generation of leucogranites via fractional crystallization a case study of the jurassic bengbu granite in the southeastern north china craton abstract the magmatic processes that form leucogranites are closely related to plate collision as the products of crustal anatexis leucogranites provide clues to intracrustal differentiation and the regional tectonic evolution the bengbu area is located along the southeastern margin of the north china craton ncc 150 km north of the dabie orogen and is bounded by the tancheng lujiang fault zone to the east late jurassic leucogranites are widely distributed in the bengbu area we collected samples of the bengbu leucogranite blg and analyzed data on whole rock geochemistry zircon u pb geochronology zircon in situ lu hf isotopes quartz in situ o isotopes and total bulk sr nd pb isotopes zircon u pb dating yielded formation ages for these leucogranites of 160 ma the samples are characterized by high sio2 72 4 wt 76 9 wt alkali 7 3 wt 9 4 wt and al2o3 13 4 wt 15 5 wt contents in addition to two samples exhibiting the rare earth element tetrad effect all rocks have high differentiation index values 95 99 extremely low iron magnesium titanium oxide contents total fe2o3

the origin and evolution of low δ18o magma recorded by multi growth zircons in granite we for the first time reported low 18o granites within craton in bengbu uplift southeast margin of north china craton integrated ion microprobe study of 18o and u pb age on single zircon grains and zircon populations gives direct evidence for the origin and later magmatic evolution of the low 18o granites three types of zircon domains are recognized inherited magmatic core type i inherited metamorphic core mantle type ii and overgrown magmatic rim type iii type i zircons were formed in neoproterozoic and have the average 18o values of 5 3 0 6 around mantle value triassic type ii zircons have extremely low and highly heterogeneous 18o values ranging from 9 4 to 8 6 consistent with the values and variations exhibited by metamorphic zircons from dabie sulu orogen this feature argues for a triassic metamorphic origin for the 18o depletion signature of zircons from ultrahigh pressure metamorphic rocks in dabie sulu orogen jurassic type iii zircons have isotopically homogeneous 18o values of 3 3 0 5 collectively zircon populations recorded the 18o variations from source to low 18o granite the primary protolith of jurassic granites in bengbu uplift is a neoproterozoic granitic intrusion in south china block later high temperature meteoric hydrothermal alteration has lowered the whole rock 18o values in various degrees the low 18o protolith was then buried to the middle lower crust by triassic continental subduction and jurassic anatexis produced the low 18o granitic magma moreover 18o values of type iii zircons are isotopically lighter than previously reported values of magmatic garnets in jurassic granites indicating later magmatic evolution of low 18o magma toward high 18o values probably as a result of infiltration of high 18o fluid from wall rocks

early stage sinkhole formation in the acque albule basin of central italy from geophysical and geochemical observations abstract sinkhole occurrence along the tyrrhenian margin of the central apennines is of great importance for applied research land management and civil protection this study reports on gps altimetry magnetic gravity geoelectric seismic and soil gas measurements of a rapidly developing sinkhole near the guidonia military airport the measurements revealed an elliptical 2 m depression elongated 220 m in the nne ssw direction with the minor axis of 110 m in the spring of 2013 two vertical cavities formed in the eastern and northeastern flanks of the depression whose depths and shapes are rapidly evolving with the formation of widespread fracturing along the same side the geophysical observations image the developing sinkhole to a depth of some 50 m the presence of the travertino lithotype around the depression down to at least 40 m and the lack of this lithotype below the lowered area the sinkhole s evolution appears to be structurally controlled by local and regional faulting these results are useful for designing further geophysical geotechnical and geochemical studies to monitor the sinkhole s evolution and to assess the hazard it presents in densely urbanized area

spt blow count vs shear wave velocity relationship in the structurally complex formations of the molise region italy abstract the relationship between the shear wave velocity vs and the blow number of the standard penetration tests nspt was investigated with reference to the structurally complex formations located in a wide sector of the southern apennine chain molise region italy novel nspt vs correlations were developed based on a balanced number of in situ tests coming from the seismic microzonation of the municipalities of campobasso district and the seismic vulnerability assessment of strategic road infrastructures it was proven that available relationships were not able to fit the data in the area of interest even making the analysis according to the soil grain size classification this circumstance was related to the nature of the geological formations which are chaotically built and affected by complex structural textural and lithological characteristics hence in this paper a rational methodology for an integrated geological and geotechnical assessment of the available field data based on lithostratigraphical features was presented and discussed three original empirical nspt vs power function relationships were derived and distinguished depending on the main lithofacies recognized in the campobasso district corresponding to structured soil deposit ssd all soils as and weathered soils ws their validation through statistical assessment of data confirmed the relevance of the results and the advantages related to their use at regional scale based on an integrated geological and geotechnical approach

experimental zircon melt and zircon garnet trace element partitioning and implications for the geochronology of crustal rocks garnet is the most commonly used mineral in thermobarometry whereas zircon is the most robust chronometer to date high grade metamorphic rocks to provide a basis for correlation of zircon and garnet growth we determined experimentally the trace element partitioningbetweenzircon ahydrousgraniticmeltandgarnetat20kbarand800 1000 cforp y rareearthelements ree zr hf th andu inrespecttomelt zirconpreferentiallyincorporatesallinvestigatedelementsapartfromreewithatomicnumberlowerthansm at this pressure and in the chosen composition the distribution coefficient between zircon and melt d zrn melt for ree increases with increasingatomicnumberofthereeandwithdecreasingtemperature dyb is 20at1000 c butmorethananorderofmagnitude higher at800 c the solubilityofzrinhydrousgraniticmelts buffered by zirconisabouta factoroftwo lower at20kbar than what has been previously established for mid crustal pressures large garnet produced in the experiments allowed determination of garnet melt trace element partitioning d grt melt at temperatures of 800 1000 c conditions relevant for partial melting of crustal rocks there is a systematic increase indree with decreasing temperature zircon contains significantly more heavy ree than garnet at temperatures of 800 850 c zircon garnetpartitioncoefficientsofheavy reedecreasewithincreasingtemperaturefromdlu of12at800 cto 1 4at1000 c middle reepartitioningisclosetounityforthewholeinvestigatedtemperaturerange differentempiricallydetermined zircon garnet partition coefficients from granulites and ultra high temperature granulites can potentially be explained by the experimentallydeterminedchangeofpartitioningasafunctionoftemperature thesedatacanassistinestablishingequilibriumbetween garnetandzirconzonesinnaturalrocks andintheconstructionofdetailedpressure temperature timepathsinhigh grademetamorphic rocks

electrical resistivity tomography applied to geologic hydrogeologic and engineering investigations at a former waste disposal site a former dolerite quarry and landfill site was investigated using 2d and 3d electrical resistivity tomography ert with the aims of determining buried quarry geometry mapping bedrock contamination arising from the landfill and characterizing site geology resistivity data were collected from a network of intersecting survey lines using a wenner based array configuration inversion of the data was carried out using 2d and 3d regularized least squares optimization methods with robust l1 norm model constraints for this site where high resistivity contrasts were present robust model constraints produced a more accurate recovery of subsurface structures when compared to the use of smooth l2 norm constraints integrated 3d spatial analysis of the ert and conventional site investigation data proved in this case a highly effective means of characterizing the landfill and its environs the 3d resistivity model was successfully used to confirm the position of the landfill boundaries which appeared as electrically well defined features that corresponded extremely closely to both historic maps and intrusive site investigation data a potential zone of leachate migration from the landfill was identified from the electrical models the location of this zone was consistent with the predicted direction of groundwater flow across the site unquarried areas of a dolerite sill were imaged as a resistive sheet like feature while the fault zone appeared in the 2d resistivity model as a dipping structure defined by contrasting bedrock resistivities

analysis of spatial variability of spt penetration resistance in collapsible soils considering water table depth abstract geostatistical kriging approach was used for mapping of water table depth and for checking its influence on penetration resistance observed in standard penetration test spt geostatistical mapping was based on a compartmentalisation of 204 spt records in two main groups using monthly and yearly rainfall marks as a segregation criterion six maps produced at 1 10 000 scale were achieved as follows water table depth variation and penetration resistance variation at the depths of 1 5 6 0 8 5 11 0 13 5 m greater variations of the penetration resistance in terms of increase and reduction of resistance were observed at the depths of 6 0 and 8 5 m

chronology and geochemistry of mesozoic granitoids in the bengbu area central china constraints on the tectonic evolution of the eastern north china craton abstract we performed zircon u pb dating and analyses of major and trace elements and sr nd pb isotopes for granitoids in the bengbu area central china with the aim of constraining the magma sources and tectonic evolution of the eastern north china craton ncc the analyzed zircons show typical fine scale oscillatory zoning indicating a magmatic origin zircon u pb dating reveals granitoids of two ages late jurassic and early cretaceous 206pb 238u ages of 160 ma and 130 110 ma respectively the late jurassic rocks jingshan intrusion consist of biotite syenogranite whereas the early cretaceous rocks huaiguang xilushan nushan and caoshan intrusions are granodiorite syenogranite and monzogranite the late jurassic biotite syenogranites and early cretaceous granitoids have the following common geochemical characteristics sio2 70 35 74 56 wt k2o na2o 0 66 1 27 mainly the occurrence of neoproterozoic magmatic zircons 850 ma and inherited early mesozoic 208 228 ma metamorphic zircons within the late jurassic biotite syenogranites together with the occurrence of neoproterozoic magmatic zircons 657 and 759 ma and inherited early mesozoic 206 231 ma metamorphic zircons within the early cretaceous nushan and xilushan granitoids suggests that the primary magmas were derived from partial melting of the yangtze craton yc basement in contrast the occurrence of paleoproterozoic and paleoarchean inherited zircons within the huaiguang granitoids indicates that their primary magmas mainly originated from partial melting of the ncc basement the occurrence of yc basement within the lower continental crust of the eastern ncc indicates that the yc was subducted to the northwest beneath the ncc along the tan lu fault zone during the early mesozoic

cretaceous ongonites topaz bearing albite rich microleucogranites from ongon khairkhan central mongolia products of extreme magmatic fractionation and pervasive metasomatic fluid rock interaction abstract ongonites were defined at their type locality at ongon khairkhan central mongolia as pristine magmatic topaz bearing albite quartz keratophyres with up to 4 wt f and containing phenocrysts of albite k feldspar quartz and rare mica and topaz hosted in a groundmass composed of the same minerals however detailed petrographic and sem eds studies indicate that these rocks underwent considerable subsolidus exchange with deuteric fluids as evidenced by the presence of albitic plagioclase ab 100 and end member orthoclase or 100 secondary li fe rich mica zinnwaldite enriched in rare metals sn w ta nb pitted feldspars containing fluid inclusions and disseminated fluorite the 120 ma old dyke rocks emplaced at a high structural level in the crust are strongly peraluminous leucogranites characterized by high al and alkalis that are also enriched in rb cs ga and ta depleted in mg ca zr ba sr and eu and have anomalous k rb rb sr zr hf and nb ta ratios compared to the average continental crust however the suite has nd isotopic ratios nd 120 1 similar to those of contemporaneous a type granites of the mongolian transbaikalian igneous province of the central asian orogenic belt the inferred primary 18 o 6 to 7 and pb isotopic values are consistent with a granitic parent magma and interaction with orthomagmatic fluids the ongonites and constituent minerals record 1 an extensive and protracted crystal fractionation history in part due to the presence of volatiles particularly f which depressed the solidus temperature of the felsic rocks and extended its duration of crystallization and 2 subsolidus exchange with fluids which includes late flux of heated meteoric water as indicated by modified whole rock 18 o values 0 5 to 2 7 the interaction of the ongonites with internally derived orthomagmatic fluids is considered to result in enrichment and or redistribution of several incompatible elements but not to have greatly modified their original major element chemistry which indicates that this suite represents the last stages of fractionation of a highly differentiated f rich granitic magma the escape of these evolved melts from the apical part of the underlying pluton is now represented by the ongonite dykes late stage magmatic water rich fluids enriched in incompatible elements including nb ta sn and w were responsible for the late to post magmatic alteration and associated w mineralization

contrasting geochemical signatures of fluid absent versus fluid fluxed melting of muscovite in metasedimentary sources the himalayan leucogranites most of the himalayan cenozoic leucogranites are products of partial melting of metapelite sources in the malashan gyirong area southern tibet the geochemical compositions of leucogranites define two groups with distinct whole rock major elements large ion lithophile elements rare earth elements high field strength elements and sr and hf isotope ratios based on published experimental results that define generalized melting reactions of metapelitic sources we infer that these leucogranites are the products of two different types of crustal anatexis fluid fluxed melting and fluid absent melting of muscovite in metasedimentary sources as compared to the leucogranites derived from fluid absent melting those from fluid fluxed melting have relatively higher ca sr ba zr hf th and light rare earth element concentrations and zr hf eu eu and nd nd but lower rb nb ta and u concentrations rb sr and 87 sr 86 sr ratios and e hf t the geochemical differences can be explained by melting behaviors of major muscovite feldspar and accessory minerals zircon and monazite during different modes of crustal anatexis the systematic elemental and isotopic signatures of different types of crustal anatexis and in particular the coupling of major and trace elements that results from common influences on rock forming and accessory mineral behaviors provide tools with which to refine our understanding of the nature of crustal anatexis

glacial outburst flood sediments within disenchantment bay alaska implications of recognizing marine jokulhlaup deposits in the stratigraphic record abstract glacial outburst floods have been observed or inferred in most glaciated regions of the world outburst flooding events along past ice sheet margins have been discussed as possible causes for changes in ocean circulation while subglacial lake drainage under ice sheets may influence ice sheet stability the recognition of these geologically instantaneous events in the marine sediment or rock record is critical in order to characterize the magnitude and frequency of past outburst events as well as to predict the likelihood of future occurrences in this paper we characterize outburst lithofacies and infer depositional processes from two outburst floods within disenchantment bay alaska and compare these deposits to other recognized outburst deposits within marine depositional settings here we show that the outburst deposits are lithologically similar and are composed of stratified mud sand and diamicton we interpret these facies to have been formed by sediment gravity flows and hypopycnal plume sedimentation these results show that the volume of sediment lithofacies and inferred depositional processes cannot be easily distinguished from normal sediment accumulation within the proximal temperate glacimarine depositional environment the paucity of fluvial subglacial discharge in polar glacimarine environments suggests the potential for recognition of such deposits in the antarctic

empirical correlations of shear wave velocity vs and penetration resistance spt n for different soils in an earthquake prone area erbaa turkey abstract the seismicity of the northern part of turkey is mainly controlled by the north anatolian fault zone nafz the nafz is one of the world s most active seismic zones and has produced destructive earthquakes and related hazards in the northern region of turkey several earthquakes and earthquake related hazards have occurred along different segments of this fault zone in the recent past the study area erbaa town is located along the eastern segment of north anatolian fault zone nafz and is one of the largest towns of tokat province in the middle black sea region of turkey the center of erbaa is located on the left embankment of the kelkit river after the disastrous 1942 ms 7 2 and 1943 ms 7 6 earthquakes the settlement was shifted southwards as a part of a seismic microzonation study of the erbaa area shear wave velocity vs values of the geological units exposed in this area were required for site response analyses the geological units in the study area consist mainly of alluvial and pliocene units these layers were evaluated on the basis of drilling in situ spt scptu and spt based uphole and laboratory testing in this study empirical correlations between shear wave velocity vs and standard penetration test blow counts spt n were considered in order to define shear wave velocity profiles for the study area the relationships between shear wave velocity standard penetration test spt blow counts and the soil properties were evaluated as functions of depth spt based uphole tests were performed to measure shear wave velocity during drilling operations in some of the borings the spt based vs values were computed with different empirical formulas and compared with the measured spt based uphole vs measurements the empirical correlations were found to require modification to provide the best correlation for this site the depth factor was considered during the development of new empirical equations therefore a site specific formula was proposed in order to obtain vs profiles for all layers in the study area

nb ta fractionation in peraluminous granites a marker of the magmatic hydrothermal transition in their late stages of evolution peraluminous granitic melts exsolve large amounts of fluidswhich can modify the chemical composition of granitic whole rock samples the niobium tantalum nb ta ratio is expected to decrease during the magmatic differentiation of graniticmelts but the behavior of both elements at the magmatic hydrothermal transition remainsunclear using a compilation of whole rock geochemical data available in the literature wedemonstrate that fractional crystallization alone is not sufficient to explain the distribution ofnb ta in most peraluminous granites however we notice that most of the granitic samplesdisplaying evidence of interactions with fluids have nb ta 5 we propose that the decreaseof the nb ta ratio in evolved melts is the consequence of both fractional crystallization andsub solidus hydrothermal alteration we suggest that the nb ta value of 5 fingerprints themagmatic hydrothermal transition in peraluminous granites furthermore a nb ta ratio of 5appears to be a good marker to discriminate mineralized from barren peraluminous granites

geotechnical assessment and engineering classification of the antalya tufa rock southern turkey abstract this study mineralogically and geotechnically assesses the antalya tufa rock types which are highly variable in nature geological observations geotechnical site investigations and in situ and laboratory tests have been performed to determine the parameters i e organic matter content rock fabric apparent porosity unit weight uniaxial compressive strength young s modulus tensile strength cohesion and angle of internal friction that may have a significant influence on tufa rock behavior and to develop a comprehensive geotechnical database for the antalya tufa rock the geotechnical database was utilized for the engineering classification of the antalya tufa rocks using the gsi classification system

behavior of a 31m high excavation supported by anchoring and nailing in residual soil of gneiss abstract a 31 m high excavation located at niteroi rj in residual soil from gneissmigmatite with high nspt 40 was performed for a building construction two levels of anchored walls were considered in order to guarantee stability when the construction of the upper wall was almost completed a crack parallel to the direction of the wall formed in the hilltop it was decided that the construction works would cease in order to perform additional studies the presence of reasonably continuous soil layers of different colors gray white and red with thicknesses varying from a few millimeters to some centimeters clearly observed in the face of the cut slope the inclination of these soil layers varied along the length of the excavation and they were in an orientation that was unfavorable for the stability of the cut laboratory tests were performed and the presence of high activity clay mineral and low shear resistance parameters was determined for the gray clayey sand soil those weakness planes i e the thin layers of gray clayey sand had not been properly detected in the previous studies that supported the design of those walls considering these new findings the original project was reviewed and it was decided that soil nailing would be used for accomplish the excavation to the original planned level the upper wall was also reinforced with additional anchors load measurements in the nails indicated that the stress state in the soil mass corresponded to the active condition at the final level of excavation significant lateral movements were measured and varied according to the direction and inclination of the cited weakness planes it was observed that the reliquiae planes were fundamentally important to the behavior of the excavation

indentation induced tearing of a subducting continent evidence from the tan lu fault zone east china abstract vertical tearing of oceanic slabs has been well documented at subduction zones it remains unclear whether a subducting continent can tear vertically origin of the continental scale tan lu fault zone tlfz in east china provides an example of the vertical tearing of the subducting continent at the convergent stage the dabie and sulu orogens between the north china plate ncp and the yangtze plate yzp are left laterally offset about 400 km along the ne striking tlfz but the fault zone terminates abruptly at the southeastern corner of the dabie orogen suggesting unique origin of the fault zone we present structural evidence to show that the tlfz initiated as a sinistral fault zone that is exposed in ductile shear belts just to the east of the dabie orogen our muscovite 40ar 39ar dating results coupled with existing age data indicate that the tlfz formed at 240 230 ma middle triassic when the yzp continental crust was subducted beneath the ncp along both the dabie and sulu sutures we also show that se directed extrusion of the subducted crust in the dabie orogen occurred during 230 209 ma late triassic and overprinted contractional deformation in the tlfz to the southeast of the dabie orogen syn collisional folds and thrusts in the yzp to the east of the tlfz exhibit evidence for large scale dragging by the sinistral fault zone whereas those in the ncp to the west are perpendicular to the tlfz without obvious evidence for drag combining these lines of evidence with published data on the tectonic evolution of the two orogenic belts we propose an indentation induced continent tearing model for the origin of the tlfz we suggest that the present southern boundary of the ncp represents its original shape with a promontory in front of the dabie orogen at the oceanic subduction stage the overriding ncp promontory led to vertical tearing of the subducting oceanic plate along the tlfz which formed the eastern boundary of the promontory once the rigid ncp indenter collided with the passive yzp along the dabie orogen the oceanic slab tear propagated into the yzp lithosphere resulting in long distance low angle subduction of the yzp underneath the ncp indenter and nne ward horizontal motion of the torn yzp east of the tlfz until the final collision at the sulu orogen thus the indentation induced the vertical tearing of the subducting yzp along the tlfz

the southwestern extension of the jiao liao ji belt in the north china craton geochronological and geochemical evidence from the wuhe group in the bengbu area abstract the wuhe complex is located at the southeastern margin of the north china craton the complex consists of metamorphosed paleoproterozoic potassic granitoids and supracrustal rocks of which the latter include the fengyang and wuhe groups meta mafic rocks from the lower wuhe group have igneous zircon u pb ages of 2126 37 ma with ehf t values of 6 22 to 8 38 and xenocrystic zircons of 2 39 2 36 ga 2 55 2 54 ga and 2 77 2 69 ga geochemically the meta mafic rocks can be classified into two groups group 1 island arc tholeiites display flat to slightly right declined ree patterns and moderately negative nb ta zr and ti anomalies group 2 mature arc calcalkaline basalts display strongly fractionated chondrite normalized ree patterns and evidently negative nb ta and ti anomalies these meta mafic rocks formed by partial melting of sub arc depleted mantle wedge which had been modified by slab derived melts at an active continental margin depositional age of the group can be constrained in the period of 2 16 2 10 ga based on ages of the youngest detrital zircons and latter intrusions u pb ages of detrital zircons yield major age peaks of 2 69 ga and 2 52 ga with minor peaks at 2 88 ga 2 78 ga 2 35 ga and 2 17 ga most of which are derived from the late mesoarchean to early paleoproterozoic granitoids in the wuhe complex and the jiaodong terrane metamorphic zircons in the marbles coexisting with garnet amphibolites or granulites occur as either single grains or overgrowth or recrystallization rims surrounding magmatic zircon cores and yield ages of 1882 19 ma to 1844 15 ma the comparable ca 2 1 ga potassic granites with a type granite affinity the ca 2 1 ga meta mafic rocks with arc like geochemical features the 2 1 1 9 ga meta sedimentary units and the 1 9 1 8 ga subduction and collision related granulite facies metamorphism suggest that the wuhe complex and the jiao liao ji belt share the same late paleoproterozoic tectonic evolution process and the former is the southwestern extension of the latter

a review of the relationships between granitoid types their origins and their geodynamic environments abstract granitoids are divided into several types according to their mineral assemblages their field and petrographical features and their chemical and isotopic characteristics this typology complements most of the recent classifications because it is not based solely on chemical and isotopic criteria but also on the field petrographical and mineralogical criteria it thus has the advantage of distinguishing the various granitoid types in the field in most cases the proposed classification shares many similarities with the twenty most used genetic classifications of granitoids both types of peraluminous granitoids are of crustal origin the tholeiitic alkaline and peralkaline granitoids are of mantle origin and both types of calc alkaline granitoids are of mixed origin and involve both crustal and mantle materials each granitoid type is generated and emplaced in a very specific tectonic setting each stage of the wilson cycle is characterised by typical associations of granitoids well typed and precisely dated granitoids can then complement structural approaches and indicate on the geodynamic environment with reference to some case studies the use of granitoids as tracers of the geodynamic evolution is also proposed and discussed

dehydration melting phenomena in leptynitic gneisses and the generation of leucogranites a case study from the kerala khondalite belt southern india

the role of porosity on the engineering geological properties of 1669 lavas from mount etna abstract a comprehensive laboratory characterization of volcanic rocks belonging to the 1669 lava flow of mount etna recognized as one of the largest and most catastrophic event ever occurred is presented herein with the aim of investigating on their peculiar mechanical attitude the multi disciplinary approach proposed herein pointed out that although originated by the same eruptive event 1669 trachybasaltic lavas are characterized by relevant differences in porosity and rock fabric from both the qualitative and quantitative points of view this is an interesting aspect because such rocks are quarried for the production of high quality material to be employed for engineering geological purposes even in the val di noto unesco world heritage site in this perspective their detailed characterization is an essential practice even preparatory for the engineering geological use to this purpose this paper provides a focus on the laboratory investigation of these rocks which according to three different porosity classes underwent petrographic physical mechanical and seismic analyses interesting statistical correlations allowed understanding the mutual dependence of the main engineering geological parameters highlighting how porosity through both vesicles and microcracks plays a leading role from the engineering geological point of view achieved results provide a scientific casuistry on this topic and are a reliable reference for studies on similar rock types worldwide since lavas are among the most used rock materials in the engineering geological practice

crustal generation of the himalayan leucogranites abstract detailed studies of the himalayan two mica leucogranites such as the manaslu pluton indicate that they have very uniform mineralogical petrological and structural characteristics one can relate their occurrence to the thickest zones of the underlying tibetan slab in these zones migmatization attains its greatest development and vertical extension the granite is emplaced at first along the main disharmonic plane above the main central thrust mct at the top of the tibetan slab infrastructure ductile deformation of the granite is variable the granite being syn to late kinematic with regard to the functioning of the mct major elements are very homogeneous except for na and k implying that p t conditions of melting were relatively uniform the melted material was of a similar composition over a vast volume and the percentage of melting was small 10 15 trace elements are highly variable some are characteristic for very evolved material ta rb cs u or show the link with the tibetan slab ba sr whilst others are problematic th ree ree and th abundances being much less in the granite than in the tibetan slab imply that they have been extracted during one of the main stages of formation possibly by monazite radiogenic pb sr nd and stable o isotopes are consistent with the origin of the granite from the tibetan slab however the heterogeneous sr isotopic ratios make age dating difficult and imply poor mixing or little fluid interaction during its evolution h isotope data indicate that magmatic compositions of the main body of the manaslu granite have been preserved late or post magmatic alterations are extremely local in the main pluton to the north another belt of two mica granites occurs whose characteristics are very similar to the high himalaya belt they were probably generated in a similar way during this recent intracontinental evolution

identifying the crystal graveyards remaining after large silicic eruptions abstract the formation of crystal poor high silica rhyolite via extraction of interstitial melt from an upper crustal mush predicts the complementary formation of large amounts of typically unerupted silicic cumulates however identification of these cumulates remains controversial one hindrance to our ability to identify them is a lack of clear predictions for complementary chemical signatures between extracted melts and their residues to address this discrepancy we present a generalized geochemical model tracking the evolution of trace elements in a magma reservoir concurrently experiencing crystallization and extraction of interstitial melt our method uses a numerical solution rather than analytical thereby allowing for various dependencies between crystallinity partition coefficients for variably compatible and or incompatible elements and melt extraction efficiency results reveal unambiguous fractionation signatures for the extracted melts while those signatures are muted for their cumulate counterparts our model is first applied to a well constrained example searchlight pluton usa and provides a good fit to geochemical data we then extrapolate our results to understanding the relationship between volcanic and plutonic silicic suites on a global scale utilizing the navdat database to identify crystal accumulation or depletion signatures for each suite we suggest that many large granitoids are indeed silicic cumulates although their crystal accumulation signature is expected to be subtle

foundation evaluation of underground metro rail station using geophysical and geotechnical investigations abstract excavations for underground space developments in a thickly populated urban area are sometimes hindered by unexpected formidable consequences like formation of sinkholes or uneven settlement of foundations such troublesome incidences occasionally damage structures in the vicinity of excavations although adequate design guidelines and codes of practices are adopted the disturbance of subsurface regime due to excavation or construction activities often leads to undesired stability issues with resultant appearance of weak zones the reinforcement of weak zones by grouting is one of the common remedies without demarcating the weak or the affected zones becomes counter productive excavation at a location in chennai mega city for metro rail was severely affected by soil piping with development of sinkholes and weakening of the surrounding strata subsequently development of cracks in the adjacent buildings and caused tilting of the nearby taller structures the mandated the geophysical and geotechnical investigations were carried out to demarcate the affected area to avoid further deterioration of the site cross hole seismic p and s wave velocities were estimated between10 pairs of boreholes up to 20 m depth on both the sides of the excavation two electrical resistivity tomography ert profiles each of 141 m in length were carried out in the same location cross hole s wave velocity profiles and resistivity tomograms clearly indicate the presence of weak zones and possible sinkhole locations site specific empirical relationship was established between s wave velocity and standard penetration test spt n value this relationship was further used for determination of spt n values from the measured vs values to compare the subsurface conditions identified under pre and post excavations the results confirmed the presence of weak zones which are responsible for the weakening of the surrounding strata in the foundation geophysical and geotechnical investigations similar to present investigation can be useful for designing metro rail projects in a subsurface environment comprising alluvium sand clay mixed with silt pebbles and boulders lying near a region of ground water pocket in a thickly populated urban area

a granulite record of multistage metamorphism and ree behavior in the dabie orogen constraints from zircon and rock forming minerals abstract a combined study of mineral inclusions u pb ages and trace elements was carried for zircon and coexisting minerals from granulite in the north dabie terrane ndt of the dabie sulu ultrahigh pressure metamorphic uhp zone east central china the results provide insights into the exhumation history of ndt and into rare earth element ree behavior during retrogression besides inherited cores and one magmatic rim zircons separated from the granulite record three episodes of metamorphism under different p t conditions 1 223 8 2 3 ma for domains that contain grt cpx rt f ap aln inclusions without plagioclase and show flat hree patterns without negative eu anomalies representing peak eclogite facies event 2 213 3 2 1 ma for domains that contain pl cpx grt qtz ap inclusions and show rather flat hree patterns with negative eu anomalies corresponding to granulite facies retrogression 3 199 9 3 3 ma for domains that contain amp pl qtz ap inclusions and show high ree contents with steep hree patterns and remarkable negative eu anomalies representing amphibolite facies overprinting therefore the uhp eclogite in ndt experienced decompression heating during the initial exhumation with local hydration in the late stage of the triassic continental collision garnet in the granulite is composed of a corroded core with embayed outline and spongy texture and an overgrowth rim there is equilibrium distribution of hree between garnet rim and granulite facies zircon domain confirming the geological interpretation of 213 3 2 1 ma for the granulite facies metamorphism there is the prograde hree depletion in porphyroblastic garnet from core to rim and the continuous decrease of hree from the eclogitic to granulitic zircons suggesting that the metamorphic transformation from eclogite facies to granulite facies took place in a closed system on the other hand the amphibolitic zircons show steep hree patterns and significantly elevated ree contents suggesting that the amphibolite facies metamorphism took place in an open system with introduction of external fluids containing more ree to the granulite facies rocks residual clinopyroxene partially replaced by amphibole has remarkably elevated ree contents relative to euhedral primary clinopyroxene there is equilibrium distribution of ree between the residual clinopyroxene and the amphibole marking fluid action during the amphibolite facies overprinting

shear wave velocity as function of cone penetration test measurements in sand and silt mixtures abstract a database of research quality piezocone test cptu results and shear wave velocity v s measurements assembled in the context of an ambitious research project carried out at the treporti test site venice italy has been interpreted in order to study the seismic response of the predominantly silty sediments forming the venetian lagoon basin as well as to explore potential correlations for such intermediate soils the experience gained so far with the treporti database and other field data collected in the lagoon area has shown that the mechanical behavior of venetian soils cannot be easily interpreted using the existing and well established cptu based approaches hence the interest in examining whether or not the seismic response of these sediments expressed in terms of shear wave velocity follows the framework published for other soils the applicability to the available data of a number of existing correlations originally developed either for sands or fine sediments has been first investigated and updated relationships have been then suggested furthermore the small strain stiffness calculated from v s measurements has been compared with the field stiffness derived from the observed performance of a full scale test embankment built in the treporti site so as to verify common design assumptions the verification and calibration of existing approaches are likely to constitute a useful contribution to the practice of geotechnics not only in the venetian lagoon area but also in the silty deposits usually present in the surrounding alluvial plain and other similar depositional environments allowing rapid estimates of seismic soil classification as well as small strain stiffness properties for preliminary design or at sites where only cone penetration data are available

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

hubbard glacier alaska 2002 closure and outburst of russell fjord and postflood conditions at gilbert point 1 hubbard glacier the largest temperate tidewater glacier in the world has been advancing since 1895 ad and has now twice dammed 60 km long russell fjord once in 1986 and more recently in 2002 this paper focuses on the 2002 event when a strong spring advance pushed shallow submarine proglacial sediments against gilbert point closing off russell fjord by late june as a consequence upstream ice flow decelerated from 5 m d 1 to 1 5 m d 1 with flow diverging to either side of gilbert point lake height reached 15 m asl before intense rains caused lake water to overtop the moraine dam on 14 august 2002 three cubic kilometers of water were released within 30 hours with peak discharge reaching 55 000 m3 s 1 24 hours after the flood began the discharge records for the 1986 and 2002 outbursts differ significantly and reflect differences in lake height 26 m versus 15 m and dam types ice versus moraine the 2002 outburst proceeded in two stages 1 relatively slow overtopping of the subaerial moraine with downward erosion rates of 1 2 m h 1 with little lateral expansion 2 followed by faster downward erosion of the submarine moraine up to 7 m h 1 with rapid lateral expansion of the channel by ice calving 7 m h 1 the annual average terminus position at gilbert point has remained constant since 2002 although there are seasonal variations of 100 200 m the deep channel strong tidal currents and seasonally warm ocean water appear to have prevented the advance of this segment of the terminus despite the glacier s continued advance elsewhere along its terminus sediments are slowly filling in the channel at a rate of about 4 m yr 1 and their steady accumulation may eventually trigger the next closure

two stages of zircon crystallization in the jingshan monzogranite bengbu uplift implications for the syn collisional granites of the dabie sulu uhp orogenic belt and the climax of movement on the tan lu fault abstract the detailed study of zircon can provide vital clues about the petrogenetic environment of granitoid rocks morphological and chemical studies of zircon grains from the jingshan monzogranite in the bengbu uplift anhui province eastern china identify three phases of growth zircon i is brown translucent ovoid and occurs as inherited cores it shows two groups of 206pb 238u ages corresponding to the country rock of the jingshan monzogranite and the basement of the bengbu uplift zircon ii is colorless transparent and idiomorphic hypidiomorphic with ipr 0 34 0 52 ipy 0 03 0 24 and iel 0 26 0 34 it shows a very bright cl due to high contents of trace elements e g y u and th and the oscillatory zoning associated with sector zoning it contains 1 40 1 66 wt hfo2 with a mean ehf t of 17 88 these features indicate the igneous crystallization of zircon ii from a peraluminous granite of mainly crustal origin based on the field geology petrography geochemical analysis and especially a weighted mean age of 222 ma for zircon ii we argue that the jingshan monzogranite is a syn collisional granite of the dabie uhp orogenic belt this provides new evidence for the northward subduction of the south china block beneath the north china block just before 222 ma and allows quantitative estimates of the rate of post uhp exhumation in the dabie orogenic belt zircon iii is also colorless and transparent but is totally idiomorphic with ipr 0 41 1 00 ipy 0 88 1 00 and iel 0 39 0 83 it occurs only as overgrowths on zircon ii and shows weak cl due to its depletion in trace elements zircon iii has widely variable contents of hfo2 1 12 to 3 01 wt and hf isotope compositions very similar to those of zircon ii these features suggest crystallization of zircon iii from small volumes of leucosome probably in the beginning stages of migmatisation zircon iii has a weighted mean age of 156 ma interpreted as representing the climax of movement on the tan lu fault this suggests that the compressive movement of the tan lu fault has decreased progressively since its climax at 156 ma these two major conclusions from the zircon studies contrast with previous interpretations of the jingshan monzogranite as a late jurassic post collisional granite in the dabie orogenic belt

linking lithospheric thinning and magmatic evolution of late jurassic to early cretaceous granitoids in the jiaobei terrane southeastern north china craton abstract late mesozoic granitoids are widely distributed in the jiaobei terrane southeastern north china craton ncc and crucial to understanding the processes and mechanisms of the lithospheric thinning here we present petro geochemical zircon u pb lu hf and o isotopic constrains on three stages of granitoids building an integrated model of lithospheric thinning from beginning through peak to waning stages the early stage linglong granite 166 158 ma is geochemically comparable to adakitic rocks with negative nd t 21 3 to 19 2 zircon hf t 26 8 to 18 7 and high zircon 18o 6 7 8 3 it was originated from the subduction thickened lower crust of the eastern ncc with minor contribution from the subducted yangtze block in an extensional setting representing the beginning of lithospheric thinning the middle stage guojialing granodiorite 130 128 ma characterized by higher sr y ba 898 5075 ppm sr 657 2256 ppm nd t 19 1 to 11 5 zircon hf t 19 0 to 11 6 and 18o 7 5 8 7 than the linglong granite addressing a fluid metasomatized lithospheric mantle and extensive crust mantle interaction in the paleoproterozoic crustal source is coeval with peak lithospheric thinning due to roll back of the subducted pacific plate the late stage aishan complex 118 115 ma which is composed of granodiorite syenogranite porphyritic quartz syenogranite alkali granite and monzodiorite exhibits slightly lower nd t 17 9 to 16 2 zircon hf t 21 4 to 15 3 and 18o 6 6 7 9 than the guojialing granodiorite it was derived from the melting of neoarchean paleoproterozoic crust with limited crust mantle interaction and experienced crustal assimilation and fractional crystallization indicating an extended process associated with the waning stage of lithospheric thinning we document the magmatic responses to the lithospheric thinning at different stages which account for the genesis and evolution of the continental adakitic rocks and decratonization of the ncc

integrated geophysical approach in assessing karst presence and sinkhole susceptibility along flood protection dykes of the loire river orleans france abstract non invasive geophysical methods are often used for detecting near surface defects and monitoring seepage in river dykes or dams between 2008 and 2009 a series of geophysical experiments was conducted to detect karst features below the dykes of the loire river orleans france multi channel analysis of seismic surface waves masw was used to obtain the shear wave velocity vs profile of the subsurface below the dykes as an effective approach to investigating the structure of the dykes multi channel resistivity surveys were also used to evaluate the electrical properties of material inside and under the dykes this study discusses the exploration strategy and results for several sections of the dyke system based on the experimental data vs contours are used to geometrically and qualitatively describe the subsurface under the dykes and identify areas of mechanical weakness corresponding to karst features while resistivity contours allow distinguishing interactions between the karst and the dykes through the identification of areas of downward material movement known and unknown anomalies are identified a practical approach that combines seismic and electric resistivity results is proposed to assess karst presence and sinkhole hazards along the investigated dykes using a susceptibility index referring to the likelihood level of the events as a validation method areas of strong karst susceptibility index along the dykes are compared to known collapse event sinkholes dyke breaches etc locations available in databases

zircon age and nd hf isotopic composition of the yunnan tethyan belt southwestern china the baoshan block of the tethyan yunnan southwestern china is considered as northern part of the sibumasu microcontinent basement of this block that comprises presumably greenschist facies neoproterozoic metamorphic rocks is covered by paleozoic to mesozoic low grade metamorphic sedimentary rocks this study presents zircon ages and nd hf isotopic composition of granites generated from crustal reworking to reveal geochemical feature of the underlying basement dating results obtained using the single zircon u pb isotopic dilution method show that granites exposed in the study area formed in early paleozoic about 470 ma pingdajie granite and in late yanshanian about 78 61 ma late cretaceous to early tertiary huataolin granite the early paleozoic granite contains archean to mesoproterozoic inherited zircons and the late yanshanian granite contains late proterozoic to early paleozoic zircon cores both granites have similar geochemical and nd hf isotopic charateristics indicating similar magma sources they have whole rock tdm nd values of around 2 000 ma and zircon tdm hf values clustering around 1 900 1 800 and 1 600 1 400 ma the nd hf isotopic data imply paleoproterozoic to mesoproterozoic crustal material as the major components of the underlying basement being consistent with a derivation from archean and paleoproterozoic terrains of india or nw australia both granites formed in two different tectonic events similarly originated from intra crustal reworking temporally the late yanshanian magmatism is probably related to the closure of the neotethys ocean the early paleozoic magmatism traced in the baoshan block indicates a comparable history of the basements during early paleozoic between the se asia and the western tethyan belt such as the basement outcrops in the alpine belt and probably in the european variscides that are considered as continental blocks drifting from gondwana prior to or simultaneously with those of the se asia

lithium isotope fractionation during incongruent melting constraints from post collisional leucogranite and residual enclaves from bengbu uplift china abstract lithium li elemental and isotopic compositions of the jurassic jingshan leucogranites including garnet rich mafic enclaves and wall rock wuhe gneisses from the southeast margin of north china craton ncc were investigated to understand the behavior of li isotopes during post collisional magmatism the jingshan leucogranites have distinct u shape ree patterns with y and ree concentrations significantly lower yet sr y ratios higher than their presumed source rocks i e the dabie sulu gneisses trace element modeling of ree and sr y suggests these elemental signatures of the jingshan leucogranites can be consistently explained by a fluid present crustal incongruent partial melting bt qz pl h 2 o grt melt leaving mainly grt bt with minor allanite in the residuum the mafic enclaves show identical sr nd isotopic compositions with their host leucogranites contrasting with the wuhe gneiss and the exposed regional lower crust the garnet rich mafic enclaves are thus interpreted as entrained residual phases formed by this incongruent partial melting the jingshan leucogranites show relatively high 7 li values 4 0 to 9 0 and low li concentrations 4 7 11 3 ppm in comparison to published data for worldwide granites in contrast the residual enclaves show low 7 li values as low as 0 6 and high li concentrations as high as 118 ppm garnet separated from residual enclaves is characterized by a narrow range of low 7 li values 1 5 to 0 1 with high li concentrations from 32 9 to 81 7 ppm by contrast coexisting quartz shows relatively high 7 li values 15 0 to 16 6 with very low li concentrations 1 ppm biotite from both leucogranite and residual enclaves shows high li concentrations 195 382 ppm and relatively heavy li isotope compositions 3 2 to 7 5 the li elemental and isotopic signatures of the residual enclaves can be modeled as a grt bt rich residuum mixed with leucogranite melt in various proportions this work indicates that the li isotopic compositions for magmatic rocks that are derived from anatexis of mid to lower crustal gneisses may not be a faithful source indicator as commonly suggested

the role of fractional crystallization in the genesis of early syn d3 tin mineralized variscan two mica granites from the carrazeda de ansiaes area northern portugal abstract a multiphase granitic complex g1 g6 in the carrazeda de ansiaes area central iberian zone was emplaced during syn kinematic stages of the variscan orogeny between 329 9 0 8 ma and 318 9 1 9 ma as determined by id tims u pb on zircon and monazite the complex intruded the metasedimentary douro group in a nw trending antiform formed during the d 1 and d 3 deformation phases but was itself affected by ductile and brittle deformation the granites have equal or higher amounts of muscovite than biotite and contain surmicaceous enclaves and more rarely xenoliths schlieren and microgranular enclaves they are s type mainly alkaline calcic and peraluminous with asi ranging between 1 21 and 1 45 and normative corundum of 2 63 4 77 they are enriched in lree relatively to hree with negative eu anomalies 87 sr 86 sr i 0 7097 0 7159 end 6 2 to 9 1 and 18 o 10 96 11 81 geochemical and isotopic characteristics show that granites g1 g2 g4 and g5 correspond to distinct pulses of magma formed by partial melting of heterogeneous metasedimentary material geochemical fractionation trends recorded by whole rocks and minerals permit to distinguish and model two fractional crystallization series g2 g3 and g5 g6 the latter also affected by crustal assimilation during fractionation granites g1 g2 g3 and g6 have 20 ppm sn and g5 16 ppm sn they are also associated with mineralized sn and w bearing quartz veins fractional crystallization was the responsible process for the increase in sn content in granites from the series and their micas

three dimensional site characterization with borehole data a case study of suzhou area abstract due to the inherent spatial variation of the site information and the limited number of boreholes which could be afforded in a specified project the geotechnical and geological information at a site could not be fully characterized which imposes a significant challenge to the analysis design and construction of the geotechnical system of concern indeed the issue of site characterization has long puzzled engineers this paper presents a three dimensional site characterization in the urban area of suzhou where plenty of borehole explorations have been undertaken with the borehole database established the relationship between the shear wave velocity and the depth is analyzed this relationship can be captured by regression based models and then a sequence extrapolation method that is based upon the linear relationship between the time average shear wave velocities is developed for the prediction of the shear wave velocity along the depth next a three dimensional characterization and visualization of the stratigraphic model in the urban area of suzhou are presented the characterization of the stratigraphic model in this paper is realized through the characterization of the elevations of the interfaces between adjacent strata in the sequence stratigraphic structure the sequence stratigraphic structure is derived with a method that is based upon the one by one comparison and updating of the borehole data and then the best unbiased estimator of the elevations of the interfaces between adjacent strata at the concerned site is predicted with the kriging based interpolation method with the aid of arcgis engine a three dimensional visualization of the characterized stratigraphic model is made possible

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

zircon u pb geochronology and geochemistry of two types of paleoproterozoic granitoids from the southeastern margin of the north china craton constraints on petrogenesis and tectonic significance abstract two types of paleoproterozoic granitoids i e k feldspar albite granites and granitic gneisses were recognized from the wuhe complex of the precambrian basement and neighboring areas in the southeastern margin of the north china craton ncc they share the identical 207pb 206pb ages of 2096 9 ma and 2096 8 ma defined by zircon shrimp u pb dating these granitic rocks are commonly enriched in hree zr nb ga and y and depleted in v cr and ni most of which have high tfeo mgo ratios and zr saturation temperatures over 850 c suggestive of an affinity with a type granite in addition both have consistent whole rock end t values 3 0 to 0 9 and zircon hf isotopic compositions ehf t 3 3 to 1 9 the latter are similar with ones of the neoarchean ttg gneisses in the eastern block of the ncc thus these 2 1 ga granitoids in the region were most likely derived from the partial melting of 2 5 ga ttg gneisses with minor involvement of coeval mafic crustal materials the zircon grains from the granitic gneisses can be categorized into core mantle and rim domains with distinct cl images and trace element characteristics the grey mantles exhibit steep ree patterns low lree th pb contents and remarkably low th u ratios

seismic tomography imaging of an unstable embankment abstract seismic tomography imaging was employed to make a diagnosis and choose a remedy for an embankment supported by a retaining wall showing clear evidence of structural instability the geometry and structural characteristics of the wall the inside geometry of cracks and the physical parameters of the underground materials were the primary objectives of the geophysical survey seismic data were acquired along two vertical sections each one delimited by the lines of the sources within an inclined borehole and of the receivers lying on the ground for each section a total of 744 travel times were inverted to obtain compressional wave velocities on a regular rectangular grid of squared cells 1 m 1 m using an inversion algorithm which is based on the simultaneous iterative reconstruction technique sirt ultrasonic tests carried out in laboratory on intact specimens together with other supplemental site information improved tomography resolution allowing global and node constraints that forced the solution of the inverse problem to match known boundary values tomography imaged two high velocity zones separated by a curved shape low velocity zone the first ones were found to be compatible with the concrete retaining wall and with the schist materials ranging from highly weathered to intact schist while the low velocity zone was interpreted as filling materials and or completely decomposed rock schist the combination of seismic tomography and laboratory measurements allowed extrapolation of important parameters over a large volume of rock mass otherwise only representative of small rock samples near boreholes it also enabled engineering characterization of subsurface rock mass providing useful and accurate information to design a remedy for the embankment

evidence for early 44 ma himalayan crustal thickening tethyan himalaya southeastern tibet abstract comprehensive understanding of himalayan orogenesis is limited in part by a poor knowledge of the eohimalayan episode a phase of tectonic activity predating the better understood neohimalayan crustal thickening associated with coaxial deformation along the main central thrust the cambo ordovician to tertiary metasedimentary sequences outcropping within the tethyan himalaya are the structurally highest units of the himalayan fold and thrust belt they and are inferred to have been the first to have accreted to asia a compilation of data from transects along the length of the main himalayan arc shows that the tethyan sequences have experienced at least five deformation events although the timing of these episodes is poorly constrained emplacement of a series of undeformed granitoid bodies following the second of these events which accounts for the majority of crustal thickening in the tethyan himalayan units is constrained by u pb zircon dating to be older than 44 1 1 2 ma thus significant crustal thickening had occurred along the length of the proto himalayan arc by the mid eocene or within 10 to 20 myr of the initiation of himalayan orogenesis

water present melting in the middle crust the case of the ollo de sapo gneiss in the iberian massif spain abstract the variscan migmatitic region of sanabria in the inner zone of the iberian massif spain provides a unique place to study the geochemistry and rheology of anatectic melts formed by water present conditions in sanabria the ollo de sapo gneiss underwent partial melting at 0 5 0 66 gpa and 690 770 c leucosomes leucogranitic bodies within the migmatite and leucogranites are widespread throughout the migmatite with the leucogranitic bodies being concordant to discordant to the foliation mass balance calculations indicate that the partial melting of the gneiss produced 62 5 wt of melt experiments and pseudosections made at the peak metamorphic p t conditions under fluid absent conditions yield much lower volumes of melt and therefore a fluid present scenario is proposed major and trace element composition and structures of leucosomes and leucogranites support this scenario trace element composition of leucosomes is variable with low to high ree zr y and th content and positive to negative eu anomalies the composition of the most felsic ree depleted eu rich leucosomes is closely similar to that of experimental melts with added water at t

application of cross hole seismic measurements in site investigation surveys application of the cross hole seismic method to site investigation surveys for civil engineering developments is illustrated by case histories from the united kingdom using the borehole sparker probe developed in mccann et al 1975 as the seismic source at newborough anglesey it is shown that this source generates both a compressional wave and a vertically polarized shear wave in the borehole the measured velocity values are used to determine the dynamic elastic moduli of the saturated sand deposit at this site at cocking sussex and east fleet dorset the presence of an air filled void between two boreholes is shown to have a significant effect on the velocity of propagation and amplitude of the transmitted seismic signals this work is extended at maidstone kent where the technique is used to confirm the presence of a cavity below the foundation of a house in the hot dry rock geothermal project at rosemanowes cornwall increased fracturing of the granitic rock mass following explosive stimul

designing foundations around sinkholes there is an increasing awareness among developers and owners of the need to conduct subsurface exploration studies before planning a project the use of geophysical methods in subsurface exploration has been established to be valuable in locating sinkhole activity and suggesting pro active measures however the value of geophysical exploration to supplement geotechnical investigation has not yet been stressed primarily out of cost concerns ground penetrating radar and electrical resistivity tests which were used to determine void spaces below proposed buildings are gaining wider acceptance as a result of information obtained from geophysical tests foundation designs were modified to use post tensioned mats or to include grouting an improved grouting technique that controls the volume of grout being pumped is also discussed this paper is an attempt to document some case studies which resulted in making design improvements to mitigate the effects of known sub surface solution activity these case studies illustrate the use of geophysical exploration methods in adding value to the engineered design

crosshole seismic testing procedures and pitfalls crosshole seismic testing is a valuable technique for determining seismic velocity profiles for critical structure siting investigations improper field procedures however can result in the acceptance of apparent velocities as true velocities leading to unconservative design values common pitfalls in crosshole seismic testing are 1 the use of source receiver borehole spacings too large to enable the determination of true formation velocities 2 the use of in hole station spacings too large to allow resolution of thin velocity layers of interest 3 the use of incremental traveltimes between widely spaced receiver boreholes and 4 the naive assumption that boreholes are vertical and hence parallel a procedure is presented whereby field programs can be more rationally planned

a high frequency sparker source for the borehole environment for tomographic investigations of shallow subsurface features of limited lateral extent a high frequency low cost borehole seismic source would be highly desirable particularly for investigators with limited budgets we constructed a simple arc discharge seismic source from off the shelf items this source consists of a salt water filled bottle containing exposed conductors of a coaxial cable across which 100 to 300 joules of electrical power were discharged this source produced a seismic pulse with a dominant frequency in the neighborhood of 1 5 khz and a half power bandwidth in excess of 1 khz repeatability of seismic signatures in a variety of environmental settings was excellent sufficient power was generated to observe seismic signals with at least a 35 db signal to noise ratio at horizontal borehole separations of 100 m for a borehole separation of 33 2 m signals with at least a 35 db signal to noise ratio were observed at angular ranges in the vertical plane to 68 degrees the hydrostatic

investigating the potential and mechanism of soil piping causing water level drops in mountain lake giles county virginia abstract mountain lake located in giles county southwestern virginia is one of only two natural lakes in the state of virginia the lake exhibits rare self draining behavior with recent episodes in 2008 2011 and 2012 that drained the lake almost completely and revealed the presence of four sinkhole like depressions with piping holes at their bottoms and sides near the northeastern and northwestern margins of the lake this phenomenon has raised concern over declining tourism to the mountain lake lodge the purpose of this study was to investigate the piping potential of lake bottom sediment and its role in seepage and lake level fluctuations sixteen grab samples of lake bottom sediment were collected from the vicinity of the depressions additionally five shelby tube samples were obtained to determine the in situ density of the sediment grain size distribution atterberg limits and compaction mold permeameter tests were used to evaluate lake sediment s susceptibility to piping grain size distribution and atterberg limits test results reveal that the lake bottom sediment consists predominantly of fine sand and silt which are well known for their susceptibility to piping results of the compaction mold permeameter test show that the critical hydraulic gradient ic the hydraulic gradient at which the sediment starts to pipe ranges between 1 and 10 depending on the density grain size distribution and plasticity characteristics of the sediment these results suggest that piping of lake sediment is the primary mechanism responsible for the formation of lake bed depressions and lake level fluctuations

petrogenesis of cretaceous granitoids in the bengbu wuhe area southeastern north china craton implications for gold mineralization abstract sinistral slip along the tancheng lujiang fault zone tlfz during the mesozoic resulted in an offset of approximately 400 km between the dabie and sulu orogens the bengbu wuhe gold belt bwgb represents an extension of the zhaoyuan yexian gold belt to the west of the tlfz early cretaceous intrusions are widely distributed throughout the bwgb gold deposits in the bwgb are commonly associated with intermediate acid dykes that are roughly contemporaneous with mineralization and some orebodies are hosted in granitoids this paper investigates granitoids within the bwgb to constrain their petrogenesis tectonic setting and metallogenic significance using systematic whole rock elemental geochemistry apatite geochemistry zircon u pb dating zircon lu hf isotopes and whole rock sr nd and pb isotopes the timing of au mineralization 134 113 ma in the area is consistent with the age of intrusive adakite like rocks 130 115 ma and normal calc alkaline granitoids 114 109 ma the adakite like samples are characterized by pronounced enrichment in light rare earth elements ree depletion in heavy ree la yb n 30 5 66 2 an absence of eu anomalies high sr contents and sr y ratios low y and yb contents and fractionated ree patterns dy yb n 1 22 1 69 they have relatively low mg values 38 42 and variable sr nd pb hf isotopic compositions 87sr 86sr t 0 7083 0 7111 end t 22 2 to 14 9 206pb 204pb t 17 219 18 010 zircon ehf t 21 0 to 12 3 these features indicate that the parental magmas of the adakites were derived from partial melting of thickened lower crust of the south china plate and or the north china craton the normal calc alkaline granitoids have low sr y 6 0 40 5 la ybn 6 8 24 7 and dy ybn 0 90 1 28 ratios exhibit negative eu anomalies and have variable sr nd pb hf isotopic compositions 87sr 86sr t 0 7082 0 7085 end t 22 7 to 17 7 206pb 204pb t 16 686 16 713 zircon ehf t 24 9 to 19 0 indicating they were derived from the middle to lower crust of the north china craton compared with the normal calc alkaline granitoids the adakite like rocks have higher zircon ce4 ce3 higher apatite so3 and lower apatite mno contents lower and more variable zircon crystallization temperatures and higher apatite molar oh f and cl f ratios indicating that the adakitic magmas were more enriched in volatiles and more highly oxidized taken together field observations and geochemical data suggest that the adakite like rocks related to the subducted south china block are the ore causative rocks

evaluation of the lateral earth pressure coefficients at rest in granular soil deposits using the anisotropic components of s wave velocity abstract determination of the lateral earth pressure coefficients at rest k0 in natural soil deposits is an important issue in geotechnical and geological engineering in this study evaluation of this parameter in a granular soil deposit was examined by using two anisotropic components of the s wave velocity sv and sh wave components to this end thirteen pairs of p and s wave seismic refraction profiles were acquired at two different granular sites in iran the collected shot gathers were processed from which the sv and sh wave velocities were derived the sv wave velocities were obtained by using the multichannel analysis of surface waves masw method while the sh wave velocities were extracted by utilizing the multichannel analysis of love waves malw technique the reference k0 values in the soil deposits were calculated by the mayne and kulhawy s formula based on the friction angles and overconsolidation ratios ocr determined from laboratory tests the curves of the reference k0 values versus the sh sv velocity ratios at both sites strongly confirmed the feasibility of k0 evaluation from the velocity components to develop a global equation for k0 evaluation in granular soil deposits a general regression analysis was conducted on the obtained data from this study combined with those reported in the literature the results showed that reliable values of k0 can be estimated using the sh sv velocity ratios the findings of this study may appropriately serve as references for economic and non invasive in situ k0 identification in granular soil deposits using the surface wave methods

the key role of mica during igneous concentration of tantalum igneous rocks with high ta concentrations share a number of similarities such as high ta nb low ti lree and zr concentrations and granitic compositions these features can be traced through fractionated granitic series formation of ta rich melts begins with anatexis in the presence of residual biotite followed by magmatic crystallization of biotite and muscovite crystallization of biotite and muscovite increases ta nb and reduces the ti content of the melt titanium bearing oxides such as rutile and titanite are enriched in ta and have the potential to deplete ta at early stages of fractionation however mica crystallization suppresses their saturation and allows ta to increase in the melt saturation with respect to ta and nb minerals occurs at the latest stages of magmatic crystallization and columbite can originate from recrystallization of mica we propose a model for prediction of intrusion fertility for ta

holocene history of hubbard glacier in yakutat bay and russell fiord southern alaska stratigraphic and geomorphic data defined by radiocarbon ages tree ring dates and historical observations provide evidence of three major holocene expansions of hubbard glacier early in each advance the hubbard glacier margin blocked russell fiord to create russell lake raising base level and causing stream beds and fan deltas throughout the russell drainage basin to aggrade each hubbard glacier expansion continued with an ice lobe advancing through disenchantment and yakutat bays in the west and an eastern lobe advancing into russell fiord the earlier two holocene expansions were respectively under way at 7690 and 5600 calibrated yr b p and each advance culminated more than 1 k y later the late holocene advance was under way by 3100 yr ago and reached 13 km farther south in russell fiord than the preceding two expansions late holocene deglaciation of yakutat and disenchantment bays was complete before a d 1791 nunatak glacier flowing from neves east of russell fiord became the primary ice source to the russell fiord lobe at or before this date ice retreat from the southern end of russell fiord began in the late eighteenth century and the penultimate russell lake drained ca a d 1860 the relatively slow advances and more rapid retreats of hubbard glacier are consistent with the model of the iceberg calving glacier cycle hubbard glacier is currently advancing and will likely reestablish russell lake in the near future affecting local fisheries however glacier lobes are unlikely to reach the area of the town of yakutat built on late holocene glacial deposits in the next 1 k y