On the relations between morphotectonics, seismicity, perennial and sporadic hydrothermalism on the volcanic island complex of Milos (Greece)

The objective of this study is to develop a conceptual flow-path model for nuclide migration in fractured crystalline rock at the Kamaishi In-Situ Test Site because improvement of existing models of matrix diffusion |e.g. 1,2|, based on realistic geological data, is necessary for a better understanding of nuclide migration into rock matrix. Data from field observations indicate that fractures at the Kamaishi In-Situ Test Site can be classified into three types; type A with a zone of fracture fillings, type B with a zone of fracture fillings and an altered zone, type C consisting of several fractures with a zone of fracture fillings and an altered zone. Fracture type B was studied in detail by laboratory experiments because type B is predominant in the studied area with more than 60 % of a total of 400 fractures observed in the fracture mapping. Data from laboratory experiments on core, crosscutting a water-bearing fracture and the surrounding rock, indicate that the zone of fracture fillings and the altered zone in the vicinity of the fracture contain flow-paths in which nuclides can migrate and be trapped. The fracture fillings contain more interconnected and permeable flow-paths than the altered and unaltered zones. This implies that migrating nuclides can access flow-paths in the altered zone. The altered zone adjacent to the zone of the fracture fillings contains flow-paths such as microfractures, cracks within quartz, and grain boundaries between altered minerals, through which nuclides will migrate from the fracture fillings into the altered zone and be trapped. The fracture fillings and the specimen of the altered zone have higher sorption capacity than the specimen of the unaltered zone. These data suggest that retention of nuclides can be expected in the vicinity of the fracture. In conclusion, a conceptual flow-path model consisting of a zone of fracture fillings, an altered zone, and an unaltered zone has been developed for a better understanding of nuclide migration in fracture type B.

Abstract. The results of modern processes observations of the sedimentation in the volcanic lakes of the region are summarized with the use of material from other regions of the world. The available data on the drained volcanic lakes deposits, Uzon-Geysernaya caldera as example, was analysed. The main sources of material (volcanic and post-volcanic activity, gravitational displacements on slopes, and erosion-denudation processes) and the mechanisms of its entry into volcanic lakes, as well as the features of the subsequent deposits transformation as a result of hydrothermal, seismic, and volcano-tectonic activity, are identified. The results of the studies carried out allow us to conclude that the volcanic lakes deposits are complexly constructed polyfacial complexes with alternating fine-grained lacustrine and lacustrine-swamp deposits with pyroclastic horizons and interlayers of untreated or poorly processed coarse clastic material coming as a result of volcano-tectonic activity, gravitational and erosion processes. The irregularity of horizons along strike is typical; and is characterized by the large-scale sediments deformation under the influence of seismic activity, growth of effusive and extrusive domes, phreatic explosions, etc. Hydrothermal activity contributes to the weathering and cementation of the lake sediments. Lava outpourings and the high-temperature pyroclastic flows provokes sintering of contacting horizons sediments.

Gold-related Alteration Zones Detection at the Um Balad Area, Egyptian Eastern Desert, using Remote Sensing, Geophysical, and GIS Data Analysis

A homogeneous finite–state discrete–time Markov model is applied for the earthquake occurrence in the Hellenic Subduction Zone (Greece), a region accommodating high seismic activity, being a key structure from a seismotectonic point of view. An attempt is made to provide a stochastic representation of the earthquake process and to assess the seismic hazard through the application of the Markov model. The model is applied on a complete data sample comprising strong () eart h-quakes that occurred in the study area since 1911 up to present. The continuous magnitude scale is divided into appropriate intervals to specify discrete states of the model. As the stochastic behavior of the model is governed by its transition probability matrix, we firstly estimate its well–known maximum likelihood estimator. The estimation of the transition probability matrix leads to the estimation of important indicators of the Markov chain, including hitting times and failure rate functions. The mean number of steps for the first occurrence of an anticipated earthquake (belonging to the class with the stronger events, which we are more interested in) is estimated along with its variance. In a next step, we calculate the confidence interval of the aforementioned estimators.

Western Anatolia has been formed by the motions of the African plate, Arabian plate and Hellenic Subduction zone. The Hellenic Subduction zone, which has high seismicity, is the main tectonic feature of the eastern Mediterranean Sea related to the subduction of the African Plate beneath the Aegean Sea Plate. The Hellenic Subduction zone has a complex lithospheric structure and shows complex differences in the Aegean Sea in terms of continental crust thickness and mantle velocity. In the study area, the directions of Global Positioning System (GPS) velocity vectors which are towards SE change towards S from North of Western Anatolia to Hellenic Subduction zone. It is thought that the factor which controls this mechanism is the shear force or subduction zone located in Aegean Sea. Western Anatolia region, which is located in Western Anatolia Extensional province, includes several morphologically significant N–S trending active normal faults. Besides, the NE–SW and NW–SE trending faults, which their kinematic features change from north to south, are very effective on the tectonic regime of the region. Additionally, for determining the boundaries of these tectonic elements, the Complete Spherical Bouguer (CSB) gravity anomaly of study area was calculated by using World Gravity Map (WGM2012) model. Moreover, in historical and instrumental studies, the high seismicity of the study area is remarkable. It is thought that this case is also related with the mechanism which oriented the GPS velocity vectors to southward. Consequently, the dominant kinematic structure of the region was classified by combining the GPS velocity vectors computed for Izmir and its surroundings bounded by Western Anatolia, Aegean Sea and Eastern Mediterranean and the CSB gravity anomaly. Finally, the results were interpreted together with focal depth distributions of earthquakes and Bouguer gravity data.

Prospecting for gold mineralization with the use of remote sensing and GIS technology in North Kordofan State, central Sudan

Compressional origin of the Aegean Orogeny, Greece

The aim of current study is the identification of hydrothermal alteration by remote sensing methods in Tirka area, NE Iran. The field of study with area about 13 km2 (scale: 1:20,000) is part of the Toroud–Chahshirin magmatic belt, which is located in central Iran structural zone. Hydrothermal alteration zones are interpreted based on Advanced Spaceborne Thermal Emission and Reflection Radiometer remote sensing data. In the first stage, atmospheric, topographic and geometric corrections were performed on satellite imagery. Then, different image interpretation techniques consisting of band ratio, principal component analysis, minimum noise fraction, least squares fitting (LS-Fit), spectral angle mapper and spectral feature fitting (SFF) methods were used. Therefore, VNIR bands for iron oxide alteration, SWIR bands for argillic, phyllic and propylitic alterations, and TIR bands for silicification were applied. The results showed iron oxide and propylitic alterations occurred at the SW and the argillic and phyllic alteration zones were existed in the northern and SE parts of the area. Silicification happened sporadically in the region. Lineaments were processed by false color composite, high-pass filters and hill-shade digital elevation model methods, and two NW–SE and NE–SW major trends were revealed. Field observation and laboratory analysis were used for accuracy of satellite studies. Finally, alteration and lineament maps were integrated for the recognition of high-potential mineralization. Petrographic studies showed that SFF and LS-Fit methods are more reliable than other techniques for the determination of hydrothermal alterations.

Using paleoseismology and tephrochronology to reconstruct fault rupturing and hydrothermal activity since c. 40 ka in Taupo Rift, New Zealand

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) SWIR bands are used in identification of alteration zones which have developed during hydrothermal activity. Among the available methods of hyperspectral data analysis, PCA and RBD techniques are found to be useful in delineation of clay alteration and iron oxide zones. ASTER data analysis by PCA and RBD of (B5+B7)/B6 shows delineation of two distinct alteration zones with characteristic mineral assemblages viz. propylitic zone (chlorite, epidote, montmorillonite and calcite) and phyllic zone (illite, kaolinite, white mica and quartz). Iron oxide rich zones (gossans) have been delineated using ASTER band ratio technique (B2/B1). Geochemical dispersion of soil samples shows that Pb and Zn concentration is higher in phyllic and propylitic zones around Sawar and Malpura area respectively. Thus, ASTER data shows the potential in discrimination of metasedimentary rocks and delineation of alteration zones for targeting base metals around Sawar-Malpura area in central Rajasthan.

On the basis of the previous studies and reconnaissance survey in the studyarea covering Sangon, Kalirejo, Kokap Sub-district, Kulon Progo Regency, Special Region of Yogyakarta, it reveals some facts of the occurrence of quartz veins with massive, crustiform, comb, drusy cavity, saccharoidal, granular, and reniform/mammillated textures, the appearance of lattice bladed barite and hydrothermal breccia veins. Referring to those characteristics, the deposit type in the study area is interpreted to be low sulfidation epithermal type. This study is aimed to understand and characterize the geological condition, rock and ore geochemistry and the mineralizing fluids. The alteration and ore mineralization are almost observed in entire rock units particularly the intrusive andesite 1. Their formation is controlled by the tension fractures (NW–SE and NE–SW) which associate with sinistral strike slip faults (NE–SW), dilational jog (NNW–SSE), oblique normal fault (WNW–ESE), and predictable normal fault at the NE of study area (NW–SE). The alteration zones are developed to be silica-clay (quartz-illite-kaolinite-kaolinite/smectite), argillic (smectite-illite/smectite), and propylitic (chlorite-calcite±epidote). The precipitationof ore minerals is controlled by boiling, mixing, and wall-rock alteration, and canbe found in the quartz veins (quartz-adularia-sericite) and disseminated in the alteration zones, which their high variability is only can be found in the quartz veins, including pyrite, sphalerite, chalcopyrite, galena, marcasite, and arsenopyrite. Based on the ICPAES measurement of 5 quartz vein samples, the Cu, Zn, Pb, and As grade reach about 5,171 ppm, 8,995 ppm, 6,398 ppm, 34.1 ppm, and 1,010.5 ppm, respectively. Gold is not detected. Fluid inclusion microthermometric analysis shows Th of 242.1–257.6 °C and salinity of 1.57–3.87 wt.% NaCl equiv., which indicate a depth below the paleosurface of 384–516 m, and pressure of 101.7–136.6 bar. The ore deposit in the study area is interpreted to be a deep basemetal low sulfidation epithermal type. Gold might be depleted in this epithermal type.

The Biga peninsula (NW, Turkey) hosts numerous polymetallic mineral deposits including skarns, porphyry Cu-Mo, vein type Pb-Zn, and epithermal Au–Ag. These mineralizations are mainly associated with widespread high-K magmatism in the Oligo-Miocene period. Of these the epithermal veins which have economic grade Au-Ag concentrations are generally found in volcanic rocks such as dacites, andesites, and pyroclastic rocks. The hydrothermal aureoles' interaction with highly permeable volcanic rocks caused voluminous alteration zones with potential precious metal enrichments. The Kısacık (Biga Metallogenic Province of NW, Turkey) area can be considered as a promising precious metal mineralization zone due to the high-intensity alterations observed in Miocene volcanic rocks (dacites and pyroclastic rocks). In the study area, the hydrothermal activity can also be seen in basement metamorphic (calcschists) and ophiolitic (basalts - dolerites) rocks. The identified hydrothermal alterations in the field are sericitic and argillic alterations with intense silicifications. The silicifications are mostly observed in cracks and joint fractures of volcanic rocks in the form of veinlets and cavity fills. Major oxide-Trace Element and ICP-MS Ag-Au-PGE’s analysis was performed on the samples taken from the field. The calculated alteration indexes (AI) are ranging between %82-99.2 and Chlorite-Carbonate-Pyrite Indexes (CCPI) values are between %73-97 according to major oxide values of altered volcanics. The Au content varies between 0.03 – 21.34 ppm. When the hydrothermal trend is examined in the AI-CCPI diagram, the altered high grade volcanics shows a chlorite-sericite-pyrite alteration trend. These implications are parallel with field observations. The less altered volcanics are located within the andesite/basalt field. Highly altered volcanics are located in the "ore center" area of the diagram. The calculated alteration index (AI&CCPI) values of the volcanic rocks are high, mainly caused by the removal of mobile cations such and a significant enrichment in immobile cations such as Al and Fe. In addition, a silica-carbonate alteration zone around ophiolitic rocks was observed and gold content of up to 0.16 ppm was detected in samples from this area which indicates a listwanite-type Au deposit.Keywords: Alteration indexes, Miocene Volcanics, Hydrothermal Deposits, Biga Peninsula, Turkey

Altered and mineralised rocks at Peak Hill, are confined to a 300–500 m wide, north-south striking, steeply dipping, shear zone that is flanked by the Mingelo Volcanics along its western side, and Cotton Formation siltstones along its eastern side. This shear zone is defined by extensive zones of cataclasite and strongly foliated micaceous schists in marked contrast to the largely undeformed nature of the adjacent rocks. Advanced argillic assemblages (quartz-kaolinite-pyrite ± alunite ± illite) occur throughout the core of the Peak Hill deposit. Propylitic assemblages, including albite, quartz, interlayered chlorite-smectite, illite and ankerite, and a narrow discontinuous zone of argillic (quartz-illite-pyrite) alteration are developed in the Mingelo Volcanics along the western side of the deposit. Propylitic, argillic and advanced argillic assemblages are overprinted by an internally zoned phase of phyllosilicate alteration that grades inwards from a peripheral sericite-clay-chlorite assemblage, through phyllic assemblages (muscovite/illite-pyrite ± paragonite) to a pyrophyllite-pyrite ± diaspore ± andalusite altered core. Au-Cu mineralisation is hosted by barite-pyrite veins that cut the advanced argillic assemblage, but pre-date the phyllosilicate-dominated alteration. Native Au (lacking Ag), calaverite, Te-rich tennantite-tetrahedrite (goldfieldite), chalcopyrite, covellite and chalcocite occur in the barite-pyrite veins. No ore-bearing minerals were detected in any of the alteration assemblages. The total gold content of the Peak Hill deposit is currently 720 K ounces and this includes 100 K ounces of unmined reserves. Within the shear zone phyllosilicate minerals are developed in strain shadows and partly define the stretching lineation associated with dip-slip movement. The zonation within the phyllosilicate assemblages mimics the geometry of bends in the shear zone and minor internal structures. These textures indicate that the phyllosilicate alteration developed synchronous with movement on the shear zone. Earlier advanced argillic alteration and mineralisation are developed in rocks derived from both sides of the shear zone. Hydrothermal activity associated with the earlier advanced argillic alteration was therefore either synchronous with juxtaposition of these distinct rock units, or occurred during a later phase of movement on the shear zone. Cross-cutting fibrous textures in the auriferous barite-pyrite veins indicate that repeated fracturing of the advanced argillic altered rocks accompanied development of successive generations of auriferous veins. Concentrations of auriferous veins are localised in steeply plunging shoots that are oriented parallel to the stretching lineation in the shear zone. These features all indicate movement on the host shear zone accompanied each phase of hydrothermal activity in the Peak Hill deposit. The location, alteration zonation and distribution of mineralised veins within the deposit are intimately controlled by deformation on the host shear zone synchronous with hydrothermal activity. The development of high-sulphidation hydrothermal systems synchronous with deformation along brittle-ductile shear zones is a predictable consequence of intrusive activity during deformation in areas characterised by a high geothermal gradient. The close relationship between tectonism and hydrothermal activity indicates that these deposits are likely to be located in the vicinity of regional-scale shear zones. Deposits are likely to be aligned parallel to the regional-scale structural “grain” and restricted to areas of conspicuous deformation as is the case at Peak Hill (and Temora, NSW). Aluminous alteration zones concentrated in the vicinity of regional-scale structures in the Carolina Slate Belt may be a further example of this style of hydrothermal activity.

The relief and geological structure of Carpathian Biosphere Reserve represent the features of the geological and geomorphological structure of the four geomorphological regions of the Ukrainian Carpathians. The block mid-mountains of the Polonynsko-Chornohirsky Carpathians (Chornohora, Svydovets, and Uholsko-Shyrokoluzhansky massifs) and the folded mid-mountains of Marmarosy crystal massif (Marmarosy and Kuziy-Trybushansky massifs) are well protected within the reserve. The analysis of the morphostructure and morphosculpture of the reserve is carried out taking into account the longitudinal (NW–SE) and transverse divisions of the Ukrainian The analysis of the morphostructure and morphosculpture of the reserve is carried out taking into account the longitudinal (NW–SE) and transverse divisions of the Ukrainian Carpathians. The longitudinal division is associated with morphostructures of higher orders, such as second and third. The transverse division is associated with the fourth and fifth orders of morphostructures. In the analysis of morphosculpture of the reserve, the types characterized for all regions of Flysch and Crystal Carpathians are allocated. All mountain massifs and ridges could be characterized by an asymmetrical structure, such as steep northeastern slopes and acclivous southwestern slopes. The relic morphosculpture is represented by: 1) fragments of denudation surfaces of different ages such as Polonynska, Pidpolonynska, and riparian; 2) ancient glacial and extra glacial landforms; 3) areas of ancient longitudinal valleys. River valleys with a complex of different age terraces represent inherited morphosculpture. Modern morphodynamic processes are represented by height (tier) differentiation. The processes of sheet erosion, deflation, and rill erosion play an important role in the relief modeling for the tiers of strongly dissected mid-mountain relief. The lower tier of the terraced and non-terraced bottoms of the valleys are associated with the processes of leaching and erosion as well as a significant accumulation of erosion products and mudflows. Stabilized and active displacements are the most recorded among the gravitational processes and block motions. Key words: Carpathian Biosphere Reserve; Ukrainian Carpathians; relief; morphostructure; morphosculpture.

http://dx.doi.org/10.17014/ijog.vol2no1.20072Papandayan is a strato volcano situated in West Java, Indonesia. After the last magmatic eruptionin 1772, only few phreatic explosions have been occurring. At the present time, the activity is centeredin the northeast crater manifested by the presence of fumaroles and hot springs. In November 2002an explosive eruption occurred and ejected ash and altered rocks. Study of the altered rocks revealedthat an advanced argillic alteration took place in the hydrothermal system by an interaction betweenacid fl uids and rocks. Four zones of alteration have been formed as a limited extension along faults oracross permeable structures at different levels beneath the active crater of the volcano.Two types of acid fl uids are distinguished in the crater of the Papandayan Volcano: (1) acidsulphate-chloride water with pH values between 1.6 and 4.6, and (2) acid sulphate water with pHvalues between 1.2 and 2.5. The samples collected after the eruption revealed an increase in the SO4/Cl and Mg / Cl ratios. This evolution is likely explained by an increase in the neutralization of acidfl uids which tends to show that water-rock interactions were more signifi cant after the eruption. Thechanges in chemistry observed in 2003 were the consequence of the opening of new fractures whereunaltered or less altered volcanic rocks were in contact with the ascending acid water. The high δ34Svalues (9-17‰) observed in the acid sulphate-chloride water before the November 2002 eruptionsuggest that dissolved sulphates were mainly formed by the disproportionation of magmatic SO2. Onthe other hand, the low δ34S values (-0.3-7 ‰) observed in acid sulphate-chloride water sampled afterthe eruption suggest that the origin of dissolved sulphates for these waters is the surfi cial oxidation ofhydrogen sulphide.