diagenesis of plio pleistocene sediments of the colorado river delta southern california abstract interbedded mudrocks and fine grained sandstones from three wells in the plio pleistocene colorado river delta in the imperial valley southern california were examined by x ray powder diffraction methods chemical analyses and scanning electron microscopy sem to determine the extent and course of low temperature metamorphic reactions this sequence was compared to tertiary rocks from the u s gulf coast in an effort to explore the kinetics of low temperature reactions in natural systems mineralogical changes observed are 1 the progressive transformation of mixed layer illite smectite to pure illite over the temperature range 70 c to 210 c 2 the apparent appearance of chlorite as a diagenetic mineral at 180 c to 194 c coincident with the onset of r symbol 3 ordering in the illite smectites 3 the loss of kaolinite above approximately 210 c and 4 a progressive decrease in the amount of detrital potassium feldspar over the same temperature interval that brackets the illitization reaction comparison of bulk chemical analyses with analyses of the comparison of tertiary sequences with this plio pleistocene sequence indicates that kinetics significantly influence the appearance of clay mineral assemblages at temperatures below approximately 175 c at temperatures above 175 c temperature rather than time appears to govern the reactions

structural styles and regional tectonic setting of the gela nappe and frontal part of the maghrebian thrust belt in sicily the gela nappe of south central sicily provides an example of a curved segment of an orogenic front that can be examined both onshore and offshore for deformational style and amount of shortening synorogenic sediments allow the deformation to be dated two distinct structural styles are observed in the gela nappe the central salient part of the nappe caltanissetta basin consists of a single thrust sheet containing a train of continuously tightening folds and the reentrant margins of the nappe sciacca and monte judica consist of a stack of several thrust sheets these different structural styles correspond to the pretectonic mesozoic stratigraphy of the foreland plate carbonate platforms exist on the adventure bank and hyblean plateau ahead of sciacca and monte judica respectively while the caltanissetta basin region appears to have accumulated basinal clay facies where the resistant carbonate stratigraphy provides a buttress to the propagation of the thrust front deformation is taken up by imbrication on steep ramps through the carbonates generating a relatively thick orogenic wedge in the basinal setting where no strong rheology exists the low angle of friction on the clay detachment levels requires the growing thrust wedge to be much thinner with a very low foreland dip hence the thrust front propagates much farther forward into the basin than it does in the adjacent platformal areas producing a nonlinear thrust front in the basinal region accretion of foreland material to the nappe by imbrication was only prominent during the messinian when subaerial exposure prevented low friction transport of the nappe across the highest levels of the stratigraphy a steady thickening of the nappe by internal folding suggests an increase in friction along the basal detachment possibly due to progressive compaction of the clays

the coalification pattern in the northern apennines and its palaeogeothermic and tectonic significance the rocks of the northern apennines predominantly consist of non metamorphic terrigeneous deposits flysches and molasses some of which are preorogenic some synorogenic and others postorogenic with respect to the nappe tectonics miocene as plant fragments frequently occur in these sediments a study of coal rank based on reflectance measurements on vitrinites rm mean value of the random reflectance in non polarized light contributes to the clarification of the relation between the orogenic and the palaeogeothermal development the determination of the rm values of more than 180 samples from outcrops and three deep drillings revealed some important features within the pile of liguride and tuscanide nappes the coal rank increases from the uppermost nappe to the lower nappes until lowgrade metamorphism is reached in the lower tuscanides in the single nappes the rank decreases from the tyrrhenian coast internal zone towards the po plain external zone this regional trend is disturbed only locally by young post coalification tectonics in the uppermost liguride nappe m antola unit a pre oligocene i e pre apenninic thermal event was detected postorogenic heating is connected with the magmatic activity of late miocene to pleistocene age in tuscany except for these preorogenic and postorogenic thermal events the main coalification is generally younger than the emplacement of the nappes in the nappe pile during the apenninic orogeny in the miocene but it is older than the last thrust movements and the final tensional tectonics in the internal zones of the chain for these reasons the main regional thermal event has to be considered as synorogenic or more precisely as late synorogenic

a note on induced stress changes in hydrocarbon and geothermal reservoirs abstract earthquakes have been induced by oil and gas production where pore pressures have decreased in some cases by several tens of mpa it has previously been suggested that such earthquakes are caused by poroelastic stressing of crust surrounding the reservoir induced earthquakes are also common in geothermal fields such as the geysers where strong correlations between both steam production and condensate injection and earthquake activity have been observed over the last several decades stress measurements within hydrocarbon reservoirs show that the least horizontal stress decreases with declining reservoir pressure as predicted by poroelasticity for circular disk shaped reservoirs isothermal reduction in pore pressure induces a relative horizontal tension within the reservoir production induced stressing may promote frictional sliding on pre existing faults within the reservoir itself normal faulting is promoted if the regional stress is extensional and the biot coefficient is sufficiently large 0 85 for reasonable coefficients of friction on the other hand dilatant fracturing and normal faulting are always promoted in extensional environments near the edge of the reservoir or in regions of high pore pressure gradient it is suggested that such fracturing could enhance fracture permeability in tight rocks adjacent to portions of the reservoir that experience large reductions in pore pressure due to production in regional compressional environments production modestly favors reverse faulting above and below the reservoir the ratio of thermal to poroelastic stress can be quite large in geothermal reservoirs such as the geysers reservoir wide energy balance considerations suggest that the average temperature has declined at the geysers by 6 c during the past 20 years reservoir average stress changes are thus on the order of 2 mpa and are certainly much larger near injection wells and steam producing fractures

discriminating between tectonic and sedimentary burial in a foredeep succession northern apennines an extensive apatite fission track survey has been carried out on the marnoso arenacea foredeep succession in the northern apennines the data show a general decrease of the maximum paleotemperature undergone by the sediments toward the foreland areas the maximum burial calculated by using a geothermal gradient of 20 c km 1 spans from more than 5 km to less than 2 5 km and indicates that the previously assessed total thickness of the marnoso arenacea succession is not enough to justify the determined values it is concluded that a now eroded ligurian wedge up to 5 km thick was present on top of the marnoso arenacea sediments

altered carbon cycling and coupled changes in early cretaceous weathering patterns evidence from integrated carbon isotope and sandstone records of the western tethys abstract in this study we investigate if a major perturbation of the early cretaceous carbon cycle was accompanied by altered weathering and erosion rates the large aptian carbon isotope anomaly records the response of the biosphere to widespread volcanic activity and probably resulting changes in atmospheric pco 2 levels elevated pco 2 levels should also result in an accelerated hydrological cycle and increased silicate weathering creating a negative feedback loop removing co 2 from the atmosphere we propose to interpret the widespread occurrence of quartz sandstones in the tethys atlantic seaway as a result of altered weathering and erosion rates in the wake of the aptian carbon cycle excursion we challenge the traditional notion that these are flysch deposits associated with early cretaceous orogenic movements in the western tethys we propose that these sandstones were most likely part of a large conveyor belt system acting along the iberian and european margin of the tethys seaway using chemostratigraphic correlations we show that the activity of this system was only short lived and coeval with changes in coastal ecology and the aptian carbon cycle perturbations we tentatively relate the existence of this system to a transient climate regime characterized by fluctuating pco 2 levels

correlation of diagenetic data from organic and inorganic studies in the apenninic maghrebian fold and thrust belt a case study from eastern sicily abstract temperature dependent clay mineral assemblages and vitrinite reflectance data have been used to investigate levels of diagenesis from the apenninic maghrebian fold and thrust belt in eastern sicily at the footwall of the peloritani calabride arc data are from units sampled along a regional transect between the nebrodi mountains to the north and mount judica to the south these units developed in very different tectonic settings from those of oceanic to passive continental margin domains deformed during the cenozoic mountain building and related active margin deposits the integration of organic and inorganic thermal indicators allowed us to distinguish among different tectonic settings with thermal maturity generally decreasing from hinterland to foreland as a result of progressively less severe thermal evolution and or tectonic loading during the mountain building specifically the highest vitrinite reflectance vro values ca 0 60 0 75 and percentages of illite layers in illite smectit

reservoir creep and induced seismicity inferences from geomechanical modeling of gas depletion in the groningen field the groningen gas field in the netherlands experienced an immediate reduction in seismic events in the year following a massive cut in production this reduction is inconsistent with existingmodels of seismicity predictions adopting compaction strains as proxy since reservoir creep would then result in a more gradual reduction of seismic events after a production stop we argue that the discontinuity in seismic response relates to a physical discontinuity in stress loading rate on faults upon the arrest of pressure change the stresses originate from a combination of the direct poroelastic effect through the pressure changes and the delayed effect of ongoing compaction after cessation of reservoir production both mechanisms need to be taken into account to this end we employed finite element models in a workflow that couples kelvin chain reservoir creep with a semi analytical approach for the solution of slip and seismic moment from the predicted stress change for ratios of final creep and elastic compaction up to 5 the model predicts that the cumulative seismic moment evolution after a production stop is subject to a very moderate increase 2 10 times less than the values predicted by the alternative approaches using reservoir compaction strain as proxy this is in agreement with the low seismicity in the central area of the groningen field immediately after reduction in production the geomechanical model findings support scope for mitigating induced seismicity through adjusting rates of pressure change by cutting down production the author s 2017 published by oxford university press on behalf of the royal astronomical society

impact of co2 geological sequestration on the nucleation of earthquakes 1 can co2 storage cause earthquakes what is the maximum possible earthquake magnitude resulting from co2 injection here as a theoretical case study we investigate these questions using coupled hydromechanical modeling with multiphase flow and seismological variables for quantifying earthquake magnitude and energy our simulations consider transient fluid flow and stress coupling and the evolution of fault properties we simulate co2 injection into a reservoir caprock system bounded by a subvertical normal fault subjected to different extensional stress regimes and over a range of initial fault permeability values for our assumed system and injection rate the simulation results show that sudden stress drop and fault slip primarily initiated along the fault portion intersecting the storage reservoir after a few months of injection when a sufficiently high reservoir pressure has been reached the size of the rupture area and consequently the earthquake magnitude and energy depends on initial horizontal to vertical stress ratio and fault permeability which strongly influences the size of the pressurized area and subsequent stress variations

rifted margin formation in the south tyrrhenian sea a high resolution seismic profile across the north sicily passive continental margin a new 150 km long seismic line across the continental margin of north sicily has been acquired and interpreted the overall structure of the margin is controlled by extension which caused crustal thinning and widespread normal faulting two main thinned zones are observed in the south in correspondence with the cefalu basin and farther to the north at the continent ocean transition zones of thinned crust coincide with zones of intense normal faulting extension began in late tortonian times and caused the opening of the cefalu basin controlled by a northward dipping listric fault messinian stretching affected most of the future margin and provoked a widening of the cefalu basin and normal faulting in the north following a phase of relative quiescence in the early pliocene renewed extension determined further opening of the cefalu basin and subordinate normal faulting in the north here however the record is unclear because of the emplacement of the calc alkaline sisifo volcano with associated volcanoclastic deposits breakup took place in the late pliocene and was followed by the deposition of postrift pleistocene sediments at the lithospheric scale the sites of extension thinning did not migrate during rifting on the smaller scale on the contrary the cefalu basin displays a remarkably systematic pattern of migration toward the foot wall of the listric fault which controlled the opening of the basin the spacing of 4 6 km between faults is also quite systematic elongation experienced by the continental part of the margin presently 97 km has been derived by comparing the present day and the preextensional lengths and is 10 km the corresponding strain rate is 5 10 16 s 1

insights from closed form expressions for injection and production induced stresses in displaced faults we consider fluid induced seismicity and present closed form expressions for the elastic displacements strains and stresses resulting from injection into or production from a reservoir with displaced faults we apply classic inclusion theory to two dimensional finite width and infinite width reservoir models first we simplify the fault model to the bare minimum while still maintaining its essential features a vertical fault in a homogeneous reservoir of infinite width in an infinite domain we confirm and sharpen findings from earlier numerical studies and furthermore conclude that the development of infinitely large elastic shear stresses in a displaced fault at the internal and external reservoir fault corners implies that even small amounts of injection or production will result in some amount of slip or other nonelastic deformation another finding is that there is a marked difference between the shear stress patterns resulting from injection and production in a reservoir with a displaced fault in both situations two slip patches emerge but at the start of injection some amount of slip occurs immediately in the overburden and underburden whereas during production the slip may remain inside the reservoir region next we derive similar but more complicated expressions for displaced inclined normal or reverse faults and conclude that our findings for vertical faults also apply to inclined faults

depth of emplacement fluid provenance and metallogeny in granitic terranes a comparison of western thailand with other tin belts the most important tin mineralization in thailand is associated with the late cretaceous to middle tertiary western thai granite belt a variety of deposit types are present in particular pegmatite vein and greisen styles of mineralization a feature common to most of the deposits is that they are associated with granites that were emplaced into the khang krachan group which consists of poorly sorted carbonaceous pelitic metasediments most of the deposits contain low to moderately saline aqueous fluid inclusions and aqueous carbonic inclusions with variable ch4 co2 ratios low salinity aqueous inclusions represent trapped magmatic fluid in at least one case the nong sua pegmatite based on their occurrence as primary inclusions in magmatic garnet aqueous carbonic inclusions are commonly secondary and neither the co2 nor nacl contents of these inclusions decrease in progressively younger inclusions implying that they are not magmatic in origin reduced carbon is depleted in the metasediments adjacent to granites and the d values greisen muscovites are variable but are as low as 134 per mil indicative of fluid interaction with organic graphitic material this suggests that the aqueous carbonic fluid inclusions represent fluids that were produced at least in part during contact metamorphism metasomatism by comparing the western thai belt with other sn w provinces it is evident that there is a strong correlation between fluid composition and pressure in general low to moderately saline aqueous inclusions and aqueous carbonic inclusions are characteristic of mineralization associated with relatively deep plutonic belts mineralized pegmatites are also typically of deeper plutonic belts and pegmatite hosted deposits may contain cassiterite that is magmatic crystallized from granitic melt or is orthomagmatic hydrothermal crystallized from aqueous or aqueous carbonic fluids in origin the magmatic aqueous fluids those that were exsolved from granitic melts are interpreted to have had low salinities as a consequence of the low salinities tin is partitioned in favour of the melt on vapour saturation thus with a high enough degree of fractionation the crystallization of a magmatic cassiterite or different sn phase such as wodginite is inevitable because tin is not partitioned in favour of the vapour phase upon water saturation of the granitic melts it is proposed that relatively deep vein and greisen systems tend to form by remobilization processes in addition many deeper greisen systems are hosted in part by carbonaceous pelitic metasediments and the reduced nature of the metasediments may play a key role in remobilizing tin sub volcanic systems by contrast are characterized by high temperature high salinity fluids owing to the high chlorinity tin is strongly partitioned in favour of the vapour and cassiterite mineralization can form by of orthomagmatic hydrothermal processes similar relationships between the depth of emplacement and fluid composition also appear to apply to other types of granite hosted deposits such as different types of molybdenum deposits

seismotectonics of the nubia plate compressive margin in the south tyrrhenian region italy clues for subduction inception 1 seismological and structural data are used to constrain the active tectonics of the nubia plate compressive margin in southern italy in this region compressional displacements have resumed at the rear of the maghrebian orogenic wedge since about 700 500 ka and are presently accommodated along a seismic belt in the south tyrrhenian area where a passive margin has developed during late neogene quaternary times earthquake data from the south tyrrhenian belt are analyzed with bayloc a probabilistic nonlinear location method results show that the seismic belt is segmented and involves a series of ne sw and nw se elongated clusters the ne sw clusters are interpreted as high angle reverse fault zones verging toward the southeast whereas the perpendicular clusters are interpreted as possible strike slip fault zones transferring the contractional displacements to advanced segments of the belt in the southeast brittle deformations observed in the quaternary volcanic island of ustica are consistent with the geometry and kinematics of the seismic belt deduced from the seismological data the south tyrrhenian active belt may constitute an early stage of subduction of the tyrrhenian oceanic crust beneath sicily a similar scenario has been hypothesized also for the westward prolongation of the south tyrrhenian belt off the algerian coast by integrating instrumental and historical seismic data with tectonic evidences we infer that the south tyrrhenian belt is probably capable of producing earthquakes with a maximum size close to magnitude 7 the analyzed data suggest a multifault system behavior for the studied compressional belt this inference is important to estimate and mitigate the seismic and tsunamic hazards in such a densely populated region

exhumation and reshaping of far travelled allochthonous tectonic units in mountain belts new insights for the relationships between shortening and coeval extension in the western northern apennines italy abstract coeval extensional and contractional tectonics are a common feature in orogenic belts especially in post collisional phases the attempt to constrain their relative timing and the responsible mechanisms led to several models taking into account different geodynamic contexts of various mountain chains in peri mediterranean collisional orogens extension and compression are commonly associated and coeval to the emplacement of far travelled allochthonous units therefore their internal deformation acquired during the translation across collisional belts is likely imprinted by the extensional and contractional tectonics affecting the orogen in the western portion of the northern apennines of italy one of the northernmost peri mediterranean tertiary orogens the far travelled allochthonous units i e the ligurian and subligurian units are widely exposed the present study integrates published and newly acquired surface geological data geological maps cross sections subsurface boreholes data and paleothermal vitrinite reflectance mixed layer illite smectite and kubler index and thermochronological data apatite fission tracks in order to investigate the deformation history and consequently the record of the extension compression relationships within these far travelled allochthonous units the study of modes and timing of reshaping of the far travelled allochthonous units allowed us to strengthen the hypothesis that extensional and contractional tectonics were coeval in the northern apennines and tightly connected by a cause effect relationship in particular the late orogenic low and high angle extensional tectonics represent the response to an overall contractional regime which induced episodes of gravitational instability in the orogenic wedge

subduction and the depth of convection in the mediterranean mantle 1 we tie together geological data paleotectonic reconstruction plate motion and tomographic analysis to unravel the history of subduction and back arc extension of the eastern and central mediterranean in these two regions extensional processes started contemporaneously around 30 myr ago but with marked differences in the eastern region the aegean basin opened slowly 1 cm yr behind a shallow dipping slab 40 45 the corresponding high velocity anomaly extends inside the upper mantle and can be also followed in the midmantle down to a depth of at least 1500 km its descent into the midmantle initiated most probably during the late cretaceous and the trench moved northeastward following the path of the eurasian plate and under the persistent push of the african plate conversely in the central mediterranean region subduction initiated later and the motion of the subducting slab is confined to the upper mantle causing punctuated and rapid episodes of back arc extension provencal and tyrrhenian basins behind a slab that dips steeply 75 we explore the causes that control how the slab subducted and interacted with the lower more viscous part of the mantle

depositional patterns and their tectonic controls within the plio quaternary carbonate sands and muds of onshore and offshore se sicily italy the straits of sicily represent an important bathymetric gateway between the western and eastern mediterranean plio quaternary seabed sediments consist of muds together with carbonate sands these are contrasted with two onshore analogues from sicily in order to better understand the linked tectonic and palaeoenvironmental controls on deposition for one analogue coastal packstones composed of fragmented shelly fauna that build large parasequences the facies fractionation was dominantly controlled by wave and storm activity the other analogue bryozoa rich packstones deposited on a shelf are inferred to have been fractionated from muds by marine current activity below wavebase these pliocene shelf packstones and basinal muds are the favoured ancient analogue for modern offshore sedimentation and may record important palaeo oceanographic data that reconstruct mixing between the ancestral western and eastern mediterranean water

remote sensing as tool for development of landslide databases the case of the messina province italy geodatabase abstract landslide geodatabases including inventories and thematic data today are fundamental tools for national and or local authorities in susceptibility hazard and risk management a well organized landslide geo database contains different kinds of data such as past information landslide inventory maps ancillary data and updated remote sensing space borne and ground based data which can be integrated in order to produce landslide susceptibility maps updated landslide inventory maps and hazard and risk assessment maps italy is strongly affected by landslide phenomena which cause victims and significant economic damage to buildings and infrastructure loss of productive soils and pasture lands in particular the messina province southern italy represents an area where landslides are recurrent and characterized by high magnitude due to several predisposing factors e g morphology land use lithologies and different triggering mechanisms meteorological conditions seismicity active tectonics and volcanic activity for this area a geodatabase was created by using different monitoring techniques including remote sensing e g sar satellite ers1 2 envisat radarsat 1 terrasar x cosmo skymed data and in situ measurements e g gbinsar damage assessment in this paper a complete landslide geodatabase of the messina province designed following the requirements of the local and national civil protection authorities is presented this geo database was used to produce maps e g susceptibility ground deformation velocities damage assessment risk zonation which today are constantly used by the civil protection authorities to manage the landslide hazard of the messina province

palynomorph optical analyses for thermal maturity assessment of upper ordovician katian hirnantian rocks from southern estonia abstract application of integrated multi proxy optical analytical techniques for the assessment of thermal maturity of organic matter was tested in katian to hirnantian upper ordovician sediments from a subsurface succession in southern estonia the investigated valga 10 drill core section consists of a biostratigraphically well constrained succession deposited in the outer part of a carbonate shelf livonian basin the diverse and well preserved palynological assemblages permitted the analysis of thermally induced modifications of optical properties of small and large acanthomorph acritarchs qualitative methods such as uv fluorescence and acritarch alteration index aai were calibrated against the quantitative palynomorph darkness index pdi the occurrence of vitrinite like organoclasts allowed reflectance measurements in some of the investigated samples the strong fluorescence and pale to yellow colour of acritarchs combined with low pdi and organoclast reflectance values suggest thermally immature kerogen and a limited burial diagenesis in the study area moreover pdi showed a good correlation with uv fluorescence allowing a calibration of these two techniques and proving the reliability of pdi for thermal maturity estimation in sedimentary rocks unsuitable for rock eval pyrolysis and vitrinite reflectance furthermore the applied methodologies permitted the differentiation of reworked from in situ organic matter and highlighted the potential of the former for sequence stratigraphic investigations

structural and tectono stratigraphic review of the sicilian orogen and new insights from analogue modeling abstract the apennines sicilian maghrebian fold and thrust belt originated from the subduction of the alpine tethys and the later collision of drifted continental blocks against the african and apulian paleomargins from north to south the sicilian fold and thrust belt sftb is divided in four main tectono stratigraphic domains 1 the calabro peloritani terrane drifted from the european margin 2 the remnants of the alpine tethys accretionary wedge atw related to the subduction of the tethys 3 the folded and thrusted platform panormide and deep water imerese sicanian series of the offscrapped african margin and 4 the african foreland hyblean unfortunately scarce quality seismic lines and outcrops of key tectono stratigraphic units make the structure and dynamic evolution of the central eastern part of the sftb controversial first this study outlines through a review of the tectono stratigraphic evolution of the central eastern sector of the sicilian orogen the major remaining issues concerning 1 the occurrence of inferred alpine tethys units far from the region where the remnants of the atw outcrop nebrodi mountains both in a forearc position above the peloritani block to the north and in an active foreland context along the present day southern front of the belt and 2 the diverging tectonic styles from stacked large scale tectonic nappes to foreland imbricated thrust systems rooted into a main basal decollement secondly new constraints are given using analogue modeling to test mechanically the hypothesized structural and tectono stratigraphic evolution of the sftb the experiment simulates the orogenic evolution of the sftb at crustal scale from the oligocene tethys subduction to the middle miocene late pliocene continental collision between the european and african paleomargins the tectono stratigraphic synthesis is used to model the first order mechanical stratigraphy of the sedimentary units involved in the sicilian belt as well as the imprint of the african margin structural inheritance the experiments succeed in reproducing the general structure and tectono stratigraphic evolution of the sftb in particular the models support field observations hypothesing a gravity driven origin of the inferred alpine tethys units intercalated within the forearc and foreland syntectonic sedimentation moreover the model testifies of the main tectonic steps that led to the sftb building first a low tapered accretionary wedge was accreted above the alpine tethys oceanic crust from the oligocene to the early miocene the following underthrusting of the stretched african continental margin and its frontal panormide platform shortened and thickened the accretionary wedge this phase provided favorable conditions for significant pulses of reworked alpine tethys units that intercalated within the forearc and foredeep successions during the middle miocene the decollement of the african meso cenozoic cover panormide platform and imerese sicanian deep water basin enhanced a deep seated deformation phase along with duplexing of the panormide platform beneath the alpine tethys wedge leading to its emersion since the late messinian activation of basement faults led to a generalized emersion of the orogenic units through large wavelength fold culminations accompanied by syn tectonic deposition at their southern limbs concurrently the prism front was partly indented to the southeast by the thick and locally already emerged hyblean platform

tectonics and metallogeny of mainland southeast asia a review and contribution abstract the southeast asia region is endowed with a diversity of mineral resources notably porphyry related skarn epithermal and sediment hosted orogenic gold deposits formation of these deposits was associated with a long and complex tectonic history of gondwana supercontinent break up arc magmatism backarc basin development together with arc continent and continent continent collisions that created the present day mainland se asia this paper summarizes historical and current se asian geological research and ore deposit studies here we present a new tectonic and metallogenic model for phanerozoic mainland se asia from this model we conclude that incipient arc backarc basin magmatism is the key to the formation of many important ore deposits in the truong son and loei fold belts the two major metallogenic belts in mainland se asia in addition triassic to cenozoic arc continent and continent continent collisions have led to the formation of many sediment hosted orogenic gold deposits in the sukhothai and the sibumasu terranes oblique cretaceous to recent subduction along the andaman sunda trench was responsible for gold and copper gold molybdenum porphyry and epithermal mineralization along the kawlin wutho mt popa arc in myanmar in the north and the sumatran volcanic arc in the south we anticipate that the present emphasis on exploring for shallower level epithermal deposits will increasingly lead to exploration for deeper level porphyry and porphyry related skarn systems in the coming decades

using high resolution stratigraphy to date fold and thrust activity examples from the neogene of south central sicily the integration of structural and stratigraphic data is fundamental for determining rates of deformation in the uppermost continental crust the high temporal resolution provided by neogene marine sediments is used here to examine deformation rates in part of a thrust belt chosen from the maghrebian orogen of sicily conventional biozonal stratigraphy calibrated against the geomagnetic polarity time scale shows that individual thrust fold structures grew steadily over many millions of years structures across the thrust belt were active at the same time and accommodated bulk shortening rates of c 0 5 mm a 1 in contrast the basal detachment operated about ten times faster these results are in broad agreement with some theoretical models for orogenic wedge kinematics shore line carbonate successions calibrated with precession cycles of sea level change provide a very high resolution temporal scale with which to chart tilt rates on fold limbs 1 27 6 ka 0 036 ka 1 these show that fold amplification was continuous although the rates may have varied with time incremental tilting of limbs during fold amplification is not predicted by popular models of fault bend and 9fault propagation9 folding geometric modelling suggests that folding occurred by limb rotation with minor hinge migration during buckling above buried thrusts thus stratigraphic data may be used to examine the kinematic evolution of thrust fold systems along regional cross sections and of local structures however the types of structural models that can be tested using estimates of deformation rates depend upon the chrono stratigraphic resolution available for the syn tectonic sediments

geochronology of the medium to high grade metamorphic units of the peloritani mts sicily the peloritani mountains are a fragment of an orogen variably attributed to the alpine or hercynian orogeny on the basis of 39ar 40ar u pb and rb sr dating the main metamorphism of the two medium high grade metamorphic units the mela and aspromonte units and most of the thrusting responsible for stacking the orogenic edifice are seen to be hercynian the main thrusting of the aspromonte unit over the lower grade units took place at 301 2 ma brittle deformation during tertiary reactivation of hercynian thrust planes did not generate any rejuvenation of white micas in the studied sector our dataset shows a great complexity and we propose to unravel it by considering different levels of information to first order the mela and aspromonte units differ in their metamorphic paths and their geochronological evolution the mela unit shows generally younger ages carboniferous than the aspromonte unit and unlike the latter was extensively retrogressed in greenschist facies the aspromonte unit is itself geochronologically heterogeneous proterozoic ages are preserved both in titanite and in amphibole relics of one tectonic subunit devonian to carboniferous amphibole ages are found in different other subunits tertiary overprint is minor and spatially limited we propose to consider the chronologically heterogeneous subunits as accreted pre hercynian terranes amalgamated late during the hercynian orogeny micas in both units give scattered mesozoic 39ar 40ar and rb sr ages with evidence for heterochemical mica generations we interpret them as a result of widespread hydrothermal circulation event s tertiary overprint is generally absent with the exception of a small area near messina where biotite and muscovite underwent a complex recrystallisation history in the interval between 48 and 61 ma

the relationship between track shortening and fission track age reduction in apatite combined influences of inherent instability annealing anisotropy length bias and system calibration abstract the relationship between reduced track density 0 and reduced mean confined track length l l 0 during annealing has been studied for both spontaneous and induced tracks in four apatite samples with different chemical composition compositional range and origin and with spontaneous tracks giving mean confined track lengths varying from 14 5 m down to 12 3 m in all four apatites induced tracks show a relationship between l l 0 and 0 composed of two regions at higher values the two appear to be equal while at lower values l l 0 is greater than 0 this can be understood qualitatively in terms of the anisotropy of annealing and the bias against revelation of short tracks data from three apatites of uniform composition show near identical relationships in a sample showing a range of apatite compositions the point of divergence from the 1 1 relationship is somewhat higher than in the uniform composition apatites because individual grains anneal at different rates and the presence of highly annealed grains affects the track density more strongly than the mean track length spontaneous tracks show similar relationships to those observed for induced tracks in each sample when the data are renormalised to allow for the natural annealing present in the spontaneous tracks previous studies which led to the idea of length reduction without density reduction for spontaneous tracks did not renormalise density data as well as length data thereby distorting the apparent relationship data for the multi compositional apatite sample where annealing has taken place in geological conditions also agrees with the laboratory annealing data for both spontaneous and induced tracks this consistency suggests that a single process is responsible in all three cases implying that a laboratory based description of annealing can be applied to geological conditions with confidence recognition that spontaneous tracks in apatite are commonly annealed suggests that in general the fission track age should be interpreted as a reflection of both the time over which tracks have been retained and the distribution of etchable track lengths since the latter is a manifestation of the thermal history the fission track age should be interpreted in similar terms

thermal maturity of the axial zone of the southern apennines fold and thrust belt italy from multiple organic and inorganic indicators the reconstruction of the thermal history of folded and thrust units is crucial to define the pattern of tectonic loading and the time space evolution of an orogen where tectonic exhumation processes occurred at shallow crustal levels in the present study a well constrained reconstruction of the thermal maturity in the axial zone of the southern apennines has been achieved by the combined use of different thermal indicators in diagenesis the major results are i documentation of a jump in thermal maturity from the apenninic platform derived tectonic unit from immature to early mature stages of hydrocarbon maturation to the lagonegro basin derived tectonic units late diagenetic zone ii documentation of along strike slighter variations in the lagonegro units concerning thermal maturity thus maximum burial temperatures this can be related to changes in amounts of tectonic burial and erosion exhumation because of the lack of cylindricity of contractional structures iii recognition of an independent thermal evolution of the allochthonous chain compared with the apulian platform tectonic unit with mt alpi area in the late mature stage of hydrocarbon generation interpreted as a sector of localized intense exhumation within the external zone of the orogen

neo tethyan magmatism and metallogeny in myanmar an andean analogue abstract plate margin tectonism magmatic and hydrothermal processes and the genesis of mineral deposits are intricately linked in myanmar two near parallel magmatic belts that together contain a significant proportion of that country s mineral wealth have contrasting metallogenic endowments the mogok mandalay mergui belt hosts crustal melt s type granites with significant tin tungsten mineralization while the wuntho popa arc comprises i type granites and granodiorites with copper gold mineralization the spatial juxtaposition of the two belts and their distinct but consistent metallogenic endowment bears strong similarities to the metallogenic belts of the south american cordillera recent u pb age dating has shown the potential for the two belts to be near contemporary from the late cretaceous to eocene here we investigate whether an andean type setting during subduction of neo tethys could explain the observed magmatism and mineralization within these two belts

thermal history of sedimentary basins maturation indices and kinetics of oil and gas generation temperature is the most sensitive parameter in hydrocarbon generation thus reconstruction of temperature history is essential when evaluating petroleum prospects no measurable parameter can be directly converted to paleotemperature maturation indices such as vitrinite reflectance tmax from rock eval pyrolysis spore coloration thermal alteration index tai or concentration of biological markers offer an indirect approach all these indices are a function of the thermal history through rather complex kinetics frequently influenced by the type of organic matter their significance and validity are reviewed besides the problems of identification e g vitrinite and interlaboratory calibration it is important to simultaneously interpret kerogen type and maturation and to avoid difficult conversions from one index to another geodynamic models where structural and thermal histories are connected are another approach to temper ture reconstruction which could be calibrated against the present distribution of temperature and the present value of maturation indices kinetics of kerogen decomposition controls the amount and composition of hydrocarbons generated an empirical time temperature index tti originally introduced by lopatin does not allow such a quantitative evaluation due to several limitations no provision for different types of kerogen and different rates of reactions poor calibration on vitrinite reflectance it is of limited interest unless one has no access to a desk top computer kinetic models based on a specific calibration made on actual source rock samples can simulate the evolution of all types of organic matter and can provide a quantitative evaluation of oil and gas generated examples from the jurassic source rocks of the paris basin monterey formation of california green river shales of utah paleozoic source eds of the algerian sahara and miocene rocks of the mahakam delta indonesia illustrate various aspects of the discussion geological geochemical models are the most efficient way to integrate geological seismic and geochemical data and they should greatly help to reduce the risk in exploration

contemporaneous thrusting and large scale rotations in the western sicilian fold and thrust belt in the western sicilian fold and thrust belt large clockwise rotations of allochthons occurred during late cenozoic contraction of part of the southern tethyan margin the magnitude of rotation decreases stepwise from over 120 in the upper sheets lying on the north coast of sicily to no appreciable rotation in the frontal portion of the belt flanking the southern coast of the island the allochthons are composed of imbricate thrust sheets derived primarily from individual basin and platform assemblages of the old tethyan margin paleomagnetic and structural data indicate that the rotation of the allochthons was accommodated by coherent torsional displacements on relatively low angle detachment surfaces timing relations for the imbrication history of the sicilian fold and thrust belt are derived from stratigraphic overlap and local involvement of sediments deposited in a series of foreland and piggyback basins the locus of deposition within successive foreland basins first migrated easterly then southerly during progressive deformation in the orogen imbrication began in the early miocene burdigalian langhian and continued at least through the early pleistocene and appears to be continuing today rotation is related to thrusting and accompanies a 70 change in the tectonic transport direction from easterly to southerly easterly striking right oblique transpressional faults and associated northeasterly trending folds postdate thrust sheet rotation in the interior of the thrust belt and were active contemporaneously with south directed thrusting in the foreland region pleistocene and possibly older late pliocene extension strongly modified the older thrust morphology along the tyrrhenian coast of northwestern sicily with the development of down to the north listric normal faults the extensional structures apparently are related to the opening and subsequent deformation of the tyrrhenian sea to the north

pattern of orogenic rotations in central eastern sicily implications for the timing of spreading in the tyrrhenian sea new palaeomagnetic data from upper triassic to pliocene sediments reveal that in eastern sicily a major 70 clockwise cw rotation took place between oligocene and late tortonian time followed by a further 30 cw rotation results from central sicily are less coherent they show 44 83 post oligocene cw rotation local 14 post late tortonian counterclockwise ccw rotation and 25 post mid pliocene cw rotation we interpret the larger cw rotation observed in eastern sicily as related to a more internal palaeogeographical position with respect to central sicily our results complement pre existing data from the northwestern sicily carbonates and indicate that all the internal carbonate nappes coherently rotated by c 100 cw during tectonic emplacement implying a west to east increase of shortening in the sicilian maghrebian belt in sicily compressive deformation started during the langhian i e just after the deposition of the upper oligocene upper burdigalian numidian flysch turbidites therefore the age of the older 70 palaeomagnetic rotation synchronous to the thrusting is constrained to occur between the langhian and late tortonian furthermore by considering a maximum possible rotation rate of 20 ma 1 we infer that cw rotation started in sicily in langhian serravallian times between 15 16 and 11 12 ma ago the 100 cw rotation observed in pre orogenic strata from the whole of sicily is mirrored by 80 orogen scale ccw rotations characterizing the internal southern apennines palaeomagnetism therefore shows that during orogenesis the southern apennines and the sicilian maghrebides rotated in a saloon door fashion synchronous to back arc spreading of the southern tyrrhenian sea consequently our palaeomagnetic data suggest that the southern tyrrhenian back arc basin started to spread during langhian serravallian times from 15 16 to 11 12 ma significantly earlier than the late tortonian age 8 ma suggested so far by oceanic drilling data

fission track reconstruction of the front of the northern apennine thrust wedge and overlying ligurian unit in the northern apennines foreland the marnoso arenacea formation ma fm records post depositional burial temperatures overlapping with those of the zone of partial annealing of apatite fission tracks because the stratigraphy sedimentology petrography and structural evolution of this turbidite succession has been intensively studied over the last 40 years the ma fm provides an ideal case to apply the apatite fission track method the data show a general decrease of the maximum paleotemperature undergone by the ma samples toward the foreland area the maximum burial calculated using a geothermal gradient of 20 c km spans from more than 5 km to less than 2 5 km and indicates that the reconstructed total thickness of the ma succession is not enough to justify the determined burial values stratigraphic data indicates that the missing section consisted of a lower component foredeep successions and an upper allocthonous component composed of disrupted and chaotic oceanic sediments and minor ophiolites ligurian unit the ligurian unit overrode the foredeep succession during deposition its advancement toward the foreland area was associated with subsidence and only locally contrasted by thrust growth the reconstructed wedge shape of the ligurian unit in its final and pre erosional configuration at time of the maximum bunal of the ma succession shows a flat upper surface which corresponds to a paleosurface of early pliocene age this surface marks at 4 to 5 ma the onset of the exhumation phase which occurred at a mean rate of 1 2 mm yr

detecting the stepwise propagation of the eastern sicily thrust belt italy insight from thermal and thermochronological constraints an extensive dataset of vitrinite reflectance ftir parameters on organic matter illite content in mixed layers illite smectite apatite fission tracks and u th he dating has been used to reconstruct the stepwise propagation of the eastern sicily fold and thrust belt during late palaeogene and neogene times the results indicate that the fold and thrust belt is divisible into two levels of thermal maturity these levels consist of a less evolved level of thermal maturity that records limited sedimentary burial and minor heating and a more evolved level of thermal maturity that indicates tectonic burial and exhumation at different times deformation and exhumation of shallowly buried units are linked to wedge forward propagation by low angle thrusts whereas the evolution of deeply buried units is associated with tectonic imbrications by duplex formation and steep thrusts the two tectonic styles alternate during evolution of the fold and thrust belt under low erosion rates

structural evolution of the sedimentary accretionary wedge of the alpine system in eastern sicily thermal and thermochronological constraints temperature dependent clay mineral assemblages vitrinite reflectance and apatite fission track data have been used to investigate levels of diagenesis and time of exhumation of the double verging sicilide antisicilide accretion ary wedge in eastern sicily the integration of organic and inorganic thermal indicators allowed us to distinguish parts of the accre tionary wedge with different thermal signature and evolution we recognize a warmer core made up of the mount soro and troina units and two colder rims antisicilide and far traveled sicilide units the antisicilide unit was thrust back toward the hinterland and the far traveled sicilide units were gravity driven toward the hyblean plateau in detail the highest percentages of vitrinite reflectance vr o values 0 60 0 96 and percentages of illite layers in illite smectite i s 60 85 are found in the mount soro and troina units apatite fission track data together with the paleotemperature estimates from vitrinite reflectance data and clay mineral based geothermometers indicate that fission tracks were partially to totally annealed during wedge accretion and that the subsequent exhumation occurred mainly in burdigalian times low vr o values 0 35 0 50 and percentages of illite layers in i s 30 60 occur in early thrust top deposits reitano flysch that unconformably overlie the sicilide complex as well as the far traveled sicilide and antisicilide units apatite fission track data for the antisicilide unit confirm low paleo temperature values thus the far traveled sicilide and antisicilide units were probably at higher structural levels in the original accretionary prism and were remobilized since late aquitanian burdigalian times

fission track analysis of the crystalline basement rocks of the calabrian arc southern italy evidence of oligo miocene late orogenic extension and erosion abstract fission track analysis is used to provide low temperature and time constraints on the late orogenic cooling and exhumational history of the crystalline basement rocks of the calabrian arc southern italy 65 samples yielded 57 apatite fission track ages 54 zircon fission track ages and 25 apatite confined fission track length distributions interpretation of this data reveals a phase of increased cooling rates related to exhumation between approximately 35 ma mid oligocene and 15 ma middle miocene evidence from the sedimentary record indicates significant oligo miocene erosion related to this period of exhumation new chronological constraints are also applied to localised late orogenic extensional tectonism that has recently been identified within the basement rocks of the calabrian arc this information is used to produce a new model of the oligo miocene tectonic evolution of the calabrian arc it proposes that the crystalline basement rocks were part of a critical orogenic wedge between the mid oligocene and the middle miocene

application of organic matter and clay mineral studies to the tectonic history of the abruzzo molise sannio area central appenines italy abstract the abruzzo molise sannio region is part of the central apennines foreland fold and thrust belt a structure that formed during the neogene as a result of the continental collision between the european and adria plates certain areas of this crust experienced anomalously high temperatures due to deep burial while others did not this burial has been investigated using optical indicators of organic matter om maturity and clay mineralogy the maximum depths of burial of tertiary surface sequences have been established based on the vitrinite reflectance ro and thermal alteration index tai of om dispersed in synorogenic sediments and from clay mineralogy of pre thrusting clayey deposits the synorogenic deposits show low levels of organic maturity having ro values less than 0 6 indicating early mature to mid mature hydrocarbon generation the pre thrusting deposits are shales characterised by a very high percentage of clay minerals with lesser amounts of quartz k feldspar plagioclase and calcite the dominant minerals are highly smectitic interstratified illite smectite ris both ro and i s ratios were used to calibrate burial and thermal evolution of this chain sector by numerical modelling the results indicate that the structural units which outcrop in the study area particularly the molise unit were never overthrust by significant thicknesses of rocks during mountain building at least before pliocene times the hypothesis that more internal units overthrust the presently exposed units also seems to be unlikely

large scale sedimentary recycling of tectonic melange in a forearc setting the ionian basin oligocene quaternary southern italy distinctive horizons of melange ranging in maximum thickness from a few tens to several hundreds of meters are conformably interbedded with the regularly stratified oligocene to quaternary predominantly marine deposits of the ionian forearc basin along the leading edge of the calabria peloritani microplate of southern italy these melange horizons were emplaced from the late early to the late miocene during collision of the southern and northern margins of the microplate with the passive margins of northern africa and the apulian platform respectively collisional deformation induced uplift of parts of the accretionary prism and ensuing sedimentary recycling of melange into the adjacent ionian forearc basin the thickest melange horizon can be traced for a distance 80 km with a consistent stratigraphic position within the forearc basin fill and ranges in thickness from 1 km near the collision zone to zero away from it it was emplaced in the late burdigalian and records oblique collision of the calabria peloritani microplate with the northern continental margin of africa in this context portions of the melange of the accretionary prism were extruded tectonically and gravitationally mobilized from southwest to northeast in the remaining undeformed parts of the forearc basin this interpretation is supported by 1 the overall geometry of the melange horizon pinching out away from the collision zone 2 its conformable contacts and chronostratigraphic relationships with the underlying and overlying stratigraphic units 3 its composition and 4 the absence of tectonic deformation at base and top of the horizon younger and thinner melange horizons are interbedded within the latest tortonian messinian succession and resulted from the erosion of thrust tip areas within the inner portion of the accretionary prism following incipient collision of the northern end of the microplate with the apulian platform integration of the results of this and other studies indicate that sedimentary recycling of large volumes of melange from accretionary prisms into forearc basins is an important process along both collisional and noncollisional active plate margins

assessing fault reactivation tendency within and surrounding porous reservoirs during fluid production or injection abstract this paper investigates fault reactivation tendency within and surrounding reservoirs during fluid injection or production induced stress analysis is performed using eshelby s theory of inclusions for a poroelastic material and the concept of coulomb failure stress change is implemented as a criterion for fault reactivation tendency a methodology is developed to find the range of fault dip angles that tend towards reactivation in either thrust or a normal fault stress regimes the results demonstrate that during production from a reservoir in a normal fault stress regime fault reactivation is likely to occur within the reservoir and adjacent to its flanks for a thrust fault stress regime only faults located in rocks overlying and underlying the reservoir tend towards reactivation the results for the analogous case of fluid injection are exactly the opposite sensitivity analyses show that the locations of the boundaries defining these regions of reactivation or stabilization tendency are not highly sensitive to the fault friction coefficient the use of the proposed methodology is illustrated for a synthetic case study

poroelastic stressing and induced seismicity near the lacq gas field southwestern france o hundreds of shallow small to moderate earthquakes have occurred near the lacq deep gas field in southwestern france since 1969 these earthquakes are clearly separated from tectonic seismicity occurring in the pyrenees 25 km to the southwest the induced seismicity began when the reservoir pressure had declined by 30 mpa repeated levehng over the field shows localized subsidence reaching a maximum of 60 mm in 1989 segall 1989 suggested that poroelastic stressing associated with volumetric contraction of the reservoir rocks is responsible for induced seismicity associated with fluid extraction to test this model we compare the observed subsidence and hypocentral distributions with the predicted displacement and stress fields we find that the relationship between average reservoir pressure drop and subsidence is remarkably linear lending support to the linear poroelastic model displacements and stresses are computed based on a priori knowledge of the reservoir geometry materim properties and reservoir pressure changes the computed vertical displacements are found to be in excellent agreement with the subsidence observed from leveling stress perturbations accompanying gas extraction computed using the same parameters are found to be 0 2 mpa or less changes in coulomb failure stress are computed assuming that shp occurs on optimally oriented planes the predicted failure zones correlate very well with the spatial distribution of earthquakes if the perturbing stresses are small in comparison to the ambient regional deviatoric stresses and if the minimum regional compresslye stress axis is vertical accurate determination of focal mechanisms of the induced events would allow a more rigorous test of the poroelastic model and could lead to important inferences about the crustal stress state

extreme threshold failures within a heterogeneous elastic thin sheet and the spatial temporal development of induced seismicity within the groningen gas field measurements of the strains and earthquakes induced by fluid extraction from a subsurface reservoir reveal a transient exponential like increase in seismicity relative to the volume of fluids extracted if the frictional strength of these re activating faults is heterogeneously and randomly distributed then progressive failures of the weakest fault patches account in a general manner for this initial exponential like trend allowing for the observable elastic and geometric heterogeneity of the reservoir the spatio temporal evolution of induced seismicity over 5 years is predictable without significant bias using a statistical physics model of poro elastic reservoir deformations inducing extreme threshold frictional failures of previously inactive faults this model is used to forecast the temporal and spatial probability density of earthquakes within the groningen natural gas reservoir conditional on future gas production plans probabilistic seismic hazard and risk assessments based on these forecasts inform the current gas production policy and building strengthening plans

induced stresses due to fluid extraction from axisymmetric reservoirs earthquakes can be induced by fluid extraction as well as by fluid injection segall 1989 proposed that poroelastic stresses are responsible for inducing earthquakes associated with fluid extraction here i present methods for computing poroelastic stress changes due to fluid extraction for general axisymmetric reservoir geometries the results ofgeertsma 1973 for a thin disk reservoir with uniform pressure drop are recovered as a special case predicted surface subsidence agrees very well with measured leveling changes over the deep lacq gas field in southwestern france the induced stresses are finite if the reservoir pressure changes are continuous computed stress changes are on the order of several bars suggesting that the preexisting stress states in regions of extraction induced seismicity are very close to frictional instability prior to production

incipient extension along the active convergent margin of nubia in sicily italy cefalu etna seismic zone 1 recent geodetic data are compatible with nne ssw tectonic extension at a rate of 5 mm yr in sicily southern italy within a broader region of net active compression along the nubian plate margin northern africa the structures that accommodate such extensional regime and its cause are still unknown from field structural surveys and seismological analyses the geometry kinematics structural architecture and seismic potential of an extensional seismic zone linking cefalu and mount etna in central eastern sicily are defined the zone includes high angle wnw striking normal and right lateral strike slip faults and subordinate north and nne striking strike slip faults either right or left lateral the occurrence of small discontinuous faults and the absence of related depressions and sedimentary basins suggest that the extensional regime is still in an incipient stage the ongoing seismic activity possibly reactivates preexisting faults instrumentally and historically recorded earthquakes are lower than about 6 in magnitude and destructive events are historically unknown since at least 1300 a d this apparent upper bound of earthquake magnitudes is consistent with the maximum magnitude values estimated from the length of the longest mapped faults and sources of seismic swarms which all together suggest a value between 6 and 6 5 as the maximum expected magnitude that can be proposed at the present stage of investigation for earthquakes in the study area lateral extension on preexisting faults and upwelling of melt mantle material beneath mount etna are considered viable processes to explain at least in part the active extensional tectonics along the cefalu etna seismic zone strike slip seismic faulting beneath mount etna may be part of a previously proposed diffuse transfer zone affecting northeastern sicily and including the tindari fault

on the physics based processes behind production induced seismicity in natural gas fields author s zbinden d rinaldi ap urpi l wiemer s abstract 2017 american geophysical union all rights reserved induced seismicity due to natural gas production is observed at different sites worldwide common understanding states that the pressure drop caused by gas production leads to compaction which affects the stress field in the reservoir and the surrounding rock formations and hence reactivates preexisting faults and induces earthquakes in this study we show that the multiphase fluid flow involved in natural gas extraction activities should be included we use a fully coupled fluid flow and geomechanics simulator which accounts for stress dependent permeability and linear poroelasticity to better determine the conditions leading to fault reactivation in our model setup gas is produced from a porous reservoir divided into two compartments that are offset by a normal fault results show that fluid flow plays a major role in pore pressure and stress evolution within the fault fault strength is significantly reduced due to fluid flow into the fault zone from the neighboring reservoir compartment and other formations we also analyze scenarios for minimizing seismicity after a period of production such as i well shut in and ii gas reinjection in the case of well shut in a highly stressed fault zone can still be reactivated several decades after production has ceased although on average the shut in results in a reduction in seismicity in the case of gas reinjection fault reactivation can be avoided if gas is injected directly into the compartment under depletion however gas reinjection into a neighboring compartment does not stop the fault from being reactivated

combined zircon molybdenite and cassiterite geochronology and cassiterite geochemistry of the kuntabin tin tungsten deposit in myanmar

nucleation and arrest of dynamic rupture induced by reservoir depletion seismic events induced by the depletion of hydrocarbon reservoirs can cause damage to housing and cause societal and economic unrest however the factors controlling the nucleation and size of production induced seismic events are not well understood here we used geomechanical modeling of production induced stresses and dynamic rupture modeling to assess the conditions controlling down dip rupture size a generic model of offset depleting reservoir compartments separated by a fault was modeled in 2 d using the finite element package diana fea linear slip weakening was used to control fault friction behavior fault reactivation was computed in a quasi static analysis simulating stresses during reservoir depletion followed by a fully dynamic analysis simulating seismic rupture the sensitivity of reactivation and rupture size to in situ stress dynamic friction critical slip distance and reservoir offset was evaluated after reactivation a critical fault length was required to slip before seismic instability could occur in a subsequent fully dynamic analysis the propagation and arrest of dynamic rupture was simulated rupture remained mostly confined to the reservoir interval but could also propagate into the overburden and underburden or sometimes transition into a run away rupture propagation outside the reservoir interval was promoted by a critical in situ stress a large stress drop a small fracture energy and no or little reservoir offset with increasing offset up to the reservoir thickness reactivation was promoted but dynamic rupture size decreased 2019 the authors

pliocene and pleistocene exhumation and uplift of two key areas of the northern apennines application of different thermochronological methods to two areas of pronounced relief apuane alps and mt falterona of the northern apennines chain documents an average exhumation rate of about 0 7m m yr this result suggests that the general exhumation of the chain is driven mainly by erosion nevertheless the long term exhumation trend seems to be perturbed by shortterm events at higher exhumation rates the time of increased exhumation rates coincides with onset of intramontane sedimentation documenting a contribution of tectonics local normal faulting to the surface uplift the data indicate an eastward shifting of the onset of topographic relief early pliocene in the apuane alps and early pleistocene in the mt falterona area r 2002 elsevier science ltd and inqua all rights reserved

reconstruction of maximum burial along the northern apennines thrust wedge italy by indicators of thermal exposure and modeling a new data set of temperature dependent clay mineral parameters and vitrinite reflectance of the tuscan successions in the northern apennines italy displays decreasing levels of thermal maturity from hinterland to foreland and abrupt changes parallel to the strike of the chain which are structurally controlled by northeast southwest trending faults e g marecchia valley lineament to the southeast of the marecchia valley lineament paleothermal indicators show deep diagenetic conditions in the hinterland and early diagenetic conditions in the foreland r o ranges from 0 80 to 0 30 illite content in mixed layer illite smectite i s from 86 to 38 to the northwest of the marecchia valley lineament in the hinterland r o is up to 0 95 and mixed layer i s have an illite content of 87 88 both gradually decreasing toward the northeast to r o of 0 33 and illite in i s of 50 thermal models allowed us to constrain the geometry of the miocene thrust wedge with special regard to the original thickness and distribution of its allochthonous uppermost structural unit ligurian unit across northeast southwest trending tectonic lineaments the thickness of the ligurian unit ranges from 1 to 1 5 km to the south of the marecchia valley lineament to 3 km to the north northwest this tectonic lineament affected wedge geometry amounts of tectonic transport and thickness of the uppermost structural unit and possibly neogene quaternary levels of exhumation

optical parameters of maturity of organic matter dispersed in sediments first results from the central apennines italy levels of organic maturity of mesozoic and tertiary sequences outcropping in the central apennines have been established using vitrinite reflectance techniques the thermal alteration index and fluorescence colours of organic matter dispersed in sediments these results provide new constraints throughout the meso cenozoic evolution of this crustal sector in exploration geology vitrinite reflectance provides data on hydrocarbon maturation by constraining organic matter maturity in sedimentary basin modelling it is adopted to define the palaeothermal regime vitrinite reflectance ro also provides information on the burial history of sedimentary basins and may be employed to estimate tectonic uplift and erosion rates thermal alteration index tai and fluorescence colour values can be correlated with ro and may be used to estimate the degree of maturation when vitrinite is absent samples derived from the sabini and tiburtini mts in slope facies between the latium abruzzi carbonate platform and the umbria marche pelagic basin from the simbruini and ernici mts in carbonate platform facies and from upper miocene turbiditic deposits outcropping between the olevano antrodoco une towards the west and the marsica slope facies towards the east both the pre terrigenous meso cenozoic sequences show a low grade of organic maturity the sabini and tiburtini mts show ro values that are less than 0 4 and the simbruini ernici range show ro values that range between 0 5 and 0 65 field analysis indicates that the cause of these low maturity levels is that thick sequences of turbidites were never deposited during the neogene evolution of the apennine thrust belt moreover upper miocene turbiditic deposits also show low maturity levels with ro values that are less than 0 5 indicating that these deposits were never overthrusted by huge volumes of rocks during the chain building the slight increase in the maturity level recorded in the marsica area may be related to local heating along shear zones in areas of strike slip tectonics

subsidence above a planar reservoir 1 a tabular reservoir circular in plan is located at depth parallel to the surface compaction of the reservoir as fluid is withdrawn causes a change in the stress and displacement fields in the surrounding medium a solution to this problem is obtained by determining the boundary conditions at the interface between the reservoir and the half space using eshelby s 1957 cut and weld technique the displacement field in the reservoir and the surrounding medium is then calculated using the reciprocal theorem the displacement field is found to be the same as that calculated by geertsma 1973a 1973b and by segall 1992 segall et al 1994 using another technique

on the origin of cleavage in the central pyrenees structural and paleo thermal study abstract the present work provides a combined structural and paleothermal fluid inclusions illite content in mixed layers illite smectite kubler index and vitrinite reflectance investigation of the alpine cleavage domain affecting the western south pyrenean zone central pyrenees integration of structural and paleothermal data allows us i to determine the position of the cleavage front in the sedimentary sequence and ii to define mechanisms and temperature conditions for cleavage development cleavage in the eastern part of the study area is approximately limited to the forelimb of the gavarnie hanging wall anticline but to the west it extends progressively southwards affecting younger turbiditic units at regional scale the cleavage front is oblique to the strike of bedding and the overall trend of macrostructures pressure solution is the main mechanism for cleavage development and a strong thermal control on the position of the cleavage front is inferred the transition between sedimentary and tectonic compressional fabric is marked by vitrinite reflectance values of 1 12 1 14 kubler index values between 0 71 and 0 74 2 and the transition between r1 and r3 mixed layers illite smectite a lower thermal boundary of 140 160 c is suggested for incipient cleavage development in the shaly beds of the turbiditic sequence as well as an upper boundary constrained by a maximum measured value of about 215 c

geology and geothermometry of vein type w sn deposits at pennaichaung and yetkanzintaung prospects tavoy township tennasserim division southern burma the pennaichaung and yetkanzintaung w sn prospects are located in tavoy township tennasserim division southern burma the w sn mineralization at the pennaichaung is closely related with a small satellitic granitoid pluton of presumably late mesozoic age which intruded the metaclastic rocks of mergui group mostly carboniferous the mineralized quartz veins at the pennaichaung penetrated the granitoid metasedimentary rocks contact in contrary to the pennaichaung deposit the w sn veins at the yetkanzintaung are exclusively in the metasedimentary rocks of slates and quartzites of margui group mineralized quartz veins in the pennaichaung area trend nne ssw nw se and ne sw with a maximum thickness of 30 cm but only quartz veins trending nne ssw are found to be productive and contained economically workable wolframite and cassiterite majority of the mineralized quartz veins in the yetkanzintaung area trend approximately n s with easterly dip of 50 70 the thickness of the ore veins in the yetkanzintaung area are thinner than those of the pennaichaung and range from 1 cm to 20 cm with an average width of 5 cm fluid inclusion studies of the quartz from the ore veins cutting the granitoid in the pennaichaung area have yielded a filling temperature range of 170 270 c with a maximum mode of 220 c while quartz crystals from the ore veins in the nearby metasedimentary rocks gave a filling temperature range of 140 220 c with a maximum mode of 160 c hence the pennaichaung deposit was thought to have emplaced under a filling temperature range of 140 270 c a similar low filling temperature range was recorded for the yetkanzintaung deposit quartz from the yetkanzintaung ore veins have yielded filling temperatures of 200 240 c whereas the fluorites associated with the mineralized quartz veins gave a temperature range of 140 160 c limited freezing runs indicate a salinity of less than 5 nacl equivalent weight percent for inclusions in quartz from both orebodies no fluid inclusion evidence of boiling of ore fluids nor presence of liquid co2 was observed in this study thus the ore fluids responsible for the w sn mineralization at the pennaichaung and yetkanzintaung areas were of low temperature diluted co2 deficient nacl brines

geological and geochemical constraints on the genesis of the huachanggou gold deposit western qinling region central china the huachanggou gold deposit is located in lueyang county shaanxi province central china it is situated in the mian lue sutural zone in the western qinling orogen and controlled by a wnw striking ductile shear zone the ore deposit is developed in spilite limestone and phyllite in the middle lower devonian sanhekou group and the wall rocks show evidence of deformation pyrite is the main gold bearing mineral and the native gold is either visible or microscopic the huachanggou gold deposit is considered to be an orogenic gold deposit controlled by a ductile shear zone related to the indosinian qinling orogenic event the ores show a strong enrichment in au ag and as but exhibit a simple assemblage of au and ag that are strongly correlated together gold was deposited from a moderate to low salinity salt solution co2 hydrothermal fluid at medium temperature variations in s pb c and o isotopic composition indicate that the sulfur was derived from the reduction of seawater sulfate in the wall rocks the lead was derived mainly from the wall rocks the carbon was derived from the dissolution of marine carbonate the variations in h and o isotopic composition indicate that the ore forming fluids were derived originally from metamorphic fluid with meteoric water mixing in later stages au migrated mainly in the form of au hs 2 to form the deposit boiling of the fluid triggered the precipitation of the metal sulfides that contain the gold

paleogeography and structure of the central mediterranean sicily and its offshore area abstract the geology of the mainland and offshore of sicily is illustrated by a few geologic sections and seismic profiles across the late cenozoic orogenic belt of central and western sicily and across the sardinia channel and sicily straits this belt is the result of several tectonic events deformation involved mainly the sedimentary cover of the old african continental margin characterized by a broad basinal domain flanked along its external southern margin by a shallow water carbonate platform attached to africa in the triassic compressional deformation started in the more internal basinal rock assemblages overlying a thinned crust the most important structural characteristic of the early phase of thrusting is the duplex pile forming the bulk of the chain in central western sicily the structure consists of a basal allochthon made up of permian to middle triassic layers an intermediate duplex wedge composed of competent mesozoic carbonates and a roof complex including upper mesozoic lower tertiary less competent rocks large scale clockwise rotation of the thrusts accompanied transpressional movements in the hinterland during the pliocene right oblique reverse faults modified the previous tectonic contacts between the allochthons in the hinterland zones contemporaneous south directed imbrications affected the southern external areas progressively incorporating foreland and piggyback basins development of the gela thrust system appears to be linked to the transpressional event its accretion is also related to contemporaneous underthrusting at deeper levels of mesozoic carbonate substratum the older buried thrust sheets were pushed up to the surface breaching the deformed tertiary cover of the gela ts northwards in the belt post messinian normal growth faults opened half graben whose sedimentary fill underwent structural inversion alternation of extension and compression tectonics characterizes the sicilian continental margin in the last million years

tectonics and seismicity of the tindari fault system southern italy crustal deformations at the transition between ongoing contractional and extensional domains located above the edge of a subducting slab 1 the tindari fault system southern tyrrhenian sea italy is a regional zone of brittle deformation located at the transition between ongoing contractional and extensional crustal compartments and lying above the western edge of a narrow subducting slab onshore structural data an offshore seismic reflection profile and earthquake data are analyzed to constrain the present geometry of the tindari fault system and its tectonic evolution since neogene including the present seismicity results show that this zone of deformation consists of a broad nnw trending system of faults including sets of right lateral left lateral and extensional faults as well as early strike slip faults reworked under late extension earthquakes and other neotectonic data provide evidence that the tindari fault system is still active in the central and northern sectors and mostly accommodates extensional or right lateral transtensional displacements on a diffuse array of faults from these data a multiphase tectonic history is inferred including an early phase as a right lateral strike slip fault and a late extensional reworking under the influence of the subduction related processes which have led to the formation of the tyrrhenian back arc basin within the present regional geodynamic context the tindari fault system is interpreted as an ongoing accommodation zone between the adjacent contractional and extensional crustal compartments these tectonic compartments relating to the complex processes of plate convergence occurring in the region the tindari fault system might also be included in an incipient oblique extensional transfer zone linking the ongoing contractional belts in the calabrian ionian and southern tyrrhenian compartments

miocene thrusting in the eastern sila massif implication for the evolution of the calabria peloritani orogenic wedge southern italy abstract alpine orogens in the central mediterranean region have revealed the concomitance of crustal extension in back arc domain and crustal shortening in frontal domain quantitative data of deformation in the frontal orogenic wedges are necessary to understand how the shortening extension pair evolves in terms of structures orogenic transport timing and exhumation rate this paper deals with kinematics and ages of the frontal thrust systems of the calabria peloritani arc italy exposed in the eastern sila massif we first present structural fieldwork onshore and offshore well log data and new apatite fission track aft thermochronology then we describe the structural architecture of the studied area as an ene verging stacking of thrust sheets involving basement units and syn orogenic sediments the aft study documents that thrust sheets entered the partial annealing zone from 18 ma to 13 ma this early middle miocene thrusting phase was coeval with exhumation of high pressure low temperature metamorphic rocks in the hinterland of the orogen coastal chain area mainly driven by top to the w extensional tectonics opposite kinematic shear senses contractional top to the e and extensional top to the w and different exhumation rates slow in the frontal more rapid in the hinterland are framed in a tectonic scenario of a critically tapered orogenic wedge during the eastward retreating of the apennine slab

origin and deformation of the neogene recent maghrebian foredeep at the gela nappe se sicily se sicily contains one of the few exposures of orogenic foreland to the maghrebian apennine orogenic system in the central mediterranean here the african foreland is represented by the hyblean plateau adjacent to the frontal thrust structures of the maghrebian chain these structures include the disrupted foredeeps to earlier parts of the thrust system one of these the gela nappe is a major structure composed of late oligocene to early pliocene sediments emplaced onto pliocene pleistocene rocks of the buried foreland this paper presents a correlation of late miocene stratigraphic units between the foreland and the foredeep basin abrupt lithological and thickness variations of these units suggest that the foredeep basin was limited towards the foreland by normal faults in the hinterland these foredeep sediments lap back onto previously emplaced thrust sheets including the far travelled units of numidian flysch the precursor oligocene serravallian foredeep may also have been controlled by normal faulting compressional tectonics are reflected in folding and thrusting which post dates deposition of lower pliocene chalks trubi formation although minor folding and erosion preceded this unit larger thrusts repeat the basin stratigraphy and carry it out onto the adjacent foreland a minimum of 8 km shortening since messinian times can be demonstrated although a more realistic figure is c 25 km at a time averaged rate off 0 5cm a 1 the stratigraphic relationships on the foredeep sedimentary sequences may provide analogues for offshore areas of the thrust belt

the oxidation state of manganese in ferromanganese nodules and deep sea sediments from the central indian ocean abstract ferromanganese nodules from different sediment facies including siliceous ooze pelagic clay sediments from transition zone of siliceous and pelagic clay and seamount crusts from the central indian ocean were analysed for chemical composition mineralogy and bulk oxidation state of mn by the iodometric method despite considerable variation in chemical composition mn fe ratio times from 1 35 to 7 42 and mineralogy the o mn ratio or mno x solid hydrous manganese oxide does not vary much from 1 73 to 1 81 suggesting most of the mn in the manganese nodules in mn iv the oxidised upper zone in the sediment cores decreases in thickness from 15 cm in the north 5 s to 11 cm in the southern part 14 s of the central indian ocean iodometric titration of deep sea sediments yields o mn ratios of 1 29 1 95 sediments from the manganese nodule field have maximum solid mn concentrations and lower o mn ratios in the core top 0 3 cm with minimum mn and o mn ratios at 11 cm depth and thus may reflect the mechanism controlling the supply of diagenetic mn to the nodules in contrast sediments from the non manganese nodule field have comparatively low solid phase mn concentrations in the core top 0 3 cm and almost uniform o mn ratios with depth indicating that mn is not preserved in the sediments but may be remobilised and deposited somewhere else