seasonal incursion of indian monsoon humidity and precipitation into the southeastern qinghai tibetan plateau inferred from tree ring δo18 values with intra seasonal resolution abstract incursion of the indian monsoon flow onto the qinghai tibetan plateau is an important regional moisture delivery mechanism but the causes of intra seasonal and longer term variations are poorly understood we observed a clear intra seasonal cycle in the oxygen isotope composition 18o of smith fir abies forrestii var georgei growing at two different altitudes high elevation site 29 39 n 94 42 e 4200 m a s l low elevation site 29 39 n 94 43 e 3800 m a s l on a se facing slope in the sygera mountains southeastern qinghai tibetan plateau mechanistic modeling suggests that 18o of precipitation which in turn depends on relative humidity and precipitation amount is important in controlling the intra seasonal tree ring isotopic cycle and we speculate that the same controls also operate on interannual and longer time scales if so multi century 18o records with intra seasonal resolution may enable us to infer long term variations in the incursion of the indian monsoon onto the qinghai tibetan plateau

the effect of soil hydrology on the oxygen and hydrogen isotopic compositions of plants source water abstract many studies have demonstrated that the isotopic composition of plants source water is the main factor affecting the isotopic composition of tree rings because of soil hydrological processes soil water as the source water for plants may isotopically differ from precipitation that contains climatic information such as surface temperature this study addresses the effects of soil hydrological processes on the isotopic compositions of soil water and discusses how these effects affect interpretations of tree ring data in isotopic dendroclimatology we collected precipitation soil gas at two depths 20 and 50 cm and twigs from a maple tree acer saccharum on a biweekly basis during the growing season in 1997 1999 at hanover nh usa water was extracted from the twig samples by vacuum distillation all water samples were analyzed for both d and 18 o soil co 2 was extracted from soil gas and measured for the 18 o values and using the soil temperature and assuming isotopic equilibrium between co 2 and h 2 o we calculated the 18 o values of soil water comparisons among the isotopic time series of each type of sample indicate the following 1 the isotopic composition of soil water is much less variable than that of precipitation suggesting isotopic mixing between waters of different precipitation events 2 in early spring soil water at all depths is isotopically similar to winter precipitation but with time the surface soil water becomes progressively enriched in deuterium and 18 o due to infiltration of summer rain and enrichment through soil water evaporation 3 the influence of summer precipitation decreases with increasing depth and soil at 50 cm can only receive water from large storms 4 replacement of old soil water with new infiltrating water is dependent upon frequency and intensity of growing season precipitation and it is generally more efficient in a wet year than in a dry year 5 the tree we studied uses water mainly from near surface soil layers 6 the d 18 o relationship in twig water indicates that soil water has experienced isotopic enrichment by evaporation these results have important implications for selecting sites for paleoclimatic studies using isotopic data of tree rings

geochemistry and geochronology of the sierra de gomez limestone hosted u deposit chihuahua implications for distribution of rio grande rift mineral deposits in northern mexico abstract uranium deposits form in a variety of settings they are partially controlled by the secular evolution of earth processes including deposits in extension related settings such as the intra cratonic rio grande rift plio quaternary volcanism mineral deposits and hydrothermal spots occur along the chihuahua central graben the age of the sierra de gomez u deposit is 1 8 ma based on la mc icp ms dating on a uranophane monocrystal which is contemporaneous with the late mineralization event of the pena blanca u deposit as well as rio grande rift rgr type deposits in chihuahua and intraplate volcanism studies of fluid inclusions in fluorite and late calcite indicate the presence of hydrocarbons and ch4 rich brine homogenization temperatures range from 87 to 112 c and the mean composition 2 0 mol nacl and 0 3 mol cacl with ch4 is comparable to mineralizing brines in mvt deposits and carbonated hydrocarbon reservoirs evolution of c and o stable isotopic values for the calcite cement in the sierra de gomez limestone hosted u deposit illustrates that two separate calcite precipitation events occurred 1 travertine filling karst structures in the presence of meteoric water and 2 u mineralization during deep hydrothermal fluid circulation that included interactions with a heat source and basement leaching in a regional context a metallogenic model suggests that the chihuahua trough area is deep enough to generate fluid migration by hydrothermal and or compaction processes through rgr extensional faults until a favorable trapping horizon is reached this causes uranium precipitation because water rock interaction processes generate a local redox barrier

hydrothermal mixing carbonate dissolution and sulfide precipitation in mississippi valley type deposits a large number of mississippi valley type mvt deposits are located within dissolution zones in carbonate host rocks some genetic models propose the existence of cavities generated by an earlier event such as a shallow karstification that were subsequently filled with hydrothermal minerals alternative models propose carbonate dissolution caused by the simultaneous precipitation of sulfides these models fail to explain either the deep geological setting of the cavities or the observational features which suggest that the dissolution of carbonates and the precipitation of minerals filling the cavities are not strictly coeval we present a genetic model inspired by the textural characteristics of mvt deposits that accounts for both the dissolution of carbonate and precipitation of sulfides and later carbonates in variable volumes the model is based on the mixing of two hydrothermal fluids with a different chemistry depending on the proportion of the end members the mixture dissolves and precipitates carbonates even though the two mixing solutions are both independently saturated in carbonates we perform reactive transport simulations of mixing of a regional groundwater and brine ascending through a fracture both saturated in calcite but with different overall chemistries ca and carbonate concentrations ph etc as a result of the intrinsic effects of chemical mixing a carbonate dissolution zone which is enhanced by acid brines appears above the fracture and another zone of calcite precipitation builds up between the cavity and the surrounding rock sulfide forms near the fracture and occupies a volume smaller than the cavity a decline of the fluid flux in the fracture would cause the precipitation of calcite within the previously formed cavities therefore dissolution of carbonate host rock sulfide precipitation within the forming cavity and later filling by carbonates may be part of the same overall process of mixing of fluids in the carbonate host rock

basin formation in the high himalaya by arc parallel extension and tectonic damming zhada basin southwestern tibet 1 the late miocene pleistocene zhada basin in southwestern tibet provides a record of subsidence and basin formation within an active collisional thrust belt the 800 m thick basin fill is undeformed and was deposited along an angular unconformity on top of tethyan strata that were previously shortened in the himalayan fold thrust belt modal sandstone petrographic data conglomerate clast count data and detrital zircon u pb age spectra indicate a transition from detritus dominated by a distal northern source to a local southern source this transition was accompanied by a change in paleocurrent directions from uniformly northwestward to basin centric at the same time the depositional environment in the zhada basin changed from a large braided river to a closed basin lake sedimentation in the zhada basin was synchronous with displacement on the qusum and gurla mandhata detachment faults which root beneath the basin and exhume midcrustal rocks along the northwestern and southeastern flanks of the basin respectively these observations indicate that accommodation for zhada basin fill was produced by a combination of tectonic subsidence and damming as midcrustal rocks were evacuated from beneath the zhada basin in response to arc parallel slip on crustal scale detachment faults

evidence for an early cretaceous mineralizing event above the basement sediment unconformity in the intracratonic paris basin paragenetic sequence and sm nd dating of the world class pierre perthuis stratabound fluorite deposit world class stratabound fluorite deposits are spatially associated with the basement sediment unconformity of the intracratonic paris basin and the morvan massif in burgundy france the reserves are estimated to be about 5 5 mt of fluorite within six fluorite deposits in this study we aim to determine the age of the major fluorite mineralization event of the pierre perthuis deposit 1 4 mt fluorite by a combined study of the paragenetic mineral sequence and sm nd dating on fluorite crystals fluorite occurs as isolated cubes or filling geodes in a triassic silicified dolomitic formation three fluorite stages associated with sphalerite pyrite galena barite and quartz have been distinguished using optical cathodoluminescence and scanning electron microscopes seven crystals of the geodic fluorite stage were analyzed for their rare earth element ree contents and their 147sm 144nd and 143nd 144nd isotopic compositions the normalized ree distribution displays homogeneous bell shaped patterns for all the geodic fluorite samples with a mid ree enrichment over the light ree and heavy ree the 147sm 144nd varies from 0 3108 to 0 5504 and the 143nd 144nd from 0 512313 to 0 512518 a six point sm nd isochron defines an age of 130 15 ma initial 143nd 144nd 0 512054 mswd 0 21 this sm nd isochron provides the first age for the stratabound fluorite sediment hosted deposit related to an unconformity in the paris basin and highlights a major early cretaceous fluid circulation event mainly above the basement sediment unconformity during a flexural deformation of the paris basin which relates to the rifting of the bay of biscay and the formation of the ligurian sea in the western europe domain

abundant climatic information in water stable isotope record from a maritime glacier on southeastern tibetan plateau climatic significance of ice core stable isotope record in the himalayas and southern tibetan plateau tp where the climate is alternately influenced by indian summer monsoon and mid latitude westerlies is still debated a newly drilled zuoqiupu ice core from a temperate maritime glacier on the southeastern tp covering 1942 2011 is investigated in terms of the relationships between 18o and climate parameters distinct seasonal variation of 18o is observed due to high precipitation amount in this area thus the monsoon june to september and non monsoon october to may 18o records are reconstructed respectively the temperature effect is identified in the annual 18o record which is predominantly contributed by temperature control on the non monsoon precipitation 18o record conversely the negative correlation between annual 18o record and precipitation amount over part of northeast india is mostly contributed by the monsoon precipitation 18o record the variation of monsoon 18o record is greatly impacted by the indian summer monsoon strength while that of non monsoon 18o record is potentially associated with the mid latitude westerly activity the relationship between zuoqiupu 18o record and sea surface temperature sst is found to be inconsistent before and after the climate shift of 1976 1977 in summer monsoon season the role of sst in the monsoon 18o record is more important in eastern equatorial pacific ocean and tropical indian ocean before and after the shift respectively in non monsoon season however the atlantic multidecadal oscillation has a negative impact before but positive impact after the climate shift on the non monsoon 18o record

origin of vein hydrothermal carbonates in triassic limestones of the espadan ranges iberian chain e spain dolomitization and hg bearing veins in the lower triassic limestones of the espadan ranges iberian chain e of spain

may september precipitation in the bhutan himalaya since 1743 as reconstructed from tree ring cellulose δ18o 1 we developed a 50 year tree ring 18o chronology for each of three tree species juniperus indica larix griffithii and picea spinulosa using a total of 12 trees four trees per species from the bhutan himalaya despite originating from different species sampled at two different altitudes the 18o chronologies are highly correlated with one another r 0 76 0 89 response analyses reveal that tree ring 18o values are controlled mainly by summer precipitation irrespective of species based on these results a robust 269 year 18o chronology was established to reconstruct the amount of may september precipitation based on data from four larch trees our tree ring 18o data show significant correlations with those from other regions of the himalaya and the tibetan plateau indicating that common signals related to monsoon activity are recorded in the data however at centennial timescales our data from bhutan show normal conditions during the 20th century whereas records from sites in western nepal and the southern eastern tibetan plateau show weakening trends in monsoon intensity during the last 100 200 years the weakening trends may be the result of a reduction in the meridional sea surface temperature gradient in the indian ocean during this time at continental scales the tree ring records show that areas more from ocean basins are particularly sensitive to reduced monsoon circulation correlation analyses suggest that the el nino southern oscillation enso plays an important role in modulating summer precipitation however the teleconnected relationship disappears during the period 1951 1970 coinciding with a negative phase of the pacific decadal oscillation pdo implying interdecadal modulation of the pdo on the influence of the enso on precipitation in bhutan

comments on u th he dating of fluorite application to the la azul fluorspar deposit in the taxco mining district mexico by pi et al mineralium deposita 39 976 982

sampling strategy and climatic implications of tree ring stable isotopes on the southeast tibetan plateau we explore the potential of tree ring cellulose d18o and d13c records for reconstructing climate variability in the southeast tibetan plateau our sampling strategy was designed to investigate intra and inter tree variability and the effects of the age of tree on d18o variation we show that intra tree d13c and d18o variability is negligible and inter tree coherence is sufficient to build robust tree ring d18o or d13c chronologies based on only four trees there is no evidence of an age effect regarding d18o in contrast with tree ring width in our warm and moist sampling site young tree d13c is not clearly correlated with monthly mean meteorological data tree ring d18o appears significantly anti correlated with summer precipitation amount regional cloud cover and relative humidity simulations conducted with the orchidee land surface model confirm the observed contribution of relative humidity to tree cellulose d18o and explain the weak correlation of d13c with climate by the non linear integration linked with photosynthesis altogether the tree ring cellulose d18o is shown to be a promising proxy to reconstruct regional summer moisture variability prior to the instrumental period 2010 elsevier b v

fluid inclusions in pre ore minerals from the carbonate hosted mercury deposits in the espadan ranges eastern spain abstract the fluids associated with pre ore minerals in the carbonate hosted mercury veins from the espadan ranges eastern spain have been studied using microthermometry cryo sem eds raman spectroscopy and crush leach analyses in order to determine their origin and the processes responsible for mineralization three primary fluid inclusion types have been found in quartz and dolomite 1 type s composed of liquid vapour mainly co 2 halite 2 type s v composed of liquid high density co 2 double bubble halite and 3 type v composed of high density co 2 n 2 mixtures type s fluid inclusions are preferentially trapped in betxi type veins characterized by the presence of hydrothermal dolomite whereas type v fluid inclusions are trapped almost exclusively in eslida type veins which were without dolomite from these data two different fluids can be inferred to occur during the period of formation of the veins 1 a complex polysaline brine of nacl kcl cacl 2 mgcl 2 so 4 2 h 2 o composition with a salinity of up to 33 eq wt nacl and a 2 co 2 n 2 rich fluid the brine halogen composition points to its secondary origin caused by the dissolution of underlying marine evaporites it is thought that these deposits were formed during jurassic or cretaceous rifting periods as a consequence of fluid mixing between a high salinity secondary brine and connate waters the generation of a co 2 n 2 rich phase caused the pressure increase of the fluids that favoured the hydraulic fracturing of the enclosing rock dolostone the origin of this volatile rich phase probably occurred due to the oxidation and thermochemical breakdown of the organic matter contained in the host rock this event is recorded by the coetaneous trapping of both aqueous and carbonic fluids in quartz crystals the formation conditions for the hypogene sulphide paragenesis are obscure but the coincidence between the preferential trapping of type v fluid inclusions the absence of hydrothermal dolomite and the major abundance of mercury in eslida type veins is thought to be linked to a mercury fractionation event to the vapour phase during the release of the volatiles

are the oxygen isotopic compositions of fitzroya cupressoides and nothofagus pumilio cellulose promising proxies for climate reconstructions in northern patagonia tree ring 18o chronologies from two native species fitzroya cupressoides and nothofagus pumilio in northern patagonia were developed to assess their potential for paleoclimate reconstructions the five annually resolved cellulose 18o chronologies two for f cupressoides and three for n pumilio are located on the andes along the steep west to east precipitation gradient over the common 60 years long interval the five site 18ocell chronologies exhibit a strong common signal as indicated by the significant mean intercorrelation r 0 61 p 0 05 and the high percentage 65 of total variance explained by the first empirical orthogonal function although correlation analyses reveal that the two mean species 18ocell chronologies are mainly modulated by december may temperature the n pumilio chronology shows a greater sensitivity to record temperature variations r 0 57 p 0 05 the 18ocell of n pumilio contains a regional temperature signal representative of a large area in southern south america under the influence of the southern annular mode this study indicates that 18ocell in n pumilio is a promising proxy to reconstruct past variations in temperature in south america south of 38 s

abrupt changes in indian summer monsoon strength during 33 800 to 5500 years b p speleothem proxy records from northeastern ne india reflect seasonal changes in indian summer monsoon strength as well as moisture source and transport paths we have analyzed a new speleothem record from mawmluh cave meghalaya india in order to better understand these processes the data show a strong wet phase 33 500 32 500 years b p followed by a weak dry phase from 26 000 to 23 500 years b p and a very weak phase from 17 000 to 15 000 years b p the record suggests abrupt increase in strength during the bolling allerod and early holocene periods and pronounced weakening during the heinrich and younger dryas cold events we infer that these changes in monsoon strength are driven by changes in temperature gradients which drive changes in winds and moisture transport into northeast india

δ 18 o records in water vapor and an ice core from the eastern pamir plateau implications for paleoclimate reconstructions this study is the first to examine 18o in daily water vapor at taxkorgan on the eastern pamir plateau the results show that changes in observed and simulated 18o values in water vapor precipitation at the event scale using a lmdz iso model were mainly affected by temperature the influences of humidity precipitation amount and different moisture sources such as the westerlies local evaporated moisture and polar air masses on 18o values are comparatively weak the combination of the 18o record from the muztagata ice core 58 km away from the study area and the lmdz iso simulated annual 18o pattern in precipitation at taxkorgan also demonstrated that temperature and particularly the temperature of the regions over which the southern branch of the westerlies flows is the most important factor controlling 18o variations the results from this study area which is dominated by the westerlies throughout the year are markedly different from those derived from parts of the tibetan plateau that are dominated by the combined influences of the westerlies in winter and the indian monsoon in summer the results suggested that the eastern pamir plateau is an ideal location to reconstruct past temperature variations and that the 18o records preserved in ice cores from the region are a suitable and robust proxy for temperature

secular temperature trends for the southern rocky mountains over the last five centuries 1 pre instrumental surface temperature variability in the southwestern united states has traditionally been reconstructed using variations in the annual ring widths of high altitude trees that live near a growth limiting isotherm a number of studies have suggested that the response of some trees to temperature variations is non stationary warranting the development of alternative approaches towards reconstructing past regional temperature variability here we present a five century temperature reconstruction for a highaltitude site in the rocky mountains derived from the oxygen isotopic composition of cellulose d 18 oc from bristlecone pine trees the record is independent of the co located growth based reconstruction while providing the same temporal resolution and absolute age constraints the empirical correlation between d 18 oc and instrumental temperatures is used to produce a temperature transfer function a forward model for cellulose isotope variations driven by meteorological data and output from an isotope enabled general circulation model is used to evaluate the processes that propagate the temperature signal to the proxy the cellulose record documents persistent multidecadal variations in d 18 oc that are attributable to temperature shifts on the order of 1c but no sustained monotonic rise in temperature or a step like increase since the late 19th century the isotope based temperature history is consistent with both regional wood density based temperature estimates and some sparse early instrumental records citation berkelhammer m and l d stott 2012 secular temperature trends for the southern rocky mountains over the last five centuries geophys res lett 39 l17701 doi 10 1029 2012gl052447

mass loss on himalayan glacier endangers water resources 1 ice cores drilled from glaciers around the world generally contain horizons with elevated levels of beta radioactivity including 36 cl and 3 h associated with atmospheric thermonuclear bomb testing in the 1950s and 1960s ice cores collected in 2006 from naimona nyi glacier in the himalaya tibet lack these distinctive marker horizons suggesting no net accumulation of mass ice since at least 1950 naimona nyi is the highest glacier 6050 masl documented to be losing mass annually suggesting the possibility of similar mass loss on other high elevation glaciers in low and mid latitudes under a warmer earth scenario if climatic conditions dominating the mass balance of naimona nyi extend to other glaciers in the region the implications for water resources could be serious as these glaciers feed the headwaters of the indus ganges and brahmaputra rivers that sustain one of the world s most populous regions

incision rate of the yellow river in northeastern tibet constrained by 10be and 26al cosmogenic isotope dating of fluvial terraces implications for catchment evolution and plateau building unlike other large rivers flowing out of tibet the yellow river escapes from the plateau towards the ne crossing no less than five nw se striking actively growing ranges and intervening basins thick plio quaternary deposits and fluvial terraces testify to a phase of aggra dation and sediment infill up to the average surface elevation 3200 3250 m a s l of the gonghe guide and qinghai lake basins a set of seven main terraces across the gonghe basin suggests progressive down cutting of the yellow river carving the 500 m deep longyang gorge at the basin exit 10be and 26al concentrations in quartz of surface and sub surface samples of four terraces constrain the timing of incision by determining the burial age of the deposit and the exposure age of its surface modelling the depth dependence of the 10be concentration and the 26al 10be ratio allows us to constrain the onset of the ongoing phase of incision to 120 250 ka these ages suggest long term incision rates between 2 6 mm a together with the present morphology of the yellow river terraces across the gonghe basin and the longyang gorge our results imply rapid river catchment evolution and interaction between river dynamics tectonic and climate in northeastern tibet

temperature signals in tree ring oxygen isotope series from the northern slope of the himalaya abstract oxygen isotope ratios 18 o are the most commonly used parameters recorded in paleoclimate archives since they link different natural archives via the water cycle tree ring 18 o 18 otr has been widely used for hydroclimate reconstructions in the himalaya however few of them record temperature signals which are dominant in himalaya ice core 18 o we hypothesize that the precipitation amount effect due to the south asian summer monsoon sasm may overprint temperature signals in 18 otr series the purpose of this study is to investigate whether temperature signals could be found in the 18 otr in locations where the influence of sasm is weak we developed a 105 yr 18 otr chronology from the northern slope of the western himalaya which greatly blocks the sasm our 18 otr clearly shows stronger correlations with temperature dominant winter and weak summer than summer precipitation signals it also agrees well with summer soil moisture 18 o simulated by the global isotope model lmdz4 r 0 72 1979 2010 in lmdz4 low winter temperature was found to increase winter snowfall and subsequent snow melt and thus to increase the contribution of winter snowfall to soil moisture in summer at the expense of summer precipitation since winter snowfall is more depleted than summer precipitation this leads to lower summer soil moisture 18 o the temperature signals found in our 18 otr series are consistent with those found in the dasuopu ice core 18 o this implies that 18 otr series from the southwest tibetan plateau tp with a weak monsoon hold great potential to capture temperature signals climate interpretations of 18 o proxies in the himalaya largely depend on the influence of seasonal water from the dominant atmosphere circulation systems of the westerlies or monsoon the 18 o proxies from the monsoon affected region have a higher potential for the reconstruction of boreal summer hydroclimate whereas 18 o proxies from westerly affected sites have a higher potential for temperature reconstructions

high elevation shrub ring δ18o on the northern slope of the central himalayas records summer may july temperatures abstract the potential of shrub ring oxygen isotopes sro as a paleoclimatic proxy is not well demonstrated in this study we explored the climate signals embedded in an sro chronology from saga on the northern slope of the central himalayas by correlation analysis with climate variables and comparison with tree ring and or ice core 18o records the saga sro had significant and positive correlations with may july temperatures in both local r 0 43 and moisture source areas r 0 49 during the period 1955 2015 ce while no significant correlations were found with hydroclimatic variables it is also in good agreement with two tree ring 18o series from the southern slope of the central himalayas the source of moisture to the site the temperature signals are further verified by an ice core 18o record from the tanggula mountains on the central tibetan plateau however it shows little similarity with the nearest himalayan ice core 18o record from dasuopu demonstrating temperature signals of different seasons this study suggests that sro could be used as an acceptable climate proxy like tree ring and ice core 18o to broaden the spatial extent of the paleoclimatic records network however we should be cautious when combining different proxies with climate signals of different seasons in paleoclimate studies

timing of fluvial terrace formation and concomitant travertine deposition in the upper sutlej river tirthapuri southwestern tibet and paleoclimatic implications abstract travertines are carbonates precipitated from hydrothermal springs and are relatively common on the tibetan plateau and occur along tectonically active faults the karakoram fault system is an active strike slip fault that extends from the pamir into southwestern tibet where it controls the course of the upper sutlej river and the occurrence of several hydrothermal springs including the tirthapuri hot springs multiple fluvial terraces that are partly capped by travertine are preserved in the tirthapuri area four main fluvial terrace levels labelled as t1 to t4 with increasing height above river were identified and several meter thick travertine platforms occur on the current river level as well as the t2 and t3 terraces sedimentological and petrographic observations suggest that the travertine platforms were deposited on active floodplains of the paleo and modern sutlej river and preserved from fluvial erosion because travertine precipitation was immediately followed by vertical river bed incision and thus terrace abandonment results of 230th u in combination with luminescence dating show that the deposition of travertine platform and river incision that led to the formation of t3 terrace 93 m above the sutlej took place at ca 127 5 ka the development of terrace t2 and overlying travertine platform 28 m above the sutlej occurred between ca 10 0 and 8 8 ka fluvial incision has arrived at the modern level at least ca 0 2 ka ago both the travertine deposition and major river incision are likely triggered by the intensified indian summer monsoon and are linked to phases of maximum monsoon strength during strong monsoon phases a large quantity of moisture is transported into southwestern tibet activating hot springs and thus travertine precipitation facilitating fluvial incision and stripping off sediments from the regional hill slopes at least over the last glacial cycle we suggest that the tirthapuri travertine and associated fluvial incision are sensitive indicators of peak monsoonal activity and can thus provide valuable insights into past climate change and climate driven landscape evolution on the southwestern tibetan plateau comparison of our findings with published data further suggests that monsoon controlled fluvial aggradation and incision during the early holocene is synchronous in southwestern tibet and the adjacent sector of the himalayan orogen north western sub to high himalaya

ice core records of climate variability on the third pole with emphasis on the guliya ice cap western kunlun mountains abstract records of recent climate from ice cores drilled in 2015 on the guliya ice cap in the western kunlun mountains of the tibetan plateau which with the himalaya comprises the third pole tp demonstrate that this region has become warmer and moister since at least the middle of the 19th century decadal scale linkages are suggested between ice core temperature and snowfall proxies north atlantic oceanic and atmospheric processes arctic temperatures and indian summer monsoon intensity correlations between annual scale oxygen isotopic ratios 18o and tropical western pacific and indian ocean sea surface temperatures are also demonstrated comparisons of climate records during the last millennium from ice cores acquired throughout the tp illustrate centennial scale differences between monsoon and westerlies dominated regions among these records guliya shows the highest rate of warming since the end of the little ice age but 18o data over the last millennium from tp ice cores support findings that elevation dependent warming is most pronounced in the himalaya this along with the decreasing precipitation rates in the himalaya region is having detrimental effects on the cryosphere although satellite monitoring of glaciers on the tp indicates changes in surface area only a few have been directly monitored for mass balance and ablation from the surface this type of ground based study is essential to obtain a better understanding of the rate of ice shrinkage on the tp

short term variability in the dates of the indian monsoon onset and retreat on the southern and northern slopes of the central himalayas as determined by precipitation stable isotopes this project launched the first study to compare the stable isotopes 18o and d in daily precipitation at kathmandu located on the southern slope of the central himalayas and tingri located on the northern slope the results show that low 18o and d values of summer precipitation at the two stations were closely related to intense convection of the indian monsoon however summer 18o and d values at tingri were lower than those at kathmandu a result of the lift effect of the himalayas coupled with convection disturbances and lower temperatures at tingri in winter the relatively high 18o and d values at the two stations appears to have resulted from the influence of the westerlies compared with those during the summer the subsidence of the westerlies and northerly winds resulted in relatively high 18o and d values of the winter precipitation at tingri winter 18o and d values at kathmandu far exceeded those at tingri due to more intense advection of the southern branch of the westerlies and higher temperatures and relative humidity at kathmandu the detailed differences in stable isotopes between the two stations follow short term variability in the onset date of the indian monsoon and its retreat across the central himalayas during the sampling period the indian monsoon onset at tingri occurred approximately 1 week later than that at kathmandu however the retreat at tingri began roughly 3 days earlier clearly the duration of the indian monsoon effects last longer at kathmandu than that at tingri our findings also indicate that the india monsoon travels slowly northward across the central himalayas due to the blocking of the himalayas but retreats quickly

fluorite deposits at encantada buenavista mexico products of mississippi valley type processes ore geol rev 23 2003 107 124 a reply we very much appreciate the comments of dr spirakis regarding the fluorite deposits of la encan tada buenavista the contribution by gonza lez par tida et al 2003 represents a partial report of thework we are carrying out on the fluorite deposits ofnorthern coahuila state mexico we have subse quently conducted further work on the deposit inorder to complement the information already pub lished addressing controls on the distribution of themineralized bodies and halogen studies of fluid inclu sions we discuss here in light of our new results theproblem of fluorine transport and precipitation at laencantada buenavista new developments in the mine showed that there isa strong structural control on the distribution offluorite bodies the latter are found at the intersectionof low permeability barriers with low angle faults layer parallel slip developed at stratification bound aries with abundant clayey materials precipitation offluorite is preceded by a dramatic increase in perme ability due to the hydraulic fracturing of the host rock enclosing rock fragments included in the newlydeveloped breccias are usually recrystallized andslightly corroded but are also rapidly covered byfluorite the precipitation of which appears to precludethe continuance of carbonate replacement a thincalcite blanket typically a few centimeters to deci meters thick is found at the boundary of the fluoritebody smoothly passing to the slightly recrystallizedenclosing limestone fluorite appears as white tocolorless corrosion free crystals indicative of passivemineral precipitation late cavities are filled up byidiomorphic cubic zoned fluorite crystals with adeep purple color in their outer zones minor idiomor phic calcite scalenoedrons and extremely rare crystalsof barite

morphodynamics and lake level variations at paiku co southern tibetan plateau china abstract proxy records from lakes on the tibetan plateau are commonly used to infer monsoon related climatic changes during the late quaternary specific influences of catchment processes and their interaction with the lake basin are seldom utilized based on morphological field investigations supported by remote sensing analyses in combination with radiocarbon dated sediment data from lacustrine sequences along paleoshorelines and terraces we can demonstrate that close relationships exist between glacier dynamics fluvial alluvial fan terrace formation and lake level and lake area changes of paiku co southern tibet our results show that the formation of large scale fluvial alluvial fans f1 predates the maximum advance of the xixiabangma glaciers the latter formed a distinct terminal moraine complex north of the present glaciers during the local lgm llgm at 42 21 cal ky bp a younger fan generation f2 developed from the llgm to the late holocene which was accompanied by lake level fluctuations with a generally decreasing trend the highest morphologically traceable lake level at 4665 m asl existed prior to 25 cal ky bp and induced a potential overflow to the neighboring langqiang co and pengqu river a high level also existed during the llgm followed by a minor decline until ca 15 cal ky bp owing to reduced meltwater discharge under cold and dry climatic conditions a return to the previous level during the late glacial early holocene period between 11 9 and 9 5 cal ky bp is likely caused by climate warming increased meltwater discharge and enhanced indian summer monsoon ism moisture supply afterwards paiku co shrank gradually toward its present level while the youngest fan f3 generation evolved as individual small sized bodies under ephemeral discharge conditions from the mid holocene to the present the formation of four terrace levels t4 1 is likely the result of sequential incision into the fan generations with a mean erosion rate of 50 cm ky caused by lake level lowering tectonic impact cannot be completely ruled out since 1976 the glaciers lost ca 15 in area accompanied by lake area loss of 3 7 between 1972 and june 2014 seasonal lake level variations of about 1 2 m in height occur in response to summer monsoon rainfall our data show a close interaction between glacial dynamics fluvial processes terrace formation and water budget changes throughout the last 25 cal ky bp in response to the well known insolation driven ism effective moisture supply during the late glacial and holocene period temperature driven meltwater dynamics were the controlling factors for variations in water balance of paiku co

normal faulting in central tibet since at least 13 5 myr ago tectonic models for the evolution of the tibetan plateau interpret observed east west thinning of the upper crust to be the result of either increased potential energy of elevated crust1 or geodynamic processes that may be unrelated to plateau formation2 3 4 5 6 a key piece of information needed to evaluate these models is the timing of deformation within the plateau the onset of normal faulting has been estimated to have commenced in southern tibet between about 14 myr ago7 and about 8 myr ago8 and in central tibet about 4 myr ago9 here however we report a minimum age of approximately 13 5 myr for the onset of graben formation in central tibet based on mineralization ages determined with rb sr and 40ar 39ar data that post date a major graben bounding normal fault these data along with evidence for prolonged activity of normal faulting in this and other tibetan grabens support models that relate normal faulting to processes occurring beneath the plateau thinning of the upper crust is most plausibly the result of potential energy increases resulting from spatially and temporally heterogeneous changes in thermal structure and density distribution within the crust and upper mantle beneath tibet this is supported by recent geophysical and geological data10 11 12 13 14 15 16 17 which indicate that spatial heterogeneity exists in both the tibetan crust and lithospheric mantle

petroleum and aqueous inclusions from deeply buried reservoirs experimental simulations and consequences for overpressure estimates abstract synthetic hydrocarbon and aqueous inclusions have been created in the laboratory batch reactors in order to mimic inclusion formation or re equilibration in deeply buried reservoirs inclusions were synthesized in quartz and calcite using pure water and mexican dead oil or n tetradecane c14h30 at a temperature and pressure of 150 c and 1 kbar one phase hydrocarbon inclusions are frequently observed at standard laboratory conditions leading to homogenization temperatures between 0 and 60 c uv epifluorescence of mexican oil inclusions is not uniform blue and green yellow colored inclusions coexist however no clear evidence of variations in fluid chemistry were observed homogenization temperatures were recorded and the maxima of th plotted on histograms are in good agreement with expected th in a range of 6 c broad histograms were reconstructed showing non symmetrical th distributions over a 20 c temperature range centered on the expected th this histogram broadening is due to the fragility of the fluid inclusions that were created by re filling of pre existing microcavities such th histograms are similar to th histograms recorded on natural samples from deeply buried carbonate reservoirs th values lower than those expected were measured for hydrocarbon inclusions in quartz and calcite and for aqueous inclusions in calcite however the results confirm the ability of fluid inclusions containing two immiscible fluids to lead to pt reconstructions even in overpressured environments

regional stratigraphy and distribution of epigenetic stratabound celestine fluorite barite and pb zn deposits in the mvt province of northeastern mexico northeastern mexico hosts numerous epigenetic stratabound carbonate hosted low temperature hydrothermal deposits of celestine fluorite barite and zinc lead which formed by replacement of mesozoic evaporites or carbonate rocks such deposits can be permissively catalogued as mississippi valley type mvt deposits the deposits studied in the state of coahuila are associated with granitic and metasedimentary basement highs horsts marginal or central to the mesozoic sabinas basin these horsts controlled the stratigraphy of the mesozoic basins and subsequently influenced the laramide structural pattern the sabinas basin consists of 6 000 m thick jurassic to cretaceous siliciclastic carbonate and evaporitic series the mvt deposits are mostly in barremian and in aptian albian to cenomanian formations and likely formed from basinal brines that were mobilized during the laramide orogeny although earlier diagenetic replacement of evaporite layers barite and celestine deposits and lining of paleokarstic cavities in reef carbonates zn pb deposits is observed fluid inclusion microthermometry and isotopic studies suggest ore formation due to mixing of basinal brines and meteoric water homogenization temperatures of fluid inclusions range from 45 c to 210 c salinities range from 0 to 26 wt nacl equiv and some inclusions contain hydrocarbons or bitumen sulfur isotope data suggest that most of the sulfur in barite and celestine is derived from barremian to cenomanian evaporites regional geology and a compilation of metallogenic features define the new mvt province of northeastern mexico which comprises most of the state of coahuila and portions of the neighboring states of nuevo leon durango and perhaps extends into zacatecas and southern texas this province exhibits a regional metal zonation with celestine deposits to the south fluorite deposits to the north and barite and zn pb deposits mostly in the central part