Major Tectonic Elements Research Articles

East Barents Basin and Admiralty High Composite Tectono-Sedimentary Elements, Barents Sea

Abstract The East Barents Sea (E Barents Sea) includes two major tectonic elements, the East Barents Basin (EB Basin) and the Admiralty High, which are, in the context of the volume, characterized as composite tectono-sedimentary elements. Whereas they share some stratigraphy, their early history may differ. The EB Basin is a dominant structural feature of the Barents Shelf, and one of the largest and deepest sedimentary basins in the Arctic. Admiralty High rims the EB Basin in the east. The advance in understanding the E Barents Sea geology was achieved during 1980s and 1990s mainly due to a significant amount of multichannel reflection seismic data and a number of drilled deep exploration wells. These wells tested many large anticlinal structures and made several large gas discoveries including a giant Shtokman gas and gas condensate accumulation. In the following decades, many important geological results were published in the international and Russian literature. In this chapter we provide a summary of the geology and petroleum geology of the E Barents Sea based on published results and public-domain geological reports.

Structure–Tectonic Characteristics of the Aldan–Maya Potential Petroleum Area Based on the Interpretation of Regional Seismic Data

Abstract —The results of regional geological exploration over the past 18 years within the Aldan–Maya potential petroleum area were used as the basis for the refinement of the geological structure of the study area. The study considers the key structural features of the sedimentary cover of the Aldan–Maya region and major tectonic events that affected its structure. The generalization and interpretation of regional seismic survey data provided the basis for building a series of geoseismic sections and structure maps, which, in turn, were used in structural tectonic zoning of the study area. The map showing outcrops of Riphean formations and groups on the pre-Vendian erosion surface was complied. Tectonic schemes for three structural levels (upper Karelian–Lower Riphean, Middle–Upper Riphean and Vendian–Cambrian) confirmed their fundamental difference. In particular, the large Maya inclined swell was detected only in the topography of the Lower Riphean and is absent in the overlying structures of Middle Riphean–Vendian age, which are represented by weakly differentiated monoclines. The parameters of the major tectonic elements were determined.

Crustal structure across the Central part of Narmada-Son Lineament, India based on the interpretation of aeromagnetic and gravity data: Geological implications

Narmada-Son Lineament (NSL) is a prominent geo-tectonic feature located in central India, characterised by complex geological structures and evolution history. In this study, we present a detailed joint interpretation of the aeromagnetic and gravity anomaly maps to delineate the crustal structure in order to address the thermo-tectonic activity below the NSL region. The NW-SE linear trend observed in the aeromagnetic anomaly map correlates well with the major tectonic elements of the NSL and the Vindhyan basin. The low-pass filtered regional gravity anomaly map and corresponding residual anomaly map revealed several crustal-scale structural features in the study area. The Curie depth map of the region prepared from the magnetic anomaly map shows the variation between 24-48 km. The corresponding heat flow map correlates well with the trends in surface heat flow data. The gravity-derived Moho depth map reveals that the values vary between 30-40 km in the NSL region with deeper Moho below the Vindhyan basin. Further, the crustal models obtained from the constrained potential field modelling for two long transects across the NSL in the present study area revealed i) the absence of crustal underplating in the eastern part of NSL below Hirapur-Mandla region, ii) the presence of mid-crustal horst like structure below NSL in both the transects, iii) undulating Moho with higher density crustal rocks within the NSL compared to the surrounding areas. The modelled crustal structure and the analysis of Curie depth as well as heat flow maps of the study area, reveal that the NSL region was affected by repeated tectonic activities since the Proterozoic times, and the present-day tectonics of this belt is greatly influenced by the reactivation of pre-existing faults along the NSL.

Lateral Variations of Attenuation in the Crust of Alaska Using Lg Q Tomography

ABSTRACT We have conducted a crustal seismic (QLg) attenuation tomography study across Alaska using recordings from the EarthScope USArray from 2014 to 2019. The resolving power of the inversion is 150 × 150 km for most of Alaska, and it is 75 × 75 km in central and southern Alaska. Numerous fault systems and high mountain ranges are present across Alaska and accommodate compression in the north–south direction and shearing of southern Alaska toward the west. These mountain ranges include the Brooks range in the north, the Alaska range in central Alaska, and the Aleutian range in the southwest. The average LgQ for all of Alaska is significantly higher than in the western United States and Canada. This lower average attenuation impacts seismic hazard estimates for the region. According to the tomographic results, we see a significant variation of the QLg values from low to high across the southern part of the Brooks range. Also, we found higher attenuation in the southeast region of Alaska, where the Wrangell volcanoes are located. Moreover, we see an area of lower attenuation associated with weak frequency dependence in the south-central region of Alaska next to Anchorage. Another anomaly with lower attenuation can be seen extending from central Alaska to southeast Alaska, possibly associated with the Yukon–Tanana terrane. There are a few areas like southwest Alaska associated with the Togiak terrane and an area next to Fairbanks in Alaska’s interior that shows lower attenuation with lower frequency dependence and higher attenuation with higher frequency dependence, respectively, for low frequencies up to 3 Hz. Our model’s highest η zones (η≳95) are mostly confined to major tectonic terranes and other major tectonic elements such as faults and fractures. Regional variations in crustal attenuation can impact local seismic hazard estimates if incorporated into the hazard analysis.

Seismotectonic evidence for present-day transtensional reactivation of the slowly deforming Hegau-Bodensee Graben in the northern foreland of the Central Alps

This study presents a seismotectonic analysis of the Miocene-aged Hegau-Bodensee Graben, a major tectonic element in the northern foreland of the European Central Alps. The graben is characterized by comparatively low strain rates and low-to-moderate seismicity. Our study builds on the seismological analysis of earthquakes recorded by a recently densified seismometer network. The derived high-precision absolute and relative hypocenter relocations allow to identify seismogenic structures in the pre-Mesozoic basement, which we relate to bounding faults on either side of the NW-SE striking graben. A cluster of seismicity on the SW side of the graben is associated with the previously mapped Neuhausen Fault. In contrast, the seismogenic, SW-dipping bounding faults on the opposite side of the graben, between the extinct Hegau volcanic field and the Bodanrück peninsula of Lake Constance, cannot be associated with any known fault. A set of 51 focal mechanisms allows for a high-resolution analysis of kinematics and stress regime of the graben. Our results show that the bounding faults of the graben are optimally oriented to be reactivated in transtensional mode in the present-day stress field. Slip rates across the Neuhausen and Randen Faults estimated from geodetic data are likely <0.1 mm/yr. In comparison with historical seismicity over the past 600 years and geomorphic field observations, geodetic rates of 0.1 mm/yr appear overestimated. Nevertheless, historical seismicity suggests that slip rates have the potential to generate MW 5.0 earthquakes within this slowly deforming, transtensional fault zone in the foreland of the Alpine collision zone on timescales of several hundred years.

Quaternary Tectonics as the Neotectonics in Turkey

The base of the Quaternary was formally redefined in 2009 by the International Commision on Stratigraphy at 2.6 Ma by shifting a 800 ka, formerly part of the Pliocene epoch, into the Pleistocene. It has made tremendous impression in literature. The Quaternary period is unique because of its climatic characteristics; however, it is a geochronological unit, and a redefinition of its position would affect many areas, such as the definition of neotectonic period in Turkey. The major tectonic elements of the Eastern Mediterranean region are located in there. Recent studies related to neotectonics in Turkey present a consensus on the driving mechanism and age of this tectonic period: the late Pliocene (before the formal adding of Gelasian stage into the Quaternary period) westward escape of the Anatolian plate. Following the collision of the Arabian and Eurasian plates at ~11 Ma BP, the North Anatolian Fault Zone created in the east and the escape tectonics could not occur until the propagation of the North Anatolian Fault Zone to the Aegean Arc at ~2.5 Ma BP and gaining a transform fault character with a similar slip rate as in today. The spatial distribution of active faults in Turkey also supports such an approach. The great majority of them have no relations with the pre-Quaternary formations, on the other hand are bounding the Quaternary basins. In this study, the neotectonics of Turkey discussed within the view of the redefined Quaternary. The comparison suggests the using of the term Quaternary tectonics substantially coincides with neotectonics in literature for Turkey, because the base level of this period in this region overlaps with the redefined base level of the Quaternary period.

Deaggregation of probabilistic seismic hazard for selected cities in the Arabian Peninsula

Probabilistic seismic hazard assessment (PSHA) for 26 cities in the Arabian Peninsula in terms of unified hazard spectra at rock conditions for 475 and 2475 years return periods was performed. PSHA integrates overall potential earthquake sources with various magnitudes and distances with resulting ground motion prediction intensities. The combination of all these scenarios together cannot inform which particular scenario is most likely contributing to the rate of exceedance of a given ground motion intensity. In order to determine which earthquake contributes most to the hazard, PSHA results are deaggregated for the selected cities based on equal spacing in magnitude and distance for the amplitudes of PGA, SA (T = 0.2 s), SA (T = 1.0 s) and SA (T = 2.0 s) at 2% and 10% probability of exceedance in 50 years (equivalent to 2475, and 475 year return periods, respectively). Seismic hazard at cities close to major active tectonic structures is influenced mostly by earthquakes at nearby distances for both 475 and 2475 years return periods for all considered spectral periods. For cities close to low active seismic sources or relatively far away from the major tectonic elements, the seismic hazard is generally controlled by remote larger earthquakes for long spectral periods and by nearby small to moderate events for shorter ones.

Structure and exhumation of the Cap des Trois Fourches basement rocks (Eastern Rif, Morocco)

The Cap des Trois Fourches (Eastern Rif, northern Morocco) metamorphic basement exposes two major tectonic units, namely the Taïdant unit underthrusting the overlying Tarjât tectonic unit. The Tarjât tectonic unit is composed of metamorphic rock originating from detrital material. This upper Tarjât tectonic unit exhibits: (1) orthogneiss bodies being Paleozoic in age and (2) evidences showing a retromorphose during the Alpine orogenesis. U-Pb SHRIMP zircon geochronology from the orthogneiss bodies has yielded Sakmarian (early Permian) ages for the intrusion of their protoliths. The lower Taïdant unit is formed of green and brown shales associated with quartzite beds. A Mesozoic age is commonly accepted for this unit.The internal structure of the Tarjât tectonic unit consists in km-scale folds trending ENE-WSW with an up-dip direction towards the SE. This compressional deformational stage was superimposed on internal thrust sheets controlled by ductile shear zones with a SW-vergent transport sense. The lower Taïdant unit shows conspicuous bedding associated with a penetrative foliation outlining a monocline structure dipping gently towards the NW. The major ductile-brittle detachment fault bounding the upper Tarjât tectonic unit from the lower Taïdant unit –i.e. the local basement– exhibits evidences for a top-to-the-west sense of motion. We assume that this specific fault is the prolongation into the Cap des Trois Fourches area of the extensional detachment previously described in the Temsamane area. Therefore, this low angle detachment fault is a major tectonic element extending hundreds of km through the Eastern Rif. We postulate that this major detachment roots deep in the Eastern Rif basement. This detachment is cut at the surface by the Nekor normal-sinistral strike-slip fault that separates thin 24–32 km thick metamorphic Eastern Rif crust from the 50–55 km thick crust of the Western Rif. This transtensive fault system exhumes the Rif middle crust, represented by the Temsamane massif units, along the Nekor sinistral STEP boundary at the southern edge of the Betic-Rif subduction system.

3D geodynamic models for the development of opposing continental subduction zones: The Hindu Kush–Pamir example

The development of opposing continental subduction zones remains scantly explored in three dimensions. The Hindu Kush–Pamir orogenic system at the western end of the Himalayan orogen provides a rare example of continental collision linked to two opposing intra-continental subduction zones. The subducted plates feature a peculiar 3D geometry consisting of two distinct lithospheric fragments with different polarities, subduction angles and slab-curvatures beneath the Hindu Kush and Pamir, respectively. Using 3D geodynamic modeling, we simulate possible development of two opposing continental subduction zones to understand the dynamic evolution of the Hindu Kush–Pamir orogenic system. Our geodynamic model reproduces the major tectonic elements observed: (1) the deeper subduction depth, the steeper dip angle and the southward offset of the Hindu Kush subduction zone relative to the Pamir naturally occur if convergence direction of the subducting Indian plate and dip-direction of the Hindu Kush subduction zone match. (2) The formation of the highly asymmetrically curved Pamir region and the south-dipping subduction is promoted by the initial geometry of the indenting Indian lithosphere together with the existence of a major strike-slip fault on the eastern margin of the Pamir region. (3) Subduction of only the lower continental crust during continental collision can occur if the coupling between upper and lower crusts is weak enough to allow a separation of these two components, and that (4) the subduction of mainly lower crust then facilitates that conditions for intermediate-depth seismicity can be reached. (5) The secondary tectonic features modeled here such as strike-slip-fault growth, north–northwest striking extension zone, and lateral flow of the thickened ductile upper crust are comparable to the current tectonics of the region. (6) Model results are further compared to the potentially similar orogenic system, i.e., the Alpine orogen, in terms of the curved Western Alpine arc and the two opposing subducted slabs beneath the Alps and the Dinarides.

ГЕОЛОГО-ГЕОМОРФОЛОГИЧЕСКАЯ ХАРАКТЕРИСТИКА И ПОЛЕЗНЫЕ ИСКОПАЕМЫЕ КЕМЕРОВСКОЙ ОБЛАСТИ

&lt;p&gt;The article deals with the geological structure, geomorphic features and mineral resources ofKemerovoregion. It describes stratified formation of late Precambrian (Riphean and Vendian), Paleozoic, Mesozoic and Cenozoic eras. The article considers four main tectono-magmatic stages of geological development of the area (posteritas-early Ordovician, Ordovician-Silurian, Devonian-late Permian and late Permian-Mesozoic). It enumerates the characteristics of the major tectonic elements of the Kuznetsk Alatau and Mountain Shoria, Salair and Tom ' -Kolyvan areas of the Kuznetsk coal basin. It lists deposits of iron, manganese, polymetallic lead-zinc and copper ore, aluminum raw materials. One of the oldest and valuable minerals of the region is gold. The coalbearing formations of the Kuznetsk coal basin described in the article are the largest of all the exploited coal basins of the world, in terms of reserves and quality of coal. The article lists non-metallic minerals, and the geography of their fields. It describes the main morphostructural elements: the Salair ridge, Alatau-Shor highlands, Tom ' -Kolyvan hill, the Kuznetsk basin and theChulymvalley.&lt;/p&gt;

Morphotectonic records of neotectonic activity in the vicinity of North Almora Thrust Zone, Central Kumaun Himalaya

The landform development and valley floor morphology of active regions is significantly controlled by tectonic processes. In the present study the upper catchments of Kosi and Gagas river valleys have been investigated with special emphasis on aggradational landforms to explain the spatial and temporal variability of aggradation/incision in response to tectonic activity during the late Quaternary and Holocene in Central Kumaun Himalaya. Major tectonic elements such as the North Almora thrust (NAT), Rasiyari fault (RF), and Gagas fault (GF) are considered to be controlling the development of landforms in the region. The valleys have preserved debris flow terraces, bedrock strath terraces, and fluviolacustrine terraces that provide signatures of tectonic activity. Morphostratigraphy of the terraces reveals that the oldest landforms are preserved in the hanging wall block of the NAT, RF, and along the GF. Reconstructions based on morphostratigraphy through the application of optical chronology suggests multiple phases of fluvial aggradation in the upper catchment of the Kosi and Gagas rivers that were initiated around 34ka. The youngest phase of aggradation is dated to be around early to mid-Holocene (7–1ka). Based on terrace morphology, four major phases of enhanced uplift have been estimated during 34, 15.8, 7, and 3ka. The older uplift event dated to be around 34ka is represented uplift along GF, which accommodated onset of valley-fill aggradation in Gagas valley. The 15.8ka event represents uplift along RF, which led to the generation of debris flow from adjacent hillslopes. The 7ka event represents uplift of a hanging wall block of the NAT and deposition of debris flow terraces. However, the youngest 3ka event represents enhanced uplift, which is responsible for the incision of the older valley fill sediments and bedrock. Following this, a phase of accelerated incision/erosion owing to an increase in uplift rate occurred, as evident from the strath terraces between 7 and 1ka.

3D gravity and magnetic modeling - its past and future contribution to understanding the geology of Australia Minerals keynote paper

Geoscience Australia (a.k.a. BMR and AGSO) pioneered the acquisition of regional gravity and magnetic data to aid geological mapping. These data revealed for the first time the extent and nature of the major tectonic elements of the Australian continent. In the 1980's, airborne survey and major exploration companies extended this concept to higher resolution at the province scale, further bringing the geology into focus. Qualitative interpretation of this type of information in 2D plan view has proved invaluable. Thoughts turned to 3D modeling and interpretation. Despite an array of software tools to perform the modeling, we are yet to feel that it has really met expectations. As we move into the future, the grand challenge for us all will be to inject more geological knowledge (prior information) into the modeling. Technology in the form of better geophysical data acquisition capabilities, improved software tools, High Performance Computing facilities, and novel ways to integrate interpretations and visualize 3D spaces will all contribute to the solution. However, user input will remain the key ingredient for success. Injecting geological knowledge into the modeling process and understanding the results that modeling provides will enable us to reveal more detail of the 3D subsurface structure and to identify and manage the resources that are hidden therein.

Major tectonic elements of the Scotia Plate

The opening of the Drake Passage and formation of the Scotia Plate started in the Early Oligocene (∼30 Ma). In spite of the intense studies of the last decades, the tectonic structure of the plate and its evolution remain a matter of debate. This work presents the ideas on the tectonic zoning of the Scotia Plate based on the complex analysis of the morphological peculiarities of the bottom relief, the anomalous gravity field in various reductions, and the anomalous magnetic field. The western, central, and eastern blocks of the plate distinct in the relief structure and geophysical fields are distinguished, and the possible evolution scenario of the plate is suggested.

Plate reconstructions in the Arctic region based on joint analysis of gravity, magnetic, and seismic anomalies

Based on the analysis of various geophysical data, namely, free-air gravity anomalies, magnetic anomalies, upper mantle seismic tomography images, and topography/bathymetry maps, we single out the major structural elements in the Circum Arctic and present the reconstruction of their locations during the past 200 million years. The configuration of the magnetic field patterns allows revealing an isometric block, which covers the Alpha–Mendeleev Ridges and surrounding areas. This block of presumably continental origin is the remnant part of the Arctida Plate, which was the major tectonic element in the Arctic region in Mesozoic time. We believe that the subduction along the Anyui suture in the time period from 200 to 120 Ma caused rotation of the Arctida Plate, which, in turn, led to the simultaneous closure of the South Anyui Ocean and opening of the Canadian Basin. The rotation of this plate is responsible for extension processes in West Siberia and the northward displacement of Novaya Zemlya relative to the Urals–Taimyr orogenic belt. The cratonic-type North American, Greenland, and European Plates were united before 130 Ma. At the later stages, first Greenland was detached from North America, which resulted in the Baffin Sea, and then Greenland was separated from the European Plate, which led to the opening of the northern segment of the Atlantic Ocean. The Cenozoic stage of opening of the Eurasian Basin and North Atlantic Ocean is unambiguously reconstructed based on linear magnetic anomalies. The counter-clockwise rotation of North America by an angle of ~15° with respect to Eurasia and the right lateral displacement to 200–250 km ensure an almost perfect fit of the contours of the deep water basin in the North Atlantic and Arctic Oceans.

The Maritsa strike-slip shear zone between Kostenets and Krichim towns, South Bulgaria — Structural, petrographic and isotope geochronology study

The present study describes the characteristics of the Maritsa Shear Zone (MSZ), a major tectonic element in the Balkanides in South Central Bulgaria. Metamorphic rocks of four lithotectonic units — Madan, Chepinska, Asenitsa and Thrace units crop out in the study area. Strike-slip ductile deformation in MSZ affects the Thrace Lithotectonic Unit (TLU) for up to 15km. The stratigraphy of this unit is divided in two: Parvenets succession and variegated succession. U–Pb zircon dating reveals Late Jurassic protolith age for metagranitoids and metagabbros of the variegated succession. For its metasedimentary part Triassic to Upper Jurassic age is suggested based on the strontium isotope signature of the marbles. The Parvenets succession affiliates to the Variscan metamorphic basement of Europe.The metamorphic evolution of the zone is subdivided into synmetamorphic strike-slip deformations and annealing stages. The ductile shearing occurred in greenschist to lower amphibolite facies between 130Ma (discordant U–Pb ages) and 82–78Ma (late-syntectonic granites). This stage is connected with the oblique collision of the Rhodope Late Jurassic arc with the European platform. With the docking of the arc and the triggering of the strike-slip movements, MSZ represents an orogen-scale border between the Rhodope south-vergent thrust complex and the north-vergent deformations in the Srednogorie and Sakar-Strandzha zones. During the Late Cretaceous MSZ is the contact between the Srednogorie magmatic arc (part of the Apuseni–Banat–Timok–Srednogorie Belt) and the Rhodopean metamorphic core complexes. NW–SE dextral faulting characterized the brittle tectonics along the zone. Strike-slip faults of the southern border of the TLU are transferred into reverse faults, along which the TLU overthrusted Oligocene sediments.MSZ is an orogen-scale transpressional shear zone and an important border in the structure of the Balkanides. This multidisciplinary research emphasizes its role as a major tectonic element by presenting new structural, petrographic and isotope geochronology data.

トカラ列島における中期更新世の酸性海底火山活動

To understand the submarine volcanism surrounding the Tokara Islands, a submarine topographic analysis and 67 dredge samplings were carried out. Prior to the submarine investigations, we reviewed comprehensively geological and geophysical data on this region and confirmed the complexity of both volcanic activity and tectonic setting of the Tokara Islands. In contrast to the homogeneous subaerial volcanic rocks comprising predominantly two-pyroxene andesite lava flows, the dredged samples vary from basaltic andesite to rhyolite in composition. Furthermore, we reveal that dacitic and rhyolitic pumices are abundant and broadly distributed throughout the submarine area. The recovered volcanic rocks were mainly subangular to angular cobble-boulder fragments of lava, scoria, and variably vesiculated pumice. Volcanic rocks with hornblende phenocrysts occur only north of the Tokara strike-slip fault, which is a major tectonic element of volcanism. The pumices can be classified into three categories based on the size and abundance of the phenocrysts: aphyric pumice, fine-grained porphyritic pumice, and coarse-grained porphyritic pumice. Occurrences, such as amount in a dredge, shape without extensive abrasion, large fragment size, and bulk rock chemical compositions of the major pumice fragments suggest that they are in situ, rather than originating as drifted pumice or air fall, exotic pyroclastic fragments derived from the four super-eruptions of Kyushu Island. Because dredged samples contained fresh volcanic glass in the groundmass, and are not covered by iron-manganese oxide crust, they appear to have originated from the Quaternary eruptions. Indeed volcanic islands have developed above the submarine erosional terraces (indicated as knick points at approximately 110 m in depth), which is assumed to have formed during the last glacial age. K-Ar age dating on the representative pumice samples resulted in ages of 0.60 ± 0.20 Ma and < 0.2 Ma, respectively. These newly obtained submarine data support that acidic volcanisms occurred around the submarine calderas during the Mid-Pleistocene age.

Shaded relief magnetic anomaly map of Italy and surrounding marine areas

Magnetic observations made onshore the Italian Peninsula, and across the adjacent seas, have been compiled in a new digital database that provides the first complete regional scale view of the crustal scale magnetic anomalies of the region at sea level. The offshore data were acquired between 1965-1972 by the Osservatorio Geofisico Sperimentale (OGS) while the ground measurements were performed within the framework of the Progetto Finalizzato Geodinamica of the Consiglio Nazionale delle Ricerche (PFG-CNR) between 1977 and 1981. The new shaded relief magnetic anomaly map of total intensity of the Earth's magnetic field for Italy and the surrounding seas has been produced at sea level, for the geomagnetic epoch 1979.0. The most remarkable result of this new map, with respect to the previous compilations and to the aeromagnetic map of Italy, is an unprecedented view of the magnetic signature of the major tectonic elements in their regional setting. There is good correlation between known structural geology and the magnetic anomalies, and now that the longer wavelength signatures have been corrected, deeper interpretations are possible.

The Chailag-Khem fluorite-barium-strontium rare earth carbonatite occurrence, the Western Sayan Range, Russia

The geological and mineralogical data on the Chailag-Khem F-Ba-Sr-REE occurrence in the Western Sayan Range, Russia, are discussed. The chemical compositions of rocks, ores, and minerals (ICP-MS, Link) are reported. The occurrence is localized in a tectonic crush zone composed of Cambrian quartz-sericite slates intruded by quartz syenite porphyry. Ore mineralization occurs as veins, cement of tectonic breccia, and metasomatic disseminations in host rocks. Massive ore consists of calcite, strontianite, and quartz; impregnations of euhedral fluorite, ankerite, and bastnaesite crystals; and fine-grained barite aggregate. Accessory minerals include parisite, synchysite, barytocelestine, sulfides, rutile, and uraninite. Late metasomatic calcite and strontianite segregations and veinlets are abundant. In genetic, mineralogical, and geochemical features, the Chailag-Khem occurrence is similar to the Late Mesozoic carbonatite deposits of Central Tuva, of which the Karasug Fe-F-Ba-Sr-REE deposit is the largest and best known. All carbonatite deposits and occurrences are located within a longitudinal zone transverse to the major tectonic elements of the region.

Pattern of deformation around the central Aeolian Islands: evidence from multichannel seismics and GPS data

AbstractThe tectonics of the central Aeolian Islands, which are located within the Tyrrhenian backarc basin, has been investigated through a marine seismic reflection survey. We find that compressional structures dominate around the islands, whereas extensional faults occur only to the north of Salina and Filicudi, towards the Marsili basin. This pattern of deformation, although different from previously reported, is in agreement with the strain field and stress regime obtained from GPS measurements and seismological data. Age constraints suggest that contractional deformation was active since middle Pleistocene, being coeval with the building of the volcanic edifices of the Aeolian Islands, and is superimposed on pre‐existing extensional deformation. Compressional and extensional regimes, therefore, can coexist within a backarc setting. Seismic profiles show that the Tindari‐Letojanni fault, considered as a major tectonic element, does not extend to the north towards the island of Vulcano as a throughgoing fault; rather, deformation is accommodated in a broader belt displaying greater structural complexity.

Applying FALCON® gravity gradiometry to hydrocarbon exploration in the Gippsland Basin, Victoria

The Bass Strait FALCON airborne gravity gradiometcr (AGG) survey was flown over an area of the Gippsland Basin in Bass Strait in July 2002. The survey, centred on the gas-producing Marlin and Snapper fields, coincidcd with a contemporary, detailed marine gravity survey. These marine gravity data, as well as pre-existing data from satellite gravity and sparse marine gravity surveys, were used in comparisons with the FALCON data.The vertical gravity gradient data outlined a major Eocene channel. Interpretation, including modelling of representative seismic lines, revealed the particular usefulness of these data for mapping shallow faults. Conventional vertical gravity from the FALCON survey was better at the longer wavelength features, typically the major tectonic elements such as basin bounding faults, and relative sediment thickness. Comparisons with the marine and satellite gravity data showed that the FALCON gravity reproduced all the information available in the other surveys at wavelengths up to the survey size. At shorter wavelengths, the FALCON data had higher sensitivity than all other datasets, including the detailed marine gravity. Incorporation of longer wavelengths from the satellite or other gravity into the FALCON gravity proved successful in improving the longer wavelength information and regional context. As a result of this study, the standard FALCON processing has been improved to allow such incorporation on all surveys where separately acquired sparse gravity data are available.