mud volcano eruptions and earthquakes in the northern apennines and sicily italy abstract the relations between earthquakes and the eruption of mud volcanoes have been investigated at the pede apennine margin of the northern apennines and in sicily some of these volcanoes experienced eruptions or increased activity in connection with historical seismic events showing a good correlation with established thresholds of hydrological response liquefaction to earthquakes however the majority of eruptions have been documented to be independent of seismic activity being mud volcanoes often not activated even when the earthquakes were of suitable magnitude and the epicentre at the proper distance for the triggering this behaviour suggests that paroxysmal activity of mud volcanoes depends upon the reaching of a specific critical state dictated by internal fluid pressure and implies that the strain caused by the passage of seismic waves can activate only mud volcanoes in near critical conditions i e close to the eruption seismogenic faults such as the pede apennine thrust often structurally control the fluid reservoirs of mud volcanoes which are frequently located at the core of thrust related folds such an intimate link enables mud volcanoes to represent features potentially suitable for recording perturbations associated with the past and ongoing tectonic activity of the controlling fault system

a unique association of scheelite and magnetite in the tiemuli w fe skarn deposit implications for early cretaceous metallogenesis in the nanling region south china abstract the tiemuli scheelite magnetite deposit in the central part of the nanling region south china is genetically related to a porphyritic biotite granite pluton the w fe orebodies are hosted within upper cambrian calcareous sandstone or impure limestone in the external zones la icp ms u pb dating of zircons from the granite yielded a weighted mean age of 136 6 1 1 ma the main ore minerals are magnetite scheelite and arsenopyrite and the gangue minerals are clinopyroxene grossularite vesuvianite amphibole and mica three paragenetic stages of skarn formation have been recognized i a skarn stage ii a retrograde stage and iii a quartz sulphide calcite stage massive magnetite and scheelite orebodies associated with hydrous minerals formed during stage ii molybdenite grains separated from tiemuli skarns yielded re os model ages of 136 3 133 8 ma with a weighted mean age of 135 1 0 8 ma biotite associated with fine grained magnetite from the ores has a 40 ar 39 ar plateau age of 132 67 0 43 ma these three independent dating techniques show that the granitic magmatism and tungsten mineralization were coeval within error whereas the late stage alteration recorded by biotite could be ca 2 m y younger than the early stage the granite is classified as an a type body on the basis of its geochemistry and mineralogy zircon grains from the granite show negative ehf t values of 7 7 to 2 3 and molybdenite grains from the skarn ores contain low re contents of 0 93 to 2 97 ppm these data indicate that the magma and ore forming components at tiemuli were derived mainly from crustal materials although mafic xenoliths in the granites are consistent with some mantle contribution the tiemuli deposit was produced by crust mantle interaction in an extensional regime possibly caused by rollback of the subducting paleo pacific plate during early cretaceous the skarn scheelite and magnetite association formed by interaction between magmatic fluids and calcite bearing sandstone or impure limestone of the host strata

mountains and arid climates of middle latitudes simulations from a global climate model with and without orography have been used to investigate the role of mountains in maintaining extensive arid climates in middle latitudes of the northern hemisphere dry climates similar to those observed were simulated over central asia and western interior north america in the experiment with mountains whereas relatively moist climates were simulated in these areas in the absence of orography the experiments suggest that these interior regions are dry because general subsidence and relatively infrequent storm development occur upstream of orographically induced stationary wave troughs downstream of these troughs precipitation bearing storms develop frequently in association with strong jet streams in contrast both atmospheric circulation and precipitation were more zonally symmetric in the experiment without mountains in addition orography reduces the moisture transport into the continental interiors from nearby oceanic sources the relative soil wetness of these regions in the experiment without mountains is consistent with paleoclimatic evidence of less aridity during the late tertiary before substantial uplift of the rocky mountains and tibetan plateau is believed to have occurred

the mesozoic magmatic sources and tectonic setting of the zijinshan mineral field south china constraints from geochronology and geochemistry of igneous rocks in the southeastern ore segment abstract the zijinshan mineral field is a large porphyry epithermal cu au mo ag ore system located in the southwestern fujian province china the southeast cu mo ore segment soe is a newly discovered section located in the southeastern portion of the zijinshan mineral field zircon u pb and molybdenite re os ages as well as the geochemical compositions of intrusive and volcanic rocks and zircon hf isotope data are used to constrain the timing petrogenesis tectonic setting and the relationship between magmatism and metallogenesis in the soe and zijinshan mineral field major and trace element geochemistry indicates that igneous rocks from soe are mainly shoshonitic granitoids that are lile enriched rb ba th u with hfse depletion nb ta zr hf and y indicating a subduction related setting new u pb zircon analyses yield weighted mean ages of ca 160 ma for the caixi pluton ca 110 ma for the sifang granodiorite ca 107 105 ma for the luoboling granodiorite porphyry ca 105 ma for the quartz diorite porphyry ca 108 105 ma for the dacite porphyry ca 98 ma for the rhyodacite and 97 ma for the rhyolite in the soe these dates integrated with previous geochronological data indicate that there were two main magmatic events in this area 1 a middle to late jurassic event 165 150 ma and 2 a cretaceous event 110 95 ma which can be further divided into two groups i e the late early cretaceous event 110 105 ma and the early late cretaceous event 100 95 ma the late early cretaceous intrusions contain higher e hf t values 0 1 to 3 6 with t dm2 varying from 1 4 to 1 0 ga which may come from mixing between crustal and subduction related mantle derived melts in contrast to the middle to late jurassic intrusions that may come from the partial melting of the cathaysia block basement the early late cretaceous intrusions display a broader range of e hf t values 0 9 to 9 4 with t dm2 varying from 1 8 to 1 2 ga suggesting a similar source to the late early cretaceous rocks but with more crustal material the molybdenite re os ages for mineralization range from 110 ma to 105 ma consistent with ages of the late early cretaceous rocks zircon trace elements analyses imply that the early late cretaceous rocks ce 4 ce 3 113 1800 are characterized by higher oxygen fugacity with higher mineralization potential than the late early cretaceous ce 4 ce 3 9 545 and the middle to late jurassic rocks variability in ages geochemistry and oxygen fugacity indicate that the middle to late jurassic magmatic event represents pre mineralization intrusions whereas the late early cretaceous is syn mineralization and the early late cretaceous intrusions post mineralization we propose that both the middle to late jurassic and the cretaceous magmatic events may relate to the subduction of the pacific slab and the changing direction of the subducted slab may result in the different sources for the two magmatic events

genetic relationship between granitic magmatism and w mineralization recorded in the nanling scientific drilling sp nlsd 2 in the pangushan w mining district south china abstract the nanling region in south china hosts numerous w dominated polymetallic deposits that are related to mesozoic granites although considerable amounts of age data have been obtained the genetic relationship between granitic magmatism and w mineralization remains unclear the nanling scientific drilling sp nlsd 2 in the pangushan w deposit has penetrated upper devonian sedimentary rocks 4 1 721 9 m sinian sedimentary rocks 721 9 1287 9 m and mesozoic granite 1287 9 2012 1 m the drill hole clearly reveals a zonation including exocontact w bearing quartz veins alkali autometasomatic zone and primary k feldspar granite the k feldspar granite at the depth of 1880 m and rocks of potassium autometasomatic zone at 1414 m and greisenized zone at 1288 m have magmatic zircon grains with u pb ages of 164 8 1 4 ma 161 7 1 6 ma and 153 8 1 2 ma respectively molybdenite re os ages of endocontact mineralization at the depths of 1302 m and 1291 m are 155 9 3 1 ma and 155 0 2 3 ma respectively muscovite ar ar ages of exocontact mineralization at the depths of 1050 and 885 m are 154 9 1 5 ma and 154 0 3 0 ma respectively and molybdenite re os age of exocontact quartz vein type mineralization at 860 m is 152 0 2 6 ma these new ages indicate that the granite emplacement potassium autometasomatism greisenization and w mineralization occurred at 164 8 ma 161 7 ma 153 8 ma and 155 9 152 ma respectively the w mineralization was approximately 9 13 myr younger than the hosting granite the whole rock and feldspar chemical compositions of k feldspar granite potassium autometasomatic zone greisenized zone and feldspar quartz veins indicate the sequence of metal transportation and concentration to form the zonation the granite crystallized from high k calcalkaline metaluminous to peraluminous highly differentiated magmas that were enriched in w and bi during crystallization the magmas underwent potassium autometasomatism caused by post magmatic fluids which were rich in k fe w and rare earth elements ree but poor in na and ca and formed the potassium autometasomatic zone the evolved post magmatic fluids became rich in k si ca ree and w but poor in na and fe and initiated greisenization to generate the greisenized zone which almost exhausted ca ree na and fe of the fluids the later crystallization of feldspar quartz veins exhausted k and caused the residual post magmatic fluids to be rich in si and w the fluids formed w bearing quartz veins with decreasing temperature and pressure the main reason for w enrichment in the hydrothermal fluids was due to the successive crystallization of minerals rather than autometasomatism

hydrothermal fluids circulation and travertine deposition in an active tectonic setting insights from the kamara geothermal area western anatolia turkey abstract coexistence of thermal springs travertine deposits and tectonic activity is a recurring feature for most geothermal areas although such a certainty their relationships are debated mainly addressing on the role of the tectonic activity in triggering and controlling fluids flow and travertine deposition in this paper we present the results of an integrated study carried out in a geothermal area located in western anatolia turkey nearby the well known pamukkale area denizli basin our study focused on the relationships among hydrothermal fluids circulation travertine deposition and tectonic activity with particular emphasis on the role of faults in controlling fluids upwelling thermal springs location and deposition of travertine masses new field mapping and structural kinematics analyses allowed us to recognize two main faults systems nw and ne trending framed in the neogene quaternary extensional tectonic evolution of western anatolia a geo radar gpr prospection was also provided in a key area permitting us to reconstruct a buried fault zone and its relationships with the development of a fissure ridge travertine deposit kamara fissure ridge the integration among structural and geophysical studies fluids inclusion geochemical isotopic data and 230 th 238 u radiometric age determination on travertine deposits depict the characteristics of the geothermal fluids and their pathway up to the surface hydrological and seismological data have been also taken in account to investigate the relation between local seismicity and fluid upwelling as a main conclusion we found strict relationships among tectonic activity earthquakes occurrence and variation of the physical chemical features of the hydrothermal fluids presently exploited at depth or flowing out in thermal springs in the same way we underline the tectonic role in controlling the travertine deposition making travertine mainly banded travertine a useful proxy to reconstruct the seismological history of an area as well as the characteristics of the parent geothermal fluids adding an effective tool for geothermal exploration tasks

fluid mixing in carbonate aquifers near rapolano central italy chemical and isotopic constraints chemical major and trace elements and isotopic compositions dd and d 18 o in waters and d 13 ci n co 2 and 3 he 4 he in gases of natural thermal 11 and cold 39 fluids spring waters and gases discharging from a tectonic window of mesozoic limestones in central italy have proved to be the result of mixing processes inside the limestone formations the limestones provide a preferential route for subsurface fluid migration and they gather both descending cold ca hco3 b depleted groundwaters and rising convective ca so4 hco3 co2 saturated b rich thermal waters atmospherically derived descending gas components n2 ne he dissolved in rainfall that infiltrates the limestone system mix with n2 ne he depleted hot rising waters boron in the liquid phase and n2 and ne in the gas phase are the most useful elements to trace the mixing process the deeper gas samples recognised in the area are associated with the hotter waters emerging in the area in spite of being depleted in ne and he and light hydrocarbons they have the higher measured 3 he 4 he ratios suggesting a contribution of mantle 3 he to the gas phase this contrasts with deep circulation in the crust which would lead to increased concentration of 4 he in the deeper gases paradoxically there is more relative concentration of 4 he in the more air contaminated gas samples than in the deeper gas samples a similar paradox exists when the d 13 co f co 2 in the deeper gas samples is considered the shallower air contaminated gas samples although they should be affected by the addition of soil 13 c depleted organic c have d 13 ci n co 2 more positive than the deeper gas samples recognized since any deep hydrothermal source of co2 should generate co2 with more positive values of d 13 c than those measured at surface a multiple single calcite precipitation process from hydrothermal solutions with c isotopic fractionation along the rising path inside the mesozoic limestone formations is proposed 2002 elsevier science ltd all rights reserved

dissolution reprecipitation process of magnetite from the chengchao iron deposit insights into ore genesis and implication for in situ chemical analysis of magnetite abstract magnetite formed in different environments commonly has distinct assemblages and concentrations of trace elements that can potentially be used as a genetic indicator of this mineral and associated ore deposits in this paper we present textural and compositional data of magnetite from the chengchao iron deposit daye district china to provide a better understanding in the formation mechanism and genesis of the deposit and shed light on analytical protocols for in situ chemical analysis of hydrothermal magnetite magnetite grains from the ore related granitoid pluton mineralized endoskarn magnetite dominated exoskarn and vein type iron ores hosted in marine carbonate intruded by the pluton were examined using scanning electron microscopy and analyzed for major and trace elements using electron microprobe back scattered electron images reveal that primary magnetite from the mineralized skarns and vein type ores were all partly reequilibrated with late stage hydrothermal fluids forming secondary magnetite domains that are featured by abundant porosity and have sharp contact with the primary magnetite these textures are interpreted as resulting from a dissolution reprecipitation process of magnetite which however are mostly obscure under optically primary magnetite grains from the mineralized endoskarn and vein type ores contain high sio 2 0 92 3 21 wt al 2 o 3 0 51 2 83 wt and low mgo 0 15 0 67 wt whereas varieties from the exoskarn ores have high mgo 2 76 3 07 wt and low sio 2 0 03 0 23 wt and al 2 o 3 0 54 1 05 wt this compositional contrast indicates that trace element geochemical composition of magnetite is largely controlled by the compositions of magmatic fluids and host rocks of the ores that have reacted with the fluids compared to its precursor mineral secondary magnetite is significantly depleted in most trace elements with sio 2 deceasing from 1 87 to 0 47 wt on average and al 2 o 3 from 0 89 to 0 08 wt in mineralized endoskarn and vein type ores and mgo from 2 87 to 0 60 wt in exoskarn ores on the contrary average content of iron is notably increased from 69 2 wt to 71 9 wt in the secondary magnetite grains the results suggest that the dissolution reprecipitation process has been important in significantly removing trace elements from early stage magnetite to form high grade high quality iron ores in hydrothermal environments the textural and compositional data confirm that the chengchao iron deposit is of hydrothermal origin rather than being crystallized from immiscible iron oxide melts as previously suggested this study also highlights the importance of textural characterization using various imaging techniques before in situ chemical analysis of magnetite as is the case for texturally complicated u th bearing accessory minerals that have been widely used for u pb geochronology study

obscuring of long eccentricity cyclicity in pleistocene oceanic carbon isotope records abstract long eccentricity 400 kyr cycles in carbon isotope records from the pacific and atlantic oceans and the mediterranean sea of the past 5 0 ma are compared all records show maximum 13c values 13cmax at eccentricity minima during the pliocene but this relationship obscured in the pleistocene after 1 6 ma in particular for the open ocean deep water 13c records since a clear anti phase relationship was set up between oceanic 18o and 13c in the 100 kyr band from this time we attribute the obscured 400 kyr signal to a major change in the oceanic carbon reservoir probably associated with restructure of the southern ocean a similar change occurred in the miocene at 13 9 ma when the 400 kyr cyclicity in 13c records flattened out together with a drastic cooling and antarctic ice sheet expansion a remarkable exception is the mediterranean surface water 13c record which remained paced by the long term eccentricity cycle throughout the pliocene and pleistocene suggesting a low latitude climatic origin of the 400 kyr signal that is independent of glacial interglacial forcing since the earth is currently passing through an eccentricity minimum it is crucial to understand the nature of the 13cmax events

molybdenite re os and albite 40ar 39ar dating of cu au mo and magnetite porphyry systems in the yangtze river valley and metallogenic implications abstract the area of the middle lower yangtze river valley eastern china extending from wuhan hubei province to western zhenjiang jiangsu province hosts an important belt of cu au mo and fe deposits there are two styles of mineralization i e skarn porphyry stratabound cu au mo fe deposits and magnetite porphyry deposits in several nne trending cretaceous fault bound volcanic basins the origin of both deposit systems is much debated we dated 11 molybdenite samples from five skarn porphyry cu au mo deposits and 5 molybdenite samples from the datuanshan stratabound cu au mo deposit by icp ms re os isotope analysis nine samples from the same set were additionally analyzed by ntims on re os results from the two methods are almost identical the re os model ages of 16 molybdenite samples range from 134 7 2 3 to 143 7 1 6 ma 2 the model ages of the five samples from the datuanshan stratabound deposit vary from 138 0 3 2 to 140 8 2 0 ma with a mean of 139 3 2 6 ma their isochron age is 139 1 2 7 ma with an initial os ratio of 0 7 8 1 mswd 0 29 these data indicate that the porphyry skarn systems and the stratabound deposits have the same age and suggest an origin within the same metallogenic system albite 40 ar 39 ar dating of the magnetite porphyry deposits indicates that they formed at 123 to 125 ma i e 10 20 ma later both mineralization styles characterize transitional geodynamic regimes i e the period around 140 ma when the main ns trending compressional regime changed to an ew trending lithospheric extensional regime and the period of 125 115 ma of dramatic ew trending lithospheric extension

growth of fissure ridge travertines from geothermal springs of denizli basin western turkey fissure ridge travertines grown from geothermal springs of denizli basin southwestern turkey are investigated through stratigraphic structural geochemical and geochronological methods with the aim of understanding the growth of these elongate mound shaped structures two main types of travertine deposits are recognized 1 bedded travertines which grew as flowstone on sloping surfaces and form the bulk of fissure ridges and 2 banded travertines which grew as veins within the bedded travertine chiefly along its central feeding conduit stratigraphic and structural observations shed light on the bedded banded travertine relationships where the banded features grew through successive accretion phases crosscutting the bedded travertine or forming sill like structures the bedded and banded travertines alternated their growth as demonstrated by complicated crosscutting relationships and by the upward suture in places of banded travertine by bedded travertine that was in turn crosscut by younger banded travertine the bedded travertine is often tilted away from the central axis of the fissure ridge thus leaving more room for the central banded travertine to form u series ages confirm the bedded banded travertine temporal relationships and show that the growth of the studied fissure ridges lasted up to several tens of thousands of years during quaternary time the banded travertine was deposited mainly during cold events possibly in coincidence with seismic events that might have triggered the outflow of deep geothermal fluids c and o stable isotope and rare earth element data indicate a shallow feeding circuit for the studied structures with a fluid component deriving from a deeper geothermal circuit a crack and seal mechanism of fissure ridge growth is proposed modulated by the interplay of local and regional influencing factors and mechanisms such as geothermal fluid discharge paleoclimate tectonics and the progressive tilting of bedded travertine limbs over a soft substratum creating the necessary space for the central veins to grow

constraints of multiple dating of the qingshan tungsten deposit on the triassic w sn mineralization in the nanling region south china abstract the qingshan tungsten deposit is a quartz vein type ore deposit in the nanling region south china and consists of orebodies along the contact between ordovician sandstone and the mesozoic keshuling granitic pluton there are more than 54 ore bearing quartz veins controlled by ne and nne trending faults the principal ore minerals are wolframite and cassiterite with subordinate molybdenite which formed dominantly during the early oxide and oxide sulfide ore forming stage together with extensive greisenization adjacent to the w bearing quartz veins the gangue minerals are mainly quartz and muscovite zircon grains from the keshuling pluton have a u pb age of 231 9 1 0 ma mswd 4 0 molybdenite separates from the ore bearing quartz veins have a well defined 187re 187os isochron age of 228 7 2 5 ma mswd 0 36 with model ages ranging from 227 6 3 3 to 229 7 3 2 ma hydrothermal muscovite from the greisen between the granite and country rocks has a flat 40ar 39ar plateau age spectra yielding a 40ar 39ar plateau age of 229 4 1 4 ma mswd 0 34 the u pb re os and 40ar 39ar ages are nearly identical within analytical uncertainties and these ages together with the field relationships provide tight constraints on the w sn mineralization at around 230 ma this multiple dating study reflects that the duration of the hydrothermal activity could be less than several million years our new results suggest that the triassic large scale w sn mineralization occurred throughout the nanling region

change in atmospheric mineral aerosols in response to climate last glacial period preindustrial modern and doubled carbon dioxide climates desert dust simulations generated by the national center for atmospheric research s community climate system model for the current climate are shown to be consistent with present day satellite and deposition data the response of the dust cycle to last glacial maximum preindustrial modern and doubled carbon dioxide climates is analyzed only natural non land use related dust sources are included in this simulation similar to some previous studies dust production mainly responds to changes in the source areas from vegetation changes not from winds or soil moisture changes alone this model simulates a 92 33 and 60 change in dust loading for the last glacial maximum preindustrial and doubled carbon dioxide climate respectively when impacts of carbon dioxide fertilization on vegetation are included in the model terrestrial sediment records from the last glacial maximum compiled here indicate a large underestimate of deposition in continental regions probably due to the lack of simulation of glaciogenic dust sources in order to include the glaciogenic dust sources as a first approximation we designate the location of these sources and infer the size of the sources using an inversion method that best matches the available data the inclusion of these inferred glaciogenic dust sources increases our dust flux in the last glacial maximum from 2 1 to 3 3 times current deposition

possible microbial effects on stable carbon isotopes in hot spring travertines recent and older early holocene to pleistocene hot spring travertine carbonates from central italy have two distinctive macrofabrics crystalline crusts and shrubs crystalline crusts are laminated slope deposits that formed abiotically following co 2 degassing from spring water the formation of shrub travertine irregular dendritic precipitates from pool environments is controversial and has been attributed to both abiotic and microbial processes oxygen isotope variation in our travertines can be explained by abiotic processes mainly co 2 degassing in contrast our carbon isotope data cannot be wholly explained by abiotic co 2 degassing invoked in earlier studies because photosynthesis is known to preferentially remove 12 c leaving ambient waters enriched in 13 c this fractionation should be recorded in delta 13 c values of microbially influenced travertine our shrub carbon isotope values are between 0 5 per thousand and 6 0 per thousand larger than values for associated abiotic precipitates and this difference is probably caused by microbial activity these isotope data support previous visual evidence that some shrub fabrics are microbially influenced

coeval changes in grain size and sedimentation rate of eolian loess the chinese loess plateau to determine the temporal spatial relationship between strength of the winds transporting the chinese loess and aridity conditions of the loess source area six loess sections located respectively in the northern middle and southern loess plateau were studied grain size distributions were analyzed on loess paleosol samples that are closely spaced in the sections time scales were established by tuning each of the grain size records to theoretical changes in the earth s orbital parameters results obtained show that during the last two glacial cycles particle size of the loess co varies with apparent sedimentation rates suggesting that variations in winter monsoon intensity and the aridity of the loess source area are tightly coupled this proximal relationship is in striking contrast with the observation of distal eolian clays in north pacific sediments we propose that this phenomenon may result from the proximity of the loess plateau to the source area and from the significant control of the winter monsoon on the expansion retreat changes of the deserts in the northern and northwestern china

travitonics using travertines in active fault studies abstract late quaternary travertines deposited from hot springs can reveal much about the neotectonic attributes and histories of structures on the basis of field studies in the aegean region turkey and greece the northern apennines italy and the basin and range province usa we conclude that the following relationships are of predictive value i travertine deposits are preferentially located along fracture traces either immediately above extensional fissures or in the hanging walls of normal faults ii the locations of many travertine fissure ridge deposits coincide with step over zones relay ramps between fault segments networks of intersecting tensional fissures reflecting the complex strains experienced in such settings are probably responsible for enhancing hydrothermal flow iii the morphology of travertine deposits overlying extensional fissures is controlled by the rheology of the underlying materials tufa cones towers pinnacles form on former and present lake floors where fissures underlie unconsolidated sediments whereas fissure ridges develop where fissures cut bedrocks at the surface iv fissure ridges comprise outwardly dipping bedded travertine flanking a central tensional fissure filled by vertically banded travertines fissures can be used to infer local stretching directions v where there are travertines datable by the u series method it is possible to calculate time averaged dilation and lateral propagation rates for individual fissures vi most fissures cutting fissure ridges comprise self similar angular segments with fractal dimensions in the range 1 00 1 12 the properties of bedded travertine combined with stress perturbations at fissure tips probably being responsible for such similar fractal dimensions being inferred from such a wide range of locations fissures gradually increasing in width with depth are products of continuous fracture dilation in contrast to those that form during episodic dilation which display stepped increases of width with depth vii travertine deposited from springs along fault zones accumulate in terraced mounds sited down slope of the spring line viii many post depositional fractures cutting travertine deposits are locally oriented at right angles to deposit margins and ix systematic joints in travertines are restricted to those parts of eroded sheet deposits that have been exhumed

travertine deposition and faulting the fault related travertine fissure ridge at terme s giovanni rapolano terme italy in this paper we describe an example of travertine fissure ridge development along the trace of a normal fault with metre displacement located in the eastern margin of the neogene quaternary siena basin in the terme s giovanni area rapolano terme italy this morphotectonic feature 250 m long 30 m wide and 10 m high formed from supersaturated hot waters 39 9 c flowing from thermal springs aligned along the trace of the normal fault dissecting travertines not older than late pleistocene 24 3 ka a straight continuous fissure with a maximum width of 20 cm occurs at the top of the ridge along its crest hot fluids flow from cones mainly located at the extremities of the ridge where travertine is depositing the travertine fissure ridge shows an asymmetrical profile since it buries the fault scarp the difference in height of slopes corresponds to the vertical displacement of the normal fault fissuring of the recent travertine deposits along the strike of the crestal fissure as well as recent hydrothermal circulation lead us to believe that the terme s giovanni normal fault may be currently active on the whole the terme s giovanni fissure ridge can be defined as a travertine fault trace fissure ridge adding a helpful example for studying the relationship between faulting and travertine deposition

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

a late cretaceous tin metallogenic event in nanling w sn metallogenic province constraints from u pb ar ar geochronology at the jiepailing sn be f deposit hunan china abstract the jiepailing deposit located in southern hunan province china is a giant sn be f deposit in the nanling w sn province the sn be f mineralization is spatially associated with the jiepailing granite porphyry la mc icp ms zircon u pb dating of the jiepailing granite porphyry yielded a weighted mean 206 pb 238 u age of 90 5 0 9 ma mswd 0 32 which is interpreted as the emplacement age of the granite porphyry hydrothermal muscovite yields a plateau 40 ar 39 ar age of 92 1 0 7 ma mswd 0 9 which is well consistent with the zircon u pb age of the jiepailing granite porphyry responsible for the sn be f mineralization indicating a temporal link between the emplacement of the jiepailing granite porphyry and the sn be f mineralization our new high precise geochronological data suggest that the jiepailing giant sn be f deposit and related granite formed during the early late cretaceous 92 90 ma which provided convincing evidence for a previously unrecognized metallogenic event related to late cretaceous granitic magmatism in nanling region the occurrence of the late cretaceous sn metallogenic event identified in southern hunan province further highlights the importance of systematic metallogenic studies of the nanling w sn province integrated with high precise geochronological data obtained previously it is suggested that the nanling region mainly experienced three tectonomagmatic activities and lithospheric thinning events during mesozoic which are responsible for three sn w metallogenic events to form the world class nanling w sn metallogenic province

radiocarbon dating of residual organic matter in travertine formed along the yumoto fault in oga peninsula northeast japan implications for long term hot spring activity under the influence of earthquakes abstract radiocarbon dating was performed on trace amounts of organic matter included in travertines formed along the yumoto fault in oga peninsula ne japan the reliability of the dating method was confirmed by the consistency of ages obtained with the stratigraphy of the travertine mound and the ratio of carbon stable isotopes the radiocarbon chronology of the travertines shows that 1 the hot springs at oga have been active for approximately 29 000 years with average depositional rates ranging from 0 24 to 1 75 mm yr and 2 the principal hot spring activity has migrated southward with time variations in the accumulation rates and the progressive migration of the main focus of the hot spring activity imply irregular spring behaviour this behaviour has not been influenced by paleoclimate but may have been controlled by the earthquakes that occur frequently in the region around oga peninsula

northern westerlies during the last glacial maximum results from cmip5 simulations abstractbased upon simulations from phase 5 of the coupled model intercomparison project cmip5 the vertical and regional characteristics of the northern westerlies during the last glacial maximum lgm are investigated in this study at the northern hemispheric scale all nine available models simulate a poleward shift of the 200 hpa jet and eight models simulate an equatorward shift of the 850 hpa jet compared to the preindustrial period these shifts are of approximately 2 3 latitude for the arithmetic multimodel mean the upper tropospheric cooling in the tropics possibly due to reduced latent heat release is expected to account for the poleward shift of the 200 hpa jet through the thermal wind relationship changes in the midlatitude baroclinic instability in response to the amplified polar cooling are associated with the jet stream in the lower troposphere through anomalous eddy activity in particular the types of predominant baroclinic eddies are regionally dependent the behavior of the 8

glacial interglacial co2 change the iron hypothesis several explanations for the 200 to 280 ppm glacial interglacial change in atmospheric co2 concentrations deal with variations in southern ocean phytoplankton productivity and the related use or nonuse of major plant nutrients an hypothesis is presented herein in which arguments are made that new productivity in today s southern ocean 7 4 1013g yr 1 is limited by iron deficiency and hence the phytoplankton are unable to take advantage of the excess surface nitrate phosphate that if used could result in total southern ocean new production of 2 3 1015 g c yr 1 as a consequence of fe limited new productivity holocene interglacial co2 levels preindustrial are as high as they were during the last interglacial 280 ppm in contrast atmospheric dust fe supplies were 50 times higher during the last glacial maximum lgm because of this fe enrichment phytoplankton growth may have been greatly enhanced larger amounts of upwelled nutrients may have been used and the resulting stimulation of new productivity may have contributed to the lgm drawdown of atmospheric co2 to levels of less than 200 ppm background information and arguments in support of this hypothesis are presented

application of dynamic programming to the correlation of paleoclimate records 1 signal matching is a powerful tool frequently used in paleoclimate research but it is enormously time consuming when performed by hand previously proposed automatic correlation techniques require very good initial fits to find the correct alignment of two records a new technique presented in this paper utilizes dynamic programming to find the globally optimal alignment of two records geological realism is instilled in the solution through the definition of penalty functions for undesirable behavior such as unlikely changes in accumulation rate examples with synthetic and real data demonstrate that the dynamic programming technique produces accurate high resolution results with much less effort than hand tuning or preexisting automated correlation techniques

molybdenite re os and muscovite 40ar 39ar dating of the xihuashan tungsten deposit central nanling district south china abstract the xihuashan tungsten deposit in the central nanling region south china is an important vein type ore deposit hosted in cambrian strata and mesozoic granitic intrusions wolframite and molybdenite are the principal ore minerals the gangue minerals are mainly quartz and muscovite wolframite and molybdenite are products of the first stage hydrothermal activity whereas muscovite formed dominantly at the second stage molybdenite re os and muscovite 40ar 39ar dating have been carried out to investigate the age of mineralization re os isotopic dating for molybdenite associated with wolframite yield a precise well constrained isochron age of 157 8 0 9 ma mswd 1 5 ar ar isotopic analyses of muscovite yield a plateau age of 152 8 1 6 ma in agreement with an inverse isochron age of 152 8 1 6 ma which is 5 mys younger than the re os age the molybdenite re os age is interpreted as the age of tungsten mineralization this age coincides well with the zircon u pb age of the host granitic intrusion reported previously the 5 mys difference between molybdenite re os and muscovite 40ar 39ar ages probably represents the duration of hydrothermal activity the results show that the xihuashan tungsten deposit is one of many important tungsten tin deposits formed during 150 to 160 ma associated with large scale lithospheric extension in south china

hydrothermal co2 degassing in seismically active zones during the late quaternary natural co2 discharges are abundant in turkey as evident from ongoing deposition of recent terrace mound travertines and emplacement of significant travertine vein and breccia deposits in fractured damage zones of active fault systems we report high precision u series age data for the vein carbonates combined with important field observations and geochemical data to evaluate the travertine veining and co2 degassing history in seismically active areas field evidence suggests that travertine filled veins and associated breccias represent hydrothermal eruption products which probably formed by hydraulic fracturing in response to overpressure of co2 rich fluids stable isotope and ree data support the field observations and indicate that travertine veins formed as thermogene deposits from rapidly ascending co2 rich fluids travertine veins from the kirsehir geothermal field give u series ages in a range from 10 6 0 3 ka to 86 16 1 24 ka with a majority of ages failing between 10 6 0 3 and 11 3 0 2 ka vein samples from the pamukkale geothermal field yield u series ages between 21 1 0 1 ka and 73 6 0 6 ka two major age groups are evident in pamukkale that cluster coherently around 21 ka and 25 ka a large number of travertine veins we dated by high precision u series technique coincide with times of cold dry climate events this is different from surface sinter deposits in geothermal fields which more frequently form during warm and wet periods we propose that a significant reduction in surface discharge of co2 by spring or geothermal waters during dry climate periods may promote oversaturation of co2 in deep reservoirs host rock fracturing in response to seismic shaking and fluid overpressure results in rapid exsolution and expansion of the dissolved gas and may lead to hydrothermal eruptions crown copyright c 2009 published by elsevier b v all rights reserved

aragonite laminae in hot water travertine crusts rapolano terme italy small 5 30 m aggregates of aragonite needles occur in calcite crystal crusts of present day hot water slope travertines at rapolano terme in tuscany italy the aggregates are mainly concentrated in irregular wispy and dark laminae which cross cut calcite crystal feathers to create a pervasive millimetre scale banded appearance in the deposit they also occur less commonly scattered irregularly through the calcite layers the aragonite needle aggregates are in the form of crosses fascicles sheaf shaped bundles or dumbbell shaped rosettes and spherulites locally irregular masses of needles also occur the fascicles rosettes and spherulites have hollow centres which resemble microbial components fungal spores bacterial colonies and pollen suggesting that the aragonite crystals are biotically nucleated the lamination is interpreted to reflect diurnal control stimulation of microbial activity during daylight concentrates cells in laminae and promotes aragonite calcification calcite feather crystals although traversed by the aragonite aggregate laminae have a clear appearance under the light microscope they form more or less continuously through the diurnal cycle by abiotic precipitation the constant association of aragonite with organic nuclei irrespective of whether the latter are in laminae or scattered through the calcite layers supports a biotic control on aragonite formation lamination in pleistocene travertines is superficially similar to that in the present day deposits but is diagenetically altered in the pleistocene deposits the calcite feathers appear dark under the light microscope and the aragonite aggregates where they are not altered to dark calcite are dissolved together with parts of the adjacent spar calcite and therefore appear light coloured

the age of the taklimakan desert the taklimakan desert is located in the foreland basin of the tibetan plateau we report here the results of stratigraphic investigations of a 1626 meter thick sequence with interbedded wind blown silt from the southern marginal taklimakan desert because the studied section is located downwind of the desert the eolian silt accumulation is closely linked to desert formation our new evidence indicates that shifting sand dunes prevailed in the tarim basin by at least 5 3 million years ago as they do today we attribute this event to late cenozoic climatic deterioration as well as to changes in atmospheric circulation induced by tibetan plateau uplift

pleistocene holocene tectonic reconstruction of the ballik travertine denizli graben sw turkey de formation of large travertine geobodies at intersecting grabens abstract travertine geobodies have been identified as potential reservoir analogues to carbonate build ups in pre salt hydrocarbon systems to investigate travertine geobody deformation faults were mapped in 35 travertine quarries that excavate the ballik travertine i e a c 12 5 km2 large travertine geobody that precipitated at the intersection of the ne margin of the denizli basin and neighbouring baklan graben sw turkey this travertine precipitated from cooling carbonate saturated thermal spring waters that resurfaced along the margin fracture fault network and through neogene unconsolidated underlying sediments from the denizli basin floor to the uplifted graben shoulders fault orientation is dominantly wnw ese oriented with major basin faults showing a left stepping trend along the upper denizli margin travertine is only deformed by extensional normal faults along the lower margin travertine starts with a subhorizontal facies but evolves to a travertine facies formed by a sloping topography with a domal architecture paleostress inversion of fault slip data reveals that an early pleistocene nne ssw extensional transtensional phase initiated the wnw ese oriented graben facing normal fault network in the middle pleistocene the ballik fault network was left lateral strike slip reactivated because it acted as a transfer zone between the nw se extending neighbouring baklan basin and nw se extension along ne sw oriented margin faults of the dghs in this stress configuration travertine precipitated along the sw margin fault of the baklan graben after strike slip reactivation a late pleistocene to current nne ssw extensional stress regime reinstalled during which margin faults widened and active travertine precipitation moved to more central parts of the dghs as different tectonic regimes affect graben intersections reservoir analogues can have a complex deformation history driven by fault reactivation and recurrent stress permutations this study concludes that large travertine geobodies can form at graben intersections because of their susceptibility to enhanced fluid flow through the complex fault fracture network

origin and tectonic significance of a mesozoic multi layer over thrust system within the yangtze block south china abstract in the yangtze block south china a well developed mesozoic thrust system extends through the xuefeng and wuling mountains in the southeast to the sichuan basin in the northwest the system comprises both thin and thick skinned thrust units separated by a boundary detachment fault the dayin fault to the northwest the thin skinned belt is characterized by either chevron anticlines and box synclines to the northwest or chevron synclines to the southeast the former structural style displays narrow exposures for the cores of anticlines and wider exposures for the cores of synclines thrust detachments occur along silurian fs and lower cambrian fc strata and are dominantly associated with the anticlines to the southeast this style of deformation passes gradually into one characterized by chevron synclines with associated principal detachment faults along silurian fs cambrian fc and lower sinian fz strata there are however numerous secondary back thrusts therefore the thin skinned belt is like the valley and ridge province of the north american applachian mountains the thick skinned belt structurally overlies the thin skinned belt and is characterized by a number of klippen including the xuefeng and wuling nappes it is thus comparable to the blue ridge province of appalachia the structural pattern of this thrust system in south china can be explained by a model involving detachment faulting along various stratigraphic layers at different stages of its evolution the system was developed through a northwest stepwise progression of deformation with the earliest delamination along lower sinian strata fz analyses of balanced geological cross sections yield about 18 1 21 total 88 km shortening for the thin skinned unit and at least this amount of shortening for the thick skinned unit the compressional deformation from southeast to northwest during late jurassic to cretaceous time occurred after the westward progressive collision of the yangtze block with the north china block and suggests that the orogenic event was intracontinental in nature

bowl shaped basin related to low angle detachment during continental extension the case of the controversial neogene siena basin central italy northern apennines abstract this paper deals with the tectonic evolution of a bowl shaped neogene basin siena basin located in the inner northern apennines and developed during an articulated tectonic evolution this basin was controversially interpreted by different authors as graben half graben or thrust top basin structural and stratigraphic data from the basin substratum and filling sediments integrated with the interpretation of reflection seismic profiles and borehole logs highlight that the siena basin consists of a tectonic depression with a complex internal architecture such a basin developed on a multilayered substratum deeply affected by extensional tectonics since the middle miocene extensional detachments produced a widespread thinning of the basin substratum and superimposed on contractional structures developed during the northern apennines collisional events extensional detachments accommodated within weak horizons and gave rise to the lateral segmentation of most competent stratigraphic horizons sediments filling the siena basin mainly deposited on the ligurian units the topmost tectonic units forming the tectonic pile in the gap between two laterally segmented geological bodies made up of the triassic siliciclastic succession of the verrucano group such a lateral segmentation produced a synformal structural depression not delimited by faults filled by late serravallian late messinian marine to continental sediments which deposited during the extensional faulting from the latest early pliocene to the middle pliocene the architecture of the basin was modified by an high angle normal fault system which affected the eastern side of the basin and produced new accommodation space for marine sediments in sum the siena basin consists of a sin tectonic basin developed on the hanging wall of staircase extensional detachments later affected by high angle normal to oblique faults the latter faults defined a half graben during the latest evolution of the basin the tectonic evolution of the siena basin made it possible to point out some differences with respect to the types of bowl shaped basins related to extensional detachments and named as supradetachment basins

the 3 6 ma aridity and westerlies history over midlatitude asia linked with global climatic cooling midlatitude asia mla strongly influenced by westerlies controlled climate is a key source of global atmospheric dust and plays a significant role in earth s climate system however it remains unclear how the westerlies mla aridity and dust flux from this region evolved over time here we report a unique high resolution eolian dust record covering the past 3 6 ma retrieved from the thickest loess borehole sequence 671 m recovered to date at the southern margin of the taklimakan desert in the mla interior the results show that eolian dust accumulation which is closely related to aridity and the westerlies indicates existence of a dry climate desert area and stable land surface promoting continuous loess deposition since at least 3 6 ma this region experienced long term stepwise drying at 2 7 1 1 and 0 5 ma coeval with a dominant periodicity shift from 41 ka cyclicity to 100 ka cyclicity between 1 1 ma and 0 5 ma these features match well with global ice volume variability both in the time and frequency domains including the mid pleistocene transition highlighting global cooling forced aridity and westerlies climate changes on these timescales numerical modeling demonstrates that global cooling can dry mla and intensify the westerlies which facilitates dust emission and transport providing an interpretive framework increased dust may have promoted positive feedbacks e g decreasing atmospheric co2 concentrations and modulating radiation budgets contributing to further cooling unraveling the long term evolution of mla aridity and westerlies climate is an indispensable component of the unfolding mystery of global climate change

late cenozoic eolian deposition in the north pacific asian drying tibetan uplift and cooling of the northern hemisphere a newly constructed record of eolian dust accumulation from the central north pacific shows that dust deposition increased by an order of magnitude quite rapidly at 3 6 ma we associate this sudden drying with the uplift of at least the northern portion of the tibetan plateau shutting off the indian ocean moisture source to central and western china this ten fold increase in atmospheric dust loading appears to be associated with the 1 m y long shift toward heavy 18o values that occurred at 3 6 2 6 ma the dust grain size record of wind intensity begins its late cenozoic coarsening a million years before the drying event at 4 5 ma the northern hemisphere cooling that results in intensification of the subpolar westerly winds may have as its ultimate cause the drawdown of atmospheric co2 in the latest miocene and the early pliocene closing of the panamanian seaway

calcite veining and feeding conduits in a hydrothermal system insights from a natural section across the pleistocene golemezli travertine depositional system western anatolia turkey abstract linking the architecture of structural conduits with the hydrothermal fluids migrating from the reservoir up to the surface is a key factor in geothermal research a contribution to this achievement derives from the study of spring related travertine deposits but although travertine depositional systems occur widely their feeding conduits are only rarely exposed the integrated study carried out in the geothermal golemezli area nearby the well known pamukkale area denizli basin western anatolia turkey focused on onyx like calcite veins banded travertine and bedded travertine well exposed in a natural cross section allowing the reconstruction of the shallower part of a geothermal system the onyx like veins represent the thickest vein network 150 m so far known new field mapping and structural kinematic analyses allowed to document a partially dismantled travertine complex bedded travertine formed by proximal fissure ridges and distal terraced pools depositional systems the banded calcite veins wnw trending and up to 12 m thick developed within a 200 m thick damaged rock volume produced by parallel fault zones th u dating indicates a long lasting middle late pleistocene fluids circulation in a palaeo geothermal system that due to its location and chemical characteristics can be considered the analogue of the nearby still active pamukkale system the isotopic characteristics of the calcite veins together with data from fluid inclusions analyses allow the reconstruction of some properties i e temperature salinity and isotopic composition and processes i e temperature variation and intensity of degassing that characterized the parent fluids and the relation between degassing intensity and specific microfabric of calcite crystals elongated microsparite micrite bands controlled by changes fluctuations of the physico chemical fluid characteristics

high resolution elemental records from the south china sea and their paleoproductivity implications 1 the biogenic related elements ca sr ba p cd scavenged al and ti were analyzed by inductively coupled plasma mass spectrometry icp ms and inductively coupled plasma atomic emission spectrometry icp aes for core ns93 5 from the west slope of the south china sea terrestrial input as estimated from the accumulation of ti was higher during glacials than during interglacials carbonate accumulation rates are inversely related to those of terrestrial input suggesting higher production of calcareous phytoplankton during interglacials the accumulation patterns of authigenic sr ba p and cd match that of carbonate further indicating higher calcareous phytoplankton production during interglacials scavenged al and excess sio2 which is related to biogenic opal exhibit higher accumulation rates during glacials and correspond with changes in terrestrial input this indicates that terrestrial input driven is important to siliceous phytoplankton production but not for calcareous phytoplankton production as calcareous phytoplankton is the dominant component of the biogenic sediments in the south china sea particularly during interglacials previous inference of higher productivity in the south china sea during glacials based on only the biogenic opal proxy needs to be reconsidered

palaeomagnetic and rock magnetic properties of travertine its potential as a recorder of geomagnetic palaeosecular variation environmental change and earthquake activity in the sicak cermik geothermal field turkey travertine the product of incremental growth of inorganic carbonate is potentially a high resolution recorder of geomagnetic palaeosecular variation psv when it incorporates small amounts of ferromagnetic material it grows most regularly in regions of neotectonic activity where geothermal waters feed into extensional fissures and deposit successive layers of carbonate as fissure travertine the same waters spill out onto the surface to deposit bedded travertine which may incorporate wind blown dust including ferromagnetic particles tectonic travertine deposits are linked to earthquake activity because the geothermal reservoirs are reset and activated by earthquake fracturing but tend to become sealed up by carbonate deposition between events this study investigates whether sequential deposition can identify cycles of psv and provide a means of estimating rates of travertine growth and earthquake frequency the palaeomagnetic record in three travertine fissures from the socak cermik geothermal field in central anatolia and nearby bedded travertines dated up to 360 000 years in age u th are investigated to evaluate magnetic properties and relate the geomagnetic signature to earthquake induced layering sequential sampling of bedded travertine from the margins earliest deposition to centres of fissures last deposition identifies directional migrations reminiscent of psv thermal demagnetisation shows that goethite pigment is not a significant remanence carrier instead hematite and more rarely magnetite is the carrier magnetic susceptibility of fissure travertine is proportional to the calcite aragonite ratio two frequency susceptibility analysis identifies a ferromagnetic content in bedded travertine dominated by fine superparamagnetic grain sizes whereas the fissure travertine has mostly single and multidomain grain sizes a difference interpreted to reflect contrasting energies of the two environments plus atmospheric input in the bedded travertine fissure travertine possesses strong lineated anisotropy of magnetic susceptibility ams with horizontal kmax axes oriented along the fissure axes and kint and kmin distributed within the orthogonal plane this is explained by rolling of ferromagnetic grains up the side of the fissure during repeated water ejection until fixed by the host carbonate precipitation in contrast bedded travertine has low magnitude ams with near neutral ellipsoid shapes controlled by settling of grains during weak outflow from the axis of the fissure ridge the source of the magnetic minerals in the fissure travertine is probably in material washed down by meteoric waters from the local terra rossa soil and concentrations of these minerals and hence magnetic susceptibility could be a signature of pluvial environments fissure travertine is a reliable recorder of the ambient field when layered although bedded travertine is found to exhibit inclination shallowing on the assumption that psv cycles record periods of 1 2 ky layering in the travertine identifies resetting of the geothermal system by earthquakes every 50 100 years in this region travertine precipitation occurs at rates of 0 1 0 3 mm year on each side of the

oxygenation changes in the deep western arabian sea during the last 190 000 years productivity versus deepwater circulation 1 fluctuations in the abundance of selected foraminiferal indicator species and diversity allowed the reconstruction of changes in deepwater oxygenation and monsoon driven organic matter fluxes in the deep western arabian sea during the last 190 kyr times of maximum surface production coincide with periods of intensified sw monsoon as shown by the abundance of globigerina bulloides and enhanced carbonate corrosion benthic ecosystem variability in the deep arabian sea is not exclusively driven by variations in monsoonal upwelling and related organic matter supply to the seafloor but also by changes in deepwater ventilation deepening of the base of the oxygen minimum zone omz below 1800 m water depth is strongly coherent on the precessional band but lags proxies of sw monsoon strength by 4 to 6 kyr the out of phase relationship between omz deepening and maximum sw monsoon strength is explained by temporal changes in the advection of oxygen rich deepwater masses of north atlantic and antarctic origin this process affected the remineralization and burial efficiency of organic matter in the deep arabian sea resulting in the observed phase lag between maximum monsoon strength and organic carbon preservation

dating the giant zhuxi w cu deposit taqian fuchun ore belt in south china using molybdenite re os and muscovite ar ar system abstract the recently discovered zhuxi w cu ore deposit is located within the taqian fuchun ore belt in the southeastern edge of the yangtze block south china its inferred tungsten resources based on new exploration data are more than 280 mt by 2016 at least three paragenetic stages of skarn formation and ore deposition have been recognized prograde skarn stage retrograde stage and hydrothermal sulfide stage secondly greisenization marmorization and hornfels formation are also observed scheelite and chalcopyrite are the dominant metal minerals in the zhuxi deposit and their formation was associated with the emplacement of granite stocks and porphyry dykes intruded into the surrounding carboniferous carbonate sediments huanglong and chuanshan formations and the neoproterozoic slate and phyllites the scheelite was mostly precipitated during the retrograde stage whereas the chalcopyrite was widely precipitated during the hydrothermal sulfide stage a muscovite 40ar 39ar plateau age of about 150 ma is interpreted as the time of tungsten mineralization and molybdenite re os model ages ranging from 145 9 2 0 ma to 148 7 2 2 ma for the subsequent hydrothermal sulfide stage of activity as the time of the copper mineralization our new molybdenite re os and muscovite 40ar 39ar dating results along with previous zircon u pb age data indicate that the hydrothermal activity from the retrograde stage to the last hydrothermal sulfide stage lasted up to 5 myr from 150 6 1 5 to 145 9 1 ma and is approximately coeval or slightly later than the emplacement of the associated granite porphyry and biotite granite the new ages reported here confirm that the zhuxi tungsten deposit represents one of the mesozoic magmatic hydrothermal mineralization events that took place in south china in a setting of lithospheric extension during the late jurassic 160 150 ma it is suggested that mantle material played a role in producing the zhuxi w cu mineralization and associated magmatism

petrogenesis of jurassic tungsten bearing granites in the nanling range south china evidence from whole rock geochemistry and zircon u pb and hf o isotopes abstract the nanling range nlr is the largest tungsten metallogenic province in china and perhaps in the world the tungsten mineralization is believed to be related to jurassic granitic magmatism however the petrogenesis of these granites and their relation to the tungsten mineralization are still debated whole rock geochemical and sr nd hf isotopic data and zircon in situ u pb ages and hf o isotopes are reported for w bearing granitic intrusions from the southern jiangxi province in the nlr in order to constrain their magmatic sources and petrogenesis the nlr granites include biotite granites two mica granites and garnet muscovite granites sims and la icpms u pb dating of zircons and monazites give emplacement ages of 161 154 ma for these rocks the granites are metaluminous to strongly peraluminous with high sio 2 72 3 wt and high k 2 o 3 7 wt petrographic and geochemical features show that they are highly fractionated i type granites the biotite granites are enriched in light rare earth elements lrees relative to heavy rees have weakly negative eu anomalies and are depleted in nb ba p and ti in contrast the two mica and garnet bearing muscovite granites have tetrad type ree patterns with strongly negative eu anomalies and are extremely depleted in ba nb sr p and ti magmatic garnets are mainly almandine and spessartine and have low mn cores and high mn rims their y hree contents are high and generally decrease from core 1 2 wt to rim average 4955 ppm all of these granites are characterized by variable whole rock initial 87 sr 86 sr 0 7053 0 8000 e nd t 12 6 to 9 4 and e hf t 12 3 to 8 5 as well as variable zircon e hf t and 18 o with values of 16 3 to 7 4 and 7 6 to 10 0 respectively they contain abundant zircon xenocrysts and xenoliths of micaceous schist all of these features are consistent with a process of crystal fractionation of crustally derived magmas coupled with strong assimilation of sedimentary rocks the assimilation of meta sedimentary materials increased the concentrations of tungsten alumina and manganese in the magmas whereas high degrees of crystal fractionation further enriched them in the evolved granitic rocks the w enriched magmatic fluids formed the tungsten bearing quartz veins revealing the genetic relationship between tungsten mineralization and emplacement of garnet bearing two mica or muscovite granites in the nlr

tectonic control on travertine and calcareous tufa deposition in a low temperature geothermal system sarteano central italy this paper presents an integrated study directed toward an understanding of the tectonic control on the hydrothermal circulation and resulting deposition of middle late pleistocene travertine in a low temperature geothermal field of southern tuscany located in the sarteano area central italy the study area is characterized by thermal springs c 25 c and related continental carbonate deposits structurally controlled by sw ne trending oblique to strike slip faults dissecting previous normal faults sedimentological stratigraphical data and 230 th 234 u radiometric age determination for the travertine indicate that continental carbonates were deposited in a tectonically controlled perched spring system from 268 22 ka at least to the present the hydrothermal system is and was characterized by meteoric waters with a minor contribution from fluids of deeper origin meteoric waters infiltrated to depth through tectonically damaged zones of mesozoic and cenozoic carbonate rocks and overheated as a result of localized anomalous geothermal gradient then fluids enriched in bicarbonate sulphate moved up along highly fractured rock masses at the intersection between strike slip faults and normal faults this paper highlights the use of continental carbonates in the reconstruction of palaeohydrothermal systems in terms of the location of the main conduits for hydrothermal fluid flow age of faulting and physical properties of hydrothermal fluids

a multi methodological approach to reconstruct the configuration of a travertine fissure ridge system the case of the cukor quarry suttő gerecse hills hungary abstract travertines are continental carbonates that precipitate from spring waters mainly due to co2 degassing they are widely quarried as building stone which has led to numerous often abandoned travertine quarry outcrops these and other outcrops however merely represent the surface expressions of the complex architecture of travertine bodies and their deep rooted feeding systems integration of field observations and geochemical analyses with crucial subsurface geophysical data is required in order to fully understand travertine systems and their relationship to the local geological framework such a multi methodological approach is illustrated here for the case of the abandoned cukor quarry radio magnetotelluric rmt and electrical resistivity tomography ert surveys provide unique insights into local tectonics geobody architecture and the topography preceding travertine deposition altogether the lens shaped isolated domal geobody with spring proximal lithofacies and subvertical bedding in addition to the contrasting geochemistry and age with surrounding travertine enabled the unequivocal reconstruction of the dismantled cukor fissure ridge this study illustrates the high potential of this multi methodological approach on poorly exposed strongly weathered quarried and tectonically deformed travertine bodies and provides information on the complex feeding system beneath travertine deposits their reconstruction can be interpreted in light of the neo tectonic expression of regional uplift helps to complete the regional tectonic history and provides insights into older landscapes that lack preservation or would no longer be immediately recognized at the surface

major types and time space distribution of mesozoic ore deposits in south china and their geodynamic settings the ore deposits of the mesozoic age in south china can be divided into three groups each with different metal associations and spatial distributions and each related to major magmatic events the first event occurred in the late triassic 230 210 ma the second in the mid late jurassic 170 150 ma and the third in the early mid cretaceous 120 80 ma the late triassic magmatic event and associated mineralization is characterized by peraluminous granite related w sn nb ta mineral deposits the triassic ore deposits are considerably disturbed or overprinted by the later jurassic and cretaceous tectono thermal episodes the mid late jurassic magmatic and mineralization events consist of 170 160 ma porphyry skarn cu and pb zn ag vein deposits associated with i type granites and 160 150 ma metaluminous granite related polymetallic w sn deposits the late jurassic metaluminous granite related w sn deposits occur in a ne trending cluster in the interior of south china such as in the nanling area in the early mid cretaceous from about 120 to 80 ma but peaking at 100 90 ma subvolcanic related fe deposits developed and i type calc alkaline granitic intrusions formed porphyry cu mo and porphyry epithermal cu au ag mineral systems whereas s type peraluminous and or metaluminous granitic intrusions formed polymetallic sn deposits these cretaceous mineral deposits cluster in distinct areas and are controlled by pull apart basins along the south china continental margin based on mineral assemblage age and space time distribution of these mineral systems integrated with regional geological data and field observations we suggest that the three magmatic mineralization episodes are the result of distinct geodynamic regimes the triassic peraluminous granites and associated w sn nb ta mineralization formed during post collisional processes involving the south china block the north china craton and the indo china block mostly along the dabie sulu and songma sutures jurassic events were initially related to the shallow oblique subduction of the izanagi plate beneath the eurasian continent at about 175 ma but i type granitoids with porphyry cu and vein type pb zn ag deposits only began to form as a result of the breakup of the subducted plate at 170 160 ma along the nne trending qinzhou hangzhou belt also referred to as qin hang or shi hang belt which is the neoproterozoic suture that amalgamates the yangtze craton and cathaysia block a large subduction slab window is assumed to have formed in the nanling and adjacent areas in the interior of south china triggering the uprise of asthenospheric mantle into the upper crust and leading to the emplacement of metaluminous granitic magma and associated polymetallic w sn mineralization a relatively tectonically quiet period followed between 150 and 135 ma in south china from 135 ma onward the angle of convergence of the izanagi plate changed from oblique to parallel to the coastline resulting in continental extensional tectonics and reactivation of regional scale ne trending faults such as the tan lu fault this widespread extension also promoted the development of ne trending pull apart basins and metamorphic core complexes accompanied by volcanism and the formation of epithermal cu au deposits granite related polymetallic sn w deposits and hydrothermal u deposits between 120 and 80 ma with a peak activity at 100 90 ma

molybdenite re os and muscovite 40 ar 39 ar dating of quartz vein type w sn polymetallic deposits in northern guangdong south china northern guangdong is an important part of nanling tungsten tin metallogenic belt south china the tungsten mineralization in this area consists of mainly quartz wolframite vein type mineralization with w sn polymetallic deposits mostly distributed at the outer contact zone between concealed late jurassic granitic stocks and cambrian ordovician low metamorphosed sandstones and shales molybdenite re os and muscovite 40ar 39ar isotopic dating of three typical tungsten vein type deposits yaoling meiziwo and jubankeng in northern guangdong show that two episodes of late jurassic w sn polymetallic mineralization occurred in this area an early episode during the late jurassic 158 159 ma represented by the yaoling hongling and meiziwo tungsten deposits and a younger event during the early cretaceous 138 ma represented by the jubankeng deposit analysis of available radiometric ages of several w sn deposits in the nanling region indicate that these deposits formed at several intervals during the mesozoic at 90 100 134 140 144 162 and 210 235 ma and that large scale w sn mineralization in this region occurred mainly between 150 and 160 ma

origin of the late jurassic to early cretaceous peraluminous granitoids in the northeastern hunan province middle yangtze region south china geodynamic implications for the paleo pacific subduction the late mesozoic granitic belt in the northeastern hunan province situated in the south of the middle yangtze region represents the western front of the large magmatic province of se china in order to determine their ages and petrogenesis we carried out zircon u pb dating hf isotope and whole rock geochemical analyses for four granitic plutons namely taohuashan dayunshan mufushan wangxiang and lianyunshan our sims zircon u pb ages together with previously published data reveal that the magmatic activities in this area can be roughly subdivided into three phases at 151 146 ma 132 127 ma and ca 117 ma and the dayunshan mufushan batholith therein is a composite pluton these four plutons are mainly composed of weakly to strongly peraluminous biotite or two mica monzogranites with a minor amount of biotite granodiorites their geochemical features are similar to s type as well as fractionated s type granites with enrichment in lrees and negative ba sr nb p and ti anomalies all samples show negative zircon ehf t values ranging from 12 5 to 3 6 corresponding to crustal hf model tdmc ages of 1 4 2 0 ga it is inferred that these granitoids were derived from partial melting of metasedimentary rocks analogous to the neoproterozoic lengjiaxi group predominantly with psammitic component fractional crystallization probably played an important role in the magma evolution while input of mantle derived magma was insignificant combined with other geological evidence our new data allow us to propose that the cretaceous 132 127 ma and ca 117 ma magmatism might be response to episodic slab rollback of the paleo pacific plate while the early stage 151 146 ma magmatism that overlapped the epilogue of jurassic magmatic flare up and subsequent magmatic quiescence probably foreshadowed the transformation from foundering of a subducted flat slab to slab rollback alternatively slab foundering after a se directed intracontinental subduction in the central scb cannot be ruled out for geodynamic interpretation of the jurassic magmatism in se china

comment on first records of syn diagenetic non tectonic folding in quaternary thermogene travertines caused by hydrothermal incremental veining by billi et al tectonophysics 700 701 2017 60 79 abstract billi et al 2017 proposed a new interpretation for the origin and internal structure of thermogene travertine deposits on the basis of evidence from two quarries located in southern tuscany italy they interpreted some travertine beds as calcite veins and argued that undulating travertine beds formed by syn diagenetic i e non tectonic folding that was caused by laterally confined volume expansion caused by incremental veining they assumed that such a process causes changes to the rock properties including porosity reduction rock strengthening and age rejuvenation the interpretations by billi et al 2017 challenge and question the current understanding and interpretation of thermogene travertine deposits this understanding based on numerous studies since the 1980s is that these deposits form from thermal water flowing downslope and precipitating calcium carbonate here we explain how the comparison with active depositional systems is essential for the understanding the origin of structures in older inactive travertine deposits such as those studied by billi et al 2017 we further argue that the three dimensional setting of travertine deposits should be taken into account in order to discuss the possible development of secondary structures indeed travertine deposition on slopes typically leads to the formation of terraced morphologies with pools bordered by rounded rims and separated from each other by steep walls the resulting three dimensional structures can be misinterpreted as asymmetric folds in two dimensional views i e in saw cut walls of quarry in this paper we debate the interpretations offered by billi et al 2017 and their criteria to recognise syn diagenetic non tectonic folds in travertine deposits and explain why many of their ideas are questionable

a rock magnetic study of loess from the west kunlun mountains west kunlun mountains have continuous loess deposits however very few papers have explored the rock magnetic characteristics of loess deposited there thus although kunlun mountains loess is one of the useful paleoclimate archives its importance has not been emphasized here we present detailed rock magnetic and bulk grain size studies on a 207 m loess core on the northern slope of the west kunlun mountains we find that magnetic susceptibility of loess from the northern slope of the west kunlun mountains is not controlled by changes in the concentration of ultrafine pedogenic magnetite and maghemite but instead controlled by changes in the concentration of aeolian multidomain magnetite and maghemite this is unsurprising given the low rainfall of the kunlun region and the lack of postdepositional weathering and soil formation in these aeolian sequences in addition we find that magnetic susceptibility values increase dramatically at 111 m corresponding to an age of similar to 0 5 ma the magnetic susceptibility increase is accompanied by coarsening of both bulk and magnetic grain size and softening of magnetic mineralogy we tentatively tie these changes in rock magnetic and grain size parameter records to an expansion of desert environment

the off fault deformation on the north anatolian fault zone and assessment of slip rate from carbonate veins abstract discrepancies in earthquake characteristics between geodetically determined and geologically observed slip rates are prominent for the eastern part of the north anatolian fault naf zone we investigated the spatial distribution of deformation across a naf fault segment near erzincan ne turkey through field observations of physiographic features along the principle fault and a carbonate filled fissure system we propose that distributed deformation across the principal fault in a stretching zone caused sigmoidal simple shear rotation of the carbonate filled fissure system displacement data of that sigmoidal fissure using isotopic age data of the carbonate fill indicates an off fault deformation rate of 15 90 3 19 mm per year for the holocene which corresponds to at least 50 of the geodetically estimated annual slip across the fault it is critical to take the distributed deformation into account for determining earthquake characteristics of active fault systems

northern hemisphere storm tracks during the last glacial maximum in the pmip2 ocean atmosphere coupled models energetic study seasonal cycle precipitation mid latitude eddies are an important component of the climatic system due to their role in transporting heat moisture and momentum from the tropics to the poles and also for the precipitation associated with their fronts especially in winter we study northern hemisphere storm tracks at the last glacial maximum lgm and their influence on precipitation using ocean atmosphere general circulation model oagcm simulations from the second phase of the paleoclimate modelling intercomparison project pmip2 the difference with pmip1 results in terms of sea surface temperature forcing fundamental for storm track dynamics is large especially in the eastern north atlantic where sea ice extends less to the south in oagcms compared to atmospheric only gcms our analyses of the physics of the eddies are based on the equations of eddy energetics all models simulate a consistent southeastward shift of the north pacific storm track in winter related to a similar displacement of the jet stream partly forced by the eddies themselves precipitation anomalies are consistent with storm track changes with a southeastward displacement of the north pacific precipitation pattern the common features of north atlantic changes in the lgm simulations consist of a thinning of the storm track in its western part and an amplification of synoptic activity to the southeast in the region between the azores islands and the iberian peninsula which reflects on precipitation this southeastward extension is related to a similar displacement of the jet partly forced by the eddies in the western north atlantic the synoptic activity anomalies are at first order related to baroclinic generation term anomalies but the mean flow baroclinicity increase due to the presence of the laurentide ice sheet is partly balanced by a loss of eddy efficiency to convert energy from the mean flow moisture availability in this region is greatly reduced due to more advection of dry polar air by stationary waves leading to less synoptic scale latent heat release and hence less precipitation also in terms of seasonality the stormy season is shifted later in the year by a few days to a month depending on the season and the model considered this shift does not directly reflect on the first order seasonal cycle of precipitation which also depends on other mechanisms especially in summer

nomenclature of amphiboles additions and revisions to the international mineralogical associations amphibole nomenclature the introduction of a fifth amphibole group the na ca mg fe mn li group defined by 0 50 b mg fe 2 mn 2 li 1 50 and 0 50 b ca na 1 50 apfu atoms per formula unit with members whittakerite and ottoliniite has been required by recent discoveries of b lina amphiboles this and other new discoveries such as sodicpedrizite which is herein slightly but significantly changed from the original idealized formula necessitate amendments to the ima 1997 definitions of the mg fe mn li calcic sodic calcic and sodic groups the discovery of obertiite and the finding of an incompatibility in the ima 1997 subdivision of the sodic group requires further amendments within the sodic group all these changes which have ima approval are summarized

origin and diagenesis of quaternary travertine shrub fabrics rapolano terme central italy millimetre to centimetre sized arborescent shrub like calcite precipitates are common constituents of hot water travertine shallow pool deposits of quaternary age at rapolano terme tuscany italy in the presently forming travertines the shrubs consist of apparently random associations of i micrite aggregates and ii subhedral to euhedral rhombic spar crystal aggregates in thin section the micrite aggregates appear dark and the spar rhomb aggregates light giving the shrubs a mottled appearance travertines are basically produced by caco3 precipitation due to degassing and evaporation of the spring waters although biological influence may also stimulate precipitation the formation of masses of erect shrubs rather than dense crystal crusts that form on slopes is probably due to limited water flow in the pool environments microbes including bacteria and diatoms are important influences on shrub microfabric and external shape the micrite aggregates are associated with bacteriform bodies seen as tiny rods and spheres the micrite precipitates around these bodies and in adjacent biofilm spar rhomb precipitation appears to be external to the biofilm and may be related to the presence of diatoms which are locally closely associated with the spar rhombs although an essentially inorganic origin particularly for the more euhedral rhombs cannot be ruled out in the older quaternary travertines the original microfabric of the shrubs has been diagenetically altered the original mottled appearance of the shrubs has become uniformly dark and micritic and the evidence for the dual micritic and spar rhomb origin of the shrubs is obscured or destroyed spar micritization of the shrubs is probably due to abiotic and locally biotic dissolution previous studies did not recognize the diagenetic micritization and attributed shrub formation entirely to bacterial activity

lateral and vertical variations in sedimentology and geochemistry of sub horizontal laminated travertines cakmak quarry denizli basin turkey abstract the laterally extensive sub horizontal laminated travertine deposits outcropping in the cakmak quarry denizli basin turkey allows reconstructing their three dimensional geobody architecture based on field observations detailed petrographic and geochemical analyses stable carbon and oxygen isotopes major and trace elements the most important controlling porosity permeability parameters in this lacustrine dominated facies in relation to microfacies and diagenetic modifications were constrained sedimentological analyses and the observed architectural geometries allowed to subdivide the sub horizontal carbonate succession into three main depositional units these units in turn based on macro and microscopic observations were subdivided into nine dominant lithotypes reflecting an overall shrub flat and a marsh pool depositional setting the shrub flat facies mainly comprises dendritic shrub crusts boundstone pustular grainstone and clotted micrite mudstone to boundstone in contrast the marsh pool environment is dominated by coated reed rudstone to boundstone cryptalgal silty bioclast rich bioturbated mudstone and peloidal packstones the diagenetic study revealed that the sediments were affected by dissolution cementation sparmicritization recrystallization and local formation of fe oxi hydroxides and chalcedony among the diagenetic products in particular the calcite cements were investigated applying micro analysis of stable carbon and oxygen isotopes accordingly the co variation between the obtained isotopic values and the elemental concentrations sr mg na and s point to a thermogene fluid system that likely circulated through the subsurface limestones dolomites and evaporites of the lycian nappes these findings ensure an in depth understanding of continental carbonate deposition i e sub aqueous travertines in the context of a lacustrine depositional system

linking co2 degassing in active fault zones to long term changes in water balance and surface water circulation an example from sw turkey abstract calcite veins are commonly found at shallow depth a few metres below the surface in damage zones of active normal fault systems in southwest turkey although earlier studies demonstrated the link between the vein formation and seismicity the association of near surface carbonate precipitation with climate driven hydrological conditions water table amount of precipitation and evaporation and water discharge is poorly understood in this study using the u th dating method we investigate the timing of vein formation and the interrelationship between tectonic and climatic related hydrological processes carbonate precipitation is interpreted to occur as a result of sudden pressure drops and co2 release after earthquake induced fracturing vein formation mostly occurred during glacial periods which coincide with slow growth rates and higher oxygen isotope values of speleothems from the eastern mediterranean region we relate these episodes to reduced winter rainfall due to the decrease in westerly flow in sw turkey these somewhat drier conditions influenced the chemical composition of circulating water creating conditions conducive to carbonate precipitation and sealing of damage zones these conditions also facilitated co2 accumulation and overpressure build up in the rupture zones failure of the faults resulted in the release of large volumes of co2 rich fluids and the generation of shallow carbonate veins it is proposed that during phases of increased winter rainfall co2 is advected to the surface and discharged as passive degassing when meteoric water circulation is enhanced while regional tectonics is the ultimate driver of fault activity and fracture formation climate driven near surface hydrological changes may have played an important role in modulating co2 rich fluid circulation and surface discharge

mineralogical crystal morphological and isotopic characteristics of smooth slope travertine deposits at reshuitang tengchong china abstract reshuitang is an important active hydrothermal area in the tengchong geothermal field and is characterized by many hot springs and their associated deposits detailed mineralogical crystal morphological and stable isotopic investigations of the smooth slope fossil travertines at reshuitang and hydrochemical studies of two active springs around the fossil travertines were conducted to study their genesis the results show that 1 the modern springs discharge waters with high temperature 70 c near neutral ph 6 3 8 34 and high saturation indices of calcite and aragonite 2 the fossil travertines contain calcite and small amounts of mn fe oxides halite thenardite and non carbonate debris 3 the calcite include ray crystals dendrite crystals platy crystals and spike crystals and 4 13c and 18o of the fossil travertines at reshuitang range from 1 59 to 0 87 and 6 48 to 7 80 respectively according to comparison between the travertines at reshuitang and other travertines in tengchong all these travertines are thermogene travertines with a large contribution of mantle degassing to their parent co2 but are formed at different temperatures the fossil travertines at reshuitang similar to those at shuzhishi are formed at high temperatures near 100 c which results in weak microbial activities during the formation of the fossil travertines most of the calcite crystals at reshuitang were non equilibrium products precipitated directly from the spring waters during the deposition process while the spike crystals originated from diagenetic dissolution of large calcite crystals comparison between the fossil travertines at reshuitang and other smooth slope travertines from other areas shows these smooth slope travertines have different lithofacies and fabrics in smooth slope environments temperature may control the distribution and development of microbes and the intensity of co2 degassing and consequently cause the precipitation of contrasting fabrics and lithofacies

a benthic δ13c based proxy for atmospheric pco2 over the last 1 5 myr 1 a high resolution marine proxy for atmospheric pco2 is needed to clarify the phase lag between pco2 and marine climate proxies and to provide a record of orbital scale pco2 variations before the oldest ice core measurement at 800 ka benthic 13c data should record deep ocean carbon storage and thus atmospheric pco2 this study finds that a modified 13c gradient between the deep pacific and intermediate north atlantic 13cp correlates well with pco2 13cp reproduces characteristic differences between pco2 and ice volume during late pleistocene glaciations and indicates that pco2 usually leads terminations by 0 2 3 7 kyr but lags by 3 10 kyr during two failed terminations at 535 and 745 ka 13cp gradually transitions from 41 to 100 kyr cyclicity from 1 3 0 7 ma but has no secular trend in mean or amplitude since 1 5 ma the minimum pco2 of the last 1 5 myr is estimated to be 155 ppm at 920 ka

nonstationary phase of the plio pleistocene asian monsoon paleoclimate records indicate that the strength of the asian summer monsoon is sensitive to orbital forcing at the obliquity and precession periods 41 000 and 23 000 years respectively and the extent of northern hemisphere glaciation over the past 2 6 million years the timing phase of strong monsoons has changed by 83 degrees in the precession and 124 degrees in the obliquity bands relative to the phase of maximum global ice volume inferred from the marine oxygen isotope record these results suggest that one or both of these systems is nonstationary relative to orbital forcing

an early cretaceous w sn deposit and its implications in southeast coastal metallogenic belt constraints from u pb re os ar ar geochronology at the feie shan w sn deposit se china the feie shan w sn deposit is in eastern guangdong province which is a newly explored deposit in the southeastern coastal metallogenic belt in order to constrain the age of mineralization in the feie shan w sn deposit we collected molybdenites and hydrothermal biotite of the feie shan w sn deposit for dating the tungsten mineralization is spatially associated with the biotite monzonitic granite porphyry la mc icp ms zircon u pb dating of the biotite monzonitic granite porphyry yielded a weighted mean pb u age of 139 2 1 7 ma which was interpreted as the emplacement age of the biotite monzonitic granite porphyry the re os model ages ranged from 137 3 2 0 ma to 146 1 2 1 ma with a weighted mean age of 140 6 1 9 ma and ar ar isotopic analyses of hydrothermal biotite yield a plateau ar ar age of 135 1 0 8 ma these dates obtained via three independent geochronological techniques constrained the ore forming age of the feie shan deposit and linked the genesis of the ore to the underlying biotite monzonitic granite porphyry combined with previous studies it is suggested that there is a period at 144 132 ma for w sn mineralization in the southeastern coastal metallogenic belt the feie shan w sn deposit belongs to the 144 132 ma metallogenic events in the scmb in a geodynamic setting of lithospheric extension

evolution of the arid climate in high asia since 1 ma evidence from loess deposits on the surface and rims of the tibetan plateau the formation and development of the arid climate in high asia remain controversial this is largely because of the scarcity of continuous high resolution geological records from the asian interior region thick loess sequences deposited on the surface of the tibetan plateau and its rims provide great potential to reconstruct a high resolution history of the formation and evolution of high asia arid climate based on detailed investigations of the grain size and carbonate content of representative loess sequences in high asia a persistent drying of high asia occurred in the past 1 ma and two major rapid drying events occurred at about 0 9 0 8 ma and 0 5 ma persistent and rapid stepwise uplifts of the tibetan plateau since the mid pleistocene might play a dominant role in the drying of high asia although the mid pleistocene global cooling may partially contribute to the event

genetic types mineralization styles and geodynamic settings of mesozoic tungsten deposits in south china abstract south china hosts the most abundant and largest tungsten w deposits in the world being a famous w metallogenic region located at the eastern part of the south china block which was formed by amalgamation of the yangtze and cathaysia blocks during the neoproterozoic these w deposits were mainly formed during the mesozoic the w mineralization is dominanted by greisen quartz vein skarn and porphyry types all of which are genetically related to the evolution of highly fractionated granitoids four episodes of w mineralization are recognized 1 late triassic 230 210 ma in the central and western parts of south china 2 middle jurassic ca 170 ma to early cretaceous ca 140 ma in the interior of south china with the mineralization being concentrated in southern jiangxi province between 165 and 150 ma 3 early cretaceous 136 120 ma with deposits across south china and 4 late cretaceous 100 80 ma mainly in the southwestern parts of south china these four periods of mineralization are closely related to the closure of paleo tethys and subduction of the paleo pacific plate in the late triassic these two events caused local extensional environments facilitating emplacement of the peraluminous granitoids and formation of the w deposits in the middle jurassic break off of the subducting oceanic plate resulted in emplacement of highly fractionated granites in the nanling region later anticlockwise rotation of the paleo pacific plate created widespread s type granitoids and associated middle jurassic to early cretaceous w mineralization in the interior of south china since 136 ma rollback of the subducting pacific plate resulted in weak w mineralization across south china finally a change of direction in the retreating plate from se to ese resulted in intensive mineralization of the southwestern part of south china

relating permeability to the structural setting of a fault controlled hydrothermal system in southeast oregon usa 1 it is generally accepted that high permeability pathways are required to bring hydrothermal fluids to the surface from depth at elevated temperatures and these pathways are commonly associated with faulting the orientation and mode of fractures that develop as a result of fault slip are dependent on the state of stress and the geometry of the fault system which in turn control the near fault permeability structure we hypothesize that temperature data collected in fault controlled hydrothermal systems may be used to delineate the extent of the near surface breakdown region of the controlling fault and may provide insight regarding the fault geometry and stress field here we present a geostatistical analysis of 1550 ground and spring temperature measurements in an area of active hydrothermal discharge located at mickey hot springs in southeast oregon indicator kriging was used to treat heterogeneity across the site prior to in category simulation of temperature as a continuous variable the analysis indicates that zones of high medium and low temperature at the site arise from different physical mechanisms which we propose are related to the underlying modes of fracturing and the dominant mechanisms of heat and mass transport i e by advection or diffusion the findings of this study suggest that thermal hydrologic data of the type presented here may be useful for understanding fault zone characteristics and for developing conceptual models of fault controlled fluid flow

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

earthquake impact on fissure ridge type travertine deposition the role of travertine fissure ridges in reconstructing tectonics and related earthquakes is a challenging issue of recent debate directed at delineating historical prehistorical seismic records indeed direct measurements on a travertine fissure ridge immediately after a seismic event have never been previously performed we describe the co and post seismic effects of a m 3 6 earthquake on fluid flow and travertine deposition in a geothermal area of tuscany italy direct observation allows us to demonstrate that thermal spring re activation is directly influenced by transient seismic waves therefore providing a basis for reconstructing seismic events in the past

asynchronizing paleo pacific slab rollback beneath se china insights from the episodic late mesozoic volcanism abstract extensive late mesozoic igneous rocks in se china have been widely considered to be generated under the paleo pacific tectonic regime previous studies suggested a fundamental oceanward younging trend for the igneous rocks further implying a nw ward paleo pacific subduction model with gradual slab rollback new la icp ms zircon u pb dating results show that early stage of the late mesozoic volcanic sequences also known as the lower volcanic series in fujian province was formed in three episodes 160 148 ma for the changlin formation 145 130 ma for the nanyuan formation and 130 127 ma for the xiaoxi formation among which the second episode made the volcanism climax thus the entire lower volcanic series in fujian were formed earlier than those in zhejiang 140 118 ma displaying a ne ward younging trend parallel to the potential subduction belt besides in situ hf isotope analyses on dated zircons yield an ehf t range of 19 2 to 1 7 for the lower volcanic series in fujian the majority of the studied volcanic rocks have more radiogenic hf than that of the metamorphic basement requiring the involvement of juvenile components in their origin moreover the zircon ehf t value increases with time in each single area as well as the igneous rocks elsewhere in se china except for the changlin formation which shows very opposite isotopic varying trend increasing zircon ehf t values imply an increasing material contribution of contemporaneous underplated mantle derived magmas which was plausibly induced by gradual crustal decompression as well as the ne ward younging trend of the lower volcanic series it is also identified that the juvenile material contribution in the igneous petrogenesis gradually took place in the same direction along the coastal area thus here we propose an asynchronizing paleo pacific slab rollback model during 150 120 ma to account for the episodic magmatism and crustal extension in se china on the contrary decreasing zircon ehf t values of the changlin formation volcanics indicate that they were formed under enhanced crustal compression probably induced by slab advance on the other hand the upper volcanic series in fujian were formed during 110 88 ma coevally to those in zhejiang with more depleted zircon hf isotopic compositions than the lower volcanic series as well indicating that the entire coastal se china was under the back arc tectonic setting during that time

earthquake triggered soft sediment deformation structures seismites in travertine deposits abstract earthquakes related soft sediment deformations seismites are relevant structures to help reconstructing the palaeoseismicity in a region nevertheless although seismites have been described for a large variety of palaeo environments and stratigraphic settings they are rare and in some cases ambiguous structures in this paper we document for the first time impressive seismites affecting a latest quaternary travertine deposit located in southern tuscany serre di rapolano italy these structures are extremely relevant as seismites have been never described for this kind of terrestrial deposits the seismites developed within a 2 5 m thick stratigraphic succession made of alternating terrigenous and carbonate sediments embedded within the travertine deposits earthquake produced liquefaction and fluidization of some terrigenous levels and the injection of fluidized silty sediments dykes and sills into carbonate and terrigenous levels slumped levels and associated decollement surfaces produced highly non cylindrical folds overall induced by the loss of brittle shear strength along the basin slopes the occurrence of these soft sediment deformations implies an important seismic event that took place in a time spam encompassed between 84 8 and 48 92 5 08 ka in an area characterized by low seismicity and scarce knowledge of its seismotectonic setting their spectacular exposition and preservation in saw cuts of an abandoned quarry cava oliviera quarry highlights their relevance and importance

substrate geology controlling different morphology sedimentology diagenesis and geochemistry of adjacent travertine bodies a case study from the sanandaj sirjan zone western iran abstract a travertine fissure ridge and travertine mound are situated 800 m from each other at the western margin of the active tectono volcanic sanandaj sirjan zone western iran despite their close proximity the two geobodies show a difference in morphology lithofacies lithotypes diagenesis and geochemistry petrographic analysis of the fissure ridge carbonates revealed homogeneous sparitic fabrics with dendritic structures reflecting precipitation under fast flowing conditions from calcite supersaturated spring water the mound carbonates are much more heterogeneous and display dominantly micritic fabrics with mainly volcanic clasts reflecting a lower energy flow regime and lower calcite saturation in contrast to the limited diagenetic overprint of the fissure ridge carbonates the more porous mound carbonates are affected by dissolution cementation and formation of mn fe oxide hydroxides attesting of a strong control on porosity by early diagenetic processes the widespread bright luminescent calcite phases especially in sparitic fabrics within both geobodies display high mn concentrations in calcite indicating suboxic precipitation conditions the overlapping 87sr 86sr signatures and 13c signatures point to a mixture of co2 that dominantly originated from dissolution of the marine carbonate qom formation oligo miocene the different 18o signatures indicate different upwelling systems caused by different substrate settings the fissure ridge formed on a hard and brittle limestone substrate with precipitation from dominantly subsurface sourced fluids the mound travertine formed on top of fairly unconsolidated and fractured volcanic strata the depleted 18o signatures and impure micrite dominated fabrics of the mound travertine reflect precipitation from thermal water that mixed with surrounding groundwater this difference is also reflected in a different calculated precipitation temperature that varies between 4 and 21 c for the mound versus 25 50 c for the fissure ridge our findings show that subsurface geology exerts a major control on precipitation processes resulting in differences in travertine morphology sedimentology diagenesis and geochemistry despite that the travertine bodies occur adjacent to each other

plateau versus fissure ridge travertines from quaternary geothermal springs of italy and turkey interactions and feedbacks between fluid discharge paleoclimate and tectonics abstract morphologically different deposits of thermal travertines are known worldwide but what factors controlled their morphology volume and growth for tens of thousands of years is only partially understood two main morphotypes of quaternary thermal travertines are reconsidered here to understand the reasons for their differential growth the fissure ridge travertines of denizli basin western turkey and the travertine plateau of tivoli central italy for comparable longevities and average vertical deposition rates the main differences between the studied travertines are as follows 1 volume of the travertine plateau is about one hundred times larger than each fissure ridge 2 despite a larger volume the travertine plateau does not produce relief whereas the fissure ridges produce a characteristic prominent topography 3 the travertine plateau grew primarily through lateral progradation whereas the fissure ridges through vertical aggradation 4 travertine deposition occurred in different environments principally low energy flat or shallow environments at tivoli and high energy inclined environments at denizli 5 the growth of the tivoli plateau occurred in a subsiding basin whereas the fissure ridges were not influenced by significant subsidence 6 c and o isotope signatures from the two studied travertines are different 7 despite similar annual precipitations the present water discharge in the tivoli area is about ten times greater than that of the denizli basin u series ages from the two deposits are correlated with paleoclimate oscillations at regional and global scales geological field evidence together with paleoclimate correlations suggest that in both the study cases the main body of travertine deposits the bedded travertine grew preferentially when the water table was high warm and or humid periods conversely when the water table was depressed cold and or dry periods the tivoli travertine underwent partial erosion and the denizli ridges were cut by axial veins and lateral sill like structures filled by banded sparitic travertine a comparative model is proposed where the main factor driving the difference in the morphostratigraphic architecture of fissure ridges and travertine plateaus is the volume of water discharge a high discharge rate resulted in the precipitation of caco3 far away from the springs hence driving the lateral progradation of the tivoli plateau a reduced discharge rate caused travertine precipitation close to the springs thus causing the vertical aggradation of the denizli fissure ridges paleoclimate oscillations must have controlled the amount of fluid discharge which in turn must have influenced the opening of the feeding fractures by an increased pore pressure

southern hemisphere forcing of pliocene δ18o and the evolution of indo asian monsoons monsoon phase relationships consistent with direct orbital forcing across the entire indo asian region including marine and terrestrial proxies from the chinese loess plateau the south china sea and the arabian sea strong pliocene summer and winter monsoons were in phase with one another strengthened at obliquity minima and precession minima the summer monsoon was also strengthened at precession maxima yielding a semiprecession spectral signal strong pliocene monsoons at orbital extremes indicate a direct response to fast physics processes including sensible heating and cooling of the asian landmass and for the summer monsoon the export of latent heat from the southern indian ocean as northern hemisphere ice volume grew into the pleistocene the timing of strong winter and summer monsoons drifted apart becoming influenced by the combined effects of fast physics and slow physics ice volume variables the phase of strong winter monsoons shifted toward ice maxima and the phase of strong summer monsoons shifted toward ice minima

development of east asian summer monsoon environments in the late miocene radiolarian evidence from site 1143 of odp leg 184 abundant radiolarians are preserved in the relatively complete upper miocene section of odp site 1143 three radiolarian zones rn6 rn7 and rn8 are recognized on the basis of diartus petterssoni total range in rn6 6 7 ma variations in the abundance of radiolarians especially pyloniid forms radiolarian flux and species diversity are good proxies of upwelling which similar to today s was likely driven by summer monsoons these radiolarian paleomonsoon proxies indicate that the east asian summer monsoon first initiated close to the middle late miocene boundary at similar to 12 11 ma and reached a maximum strength at similar to 8 24 ma therefore the initiation of the east asian summer monsoon was likely earlier than the first indian monsoon which appeared similar to 8 myr ago c 2003 elsevier b v all rights reserved

role of the tian shan mountains and pamir plateau in increasing spatiotemporal differentiation of precipitation over interior asia abstractnumerical simulations were conducted to determine the impact of the tian shan mountains and pamir plateau on arid conditions over interior asia these topographies are crucial for the diffe

shrimp u pb zircon ar ar muscovite and re os molybdenite isotopic dating of the taoxikeng tungsten deposit south china block abstract the taoxikeng tungsten deposit is located in the jiangxi province in the southern part of china and is one of the largest wolframite quartz vein type tungsten deposits in the country the deposit is situated in sinian neoproterozoic to permian strata at the contact with the buried taoxikeng granite sensitive high mass resolution ion microprobe shrimp zircon u pb analysis of the granite has yielded dates of 158 7 3 9 and 157 6 3 5 ma which are interpreted as the emplacement age of the granite molybdenite separated from ore bearing quartz veins yields a re os isochron age of 154 4 3 8 ma and muscovite separated from greisen between the granite and country rocks yields 40ar 39ar plateau ages of 153 4 1 3 and 152 7 1 5 ma these dates obtained from three independent geochronological techniques constrain the ore forming age of the taoxikeng deposit and link the ore genesis to that of the underlying granite the taoxikeng deposit is an example of a jurassic regional scale tungsten tin ore forming event between 160 and 150 ma in the nanling region of the south china block the deposit s strikingly low rhenium contents 4 9 to 13 0 10 3 g g in molybdenite suggests that the ore was derived from a crustal source this conclusion is consistent with previously published constraints from s d and o stable isotopes sr nd systematics and petrogenetic interpretations of spatially related granites

genesis and diagenesis of travertine futamata hot spring japan abstract genetic and diagenetic processes of travertine were examined at futamata hot spring where both active and inactive subfossil and fossil travertines are present geochemical and geomicrobiological analyses of active travertines reveal that abiotic process of caco3 precipitation is predominant photosynthetic inhibition of caco3 precipitation occurs at the upstream while the cyanobacterial population is low in the downstream resulting in photosynthesis induced caco3 precipitation only in the midstream nonetheless microorganisms have an effect upon depositional fabrics and filamentous cyanobacteria possessing non acidic sheaths contribute to the particle trapping binding and the generation of pore space both active and inactive travertines are mainly composed of calcite however active travertine in the up midstream also contains some aragonite due to high rates of co2 degassing active and subfossil travertines are characterized by domal topography and relatively high flow rates are assumed due to the dominance of slope facies on the other hand fossil travertines are characterized by fissure ridge topography and relatively low flow rates are assumed due to the dominance of crest and marsh facies the elemental composition of travertines primarily reflects their constituent minerals and the active travertines consisting of both aragonite and calcite show higher sr ba na and k contents whereas travertines consisting solely of calcite show higher mg and mn contents due to elevated mn content bright cathode luminescence is exhibited by the primary calcite of active travertines most fossil travertines have experienced prominent diagenetic alteration in the vadose zone and are commonly cemented and recrystallized in addition to meteoric water percolating hot spring water was also involved in the diagenetic process combined with the results of u th dating our results suggest that the formation of fissure ridge travertines at futamata hot spring began approximately 20 thousand years ago ka via fault activity which terminated at around 7 ka and the domal travertines were formed by hot spring water discharging from several vents

studying travertines for neotectonics investigations middle late pleistocene syn tectonic travertine deposition at serre di rapolano northern apennines italy middle late pleistocene tectonic activity has been inferred through studies on travertine deposits exposed in a tract of the hinterland northern apennines a detailed study on the relationships between tectonics and travertine deposition coupled with 230th 234u age determination of travertines at cava oliviera quarry located close to serre di rapolano village southern tuscany northern apennines allowed us to recognise pleistocene faults whose activity has been referred to 157 24 ka at least travertine deposition was tectonically controlled by wsw ene striking oblique and normal faults associated to a main fault named as the violante fault this structure dissected a regional normal fault known as the rapolano fault early middle pliocene in age which bounded the eastern side of the pliocene siena basin and gave rise to space accommodation for clayey and sandy marine sediments hydrothermal circulation and related travertine deposition was favoured by the damaging enhancement due to the fault fault intersection tectonic activity has been also documented by deformation recorded by travertines which suggest a main tectonic event between 64 5 and 40 5 ka the tectonic activity described for the study area agrees with the quaternary tectonic evolution documented in the surrounding areas e g mt amiata and mt vulsini as well as the tyrrhenian margin of the central apennines indicating that a widespread tectonic activity affected the inner part of the apennines until the latest quaternary

a tectono genetic model for porphyry skarn stratabound cu au mo fe and magnetite apatite deposits along the middle lower yangtze river valley eastern china abstract the middle lower yangtze river valley metallogenic belt yrb situated along the northern margin of the yangtze craton is characterized by porphyry skarn stratabound cu au mo fe deposits in the areas of uplift and magnetite apatite deposits in cretaceous fault basins following detailed field investigations and a review of published data we recognize two episodes of magmatism and mineralization in the yrb 1 156 137 ma high k calc alkaline granitoids associated with 148 135 ma porphyry skarn stratabound cu au mo fe deposits and 2 135 123 ma shoshonitic series associated with 134 9 122 9 ma magnetite apatite deposits a type granitoids and associated alkaline volcanic have a small age range from 126 5 to 124 8 ma and are temporally spatially and genetically associated with the second episode the geodynamic history of the yrb did not experience the paleozoic to mesozoic lithospheric thickening that took place in the north china craton this process is inferred to be linked to partial melting of the delaminated lower crust at high pressures resulting in the development of c type adakitic rocks the petrochemical and sr nd isotopic data show that both the shoshonitic series and a type granitoids are quite different from adakites with only some of the k calc alkaline granitoids having adakitic signatures previous ore genesis models were established based on an assumed relationship with adakites and a continuous tectono thermal evolution from 150 to 100 ma all data obtained for the middle lower yangtze river region consistently show that the tan lu regional strike slip fault zone initiated at 233 6 to 225 6 ma from the collision between the north china and yangtze cratons and was reactivated at ca 160 ma the tan lu fault was caused by the oblique subduction of the izanagi plate which along the yrb the low angle subducted slab and the overlying crust was disrupted or broken due to the disharmonious movement of the two blocks the high k calc alkaline granitoids magmas were derived from melting of the subducted slab with some input of crustal material these magmas were emplaced at the intersections between ne and ew trending faults and formed porphyry skarn stratabound cu au mo fe deposits between 156 and 137 ma after 135 ma the subducted plate changed its direction of motion to northeast now running parallel to the eurasian continental margin and leading to large scale continental extension the shoshonitic series and subsequent a type granitoids magmatism and the development of magnetite apatite ores in the yrb took place in both fault basins and ne trending rifts between 135 and 124 ma

sensitivity of climate to late cenozoic uplift in southern asia and the american west numerical experiments experiments with general circulation models with no mountains half mountains and full modern mountains show the sensitivity of atmospheric circulation patterns to progressive amounts of uplift the experiments were motivated by geologic evidence for large kilometer scale uplift in the late cenozoic in southern asia and the american west particularly within the last 10 m y in january the amplitude of the mid latitude upper tropospheric planetary waves increased with uplift and the low level winds were progressively blocked or diverted around the topographic features in july the progressive uplift caused monsoonlike circulations to develop in the vicinity of the colorado and tibetan plateaus atmospheric heating rates midtroposphere vertical motion and upper tropospheric planetary wave amplitudes varied approximately linearly with progressive uplift these results suggest that geologically recent kilometer scale uplift may have had climatic consequences comparable in magnitude and pattern to those of earlier stages of uplift comparison of the simulated climatic effects of uplift with the geologic evidence for late cenozoic climatic change especially for the last 10 m y is given in accompanying papers

an astronomically tuned 8 1 ma eolian record from the chinese loess plateau and its implication on the evolution of asian monsoon the chinese loess paleosol sequences have led to a great understanding of the evolution of the east asian monsoon eam in the quaternary however evolution of the eam in the late miocene and pliocene is quite blurry hindering our understanding of the mechanisms driving the eam thus we obtained high resolution grain size records of 8 1 ma from the thickest eolian red clay sequence at chaona on the chinese central loess plateau and astronomically tuned the grain size records to the orbital variation with a time resolution of 1 5 ka to 5 8 ka the variability of coarse size fraction a recognized proxy for the east asian winter monsoon eawm indicates a persistent but stepwise intensification of the eawm at ca 5 5 ma 3 6 ma 2 6 ma and 1 ma filtering of this proxy record at 100 41 and 21 ka bands was conducted to trace the evolution of the eawm in a frequency domain over 8 1 ma temporal variations of these three cycles show a remarkable simultaneous enhancement at ca 5 5 ma indicating a synchronous intensification of high and low latitude signals in the eawm record we suggest that the closure of panama seaway to form the north atlantic thermohaline circulation and the high latitude cooling during this time might collectively trigger such a response copyright 2011 by the american geophysical union

simulated variations of eolian dust from inner asian deserts at the mid pliocene last glacial maximum and present day contributions from the regional tectonic uplift and global climate change northern tibetan plateau uplift and global climate change are regarded as two important factors responsible for a remarkable increase in dust concentration originating from inner asian deserts during the pliocene pleistocene period dust cycles during the mid pliocene last glacial maximum lgm and present day are simulated with a global climate model based on reconstructed dust source scenarios to evaluate the relative contributions of the two factors to the increment of dust sedimentation fluxes in the focused downwind regions of the chinese loess plateau north pacific the model generally produces a light eolian dust mass accumulation rate mar of 7 1 0 28 g cm2 kyr during the mid pliocene a heavier mar of 11 6 0 87 g cm2 kyr at present and the heaviest mar of 24 5 1 15 g cm2 kyr during the lgm our results are in good agreement with marine and terrestrial observations these mar increases can be attributed to both regional tectonic uplift and global climate change comparatively the climatic factors including the ice sheet and sea surface temperature changes have modulated the regional surface wind field and controlled the intensity of sedimentation flux over the loess plateau the impact of the tibetan plateau uplift which increased the areas of inland deserts is more important over the north pacific the dust mar has been widely used in previous studies as an indicator of inland asian aridity however based on the present results the interpretation needs to be considered with greater caution that the mar is actually not only controlled by the source areas but the surface wind velocity

are u th dates correlated with historical records of earthquakes constraints from coseismic carbonate veins within the north anatolian fault zone u th dating of carbonate veins in connection with active tectonics has recently been used as an attractive tool for constraining the absolute timing of late quaternary crustal deformations in this study for the first time we correlate u th ages of travertine deposits in coseismic fissures along the north anatolian fault zone with records of paleoseismological studies supported by historical earthquake catalogued data u th ages are assessed in relation to the recurrence interval and the size and epicenter distance of major holocene earthquakes our statistical evaluations on age correlations indicate that the carbonate vein precipitation is concentrated in eight different periods along the north anatolian fault zone the periods are well correlated with historical earthquake records and with previous dating results of the nearby trench studies at least six of the periods correspond to the earthquakes reported in the historical catalogues the age correlations of carbonate precipitation intervals for the last millennium show a recurrence along the eastern north anatolian fault zone with a mode at 130 330 years that is consistent with a previously proposed paleoseismic recurrence interval of the fault recorded events in carbonate veins indicate a close epicenter d vi paleoearthquakes our results suggest that coseismic carbonate veins could be used to determine paleoseismic records as a supplementary tool to augment paleoseismological techniques this tool has advantages over traditional paleoseismological methods for the understanding of long term earthquake behavior particularly for prehistoric late pleistocene events which cannot be dated easily by traditional paleoseismological methods

delayed build up of arctic ice sheets during 400 000 year minima in insolation variability an east asian winter monsoon proxy record using grain size variations in chinese loess over the past 900 000 years shows that for up to 20 000 years after the interglacials at 400 000 year intervals the weak monsoon winds maintain a mild non glacial climate at high northern latitudes qingzhen hao and colleagues present a record of grain size variations in the chinese loess plateau a proxy of variations in the strength of the east asian winter monsoon and show that relatively high insolation at 400 000 year intervals held off the inception of the subsequent ice age for about 20 000 years relative to other glacial inceptions mechanistically the extension of warm conditions was probably linked to a weak siberian high pressure system associated with a delayed build up of northern ice and snow the authors speculate that these observations imply that arctic climate may remain in non glacial mode for more than 40 000 years even in the absence of anthropogenic greenhouse gases knowledge of the past variability of climate at high northern latitudes during astronomical analogues of the present interglacial1 may help to inform our understanding of future climate change unfortunately long term continuous records of ice sheet variability in the northern hemisphere only are scarce because records of benthic 18o content represent an integrated signal of changes in ice volume in both polar regions2 however variations in northern hemisphere ice sheets influence the siberian high3 an atmospheric pressure system so variations in the east asian winter monsoon eawm as recorded in the aeolian dust deposits on the chinese loess plateau can serve as a useful proxy of arctic climate variability before the ice core record begins here we present an eawm proxy record using grain size variations in two parallel loess sections representative of sequences across the whole of the chinese loess plateau over the past 900 000 years the results show that during periods of low eccentricity and precessional variability at approximately 400 000 year intervals the grain size inferred intensity of the eawm remains weak for up to 20 000 years after the end of the interglacial episode of high summer monsoon activity and strong pedogenesis in contrast there is a rapid increase in the eawm after the end of most other interglacials we conclude that for both the 400 000 year interglacials the weak eawm winds maintain a mild non glacial climate at high northern latitudes for much longer than expected from the conventional loess and marine oxygen isotope records during these times the less severe summer insolation minima at 65 n ref 4 would have suppressed ice and snow accumulation leading to a weak siberian high and consequently weak eawm winds

evaluating the geogenic co2 flux from geothermal areas by analysing quaternary travertine masses new data from western central italy and review of previous co2 flux data abstract quantification of carbon fluxes between solid earth and its atmosphere is necessary to understand the global geological carbon cycle some of the main co2 contributors are metamorphism and magmatic mantle degassing co2 is discharged from active and quiescent volcanoes fault zones geothermal systems and co2 rich groundwater here a new method for the estimation of the geogenic flux of co2 from tectonically active regions based on the volume composition and age of travertine deposits is proposed the method is applied to the travertine deposits of western central italy where travertine deposition is driven by degassing of co2 charged groundwater results show that the study areas are characterized since middle pleistocene by diffuse co2 degassing processes with time averaged co2 fluxes ranging between 1 24 0 12 106 mol y 1 km 2 and 1 38 0 42 106 mol y 1 km 2 these values are of the same order of magnitude of carbon dioxide fluxes measured by different methods in western central italy and are higher than the global baseline co2 flux from high heat flow regions the review of the available 234u 230th and 14c data shows that the co2 degassing processes that affects western central italy nowadays were already active at least 350 ka ago proving that this region is a globally relevant case for the study of earth degassing considering the widespread occurrence of travertine deposits in tectonically active areas worldwide the proposed approach can be used as a reliable tool to estimate the co2 flux in different geodynamic settings within system earth

multiple mesozoic mineralization events in south china an introduction to the thematic issue mesozoic mineral deposits in south china include world class deposits of w sn and sb and those that provide the major sources of ta cu hg as tl pb zn au and ag for the entire country these deposits can be classified into polymetallic hydrothermal systems closely related to felsic intrusive rocks sn w mo granites cu porphyries polymetallic and fe skarns and polymetallic vein deposits and low temperature hydrothermal systems with no direct connection to igneous activities mvt deposits epithermal au and sb deposits recent studies have shown that they formed in the triassic indosinian jurassic cretaceous early yanshanian and cretaceous late yanshanian stages indosinian deposits include major mvt pb zn ag deposits and granite related w sn deposits early yanshanian deposits are low temperature sb au and high temperature w sn and cu porphyry types many late yanshanian deposits are low temperature au as sb hg and u deposits and also include high temperature w sn polymetallic deposits the formation of these deposits is linked with a specific tectonothermal evolution and igneous activities this special issue brings together some of the latest information in eight papers that deal with the origins and tectonic environments of mineral deposits formed in these stages we anticipate that this issue will stimulate more interests in these ore deposits in south china

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

molybdenite re os dating zircon u pb age and geochemistry of granitoids in the yangchuling porphyry w mo deposit jiangnan tungsten ore belt china implications for petrogenesis mineralization and geodynamic setting abstract the yangchuling w mo deposit located in the jiangnan porphyry skarn jnb tungsten ore belt is the first recognized typical porphyry w mo deposit in china in the 1980 s stockworks and disseminated w mo mineralization occur in the roof pendant of a 0 3 km 2 monzogranitic porphyry stock that intruded into a granodiorite stock hosted by neoproterozoic phyllite and slate la icpms zircon u pb analyses suggest that of the monzogranitic porphyry and granodiorite were formed at 143 8 0 5 ma and 149 8 0 6 ma respectively six molybdenite samples yielded a re os weighted mean age of 146 4 1 0 ma geochemical data show that both granodiorite and monzogranitic porphyry are characterized by enrichment of large ion lithophile elements lile relative to high field strength elements hfse indicating a peraluminous nature a cnk 1 01 1 08 two granitoids are characterized by a negative slope with significant light ree heavy ree fractionation la yb n 8 38 23 20 and negative eu anomalies eu eu 0 69 0 76 the p 2 o 5 contents of the yangchuling granitoids range from 0 12 to 0 17 and exhibit a negative correlation with sio 2 reflecting that they are highly fractionated i type they have high initial 87 sr 86 sr ratios 0 7104 0 7116 low negative e nd t 5 05 to 5 67 and homogeneous e hf t between 1 39 and 2 17 indicating similar sources additionally two stage nd model ages t dm2 of 1 3 1 4 ga and two stage hf model ages t dm2 of 1 2 1 3 ga are consistent indicating that neoproterozoic crustal rocks of the shuangqiaoshan group could have contributed to form the yangchuling magmas considering the two groups of parallel late mesozoic ore belts namely the jiangnan porphyry skarn tungsten belt jnb in the south and the middle lower yangtze river porphyry skarn cu au mo fe ore belt yrb in the north the nanling granite related w sn ore belt nlb in the south the neighboring qin hang porphyry skarn cu mo hydrothermal pb zn ag ore belt qhb in the north as well as the southeastern coast porphyry skarn cu mo au ore belt scb recognized in south china in this paper we propose that the latest jurassic to earliest cretaceous granitoids and associated ores were formed during a tearing of the subducting izanagi slab this tearing of the subduction slab caused the upwelling of asthenosphere and the resulting mantle crust interaction the granitoid related w ore systems in jnb resulted from the remelting of the proterozoic crust the mafic ultramafic volcanic rocks of the shuangqiaoshan group intercalated with phyllite and slate ophiolitic melange and magmatic arc rocks mainly comprising i type granite basalt andesite rhyolite pyroclastics together with subduction related metasomatized lithospheric mantle would have provided additional mantle material in this case the partial melting of rocks of the shuangqiaoshan group can produce s i and transitional type granitoids after strong differentiation it formed tungsten bearing granitoids characterized by enrichment of high alkali silicon and volatile components in the yangchuling mine area the small monzogranitic porphyry stock has stronger fractionation volatile content and ore forming components than the older granodiorite resulting in the development of the porphyry w mo ore system