karst collapse susceptibility assessment a case study on the amalfi coast southern italy abstract this paper presents a study to evaluate the collapse susceptibility of a karst cave located along a slope on the amalfi coast southern italy and the presumable geomorphological evolution of the whole slope as a result of cave roof collapse in the study area several natural karst caves with volumes varying between 1000 and 10 000 m 3 were inventoried and the most likely genetic processes were identified some of them proved to be remnants of already collapsed caves while others were in precarious stability conditions the caves are usually located upslope or very close to the main populated resorts a detailed geological geomorphological and geostructural study was performed on a very wide deep cave called the saraceno cave on which the resort town of conca de marini has been built the study was carried out through a multidisciplinary approach which included classical field geological observations sometimes requiring the support of rock climbing geologists experts in photogrammetric surveys and terrestrial laser scanning techniques tls tls surveys allowed the reconstruction of an accurate geometric and geostructural model of the cave and its relationship with the upslope conca de marini resort furthermore it allowed the thickness of the cave overburden to be determined in detail ground surfaces most susceptible to collapse were also identified in the event of possible widespread collapse several buildings and transportation infrastructures could be involved as the cave is located on a very steep slope a debris avalanche could be triggered in the event of a catastrophic failure and the landslide debris characterized by a presumably high magnitude and velocity could involve a wide slope area down to the coast the failure evolution could be very similar to that which took place in amalfi in the late 19th century

paragenesis of sodic pyroxene bearing quartz schists implications for the p t history of the sanbagawa belt sodic pyroxene jadeite content x jd 0 1 0 3 occurs locally as small inclusions within albite porphyroblasts and in the matrix of hematite bearing quartz schists in the sanbagawa sambagawa metamorphic belt central shikoku japan the sodic pyroxene bearing samples are characteristically free from chlorite and their typical mineral assemblage is sodic pyroxene subcalcic or sodic amphibole phengitic mica albite quartz hematite titanite epidote spessartine rich garnet occurs in mn rich samples sodic pyroxene in epidote bearing samples tends to be poorer in acmite content average x acm 0 26 0 50 than that in the epidote free samples x acm 0 45 0 47 x jd shows no systematic relationship to metamorphic grade and is different among the three sampling regions saruta gawa asemi gawa and bessi besshi the average x jd of the saruta gawa samples 0 21 0 29 is higher than that of the asemi gawa 0 13 0 17 and bessi 0 14 0 23 the p t conditions of the asemi gawa and bessi regions are estimated at 5 5 6 5 kbar 360 c in the chlorite zone 7 8 5 kbar 440 15 c in the garnet zone and 8 9 5 kbar 520 25 c in the albite biotite zone metamorphic pressure of the saruta gawa region is systematically 1 1 5 kbar higher than that of the asemi gawa and bessi regions and materials of the saruta gawa region have been subducted to a level 3 5 km deeper than materials that underwent metamorphism at equivalent temperatures and are now exposed in the asemi gawa and bessi regions pressure slightly increases toward the north structurally high levels through the sanbagawa belt of central shikoku two types of zonal structure were observed in relatively coarse grained sodic pyroxenes in the matrix one type is characterized by increasing x jd from core to rim the other type by decreasing x jd from core to rim both types of zoned pyroxenes show an increase in x fe 2 fe2 fe2 mg from core to rim the first type of zoning was observed in a sample from the chlorite zone of lowest grade whereas the latter occurs in the garnet and albite biotite zones of higher grade the contrast in zonal structure implies that dp dt during prograde metamorphism decreased with increasing metamorphic grade and may have been negative in some samples from the higher grade zones the estimated dp dt of the prograde stage of the chlorite zone is 3 2 kbar 100 c and that of the garnet and albite biotite zones is 1 8 to 0 9 kbar 100 c the variation of dp dt at shallow and deep levels of a subduction system probably reflects the difference of heating duration and or change in thermal gradient of the subduction zone by continuous cooling of the surrounding mantle

the geomorphology of the southwest guinea margin tectonic volcanic mass movement and bottom current influences abstract slope morphology controls were examined in two topographically different areas on the southern transform margin of the guinea plateau sectors g1 and g2 tectonic control is manifested by steep faulted slopes in both study areas and by basement warping in sector g1 and magmatic emplacements in sector g2 sediment deposition and the formation of bedforms such as sediment waves on the margin are influenced by topographically intensified bottom currents within the intermediate deep water mass the north atlantic deep water nadw as well as in the shallower equatorial surface water esw antarctic intermediate water aaiw at the uppermost slope plateau edge level thus unconsolidated sediments are eroded from steep slopes the upper and lower slopes canyon walls and the slopes of the volcanic cones and concentrated into slope parallel depocentres in sector g1 and ponded in moats between the volcanic cones in sector g2 surficial sediment waves which are apparently oriented at an angle to the slope range from 0 5 to 2 km in wavelength and up to 100 m in height mass movement of the sediment cover is significant on the lower slopes of both sectors and is the result of slope steepness and instability caused by the continuing tectonic activity

characterization of an early metamorphic stage through inclusions in zircon of a diamondiferous quartzofeldspathic rock from the erzgebirge germany about 1000 zircon grains from a diamondiferous quartzofeldspathic rock of the saxonian erzgebirge were investigated for inclusions using optical microscopy and confocal laser raman spectroscopy cathodoluminescence imagery was applied to characterize the growth zone of zircon where the inclusions occurred the most abundant inclusion minerals are microdiamonds coesite was not detected however garnet and jadeite occur as rare inclusions in zircon cores where diamonds are lacking jadeite was detected for the first time in quartzofeldspathic rocks from the crystalline complex of the erzgebirge the compositions of the pristine garnets in the zircons are similar to those of core areas of millimeter sized garnets but the original garnet composition of the early metamorphic stage is only preserved in zircon intracrystalline diffusion at temperatures as high as 1000 c resulted for instance in higher ti concentrations in garnet cores compared with garnet enclosed in zircon rutile quartz and the compositions of jadeite and garnet inclusions in zircon and of phengite inclusions in cores of large garnets were applied for geothermobarometry the results related to an early metamorphic stage are 650 c and 18 kbar which represent conditions at the base of a thickened continental crust before deeper subduction

ca eskola component in clinopyroxene experimental studies at high pressures and high temperatures in multianvil apparatus abstract in order to investigate the pressure implications of silica exsolution from clinopyroxene in ultrahigh pressure metamorphic rocks we have measured systematically the values of the calcium eskola ca esk component of clinopyroxenes over a considerable range of pressure and temperature a series of anhydrous experiments using powdered glass of composition wt sio2 59 29 al2o3 23 12 mgo 5 44 cao 10 37 and na2o 1 78 were conducted in a walker style multianvil apparatus in the p t range of 6 12 gpa and 900 1200 c we find that all clinopyroxenes synthesized in equilibrium with garnet kyanite and sio2 coesite or stishovite are cation deficient the highest value of the ca esk component 32 38 mol is reached at 6 gpa followed by slight decrease beginning at 8 gpa as the pyroxene progressively dissolves into garnet and more rapid decrease at 10 12 gpa when stishovite becomes stable in the assemblage comparison of our data with those available in the literature which all together covers a wider range of p and t shows that the ca esk activity depends strongly on bulk chemistry especially the silica content in general integrated analyses of published experiments on similar compositions show that the ca esk component rises rapidly to its highest values from 1 to 4 6 gpa then slightly decreases to 9 gpa followed by remarkable decrease to 15 gpa culminating in replacement of pyroxene by garnet in equilibrium with stishovite we conclude that the sio2 exsolution lamellae observed in clinopyroxenes from many ultrahigh pressure terranes can be explained by destabilization of the ca esk component during decompression however because silica solubility in clinopyroxene reaches its maximum at 6 8 gpa the practical upper pressure limit that can be inferred from this system is 200 250 km

experimental study of subsolidus phase relations and mixing properties of pyroxene in the system cao al2o3 sio2 abstract subsolidus phase relations in the system cao al2o3 sio2 cas were experimentally determined with tight reversals of several univariant curves and with 14 equilibration experiments containing the assemblage pyroxene anorthite where pyroxene is a binary solid solution of ca tschermak cats caal2sio6 and ca eskola caes ca0 5alsi2o6 endmembers reversals were obtained on the following reactions bar c 3an gr 2ky q p 22t 700 3an cor gr 3ky p 21 8t 950 3cats gr 2cor p 55t 53900 and 6cats 1 x caesx 2 1 2x gr 4 1 2x cor 9xan observed slopes indicate 9 8 j mol k of al si disorder in ca tschermak pyroxene and 5 3 j mol k of al si disorder in anorthite at 1300 c it is suggested that al si disorder in anorthite increases by 1 9 j mol k from 700 c to 1300 c compositions of cats caes pyroxene in equilibrium with anorthite and pbo rich liquid were experimentally determined at 1400 1430 c and 22 7 30 8 kbar microprobe measurements gave compositions which are consistent with an ideal pyroxene solution and the following parameters for the reaction 3an 2cats 2caes j bar k 2rtln xcats xcaes 60200 86 4t 5 06 13 10 7p p 0 resulting in h0j 39 8 kj mol and s0 461 8 j mol k for the ca eskola endmember at 1300 c the obtained properties of the ca eskola component are necessary for thermobarometry based on pyroxene bearing assemblages containing plagioclase quartz or kyanite

the eclogite garnetite transformation at high pressure and some geophysical implications mineral assemblages displayed by morb and alkali poor olivine tholeiites have been investigated over the pressure interval 4 6 18 gpa at 1200 c both compositions crystallize to form normal eclogites between 4 6 and 10 gpa and there is little change in the relative proportions of garnet and pyroxene over this range however the proportion of garnet increases rapidly above 10 gpa as pyroxene dissolves in the garnet structure and pyroxene free garnetites stishovite are produced by 14 15 gpa dependent upon composition the garnetite facies for both compositions possess zero pressure densities of 3 75 g cm3 implying that subducted oceanic crust remains appreciably denser than surrounding mantle to depths exceeding 600 km it is demonstrated that the seismic velocity distributions in the mantle between 400 and 650 km are inconsistent with anderson s hypothesis that this region is of eclogitic composition

forsterite diopside spinel liquid equilibria in the system cao mgo al2o3 sio2 at 20 kbar and petrological applications liquidus phase relationships in the caalal sio6 mg2sio4 camgsi2o6 caalsi2o8 portion of the simplified basalt tetrahedron in the cao mgo sio2 al2o3 system have been experimentally determined at 20 kbar pressure the fo diss sp li univariant curve that pierces the fo di an join and meets the fo diss enss sp li invariant point in the basalt tetrahedron extends all the way to and pierces the di fo cats join the limit of the simplified basalt tetrahedron toward the silica undersaturated portion

holocene paleoclimate inferred from salinity histories of adjacent lakes in southwestern sicily italy marked uncertainties persist regarding the climatic evolution of the mediterranean region during the holocene for instance whether moisture availability gradually decreased remained relatively constant or increased during the last 7000 years remains a matter of debate to assess holocene limnology hydrology and moisture dynamics the coastal lakes lago preola and gorgo basso located in southwestern sicily were investigated through several stratigraphic analyses of ostracodes including multivariate analyses of assemblages transfer functions of salinity and biochemical analyses of valves sr ca 18o and 13c during the early holocene the gorgo basso and lago preola ostracode records are similar after an initial period of moderate salinity 1690 6100 mg l from ca 10 000 8190 cal yr bp syndepositional or diagenetic dissolution of ostracode valves suggests that salinity declined to 250 mg l from ca 8190 to 7000 cal yr bp at both sites after ca 6250 cal yr bp the ostracode records are strikingly different lago preola became much more saline with paleosalinity values that ranged from 2270 to about 24 420 mg l we suggest that lago preola s change from a freshwater to mesosaline lake at about 6250 cal yr bp was related to sea level rise and resulting intrusion of seawater influenced groundwater in contrast gorgo basso remained a freshwater lake the salinity of gorgo basso declined somewhat after 6250 cal yr bp in comparison to the early holocene ranging from about 550 to 1680 mg l cypria ophtalmica a species capable of rapid swimming and flourishing in waters with low dissolved oxygen levels became dominant at approximately the time when greek civilization took root in sicily 2600 cal yr bp and it completely dominates the record during roman occupation roughly 2100 to 1700 cal yr bp these freshwater conditions at gorgo basso suggest high effective moisture when evergreen olive oak forests collapsed in response to increased greco roman land use and fire ostracode valve geochemistry sr ca 18o suggests significant changes in early vs late holocene hydrochemistry either as changes in salinity or in the seasonality of precipitation harmonizing the autecological and geochemical data from gorgo basso suggests the latter was more likely with relatively more late holocene precipitation falling during the spring summer and fall than winter compared to the early holocene our ostracode inferred paleosalinity data indicate that moisture availability did not decline during the late holocene in the central mediterranean region instead moisture availability was lowest during the early holocene and most abundant during the late holocene

experimentally determined stability of clinopyroxene garnet corundum in the system cao mgo al 2 o 3 sio 2

enstatite jadeite join and its role in the earth s mantle phase relations on the enstatite jadeite join were experimentally determined at solidus temperatures and 90 152 kb and at 1400 2050 c 175 219 kb with a split sphere anvil apparatus ussa 2000 new findings include immiscibility in garnet and determination of the stability of naalsio4 calcium ferrite structure with stishovite a thermodynamic model for the enstatite jadeite join was developed to calculate a complete phase diagram for the join at 500 2500 c and 0 270 kb the results indicate that the two major discontinuities in the earth s mantle at 400 and 670 km depths could correspond respectively to the formation and the breakdown of garnet with a pyroxene composition a model for a chondritic upper mantle is proposed in which large scale chemical and mineral layering was produced by fractionation of liquidus phases in a magma ocean solidification was completed at 400 km depth by crystallization of sodium enriched residual melts which produced a pyroxene layer at 300 400 km depths

organic rich sedimentation at the cenomanian turonian boundary in oceanic and coastal basins in the north atlantic and tethys one of the most striking results of the deep sea drilling project is the proof that organic rich sediments have a widespread geographical distribution during the period from upper cenomanian to middle turonian such sediments were drilled at north atlantic dsdp sites 105 135 137 138 367 398 551 603 they are also present from outcrops or oil wells on the shelf of the african continental margin senegal tarfaya and agadir basins in the tethys former alboran block southern spain algeria tunisia and umbrian apennines italy and in the north sea although these sediments have different lithologies and depositional environments from shelf areas to the deep sea their study mainly based on organic geochemistry with additional data on sedimentology biostratigraphy and palaeo bathymetry suggests that a unique pulse of organogenic accumulation characterizes the cenomanian turonian boundary event ctbe the content and type of organic matter are related to the depositional environment and organic preservation the organogenic accumulation is distributed according to various trends off the african continental margin the organic content increases from onshore areas to the shelf casamance area and moreover increases also in deep sea areas with a gradual transition from terrestrial type iii to marine type ii the best preservation of the organic matter being in the deepest areas i e site 367 off the american continental margin site 603 shows the same toc and type of organic matter as at site 105 the ctbe is also well recorded in the northern part of the atlantic celtic margin north sea by a drastic lithological change black shales within chalks but the type of organic matter is mainly terrestrial in the tethyan area the organic matter is of marine origin and well preserved results are compared with those of pratt 1984 from the western interior basin of the usa different hypotheses to explain this synchronous widespread accumulation of organic matter are discussed 1986 the geological society

occurrence of marine mid cretaceous sediments along the guinean slope equamarge ii cruise their significance for the evolution of the central atlantic african margin abstract during the equamarge ii cruise 1988 several coring attempts made along the slope edge of the southern guinean plateau led to the recovery of middle cretaceous sediments in two cores one contained a carbonate block dated as middle albian h rischi zone the micropaleontological and sedimentological data suggest an open marine environment and paleodepths of approximately 150 200 m another core included a dark shale level corresponding to the global anoxic event ctbe cenomanian turonian boundary event w archaeocretacea zone as shown by seismic reflection profiles these mid cretaceous beds lie very close to a major unconformity which distinctly divides the sedimentary cover into two units the lower one folded and faulted the upper one undisturbed geodynamic and paleoenvironmental implications of these new data better constrain models of evolution for this crucial area of the atlantic realm the compressive and extensional events which affected the equatorial atlantic during the progressive separation of africa from south america are thus more accurately dated these results also strengthen the hypothesis of an open seaway between the central and south proto atlantic as early as the middle albian

exsolution of garnet within clinopyroxene of mantle eclogites major and trace element chemistry eclogite xenoliths from the mantle have experienced a wide variety of processes and p t conditions many of which are recorded in the mineral compositions and textures exsolution of garnet from clinopyroxene is one such texture occurring in a minority of mantle eclogites new analyses of clinopyroxene and garnet of eclogite xenoliths from kimberlites at bellsbank south africa and obnazhennaya yakutia russia are presented here and these are combined with data from the literature exsolution of garnet from clinopyroxene is generally lamellar although lens shaped garnets are also present major and trace element characteristics show a wide range of compositions and include eclogite groups a b and c rare earth element ree concentrations of garnet and pyroxene were determined by sims and the ree patterns are subtly different from those in ordinary eclogites differences include the absence of prominent eu anomalies in samples of this study and differences in the slopes of chondrite normalized ree patterns it is possible that these signatures are unique to exsolved eclogites a result of subsolidus elemental partitioning during exsolution some reconstructed whole rock compositions are aluminuous comparison with ordinary eclogites shows only minor differences implying a similar origin if the immediate precursor to the exsolved eclogites was a monomineralic pyroxenite the excess aluminium was tied up in tschermak s molecule although the occasional presence of kyanite exsolution lamellae is indicative of a ca eskola component reconstructed pyroxenes from kyanite and corundum rich samples contain unrealistic amounts of aluminium for mantle pyroxenes a protolith or parental pyroxene threshold of 24 al2o3 may exist above which as in a plagioclase cumulate the final assemblage is kyanite and or corundum bearing

40ar39ar whole rock dating and the age of cleavage in the finnmark autochthon northernmost scandinavian caledonides abstract four variably cleaved samples of red shale slate were collected from the nyborg formation vestertana group exposed in the finnmark autochthon northernmost scandinavian caledonides quartz normalized illite crystallinity values suggest metamorphism varied between upper diagenesis lower anchizone east and lower anchizone middle anchizone west the samples display similarly discordant 40 ar 39 ar whole rock age and k ca spectra with total gas ages ranging between 606 and 661 ma spectra complexity is a result of evolution of gas from relatively non retentive chlorite white mica and relatively refractory detrital plagioclase apparent ages defined by intermediate temperature increments are relatively constant within each sample but show marked intersample variations 550 575 to 635 650 ma three size fractions 1 2 2 4 and 4 8 m were separated from the sample containing the least chlorite the two coarser fractions contain numerous rock fragments and display 40 ar 39 ar age and k ca spectra similar to the whole rock the 1 2 m fraction is largely comprised of individual mineral grains gas increments evolved between 375 and 495 c record similar k ca ratios but systematically increasing apparent ages between 637 and 783 ma these results suggest that the 1 2 m fraction is composed of detrital white mica grains which were affected by a diagenetically related geologic disturbance at 635 ma although the affects of a late cambrian early ordovician orogenic event finnmarkian orogeny have been locally described from portions of the overlying caledonian allochthons no clear record of correlative tectonothermal activity has been documented within samples from the finnmark autochthon

late cretaceous to early quaternary organic sedimentation in the eastern equatorial atlantic abstract reconstructing the long term evolution of organic sedimentation in the eastern equatorial atlantic odp leg 159 provides information about the history of the climate ocean system sediment accumulation and deposition of hydrocarbon prone rocks the recovery of a continuous 1200 m long sequence at odp site 959 covering sediments from albian to the present day about 120 ma makes this position a key location to study these aspects in a tropical oceanic setting new high resolution carbon and pyrolysis records identify three main periods of enhanced organic carbon accumulation in the eastern tropical atlantic i e the late cretaceous the eocene oligocene and the pliocene pleistocene formation of upper cretaceous black shales off west africa was closely related to the tectono sedimentary evolution of the semi isolated deep ivorian basin north of the cote d ivoire ghana transform margin their deposition was confined to certain intervals of the last two cretaceous anoxic events the early turonian oae2 and the coniacian santonian oae3 organic geochemical characteristics of laminated coniacian santonian shales reveal peak organic carbon concentrations of up to 17 and kerogen type i ii organic matter which qualify them as excellent hydrocarbon source rocks similar to those reported from other marginal and deep sea basins a middle to late eocene high productivity period occurred off equatorial west africa porcellanites deposited during that interval show enhanced total organic carbon toc accumulation and a good hydrocarbon potential associated with oil prone kerogen deposition of these toc rich beds was likely related to a reversal in the deep water circulation in the adjacent sierra leone basin accordingly outflow of old deep waters of southern ocean origin from the sierra leone basin into the northern gulf of guinea favored upwelling of nutrient enriched waters and simultaneously enhanced the preservation potential of sedimentary organic matter along the west african continental margin a pronounced cyclicity in the carbon record of oligocene lower miocene diatomite chalk interbeds indicates orbital forcing of paleoceanographic conditions in the eastern equatorial atlantic since the oligocene miocene transition a similar control may date back to the early oligocene but has to be confirmed by further studies latest miocene early pliocene organic carbon deposition was closely linked to the evolution of the african trade winds continental upwelling in the eastern equatorial atlantic ocean chemistry and eustatic sea level fluctuations reduction in carbonate carbon preservation associated with enhanced carbon dissolution is recorded in the uppermost miocene 5 82 5 2 ma section and suggests that the latest miocene carbon record of site 959 documents the influence of corrosive deep waters which formed in response to the messinian salinity crisis furthermore sea level related displacement of higher productive areas towards the west african shelf edge is indicated at 5 65 5 6 5 55 5 2 4 8 ma in view of humid conditions in tropical africa and a strong west african monsoonal system around the miocene pliocene transition the onset of pronounced toc cycles at about 5 6 ma marks the first establishment of upwelling cycles in the northern gulf of guinea an amplification in organic carbon deposition at 3 3 ma and 2 45 ma links organic sedimentation in the tropical eastern equatorial atlantic to the main steps of northern hemisphere glaciation and testifies to the late pliocene transition from humid to arid conditions in central and western african climate aridification of central africa around 2 8 ma is not clearly recorded at site 959 however decreased and highly fluctuating carbonate carbon concentrations are observed from 2 85 ma on that may relate to enhanced terrigenous eolian dilution from africa

p t evolution and fluid inclusion characteristics of retrograded eclogites munchberg gneiss complex germany kyanite eclogites occur as part of the munchberger nappe pile in ne bavaria west germany eclogites are overprinted by subsequent amphibolite facies metamorphism the preservation of primary eclogitic textures as well as symplectitic textures are indicative of rapid decompression eclogite formation is estimated to have occurred under conditions of high h2o activities at pressures between 20 and 26 kbar and temperatures ranging between 590 and 660 c as is shown by the coexistence of omphacite jd 50 kyanite zoisite and quartz minimum pressure estimates independent of the water activity range between 9 and 16 kbar at the relevant temperatures detailed studies of fluid inclusion reveal two predominant groups of aqueous brine inclusions high salinity 14 17 wt nacl equiv and low salinity 0 8 wt nacl equiv inclusions fluid compositions of both groups of inclusions yield isochores passing close to the estimated amphibolite facies pt field the compositions of these fluids are in good agreement with fluid compositions considered from mineral equilibria none of the fluid inclusions has densities appropriate for eclogite facies metamorphism but probably reflect later amphibolite facies metamorphism

the groundwater budget a tool for preliminary estimation of the hydraulic connection between neighboring aquifers abstract groundwater management authorities usually use groundwater budget calculations to evaluate the sustainability of withdrawals for different purposes the groundwater budget calculation does not always provide reliable information and it must often be supported by further aquifer monitoring in the case of hydraulic connections between neighboring aquifers the riardo plain aquifer is a strategic drinking resource for more than 100 000 people water storage for 60 km2 of irrigated land and the source of a mineral water bottling plant over a long period the comparison between the direct recharge and the estimated natural outflow and withdrawals highlights a severe water deficit of approximately 40 of the total groundwater outflow a groundwater budget deficit should be a clue to the aquifer depletion but the results of long term water level monitoring allowed the observation of the good condition of this aquifer in fact in the riardo plain the calculated deficit is not comparable to the aquifer monitoring data acquired in the same period 1992 2014 the small oscillations of the groundwater level and the almost stable streambed spring discharge allows the presumption of an additional aquifer recharge source the confined carbonate aquifer locally mixes with the above volcanic aquifer providing an externally stable recharge that reduces the effects of the local rainfall variability the combined approach of the groundwater budget results and long term aquifer monitoring spring discharge and or hydraulic head oscillation provides information about significant external groundwater exchanges even if unidentified by field measurements and supports the stakeholders in groundwater resource management

phase relations of epidote blueschists phase diagrams have been computed for minerals in the system ncmash using the optimised thermodynamic data base of berman 1988 augmented by data on glaucophane and pumpellyite to illustrate the relationships between rocks containing epidote and sodic amphibole and those containing assemblages characteristic of neighbouring metamorphic facies the stoichiometries of stable bounding equilibria yield a simple list of mineral parageneses that serves to define an epidote blueschist facies and surrounding metamorphic facies the calculations suggest that when iron free the pairs zoisite glaucophane and clinozoisite glaucophane do not possess a stability field the natural fe bearing paragenesis of epidote sodic amphibole occupies a closed field in the pt diagram whose size increases dramatically as the ratio fe3 al in the minerals is increased where garnet is involved in bounding reactions such as with respect to eclogite and garnet bearing albite epidote amphibolite the epidote blueschist field decreases in size as the ratio fe2 mg is increased the classic blueschist to greenschist transition reaction is best developed in rocks with large fe3 and fe2 contents and is possibly metastable in mgal rich rocks in the latter a wedge of albite epidote actinolite barroisite amphibolite separates the epidote blueschist from the greenschits paragenesis field a first occurrence of garnet divides the epidote blueschist field into a lower temperature garnet free zone and a higher temperature garnet bearing zone although the temperatures calculated for this garnet isograd seem high the locations of all the facies boundaries are influenced by h2o activity however even minor amounts of co2 in the fluid phase x co2 0 005 render the epidote sodic amphibole paragenesis metastable so that facies boundaries cannot be shifted by varying the co2 content of the fluid phase below 600 c no mutual boundaries exist between the amphibolite facies and the epidote blueschist and eclogite facies respectively the calculated low pressure limit for the eclogite paragenesis pyralspite omphacite jd 50 quartz typical metabasite compositions is 12 to 14 kbars with h2o activity 0 9 or 1 5 to 2 kbar lower for jd 30

creation and preservation of subduction related inverted metamorphic gradients peak metamorphic temperatures and recrystallization increase structurally upward in the lower plate of several paleosubduction zones in the westernmost u s cordillera inverted metamorphic gradients are preserved in the pelona orocopia schist southern california the catalina schist california borderland the central metamorphic belt klamath province the south fork mountain schist northern california coast ranges and possibly the shuksan suite northern washington with the exception of the south fork mountain schist peak metamorphic temperatures increase structurally upward from 400 c to 650 c over 1 2 km indicating metamorphic gradients in excess of 100 c km 1 estimates of metamorphic gradients in some terranes such as the catalina schist depend critically on the effects of postmetamorphic faulting the tectonic settings and high metamorphic pressures 800 mpa suggest that the inverted metamorphic gradients formed in paleosubduction zones four out of five inverted metamorphic gradients lie structurally beneath ultramafic hanging walls whereas the pelona orocopia schist formed beneath granitic crystalline rocks the high temperatures recorded by the metamorphic rocks strongly suggest that inverted metamorphic gradients form during the early stages of subduction and thus provide insight into the early thermal history of subduction zones two separate two dimensional numerical models were constructed in order to constrain the thermal conditions under which inverted metamorphic gradients are created and preserved rapid subduction 10 cm yr 1 beneath young oceanic lithosphere 10 ma results in rapid heat conduction downward from the hanging wall and the creation of inverted thermal gradients in excess of 100 c km 1 in the top portion of the downgoing slab in order to be preserved in the geologic record the inverted metamorphic gradient must be accreted to the base of the hanging wall accretion of the upper portion of the subducting slab may occur because of declining temperatures that cause downward migration of the viscous slip zone and or greenschist facies devolatilization reactions that weaken the descending slab alternatively inverted metamorphic gradients may represent the continuous accretion of material at rates of 1 10 mm yr 1 under conditions of declining temperature continuously accreted inverted metamorphic gradients could form in oceanic lithosphere as old as 30 ma continued subduction of 1000 km of oceanic lithosphere effectively refrigerates the early accreted inverted metamorphic gradient synsubduction uplift and or moderately fast postsubduction uplift rates of 1 mm yr 1 are required to preserve the inverted metamorphic gradient the models predict that 1 the high grade metamorphic rocks in inverted metamorphic gradients form early in the subduction process and therefore effectively date the initiation of subduction and 2 inverted metamorphic gradients mark sites of major plate convergence in excess of 1000 km

seismic characteristics and identification of negative flower structures positive flower structures and positive structural inversion negative and positive flower structures and positive inverted structures imply specific modes of formation and their distinctive characteristics make them important criteria for the identification of certain structural styles a negative flower structure from the andaman sea consists of a shallow synform bounded by upward spreading strands of a wrench fault that have mostly normal separations paralleling monoclines and oblique en echelon normal faults flank the divergent wrench fault a positive flower structure from the ardmore basin oklahoma consists of a shallow antiform displaced by the upward diverging strands of a wrench fault that have mostly reverse separations en echelon folds are present on either side of this convergent wrench fault flower structures may resemble extensional or contractional fault blocks on individual seismic profiles flower structures are identified by their unique internal fault and fold architecture by their association with a straight and throughgoing zone of deformation and by their lack of a consistent sense of separation or regional upthrown side positive structural inversion at the rambutan oil field south sumatra basin has formed a shallow anticlinorium and has partly uplifted the underlying graben deeper fault segments bounding the graben have retained their normal fault profiles but at shallow levels some of these faults have reverse separations similar changes of separation with depth may be produced by strike slip but sets of faults with listric profiles and nearby blocklike trend patterns identify the inversion as a dip slip event where correlation of reflections is uncertain or deep control is unobtainable positive inverted structures may also resemble contrational fault blocks detached normal fault assemblages and certain negative inverted structures

the shallow structures of the guinea and ivory coast ghana transform margins their bearing on the equatorial atlantic mesozoic evolution abstract recent geological and geophysical data from a marine survey conducted off guinea and the ivory coast ghana region equatorial atlantic are discussed we interpret the southern guinean margin firstly as an area linked to the central jurassic atlantic and secondly as an area affected by the progressive transform opening of the equatorial atlantic in the early cretaceous off the ivory coast and ghana we have demonstrated distinct structural domains interpreted as consequences of the progressive transform contact between the west african and brazilian cratons also during the early cretaceous on both margins we observe a clear tectonic unconformity of probable late albian early cenomanian age we propose that this unconformity results from the final disruption between the two continental west african and brazilian crusts the geological structures generated along transform margins can be considered as good geological tools to constrain early phases of plate motions particularly around the equatorial atlantic

the mineral springs of the scrajo spa sorrento peninsula italy a case of natural seawater intrusion this paper deals with the mineral springs feeding the scrajo spa in the sorrento peninsula southeast of naples approximately 6 km from castellammare di stabia another spa location the scrajo mineral water is sulphureous salt bromine iodic and co2 rich the two hydromineral areas fall within the groundwater basin of mt faito formed chiefly by limestones due to the high permeability of the limestones there is considerable rainwater infiltration which recharges a basal fresh groundwater resting on denser seawater this groundwater body feeds the mineral springs of the scrajo spa the springs of castellammare di stabia and some submarine springs all the data gathered for the scrajo springs led to propose the following mineralisation scheme 1 the basal fresh groundwater of mt faito on underlying seawater receives endogenous contributions of co2 and h2s which cause a natural seawater intrusion within the fresh groundwater 2 the upwelling of gases would appear to occur via the major faults which bound sorrento peninsula to the nw 3 during the year the chemistry of the springs changes according to different degrees of seawater intrusion the minimum occurs in june and the maximum in november the close interaction between the sea and the scrajo s mineral waters but also those of castellammare di stabia highlights their particular vulnerability not only to over extraction of groundwater but also to climate change finally a hypothesis is presented to explain the connection between the mineral waters rich in co2 and h2s and the concentration of karst phenomena observed in the scrajo area

mixing properties and stability of jadeite acmite pyroxene in the presence of albite and quartz the stability of synthetic jadeite acmite pyroxene coexisting with albite and quartz has been determined at 600 700 and 900 c the end member reaction albite jadeite quartz has been determined to lie between 1 67 and 1 70 gpa at 600 c 1 88 and 1 90 gpa at 700 c and 2 44 and 2 48 gpa at 900 c jd78acm22 quartz is stable above 1 58 1 78 and 2 33 gpa at 600 700 and 900 c respectively jd61acm39 quartz is stable above 1 47 1 67 and 2 18 gpa at 600 700 and 900 c respectively addition of as much as 40 of acmite component in jadeite extends pyroxene stability by less than 300 mpa at 900 c unit cell parameters measured for synthetic jadeite acmite pyroxenes indicate linear volume composition relations the data are consistent with ideal mixing in jadeite acmite solutions

new analytical and numerical geospeedometers tested on garnet pyroxenites from braganca nappe complex ne portugal abstract two new geospeedometric approaches an analytical one phys earth planet inter 110 1999 95 and a numerical one am j sci 29 1998 30 are tested to evaluate cooling rate on upper mantle derived pyroxenites from the braganca massif ne portugal these estimations coupled with standard geobarometric techniques allow theoretically the determination of exhumation rates responsible for incorporation of these rocks within the lower crust in the present paper we discuss the most significant sources of uncertainties in geospeedometry whether numerical or analytical precision of temperature estimates and input diffusion data none of the available geospeedometrical tools when used independently is able to provide definitive results with less than a factor 10 in precision cross calibration is thus required in order to provide reliable cooling rate estimates we obtain for pyroxenites from the braganca massif a minimum cooling rate from 1000 to 750 c of the order of 250 c ma for a depth interval of 10 15 km

high pressure relics in meta sediments intercalated with the weissenstein eclogite munchberg gneiss complex bavaria the mineral assemblages in the eclogites and meta sediments of the munchberg gneiss complex suggest minimum pressures of about 15 kbar and temperatures of 600 30 c for the eclogite facies metamorphism both rock types underwent a subsequent amphibolite facies metamorphism at almost the same temperature range in the weissenstein borehole the eclogites and meta sediments show an intimate interlayering on a centimetre scale contacts between the two rock types are often sharp and untectonized suggesting in situ metamorphism of the eclogites the following features indicate that the gneisses were subjected to eclogite facies metamorphism 1 phengite relics and phengite inclusions in garnet contain up to 3 45 si per formula unit while amphibolite facies phengites have considerably lower si contents 3 0 3 25 p f u 2 omphacite relics occur in the form of na augite 6 9 mol jadeite oligoclase symplectites 3 garnets with up to 40 mol of the pyrope component occur

distribution of deep sea black shales of cretaceous age in the eastern equatorial atlantic from seismic profiling abstract the presence of thick 200 m carbonaceous shales of cretaceous age in the deep waters of the eastern equatorial atlantic was first revealed by drilling at dsdp sites 367 and 368 near the cape verde islands more recent seismic investigations show that black shales are widely distributed in this region in the gambia basin they are associated with a group of seismic reflectors lying at depths of 400 600 m below the sea floor these can be traced southwards from the drill sites into the sierra leone basin and eastwards beneath the african continental rise to depths at which ambient temperatures fall within the oil generation window in the gambia basin the reflectors continue westwards from the cape verde archipelago before terminating on turonian oceanic basement 92 ma south of the guinea fracture zone near 10 n extension of the same seismic sequence on to younger oceanic crust indicates that deep sea carbonaceous deposits formed close to the present equator as late as the early campanian 80 ma long after a series of oceanic anoxic events in the aptian albian oae1 and over the cenomanian turonian boundary oae2 led to widespread accumulation of black shales this late period of deposition may correspond to the more locally developed oae3 high surface productivity in equatorial upwelling zones during the late cretaceous probably played an important role in delivering large amounts of organic carbon to the sea floor when meridional movement of deep water between the south and north atlantic was restricted by closely spaced east west fracture zones in some areas seismic data show that the black shales level out rather than drape pre existing topography implying significant downslope transport of organic rich material from upwelling cells near the african margin

garnet pyroxene equilibria in the system cao mgo al 2 o 3 sio 2 cmas prospects for simplified t independent lherzolite barometry and an eclogite barometer new experimental data on compositions of garnets in two pyroxene garnet assemblages in the system cao mgo al2o3 sio2 cmas are presented for conditions between 1 100 and 1 570 c and 30 to 50 kb garnets in these assemblages become less calcic with increasing pressure garnet orthopyroxene barometry al solubility barometry pertinent to geobarometry for garnet lherzolites has been evaluated with a set of experimental data covering the range 900 to 1 570 c and 15 to 100 kb various formulations of this barometer work well to 75 kb phase equilibria are not sufficient to positively verify the thermodynamic validity of any of such models empirical garnet orthopyroxene barometry at least in the system cmas can be formulated to obtain a pressure estimate without previous temperature estimation p kb 34 4 19 175 1n x al m1 17 702 1n x ca m2 the potential application of an analogous garnetclinopyroxene equilibrium is limited because the amount of ca tschermaks in natural clinopyroxenes is usually quite small in garnet lherzolites and many eclogites the ca mg exchange between garnet and clinopyroxene appears however sufficiently sensitive to pressure to allow calibration of a cmas barometer the reaction 3camgsi2o6 mg3al2si3o12 3mg2si2o6 ca3al2si3o12 has a v o of 3 5 cm3 the total pressure dependency of this reaction is however closer to a theoretical v o of about 5 cm3 when excess volume properties of the phases involved are taken into account we have calibrated such a barometer mean error of estimate 2 8 kb for assemblages with pyrope rich py 80 garnets and orthopyroxenes this may provide the basis for a geobarometer for eclogites from kimberlites

biogeography and diversity of south atlantic cretaceous echinoids implications for circulation patterns abstract this survey of echinoid species living on the african and south american margins of the south atlantic ocean in cretaceous times is based on a review of published species and abundant unpublished material the synthetic approach is used to ascertain how the south atlantic was colonised by echinoids from the time it first opened in the early cretaceous until communications were established with the north atlantic and mediterranean tethys in the late cretaceous the survey focuses on the biogeographical origin of immigrant species and their relations with indo madagascan north atlantic and mediterranean tethyan faunas qualitative variations in species diversity are also studied where available fossil material permits together with the in situ evolution of certain lineages and their endemism finally echinoid colonisation of the south atlantic during the cretaceous is viewed against palaeocurrent patterns the survey shows within the limits of material available that no echinoid fauna attests to the existence of the narrow marine trough separating south america and africa in the barremian in the aptian west african echinoids display a mediterranean tethyan influence indicating a probable link between south east and west of africa via the strait opened between africa and madagascar echinoid fauna on the brazilian margin includes species found in what is now continental north america and on the pacific seaboard of south america during the albian south america separated completely from africa and normal marine communications were established with the western tethys to the north and the southern ocean domain to the south the echinoid fauna of the south atlantic during the albian and early cenomanian was particularly rich and diversified with the earliest ubiquitous species on both margins of the ocean in the late cenomanian early turonian a tethys south atlantic ocean link probably formed in west africa through the sahara and nigeria favouring the influx of mediterranean tethyan species to the south atlantic during the mid turonian coniacian the trans saharan channel closed slowing down colonisation of the south atlantic by mediterranean tethyan echinoids as the only connection was via the central atlantic this period was marked by the stability of a number of lineages that survived without major morphological changes in areas colonised during cenomanian times in the late senonian the south atlantic was largely open to the neighbouring ocean domains and a new trans saharan channel linked the mediterranean tethys and south atlantic directly this allowed substantial faunal exchanges and most senonian echinoids found on the south atlantic rim are common to both its eastern and western margins

glaucophane and barroisite eclogites from the upper kaghan nappe implications for the metamorphic history of the nw himalaya

the structure of the guinean continental margin implications for the connection between the central and the south atlantic oceans the results of a recent geological geophysical survey conducted off guinea are combined with previous data to establish a preliminary stratigraphy and provide a structural sketch of this portion of the west african continental margin three sectors are distinguished a northwestern portion of the margin comprises a wide and deeply submerged plateau the guinean marginal plateau underlain by a thick sedimentary sequence and facing westward toward the gambia abyssal plain scismic stratigraphy and structures show clear analogies to the jurassic margins of the central atlantic including the presence of a cretaceous paleoslope covered by cenozoic deposits a southern area of the margin comprises a series of aligned w e trending acoustic basement features extending along the slope and bounding the guinean plateau to the south these features basement ridges and volcanic piles are related to a fracture zone system also documented by magnetic anomalies and gravity data the bordering deep sierra leone abyssal plain also dissected by e w trending oceanic fracture zones contains a sedimentary cover apparently not older than middle cretaceous between both sectors and between two nw se trending scarps lies an intermediate area the seismic profiles show that here the margin is dissected by faults creating a series of asymmetric horst and graben features progressively narrowing towards the s e and covered by untectonized but partly eroded upper cretaceous to cenozoic sediments

muscovite k ar ages of the sanbagawa schists japan and argon depletion during cooling and deformation seventy muscovites from schists in the sanbagawa terrain in central shikoku were dated by the k ar method the muscovite ages are consistently older with increasing metamorphic grade within the same zone the ages are significantly younger in schists which have been more severely deformed these k ar age variations could be due to systematic argon depletion during deformation i e to the dynamic recrystallization of muscovites during ductile deformation that formed a large scale recumbent fold during the uplift and cooling argon loss was greater in schists that were more extensively deformed and in the lower grade zone that experienced a longer period of low temperature deformation than the higher grade zone the relationships between age and grain size in a pelitic schist suggest that coarse grained muscovites lost more argon than the finegrained ones there was no significant resetting of ages in the vicinity of major strike slip faults such as the median tecotonic line or near thrust faults the combination of geochronological and geological data constrains the cooling rate of the sanbagawa schists to 9 12 c ma in the oligoclase biotite zone in central shikoku japan

petrology of two diamondiferous eclogite xenoliths from the lahtojoki kimberlite pipe eastern finland abstract diamondiferous group a eclogites constitute a minor portion of the mantle derived xenoliths in the eastern finland kimberlites they have been derived from the depth interval 150 230 km where they are inferred to occur as thin layers or small pods within coarse grained garnet peridotites the chemical and isotopic composition of minerals suggest that they represent proterozoic mantle derived melts or cumulates rather than subducted oceanic lithosphere during magma ascent and emplacement of the kimberlites the eclogite xenoliths were mechanically and chemically rounded judging from the types of surface markings in addition those octahedral crystal faces of diamonds that were partially exposed from the rounded eclogite xenolith became covered by trigons and overlain by microlamination due to their reaction with the kimberlite magma the diamonds bear evidence of pervasive plastic deformation which is not however evident in the eclogite host this suggests that annealing at ambient lithospheric temperatures has effectively recrystallised the silicates while the diamond has retained its lattice imperfections and thus still has the potential to yield information about ancient mantle deformation one of our samples is estimated to contain approximately 90 000 ct ton diamond implying that some diamonds occur within very high grade pods or thin seams in the lithospheric mantle to our knowledge this is one of the most diamondiferous samples described

elevated primary productivity of calcareous nannoplankton associated with ocean anoxic event 1b during the aptian albian transition early cretaceous 1 previous isotopic investigations of aptian albian oceanic anoxic event oae 1b from the western north atlantic blake nose posited that increased sea surface temperatures and decreased salinity led to stratification of the upper water column resulting in lowered dissolved oxygen and enhanced organic matter preservation we examined calcareous nannofossils from the same site in the western north atlantic blake nose to evaluate changes in surface water conditions prior to during and after the aptian albian oae1b the results of our analysis conflict somewhat with the previous interpretation that oae1b at blake nose was linked to water column stratification the signal from calcareous nannofossils indicates that in the late aptian prior to oae1b oligotrophic conditions in the surface waters were replaced by mesotrophic conditions that persisted throughout the oae event and into the early albian we speculate that increased surface water productivity facilitated to some degree the development of oae1b at blake nose

the guinea continental margin an example of a structurally complex transform margin abstract the guinean continental margin corresponds to a wide hinge zone which developed between the jurassic central atlantic and the cretaceous equatorial atlantic the guinea marginal plateau that characterizes the southern border of this margin is a wide triangular morphological feature bounded to the west by a typical rifted margin slope segment while its southern edge corresponds to a narrow and morphologically complex continental slope probably resulting from intracontinental transcurrent motion during the early cretaceous on the basis of seismic profiles recorded in two selected areas located along the southern guinea margin a seismic stratigraphy is established at depth the plateau is underlain by a thick mesozoic and cenozoic sedimentary wedge made of two main ensembles a lower ensemble or sequence 1 consists of early cretaceous clastics an upper ensemble includes a series of four distinct sequences attributed to albian to tertiary deposits eastward the sedimentary cover of the southern plateau edge is locally pierced by volcanic bodies of paleocene age beneath the southern margin of the guinea plateau the sedimentary sequences appear deformed by faults and folds resulting from at least two main tectonic episodes a first event only affected sequence 1 which is cut by a set of extensional faults a second tectonic phase including folding reverse faulting and transcurrent faulting is responsible for the deformation of sequences 1 and 2 during this tectonic episode former normal faults have been reactivated as reverse faults resulting in a structural inversion a third tectonic phase was responsible for structures transverse to the general e w trend of the southern guinea margin and consisting of n s trending normal faults and associated volcanoes the spatial distribution of the tectonic trends clearly substantiates a polyphase tectonic activity that can be related to plate motion changes during early stages of the continental separation a first stage is characterized by a divergent rifting leading to n s trending synsedimentary normal faults during the cretaceous the tectonic activity increased as a general transform motion occurred between the guinea plateau and its american conjugate margin the demerara plateau local tensional stresses were responsible for a splay fault system active near the tip of the guinea plateau in late albian times a slight adjustment of the africa plate with respect to the south american one resulted in local squeezing of the whole sedimentary wedge after this short compressive event final continental separation occurred in an extensional regime characterized by a general collapse along two major scarps and volcanic activity

experimentally determined compositions of diopside jadeite pyroxene in equilibrium with albite and quartz at 1200 1350 c and 15 34 kbar abstract equilibrium compositions of diopside jadeite pyroxene coexisting with albite and quartz were experimentally determined at 25 different p t conditions using an electron microprobe for analysis the new data and the 600 c data of holland 1983 provided the following mixing properties of the diopside di jadeite jd solid solution j k g xs x jd x di 12600 9 45 t 12600 7 6 t x jd x di 21400 16 2 t x jd x di 2 the di jd solution is close to ideal above 1000 c but immiscible below 565 c the di jd solvus is slightly asymmetric with the crest at composition di 42 4 jd 57 6 excess enthalpy is positive but smaller than indicated by the enthalpy of solution measurements of wood et al 1980 disorder in the di jd solution is significantly smaller than complete disorder implied by the ionic two site model

spatio temporal patterns of holocene environmental change in southern sicily abstract few examples of natural forest remain near the mediterranean coast therefore it is difficult to study how coastal forests respond to climatic change or their resilience to human impact we developed new sedimentary record of holocene vegetation and fire history at lago preola a coastal lake in southwestern sicily italy in order to verify the existence of forest at large scale on the coast we compare pollen from lago preola a medium sized lake 33 ha to gorgo basso a small lake 3 ha located nearby with the aim of separating local from extra local vegetation dynamics through time using pollen percentages and influx we then compare lago preola pollen to the record from biviere di gela a large lagoon 120 ha situated 160 km to the east in southern sicily to examine differences in vegetation dynamics between the two coastal areas during the holocene lake level reconstructions and ostracode analyses from lago preola provide vegetation independent evidence of climate change and help to disentangle human and climatic impacts on vegetation pollen data indicate pistacia dominated shrublands replaced open grasslands in the region surrounding lago preola by 9500 cal yr bp this change coincided with rising lake levels and the development of an ostracode fauna typical of fresh waters evergreen forest dominated by quercus ilex and olea europaea started to expand by 7000 cal bp and consolidated at 6500 cal yr bp when lake levels were near their holocene high similarities between pollen from lago preola and gorgo basso demonstrate that forest was the dominant vegetation type in coastal sicily during the middle holocene at both regional and local scales and even developed in the drier climatic setting around biviere di gela lake levels fell at lago preola after 7000 cal yr bp with a strong decline accompanied by increasing salinity after 4500 cal yr bp however no transition in vegetation matched these inferred hydrological changes instead forests persisted in the surrounding region until 2200 cal bp when human disturbance intensified we propose that different climatic factors control lake levels and vegetation in coastal mediterranean ecosystems whereas lake levels are most sensitive to the abundance of winter precipitation coastal forests depend on spring precipitation and are limited by the length of summer drought moisture availability remained suitable for evergreen forests in coastal sicily during the late holocene and humans not a drier climate drove the regional forest decline

a coherent lithostratigraphic unit in the coesite eclogite complex of dabie shan china geologic and petrologic evidence abstract as a contribution to the discussion about the in situ vs exotic origin of the ultrahigh pressure metamorphic uhpm rocks and to the real size of the exhumed tectonic units the wuhe pailou unit wpu in eastern dabie shan was studied the wpu typically consists of two micas epidote gneiss marble with minor eclogite and jadeite bearing granofels with rare garnetite and eclogite nodules these lithologies are enclosed within leucocratic granitic gneiss jadeite bearing granofels is the most peculiar lithology of the wpu being the only felsic rock in dabie shan still preserving extensive relics of the uhpm mineral assemblage the uhp peak assemblage is coesite jadeite garnet epidote phengite kyanite with accessory rutile apatite and zircon all eclogites consist of garnet omphacite quartz coesite rutile or high al titanite phengite clinozoisite kyanite two micas epidote gneiss associated with the jadeite bearing granofels typically consists of epidote muscovite biotite plagioclase k feldspar rare garnet and accessory rutile titanite apatite and zircon locally the wpu paragneiss contains garnet with inclusions of phengite kyanite rutile and amphibole na plagioclase symplectite after omphacite a clockwise p t path was inferred for the wpu which consists of an early prograde part up to coesite eclogite facies conditions p 3 3 gpa and t 720 c an early decompression stage and a late part characterised by a near adiabatic decompression down to medium pressure p 1 1 gpa t 670 c and to low pressure amphibolite facies conditions followed by a final cooling to greenschist facies conditions both field and laboratory data consistently suggest that the wpu characterised by the close association of paragneiss marble eclogite and granofels is a supracrustal metasedimentary sequence which underwent subduction uhpm and exhumation as a coherent tectonic unit therefore within collisional orogens large coherent slices of continental crust may be subducted at depths greater than 100 km

excess silica in omphacite and the formation of free silica in eclogite silica lamellae in eclogitic clinopyroxene are widely interpreted as evidence of exsolution during decompression of eclogite however mechanisms other than exsolution might produce free silica and the possible mechanisms depend in part on the nature and definition of excess silica excess silica may occur in both stoichiometric and non stoichiometric pyroxene although the issue has been debated we show that all common definitions of excess silica in non stoichiometric clinopyroxene are internally consistent interchangeable and therefore equivalent the excess silica content of pyroxene is easily illustrated in a three component condensed composition space and may be plotted directly from a structural formula unit or recalculated end members in order to evaluate possible mechanisms for the formation of free silica in eclogite we examined the net transfer reactions in model eclogites using a thompson reaction space we show that there are at least three broad classes of reactions that release free silica in eclogite i vacancy consumption in non stoichiometric pyroxene ii dissolution of ti phases in pyroxene or garnet iii reactions between accessory phases and either pyroxene or garnet we suggest that reliable interpretation of the significance of silica lamellae in natural clinopyroxene will require the evaluation not only of silica solubility but also of titanium solubility and the possible roles of accessory phases and inclusions on the balance of free silica

calculation and application of clinopyroxene garnet plagioclase quartz geobarometers recently published thermodynamic and experimental data in a variety of chemical systems have been evaluated to derive gibbs free energies for hedenbergite and pyrope these were used to calculate the geobarometric equilibria

coupling of oceanic and continental crust during eocene eclogite facies metamorphism evidence from the monte rosa nappe western alps high precision u pb geochronology of ru tile from quartz carbonate white mica rutile veins that are hosted within eclogite and schist of the monte rosa nappe western alps italy indicate that the monte rosa nappe was at eclogite facies metamorphic conditions at 42 6 0 6 ma the sample area indren glacier furgg zone dal piaz 2001 geology of the monte rosa massif historical review and personal comments smpm consists of eclogite boudins that are exposed inside a south plunging overturned synform within micaceous schist associated with the eclogite and schist are quartz carbonate white mica rutile veins that formed in tension cracks in the eclogite and along the contact between eclogite and surrounding schist intrusion of the veins at about 42 6 ma occurred at eclogite facies metamorphic conditions 480 570 c 1 3 1 4 gpa based on textural relations oxygen isotope thermometry and geothermobarometry the

long term trend and fluctuations of karst spring discharge in a mediterranean area central southern italy karst springs in central southern italy are largely exploited for the human consumption since the roman times and currently feed some tens of millions inhabitants with tap water of high quality unlike other karst springs they are characterized by a steady rate during the year with modest seasonal variability however the effects of climate changes are being strongly perceived in central and southern italy as in the rest of the mediterranean basin and groundwater is obviously also affected in this paper we analyze the discharge time series of some important karst springs in the region evaluating the trends and fluctuations in relation to rainfall regime on a yearly time scale the aim is to evaluate the response of these large karst aquifers in the mediterranean area to the recharge input variation the role of the north atlantic oscillation has also been considered trends and fluctuations have been highlighted by n years moving average and transforming the time series by the rescaled adjusted partial sum the results show that a drop in the discharge has occurred since 1987 with reductions ranging from 15 up to 30 although this negative trend is now possibly attenuating or even reversing as a final remark the spring discharge of the large karst aquifers in central southern italy can be assumed as a robust indicator for climate changes as it integrates the effects of precipitation and temperature variation in time and space

tissintite ca na alsi2o6 a highly defective shock induced high pressure clinopyroxene in the tissint martian meteorite tissintite is a new vacancy rich high pressure clinopyroxene with a composition essentially equivalent to plagioclase it was discovered in maskelynite shocked plagioclase and is commonly observed included within or in contact with shock melt pockets in the tissint meteorite a depleted olivine phyric shergottite fall from mars the simple composition of tissintite an58 69 and its precursor plagioclase an59 69 together with the limited occurrence both spatially only in maskelynite less than 25 m of a shock melt pocket and in terms of bulk composition make tissintite a goldilocks phase it formed during a shock event severe enough to allow nucleation and growth of vacancy rich clinopyroxene from a melt of not too calcic and not too sodic plagioclase composition that was neither too hot nor too cold with experimental calibration these limitations on occurrence can be used to place strong constraints on the thermal history of a shock event the kinetics for nucleation and growth of tissintite are probably slower for more sodic plagioclase precursors so tissintite is most likely to occur in depleted olivine phyric shergottites like tissint and other highly shocked meteorites and lunar and terrestrial rocks that consistently contained calcic plagioclase precursors in the appropriate compositional range for a shock of given intensity tissintite ca 0 45 na 0 31 0 24 al 0 97 fe 0 03 mg 0 01 si 1 80 al 0 20 o6 is a c2 c clinopyroxene containing 42 60 mol of the ca eskola component by far the highest known the cell parameters are 9 21 17 a b 9 09 4 a c 5 20 2 a 109 6 9 v 410 8 a 3 z 4z 4 the density is 3 32 g cm 3 and we estimate a cell volume for the ca eskola end member pyroxene of 411 13 a 3 which is consistent with a previous estimate and therefore supports the importance of this component in clinopyroxenes from ultra high pressure metamorphic rocks from the earth s upper mantle at least in c2 c clinopyroxenes as sodic as tissintite the a and b cell parameters as a function of vacancy concentration intersect at 0 3 vacancies pfu much lower than the ca eskola end member 0 5 an inversion of anisotropy suggesting an elastic instability that drives clinopyroxene toward a disordered trigonal structure closely related to that of wadeite it may mark the boundary beyond which the breakdown of vacancy rich clinopyroxene to a wadeite structured phase stishovite becomes stable although this was not observed in tissint