respect to ridge segmentation the study of the shipboard and rov bathymetry shows that decameter 100 m by 60 m to kilometer scaled rockslides shape the axial valley wall slopes in this region the ashadze 1 vent field occurs on a coherent granular landslide rock mass that is elongated in an e w direction the ashadze 1 vent field comprises hundreds of active and inactive sulfide chimneys the ashadze 2 vent field is located in a nne trending linear depression which separates outcrops of gabbros and serpentinized peridotites active black smokers in the ashadze 2 field are located on ultramafic substratum in a 40 m diameter crater 5 m deep this crater recalls similar structures described at some vents of the logatchev hydrothermal field mid atlantic ridge 15 n we discuss the mode of formation for these craters as well as that for a breadcrust like array of radial fissures identified at ashadze 1 we propose that hydrothermalism at ashadze can be an explosive phenomena associated with geyser like explosions our study also constrains the geological and geophysical context of the ultramafic hosted ashadze hydrothermal system that may use the oceanic detachment fault as a preferred permeability conduit

salt crystallization in pores quantification and estimation of damage the objective of this study is to understand and predict the alteration of porous rock by crystallization of salts samples of different rocks have been tested according to the en 12370 standard test two parameters are proposed to evaluate the alteration of a rock during these tests the alteration index ai represents the cycle in which the first damages occur the alteration velocity av represents the alteration rate at the end of the experiment when the decay has become regular these parameters can be estimated with the help of a microstructural study of the rocks the most relevant intrinsic parameters of the stones for this estimation are capillary coefficient evaporation coefficient tensile strength and p waves velocity an evaluation of the alteration pattern is also proposed depending on the eventual heterogeneities and anisotropies of the rocks the influence of the dimension and shape of the samples is also discussed

geological and isotopic geochemical constraints on the evolution of the fuping complex north china craton abstract the neoarchean to paleoproterozoic fuping complex together with the adjacent hengshan and wutaishan complexes form the middle part of the central zone that separates the north china craton into the eastern and western archean continental blocks the fuping complex comprises three major lithological assemblages the 2 50 ga fuping trondhjemite tonalite granodiorite ttg gneisses the wanzi paragneisses and the 2 08 and 2 02 ga nanying granitic gneisses the ttg gneisses contain abundant enclaves of highly metamorphosed supracrustal rocks including 2 70 ga mafic granulites and amphibolites with endt of 3 29 to 3 96 and tdm of 2 72 2 82 ga and are characterized by tdm of 2 76 3 04 ga and a linear correlation between endt 1 64 to 0 96 and 1 nd indicative of mixing of melts derived from the 2 70 ga metabasic rocks and 3 0 ga crustal materials mafic dikes along the chengnanzhuang shear zone were most likely emplaced at 2 31 ga and have endt of 2 24 to 4 78 and tdm of 2 34 2 59 ga the nanying granitic gneisses with endt of 4 04 to 5 24 were most likely related to partial melting of the 2 70 ga supracrustal rocks and or the 2 50 ga ttg gneisses these geological relationships and isotopic data suggest that the fuping complex probably formed from the following five major tectonomagmatic events 1 mafic magmatism and early crustal growth at 2 7 ga with the possible existence of older 3 0 ga crust s 2 collision related crustal thickening underplating of basaltic magma high grade metamorphism crustal anatexis and ttg magmatism at 2 5 ga 3 extensional deformation and emplacement of the mafic dikes and the nanying granitic plutons along the chengnanzhuang shear zone 2 5 to 2 0 ga 4 s type granitic magmatism and associated amphibolite facies metamorphism 2 0 to 1 80 ga and 5 emplacement of granitic pegmatite dikes at 1 80 ga

laboratory simulation of the wick effect in salt weathering of rock the wick effect is the upward migration of saline solutions into rocks and their subsequent crystallization lower carboniferous sandstone blocks of rectangular shape have been subjected to this process in the laboratory using a range of salt types a range of salt concentrations and various mixtures of salts some treatments produced severe disintegration notably sodium carbonate and a mixture of sodium carbonate with magnesium sulphate whereas other salts including sodium chloride and gypsum were much less effective the debris produced by this experimental salt weathering included appreciable quantities of silt sized material which were analysed with a laser granulometer such material could provide a source for desert loess

shrimp u pb zircon ages of granitoid rocks in the luliang complex implications for the accretion and evolution of the trans north china orogen abstract the luliang complex is situated in the central segment of the trans north china orogen tnco a continent continent collisional belt along which the discrete eastern and western blocks amalgamated to form the basement of the north china craton the complex consists of supracrustal and granitoid rocks of which the latter can be subdivided into pre tectonic ttg gneisses including the yunzhongshan guojiazhuang and chijianling guandishan gneisses syn tectonic gneissic granites represented by the huijiazhuang gneissic granite and post tectonic granites including the luyashan charnockite luchaogou porphyritic granite and tangershang guandishan massive granite the pre tectonic ttg gneisses are mostly calc alkaline and considered to have formed in a magmatic arc environment shrimp u pb analyses reveal that the yunzhongshan gneisses were emplaced at 2499 9 ma representing the earliest arc related magmatic event in the luliang complex this was followed by the intrusion of the guojiazhuang gneisses at 2375 10 ma the most widespread arc related magmatic event in the region was the emplacement of the chijianling guandishan granitoid gneisses of which the tonalitic granodioritic and monzogranitic gneisses were emplaced at 2199 11 ma 2180 7 ma and 2173 7 ma respectively metamorphic zircon overgrowth rims from a tonalitic gneiss yielded a weighted mean 207 pb 206 pb age of 1872 7 ma consistent with the metamorphic age range of 1880 1820 ma defined by metamorphic zircons from various high grade rocks in the tnco thus the evolution of the luliang complex involved emplacement of the yunzhongshan granitoids at 2499 ma the guajiazhuang granitoids at 2375 ma and the chijianling guandishan granitoids at 2199 2173 ma with the final collision between the eastern and western blocks in this area occurring at 1872 7 ma the whole series of magmatic events lasting nearly 650 ma this suggests that the trans north china orogen represents a long lived magmatic arc the new shrimp zircon data combined with structural and petrological studies also reveal the existence of both syn and post collisional granites in the luliang complex the former is represented by the huijiazhuang gneissic granite that was emplaced at 1832 11 ma whereas the latter include the 1815 5 ma luyashan charnockite 1807 10 ma luchaogou porphyritic granite 1798 11 ma guandishan massive granite and 1790 14 ma tangershan massive granite

ni cu pge magmatic sulfide deposits in the yangliuping area permian emeishan igneous province sw china the ni cu pge sulfide deposits in the yangliuping area sw china are hosted in mafic ultramafic sills the four mineralized sills are located in the yangliuping tectonic dome and intrude devonian carbonaceous marble graphitic schist the sills are 200 300 m thick and 1 000 2 000 m in strike length and now consist chiefly of serpentinite talc schist tremolite schist and meta gabbro disseminated ni cu sulfide mineralisation occurs in the serpentinite in the lower parts of the sills massive sulfide mineralisation is located in the base of the sills and in the footwall along fractures beneath the mineralized serpentinite although the sulfide ores have been modified by hydrothermal activity there are relict cumulate textures in the disseminated sulfides indicating a magmatic origin for the ores the yangliuping intrusions and the dashibao formation have similar primitive mantle normalized trace element and platinum group element pge patterns indicating that they are derived from a common parental magma type the positive correlation between cu concentrations and cu zr ratios of the dashibao formation basalts indicates that the chalcophile elements were removed before eruption we propose that fractional crystallization of the yangliuping magma accompanied by the introduction of s and co2 from the wall rocks caused the magma to become s saturated leading to the segregation of magmatic sulfides that became enriched in ni cu pge the sills acted as conduits for the overlying dashibao formation basalts with the sulfide liquid along with early crystallizing olivine and pyroxene segregating from the magma as it passed through the conduits prior to eruption

salt weathering influence of evaporation rate supersaturation and crystallization pattern micro and macroscale experiments which document the dynamics of salt damage to porous stone have yielded data which expose weaknesses in earlier interpretations previously unexplained differences are found in crystal morphology crystallization patterns kinetics and substrate damage when comparing the growth of mirabilite na2so4 10h2o and thenardite na2so4 versus halite nacl the crystallization pattern of sodium sulphate was strongly affected by relative humidity rh while a lesser rh effect was observed for sodium chloride macroscale experiments confirmed that mirabilite crystallizing at rh 50 per cent and thenardite crystallizing at rh 50 per cent tend to form subflorescence in highly localized areas under conditions of constant rh and temperature this crystallization pattern was more damaging than that of halite since halite tended to grow as efflorescence or by filling the smallest pores of the stone in a homogeneous fashion a result which contradicts wellman and wilson s theoretical model of salt damage low rh promoted rapid evaporation of saline solutions and higher supersaturation levels resulting in the greatest damage to the stone in the case of both sodium sulphate and sodium chloride crystallization at any particular crystallization condition sodium chloride tended to reach lower supersaturation levels resulting in the crystallization of isometric crystals and created negligible damage while sodium sulphate reached higher supersaturation ratios resulting in non equilibrium crystal shapes resulting in significant damage esem showed no damage from sodium sulphate due to hydration instead after water condensation on thenardite crystals rapid dissolution followed by precipitation of mirabilite took place resulting in stone damage by means of crystallization pressure generation it is concluded that salt damage due to crystallization pressure appears to be largely a function of solution supersaturation ratio and location of crystallization these key factors are related to solution properties and evaporation rates which are constrained by solution composition environmental conditions substrate properties and salt crystallization growth patterns when combined with a critical review of salt damage literature these experiments allow the development of a model which explains variations in damage related to combinations of different salts substrates and environmental conditions

zircon u pb and trace element data from rocks of the huai an complex new insights into the late paleoproterozoic collision between the eastern and western blocks of the north china craton abstract the trans north china orogen tnco is interpreted as a continent continent collisional belt along which the discrete archean eastern and western blocks amalgamated to form the basement of the north china craton the timing of its formation has not been precisely constrained yet six samples including five high grade metamorphic rocks and a pegmatite dike from the huai an complex in the northern segment of the tnco were selected for zircon u pb dating and trace element analysis a tonalite trondhjemite granodiorite ttg gneiss sample and a high pressure hp mafic granulite sample contain magmatic zircon cores yielding protolith formation ages of 2503 17 and 1964 38 ma respectively detrital zircons of magmatic origin in two metasedimentary rocks show concordant or moderately discordant u pb ages of 2683 22 to 1964 13 ma indicating that they were mainly derived from the tnco with some possibly derived from the archean continental rocks of the north china craton metamorphic zircons in the ttg gneiss and two metasedimentary rocks exhibit low hree contents flat hree patterns and negative eu anomalies implying their formation coeval with garnet and feldspar under grannulite facies conditions metamorphic zircons in an hp mafic granulite and a sample of leucosome from a ttg gneiss also have depleted hree contents flat hree patterns but only weak negative eu anomalies which may also indicate formation under granulite facies conditions whereas the weak eu anomalies may be due to the whole rock composition all these metamorphic zircons have formation temperatures of 702 749 c approaching the peak metamorphic temperatures of hp granulite rocks in this area they have identical ages of ca 1845 ma within analytical errors which is the best estimate age for hp granulite facies metamorphism of the huai an complex these results confirm previous models proposing late paleoproterozoic collision between the eastern and western blocks of the north china craton along the tnco on the other hand some metamorphic zircons in the leucosome sample show planar or polygonal zoning high th u contents and high th u ratios high ree contents and steep hree patterns indicating that they crystallized during partial melting with abundant garnet decomposition they yielded a weighted mean age of 1819 13 ma which we interpret to register the time of retrograde metamorphism combined with previously published data there are three age peaks at 1876 6 1849 2 and 1814 4 ma for metamorphic zircons from high grade metamorphic rocks in the tnco these may indicate either a protracted event or at least three peaks of metamorphism a pegmatite dike cutting the foliation of a mafic granulite boudin was dated at 1806 15 ma which signifies termination of collision between the eastern and western blocks in the huai an area

carbonate veins trace seawater circulation during exhumation and uplift of mantle rock results from odp leg 209 carbonate veins hosted in ultramafic basement drilled at two sites in the mid atlantic ridge 15 n area record two different stages of fluid basement interaction a first generation of carbonate veins consists of calcite and dolomite that formed syn to postkinematically in tremolite chlorite schists and serpentine schists that represent gently dipping large offset faults these veins formed at temperatures between 90 and 170 c oxygen isotope thermometry and from fluids that show intense exchange of sr and li with the basement 87sr 86sr 0 70387 to 0 70641 7lil svec 3 3 to 8 6 carbon isotopic compositions range to high 13cpdb values 8 7 indicating that methanogenesis took place at depth the sr li c isotopic composition suggests temperatures of fluid rock interaction that are much higher t 350 400 c than the temperatures of vein mineral precipitation inferred from oxygen isotopes a possible explanation for this discrepancy is that fluids cooled conductively during upflow within the presumed detachment fault aragonite veins were formed during the last 130 kyrs at low temperatures within the uplifted serpentinized peridotites chemical and isotopic data suggest that the aragonites precipitated from cold seawater which underwent overall little exchange with the basement oxygen isotope compositions indicate an increase in formation temperature of the veins by 8 12 c within the uppermost 80 m of the subseafloor this increase corresponds to a high regional geothermal gradient of 100 150 c km characteristic of young lithosphere undergoing rapid uplift

origin of late archean and early proterozoic rocks and associated mineral deposits from the zhongtiao mountains east central china abstract late archean and early proterozoic supracrustal rocks in the zhongtiao mountains of east central china include five successions separated by unconformities or intrusive contacts the oldest successions the shushui complex 2500 ma and the jiangxian 2400 2200 ma and zhongtiao groups 2100 ma are composed chiefly of metapelites quartzites and marbles with small amounts of bimodal felsic mafic volcanics in which felsic ash flow tuffs dominate the overlying danshanshi group includes chiefly quartzites and conglomerates and the xiyanghe group 1830 ma comprises bimodal volcanics and red beds granitoids range from late archean to early proterozoic in age and vary from tonalite to granite in composition precambrian igneous rocks show a subduction zone geochemical component depletion in nb ta relative to lile and early proterozoic granitoids range in composition from i to s types geochemical and isotopic constraints favor an origin for early proterozoic zhongtiao felsic magmas either by melting of sediments or tonalites in the crust or by melting of amphibolite eclogite in a descending slab zhongtiao pelites are similar in composition to phanerozoic shales and exhibit negative eu anomalies on chondrite normalized graphs stratiform copper deposits in the zhongtiao proterozoic rocks are of three types volcanic hosted deposits of hydrothermal or exhalative origin primary sedimentary deposits and remobilized sedimentary deposits the jiangxian and zhongtiao lithologic assemblages of quartzite pelite carbonate together with primary textures and structures in these rocks suggest deposition in shallow marine tectonically stable basins whereas coarse terrigenous sediments in the danshanshi and xiyanghe groups appear to reflect near shore marine to fluvial deposition in tectonically active basins most data are consistent with deposition of the early proterozoic supracrustal rocks in a continental margin back arc basin

natural stones for monuments their availability for restoration and evaluation this paper represents the introduction to the volume focused on the various aspects of natural stone research from the topic issues studied recently four major aspects are covered 1 availability of certain stone types for monuments 2 strategies aiming to strengthen our knowledge of past resources through the establishment of natural stone databases and inventories 3 evaluation of natural stone properties and assessment of the compatibility of repair stones and 4 decay studies of natural stone on monuments and on natural exposures this paper also aims to highlight the importance of the use of local stone resources a practice that has seriously declined during the 20th century in most of the industrialized countries the availability of natural stone from monuments is also discussed in terms of sandstones and travertine in the czech republic and hungary as a typical example natural stone has become the expression to describe the versatile durable and aesthetically plausible building materials currier 1960 from the very beginning of civilization important structures and monuments were built from or were principally based on natural stone the use of local stone resources was mostly in balance with the local environment although highly durable when properly applied no stone type can be considered immortal schaffer 1932 and most of the stone varieties are affected by a polluted atmosphere winkler 1997 deteriorated stone on monuments should be preferably replaced by stone varieties of the same composition from the same quarries however this is often not possible and so stone having similar properties and appearance must be sourced p ikryl 2007 the main aim of this research is to find compatible stones in terms of appearance and geochemical physical properties this task requires a thorough understanding of both the rock properties and its response to external conditions and weathering agents availability of natural stone

chimneys in paleozoic massive sulfide mounds of the urals vms deposits mineral and trace element comparison with modern black grey white and clear smokers in the urals a wide range of well preserved chimneys are found in vms deposits which are associated with ultramafic atlantic type dergamysh mafic cyprus type buribay bimodal mafic uralian type yubileynoye sultanovskoye yaman kasy molodezhnoye uzelga 4 valentorskoye and bimodal felsic kuroko or baymak type oktyabrskoye tash tau uselga 1 talgan alexandrinskoye sequences chimneys have also been found in the safyanovskoye deposit altay type that is hosted by intercalated felsic lavas and carbonaceous shales a combination of geological mineralogical and trace element data provide a general outline for comparison between chimneys from the urals deposits and modern vent sites the chimneys from the dergamysh deposit show a broad affinity with those from the rainbow and other vent sites associated with serpentinites of the mid atlantic ridge the chimneys from the buribay deposit are similar to the black smokers of the epr vent sites including the scarcity of rare minerals the chimneys from the urals type of the vms deposits show some similarities with grey smokers from the brother volcano and pacmanus sites the chimneys from the baymak type of the vms deposits resemble grey and white smokers of the pacmanus and grey smokers of the suiyo vent sites the chimneys from the safyanovskoye deposit are similar to the black and clear smokers from the okinawa trough mineral assemblages are controlled by the combination of host rock composition and physico chemical conditions of the ore forming processes amount of colloform pyrite isocubanite and pseudomorphic pyrite and marcasite after pyrrhotite decreases in the chimneys across the range from ultramafic and mafic to felsic hosted deposits and is concomitant with increase in the contents of sphalerite galena bornite fahlores native gold and barite across this range the chimneys from the urals type contain abundant tellurides and sulfoarsenides while these minerals are rare except for hessite in the baymak type deposits in the same range the buffering capacity of host rocks decreases in contrast to the increase in s2 and o2 with the exception of the safyanovskoye deposit trace element assemblages in chalcopyrite vary to reflect the host rock ultramafic high se sn co ni ag and au mafic high co se mo and low bi au and pb bimodal mafic high te au ag bi pb co moderate se and variable as and sb bimodal felsic high as sb mo pb moderate bi and low co te and se in sphalerite of the same range the contents of bi pb ag au and sb increase versus fe se and o the variations in trace elements in colloform pyrite coincide with these changes the specific mineral changes in the local ranges from cu to zn rich chimneys in each vms deposit are similar to the general changes in the range of host rock classes of the deposits however the local t s2 and o2 changes can broadly be interpreted in terms of contribution of variable oxygenated cold seawater to the subseafloor and seafloor hydrothermal processes

unravelling the root zone of ultramafic hosted black smokers like hydrothermalism from an alpine analog mid ocean ridges host various types of hydrothermal systems including high t black smokers found in ultramafic rocks exhumed along slow spreading ridges these systems are mostly described in two dimensions as their exposure on the present day seafloor lacks the vertical dimension one way to understand these systems at depth is to study their fossilized equivalents preserved on land such observation can be done in the platta nappe switzerland where a accepted article this article is protected by copyright all rights reserved jurassic aged mineralized system is exposed in 3d serpentinites host a cu fe ni co zn rich mineralization made of sulfides magnetite and fe ca silicates either replacing serpentinites or within stockwork fe ca silicates abundant at the deepest levels vanish in the mineralization close to the paleo detachment fluids were channelized along mafic dykes and sills acting as preferential drains warm carbonation 130 c is the latest hydrothermal record we propose that this system is an analog to the root zone of present day serpentinite hosted hydrothermal systems such as those found along the mid atlantic ridge

oceanic detachment faults focus very large volumes of black smoker fluids it is generally assumed that the seawater derived fluids that feed black smoker vent fields on the seafloor are discharged vertically from depths of 1 3 km we present new oxygen and strontium isotope data that show that fluids at black smoker temperatures of 300 400 c were focused along a low angle detachment fault at 15 45 n near the mid atlantic ridge isotopic alteration is the most extreme ever reported from oceanic rocks altered at similar temperatures indicating intensely focused fluid flow both in recharge and discharge parts of the hydrothermal system rare earth element mobility in the fault rocks demonstrates isotopic alteration by evolved hydrothermal fluids not conductively heated seawater the fault zone protolith was predominantly ultramafic but also included mafic rocks with metasomatic alteration to talc tremolite chlorite schists resulting mainly from chemical exchange between these lithologies during fluid flow fluids in equilibrium with this assemblage would be similar to ultramafic hosted black smoker fluids we present a new model in which hydrothermal circulation around detachment faults evolves from basalt hosted tag type to footwall ultramafic hosted rainbow type to low temperature ultramafic hosted lost city type key features of our model are the intrusion of gabbro bodies immediately below the detachment to provide a heat source for circulation and focusing of fluid flow into the detachment fault to allow venting away from the neovolcanic axis

petrogenesis and tectonic setting of volcanic rocks in the xiaoshan and waifangshan areas along the southern margin of the north china craton constraints from bulk rock geochemistry and sr nd isotopic composition abstract as part of the xiong er volcanic belt along the southern margin of the north china craton volcanic rocks in the xiaoshan and waifangshan areas have a compositional range from the basaltic andesite andesite dacite to rhyolite which display consistent variation trends in terms of their major and trace elements and sr nd isotopic compositions the variable yb contents with nearly constant la yb and tb yb ratios of volcanic rocks in two areas suggest that the fractional crystallization may have played an important role in the differentiation from the basaltic andesite through andesite and dacite to rhyolite the volcanic rocks in these two areas are characterized by the lile and lree enrichments and negative hfse anomalies implying hydrous melting of a mantle wedge in a subduction zone variable sr nd ratios of the basaltic andesite and andesite are interpreted as a result of the fluid addition from a subducting slab non radiogenic nd isotopic compositions as well as high zr y and nb y ratios suggest that the volcanic rocks in these areas were derived from an enriched mantle source on the other hand the volcanic rocks of the basaltic andesite and andesite possess markedly higher fe ti and hfse concentrations than those of typical intra oceanic arcs implying that the mantle source from which the volcanic rocks were derived was metasomatised by siliceous melts during the archean to paleoproterozoic subduction collision in the trans north china orogen these data suggest that in the paleo mesoproterozoic the southern margin of the north china craton was most likely an andean type continental arc in which slab dehydration not only induced the melting of a pre existing metasomatised mantle source but also released lile enriched fluids into the mantle source masking the inherent hfse enriched characteristics of the volcanic rocks along the southern margin of the craton the results of this study indicate that the north china craton like many other continental components e g north america greenland baltica amazonia australia etc of the supercontinent columbia nuna also underwent a subduction related outgrowth along its southern margin during the paleo mesoproterozoic time

detrital zircon u pb ages provide provenance and chronostratigraphic information from eocene synorogenic deposits in northwestern argentina paleogene clastic sedimentary rocks in the puna plateau of northwestern argentina contain valuable information about the timing and location of early mountain building in the central andes because these rocks generally lack tuffaceous facies only paleontological ages have been available we present u pb ages from detrital zircons in the conglomeratic eocene geste formation of the central puna plateau the zircon ages indicate that the geste formation was derived from nearby high relief ranges composed of ordovician metasedimentary rocks a small population of ca 37 35 ma grains also confirms the late eocene stratigraphic age of the geste formation and suggests that u pb detrital zircon ages may provide a new tool for determining depositional ages and provenance of widespread paleogene deposits in the central andes

u pb geochronology and hf isotope geochemistry of detrital zircons from the zhongtiao complex constraints on the tectonic evolution of the trans north china orogen abstract the zhongtiao complex is located in the south segment of the trans north china orogen a continent continent collisional belt along which the discrete eastern and western blocks amalgamated to form the north china craton the complex consists of the neoarchean to paleoproterozoic granitoid plutons and low grade supracrustal rocks of which the latter are subdivided into the songjiashan jiangxian lower zhongtiao upper zhongtiao and danshanshi groups the songjiashan jiangxian and lower zhongtiao groups are composed of metaclastic rocks carbonates and metavolcanic rocks interpreted as the products of a back arc basin whereas the upper zhongtiao and danshanshi groups consist of metaconglomerates and metasandstones interpreted as molasses type siliciclastic rocks deposited in a retro arc foreland basin the u pb ages of detrital zircons from the songjiashan lower zhongtiao upper zhongtiao and danshanshi groups form four populations of 3600 3100 ma 2850 2750 ma 2630 2200 ma and 2150 1850 ma of which the population of 2630 2200 ma is the most dominant and its major sources are considered to be derived from the 2560 to 2300 ma granitoids and metavolcanics in the zhongtiao complex the source rocks of the subordinate 3600 3100 ma detrital zircons were probably derived from the paleo mesoarchean crust of the eastern block since similar aged rocks have not been found in the western block and the trans north china orogen whereas the 2850 2750 ma detrital zircons are interpreted to be derived from the 2850 to 2752 ma ttg gneisses and amphibolites in the adjacent taihua complex the age population of 2150 1850 ma is coincident with the ages of paleoproterozoic granitoids in the trans north china orogen the youngest detrital zircons in the songjiashan and lower zhongtiao groups constrain their maximum depositional ages at 2253 ma and 2168 ma respectively whereas the maximum depositional age of the overlying upper zhongtiao and danshanshi groups is defined at 1848 ma the late paleoproterozoic shift from a back arc basin to a retro arc foreland basin is consistent with the model that the collision between the eastern and western blocks to form the trans north china orogen occurred at 1 85 ga

high pressure granulites in the sanggan area north china craton metamorphic evolution p t paths and geotectonic significance high pressure basic granulites are widely distributed as enclaves and sheet like blocks in the huaian ttg gneiss terrane in the sanggan area of the central zone of the north china craton four stages of the metamorphic history have been recognised in mineral assemblages based on inclusion exsolution and reaction textures integrated with garnet zonation patterns as revealed by compositional maps and compositional profiles the p t conditions for each metamorphic stage were obtained using thermodynamically and experimentally calibrated geothermobarometers the low ca core of growth zoned garnet along with inclusion minerals defines a prograde assemblage m1 of garnet clinopyroxene plagioclase quartz yielding 700 c and 10 kbar the peak of metamorphism at about 750 870 c and 11 14 5 kbar m2 is defined by high ca domains in garnet interiors and inclusion minerals of clinopyroxene plagioclase and quartz kelyphites or coronas of orthopyroxene plagioclase magnetite around garnet porphyroblasts indicate garnet breakdown reactions m3 at conditions around 770 830 c and 8 5 10 5 kbar garnet exsolution lamellae in clinopyroxene and kelyphites of amphibole plagioclase around garnet formed during the cooling process at about 500 650 c and 5 5 8 kbar m4 these results help define a sequential p t path containing prograde near isothermal decompression itd and near isobaric cooling ibc stages the clockwise hybrid itd and ibc p t paths of the hp granulites in the sanggan area imply a model of thickening followed by extension in a collisional environment furthermore the relatively high pressures 6 14 5 kbar of the four metamorphic stages and the geometry of the p t paths suggest that the hp granulites together with their host huaian ttg gneisses represent the lower plate in a crust thickened during collision the corresponding upper plate might be the tectonically overlying khondalite series which was subjected to medium to low pressure mp lp 7 4 kbar granulite facies metamorphism with a clockwise p t path including an itd segment both the hp and the mp lp granulite facies events occurred contemporaneously at c 1 90 1 85 ga in a collisional environment created by the assembly process of the north china craton

the xiong er volcanic belt at the southern margin of the north china craton petrographic and geochemical evidence for its outboard position in the paleo mesoproterozoic columbia supercontinent abstract the xiong er volcanic belt covering an area of more than 60 000 km 2 along the southern margin of the north china craton has long been considered an intra continental rift zone and recently interpreted as part of a large igneous province formed by a mantle plume that led to the breakup of the paleo mesoproterozoic supercontinent columbia however such interpretations cannot be accommodated by lithology mineralogy geochemistry and geochronology of the volcanic rocks in the belt lithologically the xiong er volcanic belt is dominated by basaltic andesite and andesite with minor dacite and rhyolite different from rock associations related to continental rifts or mantle plumes which are generally bimodal and dominated by mafic components however they are remarkably similar to those rock associations in modern continental margin arcs in some of the basaltic andesites and andesites amphibole is a common phenocryst phase suggesting the involvement of h 2 o rich fluids in the petrogenesis of the xiong er volcanic rocks geochemically the xiong er volcanic rocks fall in the calc alkaline series and in most tectono magmatic discrimination diagrams the majority of the xiong er volcanic rocks show affinities to magmatic arcs in the primitive mantle normalized trace element diagrams the xiong er volcanic rocks show enrichments in the lile and lree and negative nb ta ti anomalies similar to arc related volcanic rocks produced by the hydrous melting of metasomatized mantle wedge nd isotope compositions of the xiong er volcanic rocks suggest that 5 15 older crust has been transferred into the upper lithospheric mantle by subduction related recycling during archean to paleoproterozoic time available shrimp and la icp ms u pb zircon age data indicate that the xiong er volcanic rocks erupted intermittently over a protracted interval from 1 78 ga through 1 76 1 75 ga and 1 65 ga to 1 45 ga though the major phase of the volcanism occurred at 1 78 1 75 ga such multiple and intermittent volcanism is inconsistent with a mantle plume driven rifting event but is not uncommon in ancient and existing continental margin arcs taken together the xiong er volcanic belt was most likely a paleo mesoproterozoic continental magmatic arc that formed at the southern margin of the north china craton similar paleo mesoproterozoic continental magmatic arcs were also present at the southern and southeastern margins of laurentia the southern margin of baltica the northwestern margin of amonzonia and the southern and eastern margins of the north australia craton which are considered to represent subduction related episodic outbuilding on the continental margins of the paleo mesoproterozoic supercontinent columbia therefore in any configuration of the supercontinent columbia the southern margin of the north china craton could not have been connected to any other continental block as proposed in a recent configuration but must have faced an open ocean whose lithosphere was subducted beneath the southern margin of the north china craton

geochemistry of high h2 and ch4 vent fluids issuing from ultramafic rocks at the rainbow hydrothermal field 36 14 n mar the flores diving cruise was part of the mast iii amores 1995 1998 program funded by the european union one of the major achievements of the flores cruise was the discovery of the rainbow hydrothermal field hosted in ultramafic rocks south of the amar segment on the mid atlantic ridge mar the rainbow hydrothermal fluids exhibit temperatures of 365 c ph of 2 8 high chlorinity 750 mmol kg and low silica 6 9 mmol kg the uniformity in endmember major minor trace element concentrations and gas contents suggests that all rainbow fluids originate from the same deep source although h2s content is relatively low 1 20 mmol kg all vent fluids show extraordinary high h2 16 mmol kg ch4 2 5 mmol kg and co 5 mol kg endmember concentrations compared to fluids collected from other vent sites along the mar hydrogen represents more than 40 of the total gas volume extracted from the fluids at rainbow h2 production is likely associated with alteration of olivine and orthopyroxene minerals during serpentinization given that exposures of ultramafic rock may be common particularly along slow spreading ridges the production of h2 may have important implications for microbial activity at and beneath the seafloor

the role of saline solution properties on porous limestone salt weathering by magnesium and sodium sulfates saline solution properties viscosity in particular are shown to be critical in salt weathering associated with sodium and magnesium sulfate crystallization in porous limestone the crystallization of sodium and magnesium sulfate within a porous limestone has been studied at a macro and microscale using different techniques including mercury intrusion porosimetry environmental scanning microscopy and x ray computed tomography such analysis enabled the visualization of the crystallization process in situ and at high magnification yielding critical information as to where and how salts crystallize sodium sulfate decahydrate mirabilite tends to crystallize in large pores as euhedral micron sized crystals formed at low supersaturation near to the surface of the stone in contrast magnesium sulfate heptahydrate epsomite tends to precipitate as anhedral wax like aggregates formed at high supersaturation and distributed homogeneously throughout the stone pore system filling large and small pores while the former crystallization behavior resulted in scale formation the latter led to crack development throughout the bulk stone ultimately the contrasting weathering behavior of the two sulfates is explained by considering differences in flow dynamics of solutions within porous materials that are mainly connected with the higher viscosity of magnesium sulfate saturated solution 7 27 cp when compared with sodium sulfate saturated solution 1 83 cp on the basis of such results new ways to tackle salt weathering particularly in the field of cultural heritage conservation are discussed

archean blocks and their boundaries in the north china craton lithological geochemical structural and p t path constraints and tectonic evolution an examination of lithological geochemical geochronological structural and metamorphic p t path data suggests that the basement of the north china craton can be divided into eastern and western blocks separated by major crustal boundaries that roughly correspond with the limits of a 300 km wide zone called the trans north china orogen the eastern block consists predominantly of late archean domiform tonalitic trondhjemitic granodioritic ttg batholiths surrounded by anastomosing networks and linear belts of open to tight synforms of minor volcanic and sedimentary rocks metamorphosed from greenschist to granulite facies at 2 5 ga with anticlockwise p t paths some early to middle archean rocks are locally present in the eastern block but their tectonic history is unclear due to reworking by the 2 5 ga tectonothermal event the western block has a late archean assemblage structural style and metamorphic history similar to that of the eastern block but it differs in the absence of early to middle archean assemblages and in being overlain by and interleaved with paleoproterozoic khondalites which were affected by a 1 8 ga metamorphic event involving clockwise p t paths a mantle plume model is proposed for the formation and evolution of late archean basement rocks in the eastern and western blocks based on a combination of extensive exposure of ttg gneisses affinities of mafic rocks to continental tholeiitic basalts presence of voluminous komatiitic rocks dominant diaprism related domiform structures anticlockwise p t paths and a short time span from the primary emplacement of ttg and ultramafic to mafic rocks until the onset of regional metamorphism between the two blocks is the trans north china orogen which is bounded by two major fault systems and is composed of late archean to paleoproterozoic ttg gneisses and granitoids interleaved with abundant sedimentary and volcanic rocks that are geochemically interpreted as having developed in magmatic arc and intra arc basin environments these rocks underwent multiple phases of compressional deformation and peak high pressure metamorphism followed by rapid exhumation during the late paleoproterozoic at 1 8 ga as a result of collision between the eastern and western blocks resulting in the amalgamation of the north china craton

u pb and hf isotopic study of zircons of the helanshan complex constrains on the evolution of the khondalite belt in the western block of the north china craton abstract the helanshan complex is located at the westernmost segment of the khondalite belt a continent continent collisional belt along which the yinshan block in the north collided with the ordos block in the south to form the western block of the north china craton the complex consists of s type granites and high grade pelitic granulite gneiss felsic paragneiss quartzite calc silicate rock and marble together called the khondalite series rocks la q icp ms u pb geochronology and la mc icp ms lu hf isotopic data of zircons combined with cathodoluminescence cl imaging enable the resolution of magmatic and metamorphic events that can be directed towards understanding the formation and evolution of the khondalite belt in the western block of the north china craton cl images reveal the coexistence of magmatic type detrital zircons and metamorphic zircons in most of the khondalite series rocks of which the metamorphic zircons occur as either single grains or overgrowth rims surrounding and truncating magmatic type detrital zircon cores la q icp ms u pb analyses on magmatic type detrital zircons reveal two distinct age populations with one in the archaean 2 85 2 53 ga and the other in the palaeoproterozoic 2 2 2 0 ga suggesting that the sedimentary protoliths of the khondalite series rocks in the helanshan complex must have been deposited at some time after 2 0 ga the hf analyses show that the archaean detrital zircons possess negative ehf t values from 7 64 to 0 15 with depleted mantle model ages ranging from 3 34 to 3 10 ga this implies the existence of a paleo mesoarchaean 3 34 3 10 ga crust in the western block which underwent a recycling event in the period 2 85 2 53 ga nearly all palaeoproterozoic 2 2 2 0 ga detrital zircons possess positive ehf t values 0 86 9 38 with depleted mantle model ages of 2 45 2 15 ga suggesting a significant crustal growth event in the western block in the palaeoproterozoic metamorphic zircons yield two groups of age with one at 1 95 ga and the other at 1 87 ga of which the former is considered as the timing of the collision between the yinshan and ordos blocks to form the western block whereas the latter is consistent with the age of 1 86 ga from two s type granites which are considered to have formed by the partial melting of pelitic granulites gneisses at the stage of the exhumation of the helanshan complex

configuration of the late paleoproterozoic supercontinent columbia insights from radiating mafic dyke swarms abstract remnants of 2 1 1 8 ga orogens can be recognized in nearly every craton assembled within reconstructions of the rodinia supercontinent although no particular pattern of laterally extensive orogenic belts emerges these cratons may be the fragments of an older supercontinent formed in response to the collision and accretion of even older cratons during the early earth history paleomagnetic constraints have played a limited role in many previous reconstructions of the early precambrian supercontinent mainly because of the poor age control and a large scatter of the paleomagnetic poles the geometry of giant radiating dyke swarms and orogenic belts provide important constraints for the reconstruction of the pre rodinian supercontinent some early unmetamorphosed and undeformed mafic dyke swarms in north china southern peninsular india and north america share coeval age of 1 85 ga if these continents are assembled the overall pattern exhibited by the mafic dyke swarms appears to constitute a giant radiating swarm with a piercing point between the cuddapah rift in south india and the xiong er aulacogen in north china this suggests that the north china craton indian craton and canadian shield may be fragmented from the same landmass the reconstruction of 1 85 ga giant radiating dyke swarm attempted in this paper suggests that the north china craton india craton and canadian shield were united together to form a landmass within the columbia supercontinent before its extension and break up the 1 90 1 85 ga andean style north orogenic belt suggests that a subduction zone existed on the northern margin of the north china craton wopmay orogenic belt developed in a 1 88 1 84 ga continental volcano plutonic arc which is interpreted as the product of eastward subduction of oceanic lithosphere the transantarctica orogenic belt in east antarctica may be another candidate to be linked with the subduction zone the north orogenic wopmay orogenic and transantarctica orogenic belts could be connected to form a continuous subduction zone the orogenic comparison strengthens the configuration of the columbia supercontinent proposed by the reconstruction of the giant radiating dyke swarm the laurentia west australia and east antarctica were relatively stable from 1 85 ga to 1 20 ga as inferred from the data on dyke swarms magmatism and the paleomagnetism these continents constituted the core of the columbia supercontinent in the late paleoproterozoic time the north china craton and indian craton were however separated from the columbia supercontinent during the mesoproterozoic time

syntectonic carbonation during synmagmatic mantle exhumation at an ocean continent transition a jurassic extensional detachment associated with carbonated serpentinites and basalts is preserved at falotta platta nappe southeastern switzerland structural data indicate that fluid circulation occurred during late increments of extension along the detachment plane at the contact between serpentinites and basalts the homogeneity of the isotopic signatures 18o 16 and 13c centered on 0 1 can be best explained by a single sudden seawater derived carbonation event at temperatures of 100 c carbonation was focused in the high permeability zone along the detachment our model yields new insights for carbonation processes related to mantle exhumation

syn collisional channel flow and exhumation of paleoproterozoic high pressure rocks in the trans north china orogen the critical role of partial melting and orogenic bending within the paleoproterozoic trans north china orogen the high pressure belt hpb is made of high pressure 15 kbar mafic granulites hosted in migmatitic gneisses in this contribution we document a set of structural analyses acquired over the whole hpb we also proposed a morphological subdivision of the partially molten rocks that compose the hpb according to changes in melt fraction a compilation of the p t and radiochronological data carried out over the last 15 years is presented the results highlight the concurrent effect of oroclinal bending and partial melting in controlling the exhumation of the deeply buried continental crust during ongoing compression of the thickening orogenic root onset of partial melting at peak metamorphism is responsible for a first strength drop that enhanced an eastward lateral flow radiometric ages show that the deep crust was partially molten over a 50 ma lasting period during which it evolved in a diatexite core mantled by metatexites this was responsible for a second strength drop with strain concentrated along the diatexite metatexite boundaries as exemplified by the newly documented datong chengde shear zone a 400 km long normal shear zone with a sinistral strike slip component that accommodated the final uprise of the high pressure rocks

petrochemistry and sr pb and nd isotopic geochemistry of early precambrian rocks wutaishan and taihangshan areas china abstract in the wutaishan and taihangshan region china the lowermost high grade metamorphic complex of grey gneiss and amphibolite the fuping complex gives a 2 2 0 2 ga pb pb isochron age with a first stage growth 7 73 and a 2 37 0 07 ga sm nd isochron age with 143nd 144nd 0 0 50963 0 00005 or nd t 1 50 nd depleted mantle model dates tdm of amhibolites 2 48 to 2 60 ga those of gneisses are 2 43 to 2 46 ga the unconformably overlying medium to low grade metavolcanic complex the wutai complex gives a 2 0 0 1 ga rb sr isochron age with 87 86sr 0 0 7025 2 a 2 27 0 02 ga pb pb isochron date with afirst stage growth 7 73 and a 2 26 0 06 ga sm nd isochron first stage 143nd 144nd 0 0 5097 2 or nd t 1 08 individual sample nd depleted mantle model date are 2 5 ga metavolcanic samples from low grade metasedimentary rocks of the hutuo group all lie close to a 2 3 ga reference line on a rb sr isochron plot have nd tdm 2 32 2 34 and 2 62 ga from previous geological work published u pb zircon dating and ourisotopic and geochemical results we infer that the fuping rocks formed 2 6 ga ago in an environment like a modern island arc the wutai complex formed by 2 5 ga ago mostly formed in a tectonic setting similar to that of the fuping complex with the exception that one volcanic cycle formed in an environment like a modern mor and one unit formed in an environment transitional between modern within plate and plate margin settings the hutuo group formed 2 4 ga ago in a within plate tectonic environment there is no evidence for continental crust before 2 6 ga in the wutaishan and taihangshan region this contradicts previous assignment of the fuping complex to 2 8 ga ol older the fuping complex is not an early nucleus of the sino korean craton the new data also confirm that the wutai complex is older than its original assignment as early proterozoic the sm nd systems for metabasaltic rocks in the region either in amphibolite facies or in greenschist facies are all significantly disturbed in contrast with the undisturbed sm nd reported in previous studies of the sino korea craton this study provides further evidence that the archean igneous rocks in china formed at different times from heterogeneous and depleted mantle sources

the rainbow vent fluids 36 14 n mar the influence of ultramafic rocks and phase separation on trace metal content in mid atlantic ridge hydrothermal fluids fluids were collected from the rainbow vent field 36 14 n on the mid atlantic ridge mar during the 1997 diving flores cruise this vent field in ultramafic rocks at a depth of 2300 m is composed of 10 black smokers emitting acidic ph 2 8 fluids at 365 c the low ph of the hot temperature rainbow fluids likely results from seawater ultramafic rock interaction that releases h ions into reducing hydrothermal fluids fluid chemistry is strongly influenced by phase separation generating cl rich brines clem 750 mm strongly enriched with mn fe co ni cu zn ag cd cs pb y and rare earth elements ree ree and transition metal abundance particularly fe and mn in the rainbow fluids is dramatically higher than in other mar fluids the abundance of trace element and ree enrichment is due to the greater solubility of these elements that is strongly favored by cl complexation at low ph and high temperature conditions chondrite normalized ree patterns show strong lree enrichment with evidence of the typical eu anomaly this ree partitioning suggests that either 1 ultramafic rocks represent only a part of rocks leached during hydrothermal alteration and or 2 that the unique rainbow fluid temperature ph and redox state issued from the ultramafic character of leached substratum can produce unique ree partitioning

deformation history of the hengshan complex implications for the tectonic evolution of the trans north china orogen structural analysis indicates that the hengshan complex underwent five distinct episodes of deformation d1 d5 the d1 episode formed small isoclinal folds f1 penetrative axial planar foliations s1 and mineral stretching lineations l1 d1 fabrics were reworked by following d2 deformation associated with d2 was the development of nw verging asymmetric folds and accompanying thrust faults both d1 and d2 resulted from crustal thickening and coherent with prograde and peak metamorphism d2 deformation was followed by transpressional dextral shearing d3 including top to nw oblique slip shearing and nne ssw dextral strike slip shearing ongoing collision led to development of the zhujiafang ductile shear zone d4 a near e w trending high strain belt across the hengshan complex d5 deformation is characterized by f5 open folds and associated normal faults probably related to exhumation of the complex structural patterns of the hengshan complex can place important insights into a recently proposed tectonic model suggesting that an ocean between the eastern and western blocks underwent eastward directed subduction beneath the western margin of the eastern block and closure of this ocean finally led to collision between the two blocks to form the coherent north china craton

polyphase deformation of the fuping complex trans north china orogen structures shrimp u pb zircon ages and tectonic implications abstract the fuping complex is located in the central part of the trans north china orogen tnco a paleoproterozoic collisional belt along which the eastern and western blocks were assembled to form the north china craton three stages of deformation d 1 d 3 have been identified in the fuping complex d 1 formed tight to isoclinal folds f 1 penetrative foliation s 1 and mineral lineation l 1 which resulted from the early nw se orientated thrusting and shearing d 2 progressively overprinted d 1 and was dominated by mostly nw se shortening and top to the se e thrusting under a compressive environment d 1 and d 2 occurred in association with the peak metamorphism m 1 d 3 occurred during the exhumation after the crustal thickening producing regional scale nww see trending open folds f 3 and associated low angle detachment faults and was responsible for the isothermal decompression m 2 metamorphism of the complex following the d 3 deformation the complex was exhumed to shallow crustal levels where the rocks underwent the retrogressive cooling m 3 metamorphism syn tectonic leucocratic dykes are widespread in the fuping complex two leucocratic dykes that did not experience d 1 but underwent d 2 yield shrimp zircon ages of 1843 12 ma and 1844 18 ma which indicate that d 1 must have occurred at some time earlier than 1844 ma whereas d 2 must have occurred at some time later than this age two weakly deformed post d 2 leucocratic dykes yield shrimp zircon ages of 1817 14 ma and 1815 45 ma suggesting that the d 2 deformation occurred in the period 1843 1815 ma the new shrimp data indicate that the collision related deformation of the fuping complex must have occurred in the paleoproterozoic not in the late archean structural and geochronological data presented in this study in association with previous lithological and geochemical data suggest that the fuping complex may have been located in the hinterland of an eastward subduction zone and underwent intensive deformation and metamorphism involved in the final collision between the western and eastern blocks at 1 85 ga