the masquerade of alkaline carbonatitic tuffs by zeolites a new global pathfinder hypothesis rapid and progressive reaction of alkaline carbonatitic tuffs with magmatic and crustal fluids disguises their initial character and origin this is collectively indicated from a the extensive literature on zeolite formation from volcanic glass precursors and alkaline fluids b mineralogical characteristics of specific zeolite species c a comparative review of global distributions of alkaline carbonatite suites and of zeolite minerals and d new trace element data from zeolite samples a unifying conceptual model based on tectonic and geological settings hydrological regime and mineralogy is presented that helps to explain the global distributions and current understanding of occurrences the model will assist in resource exploration by contributing deeper understanding of the economically important bedded zeolite deposits and further serve as a guide to the discovery of new alkaline carbonatitic suites potentially of economic significance metallic ores and rare earth elements it follows that future testing of the hypothesis will impact on models of natural carbon cycling as volcanic contributions of co2 are reviewed

isotope geochemistry sr nd pb and petrogenesis of leucite bearing volcanic rocks from colli albani volcano roman magmatic province central italy inferences on volcano evolution and magma genesis the colli albani composite volcano is made up of strongly silica undersaturated leucite bearing rocks magmas were erupted during three main periods but a complex plumbing system dominated by regional tectonics channelled magmas into different reservoirs the most alkali rich magmas restricted to the caldera forming period pre caldera are extremely enriched in incompatible trace elements and display more radiogenic sr 87sr 86sr 0 71057 0 71067 with slightly less radiogenic pb with respect to those of the post caldera period post caldera volcanic activity was concentrated in three different volcanic environments external to the caldera along the caldera edge and within the caldera the post caldera magmas produced melilite to leucitite bearing plagioclase free leucitites in contrast to the pre caldera lavas they are characterised by lower incompatible trace element abundances and less radiogenic sr 87sr 86sr 0 71006 0 71039 magmas evolved through crystal fractionation plus minor crustal assimilation in a large magma chamber during the pre caldera period the multiple caldera collapses dissected and partially obliterated the early magma chamber during the post caldera stage magmas were channelled through several pathways and multiple shallow level magma reservoirs were established a lithospheric mantle wedge previously depleted in the basaltic component and subsequently enriched by metasomatic slab derived component is suggested as the mantle source of colli albani parental magmas two different parental magmas are recognised for the pre and post caldera stages the differences may be related to the interplay between smaller degrees of melting for the pre caldera magmas and more carbonate rich recycled subducted lithologies in the post caldera magmas

the origin and growth of a recently active fissure ridge travertine over a seismic fault tivoli italy abstract an enigmatic c 2 km long and 15 m high travertine ridge the colle fiorito ridge occurs in the northwestern sector of the tivoli travertine plateau central italy the main questions addressed in this paper concern the origin and mode of growth of this prominent ridge the presence of active structures beneath the studied ridge is inferred by recent and past earthquakes located at shallow depths immediately beneath colle fiorito to understand the surficial structure of the colle fiorito ridge and the travertine depositional environment we constructed a 10 m resolution dem analyzed recent and past aerial photographs and conducted field surveys and meso to micro scale sedimentological analyses to understand the ridge subsurface structure we studied a set of 32 stratigraphic well logs available from previous works and from the local decorative stone industry and realized a 2d electrical resistivity tomography ert across the ridge results show a gentle antiformal structure affected by subvertical zones of strata discontinuity the colle fiorito structure is interpreted as a previously unknown fissure ridge travertine grown at the edge of the tivoli travertine plateau perhaps when the volumetric deposition rate reached its climax in the plateau for the abundance of fluid discharge and the rise of the water table such a fluid pressure may have activated the faults and fractures beneath colle fiorito thus opening new pathways for the ascension of geothermal fluids toward the surface

volcanology history and myths of the lake albano maar colli albani volcano italy abstract the polygenetic albano maar is the most recent centre of the colli albani volcano located just few kilometres to the south east of roma presently the maar hosts a 167 5 m deep crater lake the deepest in europe the maar is to be considered quiescent as phreatic activity is documented throughout the holocene this paper illustrates the close relationships between the activity of the maar and the history of settlement in the roman region as recorded in the geology archaeology history and legends of the area severe fluctuations of the groundwater table and catastrophic overflows of the lake albano from the maar rim had occurred prior to and after the early prehistoric settlements dated in the maar area at the eneolithic times ca iii millennium b c repeated lahars occurred along the northwestern slope of the maar filling in the paleodrainage network and forming a vast plain paleohydraulic analyses on fluvial and lahar deposits originated from the holocene phreatic activity of the albano maar indicate sediment water flows in excess of hundreds of cubic metres per second absolute age determinations of the paleosoil underlying one of the most recent deposits of the lahar succession at 5800 100 yr b p 14 c cal are in perfect agreement with the age of the overlying eneolithic age settlements the last catastrophic overflow is described in the roman literature as a consequence of the anger of poseidon against the romans in 398 b c for their war against the etruscans in 394 b c the romans decided to prevent the repetition of such events by the excavation through the maar crater wall of a 1 5 km long drain tunnel which is still operational keeping the lake 70 m below the lowest point of the maar rim this tunnel drain may be regarded as the first prevention device for volcanic hazard in history and shows an unprecedented development of the engineering technology under the pressure of hazard perception the surprising and still largely unknown results of this study are very important to redefine the hazard of the roman region

petrology of garnet clinopyroxene amphibolites from mont albert gaspe quebec the mont albert mafic ultramafic complex of central gaspe quebec is generally regarded as a partial ophiolite with an underlying metamorphic sole the metamorphic rocks include a number of mineralogical and textural varieties of amphibolite including some migmatite as well as minor metasedimentary and quartzo feldspathic gneisses the most intriguing rocks in the complex are mafic to ultramafic garnet and clinopyroxene bearing amphibolites that are restricted to the vicinity of the peridotite contact these rocks have unusual fe rich si poor bulk compositions and may represent tholeiites chemically modified by interaction with fluid or melt before or during metamorphism these amphibolites are not retrograde eclogites since andesine was present throughout the metamorphic history and the clinopyroxene is not omphacitic coexisting mineral compositions and temperature estimates overlap for core rim and matrix grains of all the major phases in the garnet clinopyroxene amphibolites implying equilib

co2 release variations during the last 2000 years at the colli albani volcano roma italy from speleothems studies abstract the colli albani is the quiescent volcano that dominates the southwestern skyline of roma italy the last eruption occurred during the holocene from the eccentric albano maar along its western slope the volcano is presently affected by cyclic seismic swarms ground uplift and diffuse co 2 degassing the degassing has caused several deadly incidents during the last years and constitutes a major civil protection concern as the volcano slopes are densely inhabited nevertheless the volcano does not have a permanent monitoring network and the background level and anomalous co 2 levels the relationship between the gas release and the seismic and ground deformation activity at the colli albani are still to be defined the aim of this work is to define the historical record of co 2 release evidences of deep co 2 periodic release during the last 2000 years in the area of colli albani volcano roma italy are offered from speleothems studies a roman age stone mine now used for mushroom cultivation is decorated with actively growing speleothems characterised by depositional hiatuses different levels of four stalactites separated by depositional unconformities and several samples from a single depositional cycle belonging to a stalagmite have been dated by u th method and analysed for their o and c isotopic composition eight cycles of deposition have been identified from 90 110 a d to 1350 1370 a d some of which are recognised across different speleothems the age gap dividing different growth layers is in the order of one to few hundred years giving a temporal span for periodic interruption of speleothems deposition o and c isotopic analyses performed on the samples collected from a single cycle the oldest have shown that the composition of the mother solutions was initially mainly meteoric and that a progressive increase in the input of a deep component rich in co 2 up to a proportion of 20 30 occurred just before the interruption of the speleothem deposition this could be due to a progressive increase of the acidity of the water solutions that caused the undersaturation of fluids if we extrapolate this mechanism to the other cycles of deposition being characterised by analogue isotopic compositions we can hypothesise periods of deposition interrupted by episodes of co 2 release which in the colli albani volcano are often recorded in coincidence with earthquakes therefore we have correlated the hiatuses with some of the largest historical earthquakes interesting to the city of rome

the colli albani mafic caldera roma italy stratigraphy structure and petrology new results for the colli albani volcano roma italy surveyed for the geological map of italy at 1 50 000 scale carg project integrated with previous data provide insights on caldera evolution the colli albani a quiescent volcano became active at 600 ka eruptive compositions are consistently mafic 50 km 3 deposits forming the villa senni eruption unit ignimbrites at ca 355 ka two edifices were built within the caldera 1 the horseshoe shaped tuscolano artemisio ta composite edifice or lithosome consists of coalescing peri caldera fissure related scoriae cones interbedded with lava flows the fissure system forms two segments controlled by regional fractures 2 the steep sided faete stratovolcano 949 m a s l filled the caldera the ta and faete lithosomes partly interfinger and were emplaced at 350 260 ka their products indicate reduced eruption rates relative to the vl period and a change to effusive and mildly explosive eruptions the most recent and still active phase of phreatomagmatic activity formed overlapping maars and tuff cones along the western and northern slopes of the volcano collectively named via dei laghi composite lithosome the colli albani caldera is poly phase 1 a piecemeal caldera is associated with large volume ignimbrites of the vl edifice the present shape of the caldera is related to the villa senni eruption 2 the ta composite edifice erupted from peripheral caldera fissures is unrelated to explosive phases of caldera collapse the ta final products cover a morphologically stable caldera wall the peripheral fractures feeding the ta composite edifice are interpreted as volcano tectonic structures activated during the late stage downsag of the caldera reduced eruption rates during the ta and the faete stages 10 1 km 3 1 ka respect to 10 0 km 3 1 ka for the vl edifice suggest a reduced recharge of the magma chamber that may have induced prolonged deflation and downsagging of the caldera floor and the opening of outward dipping peripheral fractures by this interpretation the ta edifice represents the surface expression of ring dykes at depth the absence of similar fissure structures along the western caldera rim may relate to the deep geometry of the ring faults dipping inward in those areas and therefore not favourably oriented for magma intrusion during a period of general subsidence by contrast the following and still active phreatomagmatic phase that has emplaced the via dei laghi composite edifice is located right on the western side of the caldera and may therefore relate to resurgent conditions classical petrological and pers pearce elements ratios analyses indicate that lavas are co genetic and show a differentiation trend up through stratigraphy driven by

fluid infiltration and volume change during mid crustal mylonitization of proterozoic granite king island tasmania the development of 10 30 m wide mylonite zones at mid crustal depths in late proterozoic granitoids on king island tasmania was associated with pervasive infiltration of low 18o fluids 5 to 7 on the scale of the shear zones syndeformational fluid rock interaction produced substantial differences in mineral composition and bulk rock chemistry among several adjacent shear zones which are hosted by the same granite in a shear zone at cape wickham with a normal slip component changes in whole rock chemistry between granite and mylonites indicate a gain of ca and losses of k and na during deformation which was nearly isovolumetric notable losses of k rb and si occurred during partial retrograde alteration of mylonites near the western margin of this shear zone the alteration suggests a component of up temperature fluid flow in contrast 3 km to the south east in a strike slip shear zone at disappointment bay complete albitization of plagioclase was associated with na gain and ca loss deformation also involved losses of mg and fe up to 60 volume gain occurred during the formation of closely spaced mesoscopic to microscopic quartz veins during mylonitization the substantial silica gain in this as well as in two mylonite zones further south east is interpreted to have been associated with upward flow of aqueous fluids along these shear zones on the basis of a gradient reaction model minimum time integrated fluid fluxes of 106 m3 m2 are estimated for the disappointment bay west shear zone

fracture controlled fluid circulation and dissolutional weathering in sinkhole prone carbonate rocks from central italy abstract fractures karstic cavities and calcite precipitates are analysed on mesozoic carbonate strata from the cornicolani mountains central italy to quantify the relationships between fractures and related karstic cavities and to infer the fracture controlled fluid pathways the study area is characterized by active sinkholes and other karstic caves which are among the deepest ones in the world results show a clear control of fractures on the process of dissolutional weathering and therefore on the fluid circulation a model is proposed in which two different modes of dissolutional weathering coexist i a mode of diffuse weathering consisting in the dissolutional enlargement of closely spaced joints and bedding surfaces this process affects the strata situated at depths of up to 5 m ii a mode of more concentrated weathering active along highly permeable fault damage zones at depths of at least 70 m these processes are mostly connected with the shallow circulation of calcite dissolving meteoric waters and are controlled by the disparity of permeability between the fault damage zones and the surrounding jointed strata some calcite precipitates along the studied fault damage zones may be connected with a dissolutional process operated by waters that interacted with the adjacent quiescent volcanic district such calcite dissolving waters and the presence of high permeable fault damage zones along which the waters may ascent are probably the cause for the development of some of the deep sinkholes along faults in the study area

genesis of zeolites in the neapolitan yellow tuff geological volcanological and mineralogical evidence the study proposes a model by which a thick succession of volcanic tuffs can be zeolitized by alteration of pyroclastic material in the presence of sufficient eruptive water and at temperatures close to water vapour condensation in the case of phreatomagmatic products the model simplifies interpretation of problematic deposits that exhibit pronounced vertical and lateral variation in lithification grade a major feature of the model is that thick zeolitized tuffs can be formed during emplacement of pyroclastic products in marked contrast to later alteration in an open hydrologic system geological volcanological and mineralogical data for the neapolitan yellow tuff a widespread trachytic pyroclastic deposit outcropping around campi flegrei southern italy have been used to infer the physico chemical conditions that determined mineral genesis this tuff shows a reduction in lithification grade towards the base top and with distance from the vent and very variable zeolitization within the lithified portion we suggest that during initial emplacement the erupted products chilled against the ground inhibiting zeolite crystallization during rapid deposition of the thick wet succession thermal insulation allowed the persistence of elevated temperatures for a time sufficient for enhancement of hydration dissolution processes in the volcanic glass the highly reactive alkali trachytic glass quickly buffered the acid ph of the system favouring phillipsite crystallization followed by chabazite nucleation the variable zeolite content reflects fluctuating emplacement conditions e g changes in water content and temperature cooling of the upper and relatively thin distal deposits inhibited the zeolitization process thereby preserving the primary unlithified deposit

mapping of h2s fluxes from the ground using copper passive samplers an application study at the zolforata di pomezia degassing area alban hills central italy abstract a new method for measuring h2s mass flux from the ground based on the digital analysis of the interference colours produced by the sulphidation of copper passive samplers cps is proposed and discussed in this article cps sulphidation has a wide range of linear responses to h2s doses and can be used together the accumulation chamber method to estimate gas fluxes from natural degassing areas these are often characterized by the presence of vent centred degassing areas vcdas which are recognizable from the absence or rarefaction of vegetation due to high acid gas concentrations in the soil pores and in the air at ground level a reference emission curve accounting for the advective and diffusive components of the flux can be modelled and used to estimate the total h2s mass released from each vcda the application of this method can be supported by remote sensing analysis that helps identify vcdas in the field in perivolcanic h2s degassing areas as an illustrative application h2s gas fluxes from the ground were measured in spring 2007 at the zolforata di pomezia degassing area zpda alban hills central italy using an accumulation chamber internally equipped with cps h2s peak fluxes were measured over the vents after remote sensing assisted identification of the vcdas further measurements were carried out in two ponds and one artificial channel bordering the study area the total atmospheric flux released at the zpda estimated to be about 1207 6 kg day 1 was calculated as the summation of the fluxes from all the h2s sources the background flux being negligible

accidental gas emission from shallow pressurized aquifers at alban hills volcano rome italy geochemical evidence of magmatic degassing abstract recent studies suggested that alban hills rome is a quiescent and not an extinct volcano as it produced holocene eruptions and several lahars until roman times by water overflow from the albano crater lake alban hills are presently characterized by high p co2 in groundwaters and by several cold gas emissions usually in sites where excavations removed the superficial impervious cover gas consists mostly of co 2 with minor h 2 s and the diffuse co 2 soil flux is locally very high accidental gas blowouts occurred during shallow well drillings tens to hundreds m depth in zones with no surface gas manifestations indicate the presence of gas pressurized aquifers confined underneath impermeable layers within both the volcanic rock pile and the underlying pleistocene loose sediments degassing mostly occurs in correspondence of bordering faults of buried horsts cut in the mesozoic carbonate basement hosting the main aquifer carbon isotopic composition 13 c co2 suggests that co 2 is at least partly originated by thermal decarbonation of these limestones 3 he 4 he isotopic ratio of the gas up to 1 9 ra is the same or even slightly higher than that of olivine and clinopyroxene fluid inclusions of the alban hills volcanic products indicating a possible magmatic source for the gas low r ra values compared to morb and island arc magmas are characteristic of the potassic roman comagmatic province and reflect a deep involvement of crustal material in the magma genesis the lack of high temperature fumaroles can be explained by an efficient meteoric cold water penetration and circulation in the volcano permeable terrains

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

earthquake depths and the relation to strain accumulation and stress near strike slip faults in southern california earthquakes in the major fault zones are predominantly deep earthquakes in the crustal blocks bounding the fault zones are predominantly shallow in the san jacinto fault zone maximum earthquake depths correlate with surface heat flow these relations together with focal mechanisms geodetic strain measurements and fault zone models are consistent with the following ideas 1 interseismic plate motion is accommodated by aseismic slip along an extension of the major fault zone below a brittle zone that is locked between large earthquakes 2 the aseismic slip in a narrow fault zone in the brittle plastic transition region concentrates strain at the base of the brittle fault zone 3 deep earthquakes occur in thelower part of the brittle fault zone due to stick slip failure of highly stressed patches 4 background earhtquakes and aftershocks that occur several kilometers deeper than large earthquake hypocenters suggest that a zone of mixed slip behavior may exist between the stable sliding deep and stick slip shallow regions of the fault zone furthermore the difference in seismicity between the san jacinto and southern san andreas faults suggests that the nature of this mixed zone may evolve as total displacement in the fault zone increases 5 shear stress may be lessmore in the crustal blocks than in the deep brittle fault zones and generally at a level sufficient to cause brittle failure only shallow in the crustal blocks 6 in the stress field produced by plate motion and slip in the deep fault zone the upper brittle fault zone is not oriented favorably for shear failure lack of shallow earthquakes in the fault zones and the predominance of shallow earthquakes on favorably oriented fractures in the adjacent crustal blocks suggest that either stress in the upper brittle fault zone is relatively low or the upper fault zone is effectively strong due to its orientation less

retrograde eclogite from mont albert gaspe quebec retrograde eclogite is found along the northern perimeter of ultramafic rocks in the mont albert complex gaspe quebec garnet clinopyroxene geothermometry gives 840 c as the peak temperature of metamorphism kyanite in associated metapelites requires that at this temperature pressure be a minimum of 12 kbar based on symplectic textures in the eclogitic and associated rocks and clinozoisite white mica quartz plagioclase equilibria a counterwise pressure temperature trajectory that terminates near 500 c and 8 kbar can be traced for the mont albert complex

chemical and isotopic compositions of minerals and waters from the campi flegrei volcanic system naples italy abstract based on their 34 s signature sulfate minerals and native sulfur around fumaroles and hot water pools from the campi flegrei volcanic area derive from supergenic oxidation of volcanic h 2 s their mean 34 s value 0 2 1 7 matches with that of fumarolic h 2 s at solfatara 0 3 0 3 as well as with the 34 s of 1 4 obtained for total sulfur in fresh trachyte from the area all 34 s values indicate a mostly deep seated origin for sulfur thermal waters were analysed for major and minor chemistry and for oxygen hydrogen and sulfur isotope compositions pools at pisciarelli are filled with evaporated meteoric water heated by rising magmatic gases the water 18 o 3 8 1 3 and 2 h 6 5 2 2 values in these steam heated waters are controlled by mixing and evaporation effects and the 34 s value of dissolved sulfate 1 3 0 3 basically agrees with supergenic oxidation of deep seated h 2 s as the major source of sulfur instead water from thermal springs and wells elsewhere in the campi flegrei appears to be a mixture between dilute meteoric and saline marine components the latter may be local seawater from the bay of pozzuoli the 18 o and 2 h values of waters sampled during 1993 1994 range from 5 6 to 0 3 and from 33 to 3 4 respectively the 34 s values of dissolved sulfate range between 0 1 and 19 5 in general sulfate is probably derived essentially from two sources both within the volcanic cover i e oxidation dissolution of pyrite and anhydrite and marine water an occasional source of water and sulfate is represented by magmatic gases which directly interact with shallow meteoric water as in the case of the hotel tennis well yielding steam heated water with 18 o 1 5 0 2 2 h 17 1 and 34 s 0 1

carbon dioxide degassing from the albani hills volcanic region central italy the albani hills are affected by strong co2 degassing processes the amount of co2 which rises from the depths and subsequently dissolves into shallow groundwater has been estimated to be more than 4 2 109 mol year 1 most of the gas is released in localised anomalous spots lavinio solforata and ciampino albano nemi areas generated by fluid leakage processes from buried pressurized reservoirs hosted by structural highs of the calcareous siliceous marly basement the groundwater circulating in the anomalous areas becomes co2 oversaturated generating observable gas manifestations whose composition is mainly controlled by gas liquid separation processes a gas flow rate of 6 1 108 mol year 1 has been measured from the two larger manifestations using the accumulation chamber technique the presence at shallow level of co2 oversaturated groundwater can explain several episodes of sudden release of gas which was documented by historical chronicles from roman times until now

the subduction plate interface rock record and mechanical coupling from long to short timescales abstract short and long term processes at or close to the subduction plate interface e g mineral transformations fluid release seismicity and more generally deformation might be more closely related than previously thought increasing evidence from the fossil rock record suggests that some episodes of their long geological evolution match or are close to timescales of the seismic cycle this contribution uses rocks recovered episodically from subduction zones together with insights from thermomechanical modelling to provide a new dynamic vision of the nature structure and properties of the plate interface and to bridge the gap between the mechanical behavior of active subduction zones e g coupling inferred from geophysical monitoring and fossil ones e g coupling required to detach and recover subducted slab fragments based on critical observations and an exhaustive compilation of worldwide subducted oceanic units for which the presence near the plate interface rock types pressure temperature t p gradients thickness and timing of detachment can be assessed the present study demonstrates how long term mechanical coupling exerts a key control on detachment from the slab and potential rock recovery critical assessment of rock t p characteristics indicates that these fragments can indeed be used as natural probes and provide reliable information on subduction interface dynamics down to 2 8 gpa rock clusters are identified at depths of 30 55 60 and 80 km with some differences between rock types data also reveal a first order evolution with subduction cooling in the first 5 myr which is interpreted as reflecting a systematic trend from strong to weak mechanical coupling after which subduction is lubricated and mostly inhibits rock recovery this contribution places bounds on the plate interface constitution regular thickness

age and composition of the ruisseau isabelle melange along the shickshock sud fault zone constraints on the timing of melanges formation in the gaspe appalachians melanges are common in the humber and dunnage zones of the quebec appalachians humber zone melanges are spatially associated with taconian nappes and believed to be of tectonic origin dunnage zone melanges are interpreted as relicts of an ordovician accretionary prism the ruisseau isabelle melange rim in the gaspe ap palachians was first interpreted as a dunnage zone melange because of its tectonic position along the baie verte brompton line and lithological components such as dark mudstone blocks of ultramafic rocks and greenish chromite bearing sandstone the rim comprises sedimentary rock assemblages composite shale black shale and chromite bearing sandstone assemblages an exotic block a pebbly mudstone assemblage and slivers of serpentinized peridotite and metamorphic tectonite most melanges of the dunnage zone in the quebec appalachians contain partly similar rocks but their age is not well constrained recent work on the rim and cap chat melange of the humber zone and new fossil finds in the rim rock assemblages allow us to conclude that previous distinction between melanges of the dunnage and humber zones on the basis of rock type associations is not valid according to the age of the rim rock assemblages melanges in the northern gaspe appalachians continued forming after the mid caradocian later than the dunnage zone melanges of southern gaspe appalachians the juxtaposition and structural features of the rim rock assemblages result from repeated faulting along the shickshock sud fault from late ordovi cian to middle devonian

triggering of the lusi mud eruption earthquake versus drilling initiation abstractthe lusi mud volcano in east java has erupted unabated for almost 2 yr ooding an area of 7 km 2 and displacing more than 25 000 people despite its disastrous impact the mechanism for triggering the lusi eruption remains highly controversial two distinct mechanisms have been proposed one hypothesis suggests that the eruption was triggered by the m w 6 3 earth quake that struck yogyakarta 250 km from lusi two days before the eruption however an examination of static and dynamic stress changes and stress transfer mechanisms indicates that the yogyakarta earthquake was at least an order of magnitude too small to reactivate faults and open uid ow pathways under lusi an alternate theory suggests that lusi was triggered by a blowout following drilling problems in the nearby banjar panji 1 well blowouts result from an inability to control pore uid intakes into the borehole and typically occur when the drilling win dow fracture pressure minus pore pressure is approximately zero and when there is insuf cient protective casing of the well bore pore and fracture pressure data from banjar panji 1 indicate that the well had a narrow drilling window of only 0 2 3 mpa furthermore two planned casing points were skipped during drilling resulting in 1742 m of unprotected borehole the combina tion of hazardously narrow drilling window and long uncased borehole would have made drill ing problems in banjar panji 1 dif cult to control placing the well at high risk of blowing out furthermore well bore pressures following drilling problems in banjar panji 1 reached magni tudes in excess of the fracture pressure and thus were suf cient to create uid ow pathways in the subsurface therefore we suggest that no viable method is known by which the yogyakarta earthquake could have triggered the mud ow and that a blowout in the banjar panji 1 well was the most likely mechanism for triggering the lusi eruption keywords

time dependent co2 variations in lake albano associated with seismic activity lake albano alban hills volcanic complex central italy is located in a densely populated area near rome the deep lake waters have significant dissolved co2 concentrations probably related to sub lacustrine fluid discharges fed by a pressurized co2 rich reservoir the analytical results of geochemical surveys carried out in 1989 2010 highlight the episodes of co2 removal from the lake the total mass of dissolved co2 decreased from 5 8 107 kg in 1989 to 0 5 107 kg in 2010 following an exponential decreasing trend calculated values of both dissolved inorganic carbon and co2 concentrations along the vertical profile of the lake indicate that this decrease is caused by co2 release from the epilimnion at depth 9 m combined with 1 water circulation at depth 95 m and 2 co2 diffusion from the deeper lake layers according to this model lake albano was affected by a large co2 input that coincided with the last important seismic swarm at alban hills in 1989 suggesting an intimate relationship between the addition of deep originated co2 to the lake and seismic activity in the case of a co2 degassing event of an order of magnitude larger than the one that occurred in 1989 the deepest part of lake albano would become co2 saturated resulting in conditions compatible with the occurrence of a gas outburst these results reinforce the idea that a sudden co2 input into the lake may cause the release of a dense gas cloud presently representing the major volcanic threat for this densely populated area

the albano maar lake colli albani volcano italy recent volcanic activity and evidence of pre roman age catastrophic lahar events abstract the evaluation of volcanic hazard in the roman hinterland related to the quiescent colli albani volcano has recently been the subject of renewed attention and several interpretations by many authors however very little was known of the recent history of the volcano making such interpretations rather speculative the most recent activity of colli albani volcano originated from the albano polygenetic maar lake which erupted several phreatomagmatic units the most recent of which the peperino albano ignimbrite has been dated at around 25 ka an area of several square kilometers centered around albano lake is presently the site of shallow and frequent seismic activity and gaseous emission as well as hydrothermal activity and is therefore considered the most prone to geologic hazards this paper presents new stratigraphic and geomorphologic data as well as age determinations that allow rejuvenation of the most recent activity of the colli albani volcano and particularly the albano maar lake to the holocene this study allows for the first time to identify a potential hazard related to the albano maar lake withdrawal interpreted to be related to endogenous causes namely co 2 emission the main results of the study are 1 the peperino albano is not as is generally believed the last phreatomagmatic eruption from the colli albani volcano a previously unrecognized phreatomagmatic surge deposit has been identified overlying the paleosol at the top of the peperino albano and related lahar deposits 2 two lahar deposits separated by paleosols top the stratigraphic succession and are dispersed only to the nw corresponding to the lowest point of the maar rim indicating that catastrophic hydrologic events occurred at the albano lake in recent times rapid and substantial lake level variations and lake withdrawal are reported by roman historians and recorded by the stratigraphy of the albano lake lacustrine sediments 3 microfracturing related to seismic energy release is linked to sudden variation of co 2 flow and upwelling of hydrothermal fluids these occurrences across the lake are the likely causes that triggered during holocene several episodes of lake withdrawal rising the water table and probably triggering convective rollover of the lake water

facies associations of rain generated versus crater lake withdrawal lahar deposits from quaternary volcanoes central italy abstract two syneruption lahar deposit successions from quaternary italian volcanoes are presented displaying different facies associations interpreted to reflect different water sources the lahar deposits associated with the white trachytic tuff cupa wttc ignimbrites from the quaternary roccamonfina volcano located 150 km to the southeast of rome have been interpreted in terms of rain generated lahars the wttc ignimbrites are made of more than 1 km 3 of loose pumice and lava lithic debris emplaced along the hyperbolic slope of the volcano at ca 300 ka during an interglacial period characterised by mild and wet climate the lahar deposits are organised in a coarsening upward aggradational and back stepping succession of medium to thick bedded progressively juvenile poorer non cohesive debris flow to fluvial deposits box shaped channels cut the wttc ignimbrites along the steep upper slopes channels are filled with lava lithic rich fluvial to hyperconcentrated flow sand and conglomerate which are interpreted as lag deposits related to processes of bulking due to the removal of light pumice and ash debris from the upper slope along the lower slopes of the volcano and in the surrounding ring plains where the average slope inclination decreases to few degrees lahars emplaced an aggradational succession of bedded ash rich hyperconcentrated flow deposits entirely derived from wttc components the succession coarsens upward with increasing presence of lava rich conglomerate lenses fluvial in origin interpreted to record the progressive restoration through time of the drainage network the succession is cut by incised gullies filled with polygenetic fluvial deposits which indicate the restoration of intererruption condition by contrast the ca 23 ka small volume peperino albano phreatomagmatic eruption from colli albani volcano located 30 km to the southeast of rome emplaced a valley ponded block and ash ignimbrite which along the western slope of the volcano grades laterally into a single far reaching thick lahar deposit the lahar deposit coarsens upward from coarse ash hyperconcentrated flow deposit into a lithic block rich debris flow deposit this lahar deposit has been interpreted to be directly derived from a pyroclastic flow and particularly related to the entrance of the pyroclastic flow into a pre existing maar crater lake along the pyroclastic flow path the basal sand size hyperconcentrated flow deposit is interpreted to represent early deposition from the fast frontal flood wave whereas the coarse lithic rich debris flow deposit at the top may represent the rear of the lahar the separation of the two facies can be related to processes of hydraulic sieving operated by the lake water which couples with ash particles leaving behind the coarser fraction

a newly emerged august 2013 artificially triggered fumarole near the fiumicino airport rome italy abstract early in the morning of 24 august 2013 following by hours the drilling of a shallow borehole in the same spot a new fumarole producing emissions of co2 rich gas water and mud suddenly appeared at a crossroad along the fenced area of the fiumicino international airport of rome italy similar episodes have been scientifically documented or simply reported in recent and past years to understand why gases are easily entrapped in the shallow subsurface of the fiumicino area we used five borehole cores drilled by us analyzed the stratigraphy of these and other nearby cores acquired a 2d seismic refraction tomogram and performed chemical and isotopic analyses of water samples collected from aquifers intercepted by two drilled boreholes our boreholes were realized with proper anti gas measures as while drilling we recorded the presence of pressurized gases at a specific permeable gravel level results show that in the study area gases become mainly entrapped in a mid pleistocene gravel horizon at about 40 50 m depth this horizon contains a confined aquifer that stores the endogenous upwelling gases the gravel is interposed between two silty clayey units the lower unit very hard and overconsolidated is affected by fractures that allow ascending gases to bypass the otherwise impermeable shale permeate the gravel and dissolve into the aquifer in contrast the upper unit is impermeable to fluids and seals the gas pressurized aquifer which therefore constitutes a source of hazard during human activities such as well drilling quarrying and various building related excavations as the stratigraphy of the fiumicino area is very common in large portions of the densely populated roman area and as the adjacent volcanic districts are hydrothermally active we conclude that phenomena similar to that observed at fiumicino could again occur both at fiumicino and elsewhere in the surrounding region as a prompt confirmation of our conclusion we signal that while writing this paper new artificially triggered degassing phenomena occurred off fiumicino in connection with the construction of the new harbor

hydrothermal eruptions of nisyros dodecanese greece past events and present hazard abstract the detailed analysis of the craters of hydrothermal eruptions and related products present on nisyros island demonstrates the ephemerality of these morphological forms in other words the mere recognizable existence of the craters and associated deposits implies recency of hydrothermal activity the minimum temperature required to cause the explosive phenomenon and possibly the depth of the reservoir which can be evaluated on the basis of the correlation between the diameter of the crater and the depth of explosion as proposed by fytikas and marinelli 1976 are therefore closely representative of the current hydrothermal circulation both field evidence and historical records indicate that all the deposits of hydrothermal eruption recognized on nisyros island were emplaced as debris flows almost all the ballistic ejecta were entrained in these debris flows and either redeposited far from their landing sites or involved in later crater collapse and erosion this emplacing mechanism implies that the original products were characterized by a water content higher than about 5 by weight steam driven hydrothermal eruptions one of which took place in 1871 originated deposits of limited dispersion as no sign of these erodible products can be found in the field today surface geology and fluid geochemistry together with subsurface information e g primary and hydrothermal lithologies distribution of temperature with depth physical chemical characteristics of deep water bearing zones indicate that two distinct hydrothermal aquifers are present underneath the southeastern part of the caldera floor both aquifers were probably involved in the most important historically documented hydrothermal eruptions which occurred in 1873 at that time violent earthquakes fractured the brittle aquiclude separating the two aquifers and caused a sudden transfer of fluids from the deep to the shallow aquifer thus triggering the hydrothermal eruptions hydrothermal eruptions will probably occur in future and this hazard must be taken into serious consideration the southern half of lakki plain where all past eruptions took place and active fumaroles are concentrated is the zone at highest risk at present gas geochemistry represents an effective tool to detect changes in the p t conditions of the shallow aquifer and particularly the phenomena of pressure build up that may lead to a hydrothermal eruption

a new hydrothermal scenario for the 2006 lusi eruption indonesia insights from gas geochemistry abstract the 29th of may 2006 gas and mud eruptions suddenly appeared along the watukosek fault in the north east of java indonesia within a few weeks several villages were submerged by boiling mud the most prominent eruption site was named lusi to date november 2011 lusi is still active and a 7 km2 area is covered by the burst mud breccia the mechanisms responsible for this devastating eruption remain elusive while there is consensus about the origin of the erupted mud the source of water is uncertain the origin of the gas is unknown and the trigger of the eruption is still debated in order to shed light on these unknowns we acquired a wide set of data of molecular and isotopic composition of gas sampled in several lusi vents in the surrounding mud volcanoes in the closest natural gas field wunut and in the hydrothermal vents at the neighbouring volcanic complex in the period 2006 2011 the boiling fluids erupted in the crater zone are apparently co2 dominated while colder ch4 dominated and c2 c3 bearing fluids are identified at several sites around the crater zone gas genetic diagrams maturity plots and gas generation modelling suggest that the hydrocarbons are thermogenic 13c1 up to 35 13c2 up to 20 deriving from marine kerogen with maturity of at least 1 5 ro for instance in the 4400 m deep ngimbang source rocks co2 released from the crater and surrounding seeps is also thermogenic 13c from 15 to 24 related to kerogen decarboxylation or thermal ch4 oxidation in deep rocks although three vents just outside the crater showed an apparent inorganic signature 7 5 4000 m magmatic intrusions and hydrothermal fluids responsible for the enhanced heat that altered source rocks and or gas reservoirs the neighbouring magmatic arjuno complex and its fluid pressure system combined with high seismic activity could have played a key role in the lusi genesis and evolution within this new model framework lusi is better understood as a sediment hosted hydrothermal system rather than a mud volcano

development of inverted metamorphic gradient in the internal domain of the taconian belt gaspe peninsula the mont logan nappe is part of the taconian internal domain of the quebec appalachians and is entirely made up of synrift to passive margin elastics and volcanics of the shickshock group rocks o

gas blowout from shallow boreholes at fiumicino rome induced hazard and evidence of deep co2 degassing on the tyrrhenian margin of central italy abstract a borehole drilled at fiumicino rome down to only 27 m depth in a zone where no gas emission at the surface was known caused a gas blowout from a pressurized gas pocket confined beneath a clay cover gas slowly diffused from the borehole within superficial permeable sand seven persons living in three ground floor flats of a near building had to be hospitalized due to co2 exposure all the houses in the proximity were evacuated at the request of the fire brigade two additional boreholes were drilled nearby hoping that this could rapidly exhaust the gas stored underground to the contrary the soil gas flux near houses increased and indoor co2 air concentration rapidly rose to lethal values 15 to 30 vol as a remediation we suggested to restore the continuity of the impervious gas cover by squeezing quick setting cement into the formation through new boreholes to be drilled near the existing ones although the first cement squeeze reduced drastically the co2 soil flux and indoor concentration six additional squeezes had to be carried out in order to lower the gas emission below the gas hazard threshold the gas was mostly made of co2 98 vol with minor n2 and ch4 its chemical and isotopic composition 13cco2 1 55 3he 4he 0 314 ra is similar to that of the gas manifestations of mts sabatini and alban hills volcanic areas though being somewhat contaminated by crustal and shallow organic volatiles these gases likely have a component originated in the mantle that beneath the volcanic roman comagmatic province is probably deeply contaminated with crustal material the fiumicino gas blowout indicates that the area of central italy characterized by strong co2 degassing extends westerly to include the tyrrhenian coast

gas hazard assessment in a densely inhabited area of colli albani volcano cava dei selci roma the northwestern flank of the colli albani a quaternary volcanic complex near rome is characterised by high pco2 values and rn activities in the groundwater and by the presence of zones with strong emission of gas from the soil the most significant of these zones is cava dei selci where many houses are located very near to the gas emission site the emitted gas consists mainly of co2 up to 98 vol with an appreciable content of h2s 0 8 2 the he and c isotopic composition indicates as for all fluids associated with the quaternary roman and tuscany volcanic provinces the presence of an upper mantle component contaminated by crustal fluids associated with subducted sediments and carbonates an advective co2 flux of 37 tons day has been estimated from the gas bubbles rising to the surface in a small drainage ditch and through a stagnant water pool present in the rainy season in a topographically low central part of the area a co2 soil flux survey with an accumulation chamber carried out in february march 2000 over a 12 000 m2 surface with 242 measurement points gave a total mostly conductive flux of 61 tons day co2 soil flux values vary by four orders of magnitude over a 160 m distance and by one order of magnitude over several metres a fixed network of 114 points over 6350 m2 has been installed in order to investigate temporal flux variations six surveys carried out from may 2000 to june 2001 have shown large variations of the total co2 soil flux 8 25 tons day the strong emission of co2 and h2s which are gases denser than air produces dangerous accumulations in low areas which have caused a series of lethal accidents to animals and one to a man the gas hazard near the houses has been assessed by continuously monitoring the co2 and h2s concentration in the air at 75 cm from the ground by means of two automatic stations certain environmental parameters wind direction and speed atm p t humidity and rainfall were also continuously recorded at both stations h2s and co2 exceeded by several times the recommended concentration thresholds the highest co2 and h2s values were recorded always with wind speeds less than 1 5 m s mostly in the night hours our results indicate that there is a severe gas hazard for people living near the gas emission site of cava dei selci and appropriate precautionary and prevention measures have been recommended both to residents and local authorities

isotopic and chemical assessment of geothermal potential of the colli albani area latium region italy abstract the chemical and isotopic compositions of low temperature mineral waters discharged over the colli albani region south of rome italy are those of highly immature waters of essentially meteoric origin formed through absorption of gases emanating from greater depth followed by cation leaching of country rock at shallow levels the composition of the gases discharged points to the presence at depth of a co2 producing high temperature system in its waning stage low h2 and unsaturated hydrocarbon contents as well as relative he ar and n2 contents indicate long residence time for the rising gas phase of the order of 1 ma on the basis of these findings temperatures higher than 120 c appear unlikely to exist at shallow depth

mantle derived co2 migration along active faults within an extensional basin margin fiumicino rome italy abstract fluid migration along faults can be highly complex and spatially variable with the potential for channeled flow accumulation in capped porous units fault cross flow lateral migration along strike or complete sealing extensional basin margins can be important for such migration given the associated crustal thinning and decompression that takes place combined with potential geothermal or mantle gas sources one such example is near the urban area of rome situated along the active extensional continental margin of the tyrrhenian back arc basin and surrounded by middle upper pleistocene k rich and arc related volcanoes recent research activities in the area around fiumicino a town 25 km to the west of rome has highlighted the close spatial link between degassing co 2 and the faults that provide the necessary vertical migration pathways in particular detailed soil gas and gas flux surveys have highlighted the release at surface of large volumes of asthenospheric mantle co 2 in correspondence with normal faults observed in a new seismic reflection profile acquired along the tiber river detailed reconstruction of the pleistocene holocene stratigraphy of the area dates fault activity from 20 000 to 9000 years bp it is proposed that the gas migrates preferentially along the cataclastic tectonic breccias of the faults until it encounters recent unconsolidated sediments porous units within this shallow stratigraphy act as temporary secondary traps for the leaking gas with local gas release at the ground surface occurring where the sealing of the overlying aquitards has been compromised degassing and active faults confirm the extensional tectonics affecting the area and the geodynamic scenario of a mantle wedge beneath the western apennines associated with ongoing w directed subduction moreover degassing highlights the potential geochemical and seismic risks for the highly populated urban areas near rome

incorporating surface indicators of reservoir permeability into reservoir volume calculations application to the colli albani caldera and the central italy geothermal province abstract the quaternary roman volcanic province extends for over 200 km along the tyrrhenian margin of the italian peninsula and is composed of several caldera complexes with significant associated geothermal potential in spite of the massive programs of explorations conducted by the then state owned enel and agip companies between the 1970s and 1990s and the identification of several high enthalpy fields this resource remains so far unexploited although it occurs right below the densely populated metropolitan area of roma capital city the main reason for this failure is that deep geothermal reservoirs are associated with fractured rocks the secondary permeability of which has been difficult to predict making the identification of the most productive volumes of the reservoirs and the localisation of productive wells uncertain as a consequence almost half of the many exploration deep bore holes drilled in the area reached a dry target this work reviews available data and re assesses the geothermal potential of caldera related systems in central italy by analysing in detail the case of the colli albani caldera system the closest to roma capital city a gis based approach identifies the most promising reservoir volumes for geothermal exploitation and uses an improved volume method approach for the evaluation of geothermal potential the approach is based on a three dimensional matrix of georeferenced spatial data the a axis accounts for the modelling of the depth of the top of the reservoirs based on geophysical and direct data the b axis accounts for the thermal modelling of the crust i e t with depth based on measured thermal gradients both a and b data are necessary but not sufficient to identify rock volumes actually permeated by geothermal fluids in fractured reservoirs we discuss the implementation of a c axis that evaluates all surface data indicating permeability in the reservoir and actual geothermal fluid circulation we consider datasets on i distribution and density of tectonic lineaments ii temperature and iii electric conductivity of shallow groundwaters iv partial pressure of dissolved co2 in shallow groundwaters the geothermal potential of colli albani and the implications for caldera related geothermal systems in central italy are discussed based on the role of the geometry and structure of reservoirs in relationship with volcano tectonic structures and deep geothermal fluid migration paths

eruptive history and petrologic evolution of the albano multiple maar alban hills central italy a comprehensive volcanological study of the albano multiple maar alban hills italy using i 40ar 39ar geochronology of the most complete stratigraphic section and other proximal and distal outcrops and ii petrographic observations phase analyses of major and trace elements and sr and o isotopic analyses of the pyroclastic deposits shows that volcanic activity at albano was strongly discontinuous with a first eruptive cycle at 69 1 ka producing at least two eruptions and a second cycle with two peaks at 39 1 and 36 1 ka producing at least four eruptions contrary to previous studies we did not find evidence of magmatic or hydromagmatic eruptions younger than 36 1 ka the activity of albano was fed by a new batch of primary magma compositionally different from that of the older activity of the alban hills moreover the ree and 87sr 86sr data indicate that the albano magma originated from an enriched metasomatized mantle according to the modeled liquid line of descent this magma differentiated under the influence of magma limestone wall rock interaction our detailed eruptive and petrologic reconstruction of the albano maar evolution substantiates the dormant state of the alban hills volcanic district

co2 rich gases from lakes nyos and monoun cameroon laacher see germany dieng indonesia and mt gambier australia variations on a common theme abstract helium r a 3 0 to 5 6 and carbon 13 c from 7 2 to 3 4 isotopic compositions and relative co 2 ch 4 n 2 he and ar contents of co 2 rich gases from lakes nyos and monoun cameroon laacher see germany dieng volcanic plateau indonesia and a well at mt gambier australia point to a common essentially magmatic origin absorption of the original magmatic gases into deeply circulating groundwater and equilibration of the resulting solutions with crustal rock at temperatures of about 300 c fix co 2 and ch 4 contents on further rise the solutions start to boil separating gas rich vapors which on encountering an impermeable barrier may accumulate to form gas pockets with steadily increasing pressures in the case of sufficiently high gas contents the pressures may exceed lithostatic pressures leading to a blow out or a pneumatic eruption dieng otherwise gas may accumulate to form a stable pocket mt gambier minor leakage from such pockets may lead to surface discharges of co 2 rich gases as at laacher see re absorption into shallow groundwater to the formation of the low salinity co 2 charged waters encountered at lakes nyos and monoun the occurrence of these high co 2 low temperature systems is likely to be favored in tectonically active regions allowing deep possibly mantle gases to rise but with sufficiently low regional heat flows to prevent the establishment of large scale geothermal activity

fluid flow within the damage zone of the boccheggiano extensional fault larderello travale geothermal field central italy structures alteration and implications for hydrothermal mineralization in extensional settings the neogene extensional province of southern tuscany in central italy provides an outstanding example of fossil and active structurally controlled fluid flow and epithermal ore mineralization associated with post orogenic silicic magmatism characterization of the hydrodynamic regime leading to the genesis of the polysulphide deposit known as filone di boccheggiano hosted within the damage zone of the boccheggiano fault is a key target to assess modes of fossil hydrothermal fluid circulation in the region and more generally to provide inferences on fault controlled hydrothermal fluid flow in extensional settings we provide a detailed description of the fault zone architecture and alteration mineralization associated with the boccheggiano ore deposit and report the results of fluid inclusion and stable oxygen isotope studies this investigation shows that the boccheggiano ore consists of an adularia illite type epithermal deposit and that sulphide ore deposition was controlled by channelling of hydrothermal fluids of dominantly meteoric origin within the highly anisotropic permeability structure of the boccheggiano fault the low permeability structure of the fault core compartmentalized the fluid outflow preventing substantial cross fault flow with focused fluid flow occurring at the hangingwall of the fault controlled by fracture permeability fluid inclusion characteristics indicate that ore minerals were deposited between 280 and 350 c in the upper levels of the brittle extending crust lithostatic pressure in the order of 0 1 gpa abundant vapour rich inclusions in ore stage quartz are consistent with fluid immiscibility and boiling and quartz ore vein textures suggest that mineralization in the boccheggiano ore deposit occurred during cyclic fluid flow in a deformation regime regulated by transient and fluctuating fluid pressure conditions results from this study i predict a strongly anisotropic permeability structure of the fault damage zone during crustal extension and ii indicate the rate of secondary structural permeability creation and maintenance by active deformation in the hangingwall of extensional faults as the major factor leading to effective hydraulic transmissivity in extensional terranes these features intimately link ore grade mineralization in extensional settings to telescoping of hydrothermal flow along the hangingwall block s of major extensional fault zones

time dependent geochemistry of clinopyroxene from the alban hills central italy clues to the source and evolution of ultrapotassic magmas abstract we investigated chemical and isotopic compositions of clinopyroxene crystals from well age constrained juvenile scoria clasts lava flows and hypoabyssal magmatic ejecta representative of the whole eruptive history of the alban hills volcanic district the alban hills is a quaternary ultra potassic district that was emplaced into thick limestone units along the tyrrhenian margin of italy alban hills volcanic products even the most differentiated are characterised by low sio2 content we suggest that the low silica activity in evolving magmas can be ultimately due to a decarbonation process occurring at the magma limestone interface according to the liquid line of descent we propose the differentiation process is driven by crystallisation of clinopyroxene leucite apatite magnetite coupled with assimilation of a small amount of calcite and or with interaction with crustal co2 by combining age chemical data strontium and oxygen isotopic compositions and ree content of clinopyroxene we give insights into the evolution of primitive ultrapotassic magmas of the alban hills volcanic district over an elapsed period of about 600 kyr geochemical features of clinopyroxene crystals consistent with data coming from other italian ultrapotassic magmas indicate that alban hills primary magmas were generated from a metasomatized lithospheric mantle source in addition our study shows that the 87sr 86sr and lree hree of alban hills magmas continuously diminished during the 600 35 ka time interval of the alban hills eruptive history possibly reflecting the progressive depletion of the metasomatized mantle source of magmas

pressure temperature time evolution of paleozoic high pressure rocks of the acatlan complex southern mexico implications for the evolution of the iapetus and rheic oceans new thermobarometric and u pb and 40 ar 39 ar geochronologic data coupled with ages obtained from the acatlan complex the basement of the mixteco terrane of southern mexico reveal the existence of three distinctive high pressure metamorphic events of early to middle paleozoic age each recorded in a separate lithological suite xayacatlan suite eclogites with oceanic affinity underwent peak metamorphism at 609 491 c and 13 12 kb during the early ordovician ca 490 477 ma u pb zircon followed by a partial overprint at 600 c and 9 6 kb and then at 500 c and 6 7 kb an overprinting event at 525 500 c and 9 5 kb is ascribed to the devonian the pressure temperature p t path of the xayacatlan suite indicates a subduction exhumation process followed by tectonically related reburial ixcamilpa suite blueschists with oceanic affinity underwent epidote blueschist metamorphism t 200 390 c p 6 9 kb and then epidote amphibolite t 390 580 c p 9 6 kb events ascribed to the late ordovician early silurian esperanza suite eclogites with continental affinity underwent peak metamorphism at 830 730 c and 17 15 kb amphibole from eclogite yields a 430 5 ma 40 ar 39 ar age dating the high pressure hp event p t paths of high temperature ht eclogites like those of the esperanza suite have been related to the collision of continental blocks partial overprinting occurred at 690 640 c and 14 10 kb prior to 374 2 ma 40 ar 39 ar phengite the three hp suites were tectonically juxtaposed at different times before the mississippian period resulting in the closure of the iapetus ocean phengite 40 ar 39 ar geochronology reveals the existence of a widespread tectonothermal event between 345 and 323 ma which may be related to the juxtaposition of the hp composed block and the gondwanan affinity cosoltepec suite causing the closure of the rheic ocean the tectonothermal events in the acatlan complex coincide in time physical conditions and tectonic setting with events in the appalachian caledonian orogen suggesting their relation on that basis the geology of the acatlan complex can lead to a more comprehensive understanding of the tectonic evolution of the appalachian orogen and of the gondwana laurentia interactions preceding the pangean assembly

fluids in early stage hydrothermal alteration of high sulfidation epithermal systems a view from the vulcano active hydrothermal system aeolian island italy abstract high sulfidation hs epithermal systems have elements in common with passively degassing volcanoes associated with high t acid fumarole fields or acid crater lakes they are considered to form in two stages the first of which involves advanced argillic alteration resulting from intense strongly acidic fluid rock interaction the la fossa hydrothermal system vulcano island represents a classic example of such an active hs system and can be considered as a modern analogue of this early stage of alteration resulting in a core of intense silicic 90 95 pure sio2 alteration surrounded by alunitic alteration zones this paper focuses on a geochemical and stable isotope study of the surficial alteration facies of vulcano particularly the horizon characterized by strong silicic alteration and on deep seated xenoliths ejected during the last eruption of la fossa volcano 1888 90 that can be considered as representative of fragments of the deep conduit system of la fossa volcano using directly measured temperatures at the sites of sampling we have calculated fluid composition in isotopic equilibrium with the alteration products the large range of measured silica 18o 12 3 to 29 reflects the wide range of formation temperatures 80 240 c the fluid compositions calculated for intense silicic alteration vary from 0 9 to 6 5 these are significantly heavier than local meteoric water 6 and are consistent with derivation from the condensation of high temperature fumarolic gases dominated by magmatic fluids and rich in acid gases so2 h2s hcl hf into shallow groundwaters of meteoric origin with dynamically variable ratios of fumarolic steam meteoric water the calculated 18o and d of water in equilibrium with alunite also suggest the mixing of magmatic and meteoric waters for the fluids involved in the genesis of advanced argillic alteration facies the calculated 18o of water in equilibrium with hedenbergitic clinopyroxene found in a veinlet in a metasomatized xenolith is 8 9 this value cannot reasonably result from water rock interaction between the host volcanic rocks and surface water instead it most likely represents a fluid brine exsolved from magma which was responsible for high temperature metasomatism in the deep conduit system

the 2002 2003 submarine gas eruption at panarea volcano aeolian islands italy volcanology of the seafloor and implications for the hazard scenario abstract a submarine gas eruption started in november 2002 offshore of panarea volcano aeolian islands italy the intensity of the gas emission and the considerable anomalies of the geochemical and geophysical parameters have alarmed the volcanological community and the italian civil protection agency on the possibility that this activity may represent a volcanic unrest at panarea volcano we used a high resolution marine digital terrain model mdtm with 0 5 m accuracy and detailed underwater surveys by scuba diving to study the exhalation centres and the geological morphological and structural features of the seafloor and to clarify the relationships between gas vents distribution submarine volcanological structures and the recent deformation of this area the underwater surveys revealed an exhalative field characterised by 21 main active gas vents and craters from metres to tens of metres in diameter and a pervasive exhalation from the seafloor hundreds of fossil craters associated with gas pipes and hydrothermal alteration are also present on the seafoor craters pipes and conduits are not associated with juvenile deposits and relate to a long standing history of gas exhalation and eruptions we present the first geological sketch map of the seafloor surrounding the exhalative area and establish the role of ne and nw trending fractures as the main pathways for the gas exhalation

glacial dispersal of rock debris in central gaspesie quebec canada the lithological content of tills in central gaspesie is evaluated by pebble counting of 231 samples collected in excavation pits and containing 200 pebbles each the results are used here to establish the pattern of debris dispersal and to infer the glacial history of the area the dispersal pattern is characterized by well defined southeasterly 160 170 and northeasterly 40 60 trending trains half distance values of glacial transport along the trains range from 5 to 9 km for both directions suggesting ice flow events of considerable magnitude the volume of material in the trains represents 1 6 m of glacial erosion of the bedrock glacial cirques and short u shaped valleys about 100 200 m deep are incised into the mcgerrigle mountains granite pluton as well as the adjacent metabasalt the corresponding trains are aligned with these erosional features indicating that their clast content was derived from those features during an early alpine glacier phase the southeasterly trending dispersal tr

sudden deep gas eruption nearby rome s airport of fiumicino 1 on 24 august 2013 a sudden gas eruption from the ground occurred in the tiber river delta nearby rome s international airport of fiumicino we assessed that this gas analogous to other minor vents in the area is dominantly composed of deep partially mantle derived co2 as in the geothermal gas of the surrounding roman comagmatic province increased amounts of thermogenic ch4 are likely sourced from meso cenozoic petroleum systems overlying the deep magmatic fluids we hypothesize that the intersection of ne sw and n s fault systems which at regional scale controls the location of the roman volcanic edifices favors gas uprising through the impermeable pliocene and deltaic holocene covers pressurized gas may temporarily be stored below these covers or within shallower sandy permeable layers the eruption regardless the triggering cause natural or man made reveals the potential hazard of gas charged sediments in the delta even at distances far from the volcanic edifices

taconian and acadian transpression between the internal humber zone and the gaspe belt in the gaspe peninsula tectonic history of the shickshock sud fault zone the shickshock sud fault has a history of ordovician taconian silurian salinic and devonian acadian movements taconian deformation involving ductile dextral oblique slip faulting is recorded in cambrian rocks in the footwall of the shickshock sud fault metabasalt and metaarkose at amphibolite grade are converted into phyllonite and mylonitic schist shear bands asymmetric garnet porphyroclasts c s fabrics and mica fish textures indicate dextral shearing the regional sense of shear is top to west and southwest on generally southeast dipping shear zones hornblende of metabasalt yielded an 40ar 39ar age of 455 9 2 ma and muscovite from the mylonitic schist yielded an 40ar 39ar age of 454 3 0 9 ma which indicate metamorphism and deformation during the taconian orogeny evidence for silurian activity is indicated by the salinic unconformity to the south related to normal block faulting deformation features in the ordovician and silurian devonian rocks in the hanging wall were predominantl

hazardous gas emissions from the flanks of the quiescent colli albani volcano rome italy abstract gas hazard was evaluated in the three most important cold gas emission zones on the flanks of the quiescent colli albani volcano these zones are located above structural highs of the buried carbonate basement which represents the main regional aquifer and the main reservoir for gas rising from depth all extensional faults affecting the limestone reservoir represent leaking pathways along which gas rises to the surface and locally accumulates in shallow permeable horizons forming pressurized pockets that may produce gas blowout when reached by wells the gas mainly composed of co 2 90 vol contains appreciable quantities of h 2 s 0 35 6 vol and both represent a potentially high local hazard both gases are denser than air and accumulate near ground where they may reach hazardous concentrations and lethal accidents frequently occur to animals watering at local ponds in order to evaluate the rate of degassing and the related hazard co 2 and h 2 s diffuse soil flux surveys have been repeatedly carried out using an accumulation chamber the viscous gas flux of some important discrete emissions has been evaluated and the co 2 and h 2 s air concentration measured by portable devices and by tunable diode laser profiles the minimum potential lethal concentration of the two gases 250 ppm for h 2 s and 8 vol for co 2 is 320 times higher for co 2 whereas the co 2 h 2 s concentration ratio in the emitted natural gas is significantly lower 15 159 this explains why h 2 s reaches hazardous even lethal concentrations more frequently than co 2 a relevant hazard exists for both gases in the depressed zones channels excavations particularly in the non windy early hours of the day

a way to hydrothermal paroxysm colli albani volcano italy the main issue addressed in this work is the process leading to fluid subsurface entrapment and pressure increase up to hydrofracturing and possibly to paroxysm in a hydrothermal setting in order to envisage such processes and mitigate their effects in the volcanically active study area and elsewhere a field and laboratory multidisciplinary approach is used in the fossil late pleistocene portion of an active hydrothermal system colli albani volcano rome italy in this area sulfate and sulfide mineralizations and strongly altered ignimbrites are exposed the alteration acme occurs on top of a buried normal fault where abundant degassing is still active and fades away in 2 3 km based on pervasive versus discrete alteration styles mineral assemblages and further evidence proximal and distal alteration domains are recognized both domains underwent steam heated advanced argillic alteration with likely temperatures up to 400 c in the proximal domain and less than 150 c in the distal domain the process of hydrothermal alteration progressively and severely depleted many elements from the most permeable rock units whereas the lowest permeable unit tufo lionato underwent fracture and porosity healing accompanied by both mass and volume gain in the proximal domain the advanced argillic hydrothermal alteration eventually formed a substantial barrier to fluids the hydrothermal fluids accumulated in and below this barrier which was then suddenly hydrofractured when heat driven hydraulic pressure overcame the effective stress thus possibly leading to hydrothermal paroxysm the decompression associated with hydrofracturing enhanced gas exsolution and mineral precipitation from the entrapped overpressured fluids mineral precipitation contributed in turn to fracture healing and to reinitiation of a new cycle of hydrothermal fluid entrapment the key preconditions for the occurrence of the inferred processes are the contrasting compositions of k alkaline host rocks and acidic alteration fluids as also previously documented in other similar settings elsewhere

occurrence of zeolites in sedimentary rocks an overview zeolites have been known since the mid 1750s but prior to the early 1950s most reported occurrences of zeolites were in fracture fillings and amygdules in igneous rocks particularly basaltic lava flows indeed most of the large attractive zeolite specimens in museum collections were obtained from lavas in recent years zeolites have been recognized as important rock forming constituents in low grade metamorphic rocks and in a variety of sedimentary rocks most zeolites in sedimentary rocks are finely crystalline that is they occur as microscopic or submicroscopic crystals and they are therefore of little appeal to mineral collectors however deposits of this type are voluminous and have great geologic significance and economic potential zeolites are among the most common authigenic silicate minerals that occur in sedimentary rocks and they form in sedimentary rocks of diverse lithology age and depositional environment about twenty species of zeolites have been reported from sedimentary rocks but only eight zeolites commonly make up the major part of zeolitic rocks these are analcime chabazite clinoptilolite erionite heulandite laumontite mordenite and phillipsite this chapter will consider chiefly the zeolites in sedimentary rocks with emphasis on volcaniclastic deposits which contain the largest concentrations of zeolites the occurrence of zeolites in lava flows is mentioned only briefly journal articles on the occurrence and origin of natural zeolites have multiplied at a rapid rate since the mineralogy and geology of natural zeolites was first published in 1977 as volume 4 of the mineralogical society of america s reviews in mineralogy the present review will highlight areas of more recent research on the occurrence and origin of zeolites and some of the coexisting minerals a wide variety of zeolites has been identified in sedimentary deposits with the most common being clinoptilolite analcime heulandite laumontite and phillipsite less abundant zeolites include chabazite erionite mordenite natrolite