Subvolcanic Bodies Research Articles

Hydrogeochemistry of Isti Su hot spring, Western Azerbaijan, Iran

The Isti Su hot spring is located in southeast of Salmas, in Western Azerbaijan, Iran. The area is a small part of Sanandaj–Sirjan geological zone which hosts many hot springs. The magma chamber of Salmas region is the main heat source of the hot springs in Isti Su area. Abundant rainfall and relatively long duration of snowfall as well as several deep faults in the area create the best conditions to have several hot springs in the area. The host rocks of the area are sedimentary and metamorphic rocks of Cambrian to Recent sediments which are intruded by several granite and ophiolite bodies. Several hot springs have been formed in the vicinity of these plutonic to sub-volcanic bodies. The Isti Su hot spring is one of the most typical hot springs of the Salmas region. Eight samples were collected from the study area. To investigate the seasonal changes in the field and chemical parameters and to measure trace element concentrations in dry and wet seasons, springs were sampled twice in May and November. Temperature, pH and electrical conductivity of the water samples were measured on-site. Temperatures of the selected samples range from 26.3 to 38.5 °C. The pH values of the samples vary between 6.4 and 7.5. TDS contents range from 9200 to 1790 mg/L. The results of geochemical analysis show that the As, Li, Fe, Hg, Na, and Cr are not more than WHO’s standard level. As and B are two times more than WHO’s standard level. The As and B concentrations in the hydrothermal and geothermal solutions rise higher than its standard level. World Health Organization recommended As level for drinking water is 0.01 mg/L. The Na–SO4–HCO3 triangular diagram shows that the samples are of HCO3 and Na types. Open skin scars, gangrene, malignant cancers and environmental problems are among the consequences of high concentrations of As and B. The high content of As and B in water of this hot spring can be harmful to the environment and people of the area.

LATE PALEOZOIC ALKALI-GRANITOID MAGMATISM OF SOUTHERN KAZAKHSTAN AND ITS ROLE IN THE FORMATION OF THE ORE-BEARING VOLCANIC STRUCTURES OF KENDYCTAS-CHU-ILI-BETPAK-DALA URANIUM ORE PROVINCE

Areas of distribution of alkaline granitoids in southernKazakhstanhave been identified, most of which are located within the Kendyktas-Chu-Ili-Betpakdalin uranium-bearing province, traditionally considered as Late Devonian-early Carboniferous. Arguments in favor of late Paleozoic age of alkaline rocks have been given. The proximity of the petrographic composition, petrochemical and geochemical features of the alkaline granites of the Chu-Ili-West-Balkhash area and late Paleozoic alkaline granites of the Zailiysky area has been established, confirming their age and continental rift origin. Similarity in the development of magmatism and hydrothermal mineralization of ore-bearing volcanic structures of the Chui area (Kurmanshitinskoe) and North-Western Chingiz (Ulkentuz and Dostar) has been revealed. In these structures, Devonian volcanic rocks are interspersed with subvolcanic bodies of comendites and later dikes of microgabbrodiorites and microdiorites. The hydrothermal mineralization of these structures took place in multiple stages. The early stage includes secondary quartzites, which developed in Devonian volcanogenic rocks. Comendite is associated with K-feldspated and albitized rocks, as well as with zones of rare-metal (Zr, Nb, Th, U and TR) Fe-Mg metasomatites that originated in the middle stage. In the later stage, after the introduction of microgabbrodiorite dikes, berezites with U-Mo mineralization formed. Comendites in the structures of the North-Western Chingiz break through the deposits D2-3 and D3-C1 and are considered to be the comagmatic alkaline granites of the neighboring late Paleozoic massifs (Tleumbet and Kuyrektykol). The noted similarity may also indicate that the Chui area comendites are likely to be dated to the late Paleozoic age. Examples have been given to the superposition of berezites and U-Mo mineralization on the late Paleozoic granosyenites, which are widespread in the Kurdai volcanic structure, as well as on the alkaline granites of Karasai volcanic structure. Their age may also be late Paleozoic. Additional research has been recommended for the final conclusions on the age of alkaline rocks and uranium mineralization.

Estudo de inclusões fluidas em quartzo do garimpo do Papagaio, um sistema magmático-hidrotermal, Província Aurífera de Alta Floresta (MT), Cráton Amazônico

O garimpo aurífero do Papagaio, localizado em Paranaíta, Mato Grosso, insere-se no setor noroeste da Província Aurífera de Alta Floresta, sul do Cráton Amazônico. Está hospedado em dacito porfirítico inicialmente afetado por alteração potássica, sobreposta por forte alteração sericítica pervasiva e, por fim, por alteração propilítica. O minério é representado pela paragênese pirita + calcopirita + esfalerita ± galena ± calcocita ± covelita e ocorre associado a sistemas de veios de quartzo e stockworks que truncam os setores de alteração potássica e sericítica. Estudos de inclusões fluidas dos veios mineralizados e estéreis presentes no garimpo permitiram identificar três grupos de inclusões fluidas: tipo I) inclusões aquocarbônicas; tipo II) aquosas bifásicas; tipo III) aquosas tri a multifásicas. Nos veios mineralizados houve a crepitação das inclusões do Tipo I a 325ºC. Foram encontradas temperaturas de homogeneização de 115,1 a 216,2ºC e salinidades entre 0,5 a 24,0% para as inclusões do Tipo II. Nos veios estéreis, as inclusões do Tipo II resultaram em temperaturas de homogeneização total entre 135,9 e 190,3ºC e salinidades de 26,0 a 30,2%. No Tipo III a homogeneização total ocorreu entre 323,2 e 402,9ºC com salinidade superior a 40,0%. Portanto, fluidos de elevada temperatura e salinidade com características de origem magmática tiveram um papel essencial na formação das zonas mineralizadas do garimpo. Nesse contexto, a colocação de corpos subvulcânicos teria sido essencial na gênese da mineralização aurífera do Papagaio, pois teria servido como fonte de calor, fluido e metais para a instalação de um sistema magmático-hidrotermal profundo, relacionado ao ambiente dos depósitos do tipo pórfiro e intrusion-related gold systems (IRGS).

Intrusive hyaloclastite and peperitic breccias associated to sill and cryptodome emplacement on an Early Paleocene polymagmatic compound cone-dome volcanic complex from El Guanaco mine, Northern Chile

This work explores the textural characteristics, morphology and facies architecture of well-preserved Paleocene hyaloclastic and peperitic breccias associated with subvolcanic intrusions at El Guanaco gold mine (Northern Chile). The El Guanaco mine volcanic sequence is part of a polymagmatic compound cone-dome volcanic complex grouping several dacitic domes and maar-diatremes, and subordinated subvolcanic intrusions of basaltic, andesitic and dacitic compositions. The Soledad-Peñafiel Fault System is a first order regional structure controlling the location and style of the volcanism in the region. Three different intrusive bodies (Basaltic sills, Dacitic cryptodomes and Andesitic cryptodomes) were found to intrude into a wet and poorly consolidated pyroclastic sequence representing the upper portions of a maar-diatreme. Consequently, extensive quench fragmentation and fluidization along their contacts occurred, leading to the formation of widespread breccia bodies enclosing a coherent nucleus. Differences in matrix composition allows to define two main breccias types: 1) poorly-sorted monomictic breccias (intrusive hyaloclastites) and 2) poorly-sorted tuff-matrix breccias (peperites). The observed facies architecture is interpreted as the result of the interplay of several factors, including: 1) magma viscosity, 2) the geometry of the intrusives, and 3) variations on the consolidation degree of the host rocks. Additionally, the overall geometry of each intrusive is interpreted to be controlled by the effective viscosity of the magmas along with the available magma volume at the time of the intrusions. The presence of three compositionally different subvolcanic bodies with intrusive hyaloclastite and peperite envelopes indicate, not only that all these intrusions occurred in a short period of time (probably less than 2–3Ma), but also that the volcaniciclastic pile suffer little or none compaction nor consolidation during that time. The presence of three compositionally variated synvolcanic intrusives can be explained either by the presence of a zoned magmatic chamber feeding the volcanic complex, or more likely by the influence of the Soledad-Peñafiel Fault Zone acting as a preferential pathway for different magma compositions/sources to rise to the surface.

Geochemistry of heavy minerals and U–Pb detrital zircon geochronology in the Manantiales Basin: Implications for Frontal Cordillera uplift and foreland basin connectivity in the Andes of central Argentina

The Manantiales Foreland Basin, located at ~32°15′S in the Frontal Cordillera, Argentina, contains the sedimentary record of erosion of igneous basement and Miocene volcanic rocks exhumed during the Andean orogeny. U–Pb ages of detrital zircons from the basin fill succession (Chinches Formation) constrain the onset of deposition to ca. 22Ma (early Miocene). We present the first geochronological control (ca. 22Ma) from the lower part of the Manantiales Foreland Basin (Areniscas Chocolate member) on the basis of U–Pb ages of detrital zircons, shedding light about an older initiation of this foreland basin. The main heavy mineral association in the sedimentary basin, clinopyroxene+amphibole, indicates two events of volcanic supply, probably corresponding to the Farellones Formation in the Principal Cordillera, and the La Ramada Volcanic Complex and subvolcanic rocks similar to the La Laguna body in the Argentinean Frontal Cordillera. Detrital zircon geochronology indicates dominant sourcing from upper Paleozoic–lower Triassic Choiyoi Magmatic Province rocks. Initial sediment supply at ca. 22–19Ma was from the Cenozoic volcanic arc of the Principal Cordillera. At ca. 19Ma, exhumation of the Frontal Cordillera was registered by supply from the Choiyoi Magmatic Province, related to tectonic uplift of a western block (La Ramada–El Espinacito ranges) through a thrust of the La Ramada fold-and-thrust belt. At ca. 16Ma, supply from the Cenozoic volcanic arc recommenced, providing evidence for capture and erosion of the Principal Cordillera, which could be related to thrusting in normal sequence of the La Ramada fold-and-thrust belt. At ca. 10Ma, the La Ramada Volcanic Complex and rocks similar to the La Laguna subvolcanic body became a local source of sediment for the basin. The Manantiales Foreland Basin was linked to Neogene sedimentary basins in the Precordillera at its first part in its history, between ca. 22 and 19Ma and probably until ca. 12Ma, when the eastern Frontal Cordillera (Cordillera del Tigre) and Precordillera were uplifted, and the foreland basin was broken. Thus, the Frontal Cordillera was uplifted through two diachronous thick-skinned blocks from west (La Ramada–El Espinacito ranges) to east (Cordillera del Tigre). This result can explain the diverse ages for uplift deduced for the Frontal Cordillera in previous studies, where it has been considered rather as a singular N-S block. The source of late Mesoproterozoic detrital zircons registered in the Manantiales Basin is uncertain, but we infer recycling from Mesozoic sedimentary rocks of the Principal Cordillera.

Voluminous and crystal-rich igneous rocks of the Permian Wurzen volcanic system, northern Saxony, Germany: physical volcanology and geochemical characterization

The North Saxon Volcanic Complex (NSVC) is a nested caldera edifice dominated by the c. 295 Ma Rochlitz Volcanic System and the c. 289 Ma Wurzen Volcanic System (WVS). The climactic activity of the WVS resembled a VEI ≥ 7 fissure ‘supereruption’ resulting in voluminous and crystal-rich caldera-fill ignimbrites (minimum volume c. 199 km3); caldera outflow facies is not known sofar. Precursory to the WVS ‘monotonous intermediates’, rhyolitic and rhyodacitic volcanic activity led to deposition of the low-volume Wermsdorf and Cannewitz ignimbrites. Modal analysis of the WVS pyroclastic units reveals an inhomogeneous crystal population (≤ 58 vol%) comprising k-feldspar, plagioclase, quartz, ortho- and clinopyroxene and minor amounts of biotite. The Wurzen caldera fill ignimbrites feature three types of fiamme: (1) felsic fiamme; (2) mafic fiamme; and (3) granite-porphyry fiamme. This, the modal variation, and the common presence of clinopyroxene and biotite indicate a strong magma mingling component in the WVS—characteristics which have not been observed in the precursory, Wermsdorf and Cannewitz ignimbrites. The caldera fill ignimbrites feature a large compositional variation from (basaltic) trachyandesite to rhyolite caused by basaltic injection and magma mingling. It is proposed that magmatic underplating led to reheating crystal mush and finally to convection processes within the WVS magma chamber. The predominance of either pyroxene or biotite as mafic mineral in the (trachy-) dacitic to rhyolitic ignimbrites indicates eruption of crystal mush from different magma batches. Prominent negative Nb and Ta anomalies of the Wurzen caldera fill ignimbrites, porphyries, and mafic dykes indicate enhanced melt–crust interaction or contamination of mantle melt. In the aftermath of the WVS caldera eruption, basaltic, trachyandesitic, andesitic and rhyolitic melts ascended puncturing the Wurzen-α and β ignimbrites leading to an array of NW–SE-trending dykes, subvolcanic bodies, and lava domes. Among these, voluminuous granite-to-syenite porphyries emplaced. The deeply eroded WVS caldera allows insight into one of the major magmatic processes that governed the post-collisional phase of the Variscan orogeny in Europe. The study of the deeply eroded supervolcano caldera will lead to the understanding of the connection between a monotonous intermediate ignimbrite and related post-eruptive intrusions.

Porphyry-Style Petropavlovskoe Gold Deposit, the Polar Urals: Geological Position, Mineralogy, and Formation Conditions

Geological and structural conditions of localization, hydrothermal metasomatic alteration, and mineralization of the Petropavlovskoe gold deposit (Novogodnenskoe ore field) situated in the northern part of the Lesser Ural volcanic–plutonic belt, which is a constituent of the Middle Paleozoic island-arc system of the Polar Urals, are discussed. The porphyritic diorite bodies pertaining to the late phase of the intrusive Sob Complex play an ore-controlling role. The large-volume orebodies are related to the upper parts of these intrusions. Two types of stringer–disseminated ores have been revealed: (1) predominant gold-sulfide and (2) superimposed low-sulfide–gold–quartz ore markedly enriched in Au. Taken together, they make up complicated flattened isometric orebodies transitory to linear stockworks. The gold potential of the deposit is controlled by pyrite–(chlorite)–albite metasomatic rock of the main productive stage, which mainly develops in a volcanic–sedimentary sequence especially close to the contacts with porphyritic diorite. The relationships between intrusive and subvolcanic bodies and dating of individual zircon crystals corroborate a multistage evolution of the ore field, which predetermines its complex hydrothermal history. Magmatic activity of mature island-arc plagiogranite of the Sob Complex and monzonite of the Kongor Complex initiated development of skarn and beresite alterations accompanied by crystallization of hydrothermal sulfides. In the Early Devonian, due to emplacement of the Sob Complex at a depth of approximately 2 km, skarn magnetite ore with subordinate sulfides was formed. At the onset of the Middle Devonian, the large-volume gold porphyry Au–Ag–Te–W ± Mo,Cu stockworks related to quartz diorite porphyry—the final phase of the Sob Complex— were formed. In the Late Devonian, a part of sulfide mineralization was redistributed with the formation of linear low-sulfide quartz vein zones. Isotopic geochemical study has shown that the ore is deposited from reduced, substantially magmatic fluid, which is characterized by close to mantle values δ34S = 0 ± 1‰, δ13C =–6 to–7‰, and δ18O = +5‰ as the temperature decreases from 420–300°C (gold–sulfide ore) to 250–130°C (gold–(sulfide)–quartz ore) and pressure decreases from 0.8 to 0.3 kbar. According to the data of microanalysis (EPMA and LA-ICP-MS), the main trace elements in pyrite of gold orebodies are represented by Co (up to 2.52 wt %), As (up to 0.70 wt %), and Ni (up to 0.38 wt %); Te, Se, Ag, Au, Bi, Sb, and Sn also occur. Pyrite of the early assemblages is characterized by high Co, Te, Au, and Bi contents, whereas the late pyrite is distinguished by elevated concentrations of As (up to 0.7 wt %), Ni (up to 0.38 wt %), Se (223 ppm), Ag (up to 111 ppm), and Sn (4.4 ppm). The minimal Au content in pyrite of the late quartz–carbonate assemblage is up to 1.7 ppm and geometric average is 0.3 ppm. The significant correlation between Au and As (furthermore, negative–0.6) in pyrite from ore of the Petropavlovskoe deposit is recorded only for the gold–sulfide assemblage, whereas it is not established for other assemblages. Pyrite with higher As concentration (up to 0.7 wt %) is distinguished only for the Au–Te mineral assemblage. Taking into account structural–morphological and mineralogical–geochemical features, the ore–magmatic system of the Petropavlovskoe deposit is referred to as gold porphyry style. Among the main criteria of such typification are the spatial association of orebodies with bodies of subvolcanic porphyry-like intrusive phases at the roof of large multiphase pluton; the stockwork-like morphology of gold orebodies; 3D character of ore–alteration zoning and distribution of ore components; geochemical association of gold with Ag, W, Mo, Cu, As, Te, and Bi; and predominant finely dispersed submicroscopic gold in ore.

Geochemistry and tectonic setting of triassic magmatism from the Lercara Basin (Sicily, Italy)

Petrological and geochemical data of Triassic magmatic rocks from Lercara Basin (Central Sicily), are discussed to provide new information about the intraplate volcanism related to the Pangea break up. The magmatic rocks crop out as subvolcanic bodies and are packed in several Lower Triassic clayey lithologies correlated to the sedimentation into the Imerese and Sicano domains. The samples were divided in two groups. The first group includes transitional to alkaline basalts, with crystalline sub - ophitic texture mainly characterized by plagioclase, clino- and orthopyroxene, and olivine crystals. The second group includes more altered rocks, with porphyritic texture, showing alkali basaltic to phonolitic compositions. Major and trace element data of single groups show small variations indicating fractional crystallization processes. Abundances and ratios of incompatible trace elements indicate that rocks were formed in an intraplate continental environment from different mantle sources with E-MORB to OIB-type compositions. Low degrees of partial melting at the transition between spinel and garnet lherzolite fields can be hypothesized for parental magmas of the Lercara Basin. Magmas ascended to the surface as various batches of magmas along lithospheric fractures originated by flexure and uplift of the Mesozoic Pangea supercontinent.

Composition and conditions of formation of the parental melts of Jurassic dolerites of southwestern Crimea: Evidence from melt inclusions in olivine phenocrysts

This study focuses on Jurassic shallow intrusions and subvolcanic bodies from around Trudolyubovka village in the southwestern Crimea. All the rocks are similar in mineral composition and have similar geochemical features and occur in close spatial and geological association. This allows us to assign the intrusions to a single magmatic series and interpret them as differentiation products of a single parental melt. The investigation of melt inclusions in olivine from the most magnesian sample showed that the composition of igneous melts ranged from basalt to basaltic andesite of a moderately potassic subalkaline affinity. Compared with N-MORB, they are enriched in LILE, but have similar HFSE and REE contents. The early magmatic melts crystallized at temperatures ranging from 1240 to 1125°C, pressures of 6–8 kbar, and an oxygen fugacity of ΔQFM = +0.6; and later melts crystallized at 1090–940°C, ~1.5 kbar, and oxygen fugacity increasing from ΔQFM + 0.9 to ΔQFM + 2.3. The minimum pressure of groundmass crystallization was estimated as 40–60 bar. The primitive melts were formed in a mature island arc or an active continental margin setting by ~13% melting of a DMM-like source. The melting occurred at spinel-facies depths under the influence of a slab-derived fluid at a temperature 25°C below the dry peridotite solidus.

The Parkam exploration district, Kerman, Iran: Geology, alterations, and delineation of Cu- and Mo-mineralized zones using U-spatial statistic with associated software development

The Parkam exploration district represents an area of approximately 4 km2 located 50 km north of Shahr-E-Babak (Kerman Province, Iran) , and has several traces of old copper mining and smelting activities. This area lies in the Kerman Copper Belt which is part of the larger Sahand-Bazman igneous and metallogenic zone hosting numerous known porphyry copper deposits and systems. The geology of the Parkam exploration district demonstrates that the area contains a diorite-type porphyry copper system hosted by volcanic and pyroclastic rocks of predominantly andesitic composition. Based on field and microscopic investigation, it was determined that the dominant types of alteration were propylitic, phyllic, argillic, and potassic, and the alteration map of the study area was produced. Expect for the propylitic alteration which was observed mainly in the host rocks, the other types of alteration are associated mainly with the dioritic subvolcanic body. Accompanied by subordinate amounts of primary sulfides, fracture-filling malachite is widespread in the potassic and phyllic zones and comprises the dominant style of mineralization at the surface of the porphyry system. Lithogeoc hemical data resulting from 377 samples were analyzed, and the results of background and anomaly separation by means of conventional and the U-spatial statistic method were compared. The Cu and Mo mineralizations were subsequently delineated using the U-spatial statistic. The delineated Cu mineralization is closely associated with the defined zone of potassic alteration, which is also consistent with the field and microscopic observation of the Cu mineralization in this alteration zone. The Mo mineralization delineated by the U-statistic method is mostly associated with the phyllic alteration and is spatially conformable with the zone defined for it. The source code for a software program, which was developed in the MATLAB programming language in order to perform the calculations of the U-spatial statistic method, is additionally provided. This software is compatible with geochemical variates other than Cu and Mo and can be used in similar exploration projects.

The age of young intrusions of Tsana Complex (Greater Caucasus) and isotope-geochemical evidence for their origin from hybrid magmas

This paper presents isotope-geochronological and petrological study of granitoids of the potentially ore-bearing (Au–As–Sb–Sn–Mo) Early Pliocene Tsana Complex, which are confined to the Main Caucasus fault zone (upthrow fault) in the central part of the Greater Caucasus Range. The Tsurungal and Karobi groups of magmatic bodies are distinguished based on spatial criterion. The Tsurungal group includes three small granite—granodiorite massifs (Tsurungal, Chorokhi, and Toteldash) and numerous acid and intermediate dikes in the upper reaches of the Tskhenistsqali River (Kvemo Svaneti, Georgia). The Karobi group comprises three subvolcanic rhyodacite bodies located in the upper reaches of the Chashuri River (Zemo Racha, Georgia) and numerous N–S-trending trachyandesite dikes near the axial zone of the Main Caucasus Range. The K-Ar and Rb-Sr isotope dating shows that the granitoid massifs and dike bodies of the Tsana Complex were formed in two different-age pulses of the Pliocene magmatism: phase I at 4.80 ± 0.15 and phase II at 4.15 ± 0.10 Ma. All hypabyssal rocks of the Karobi group, unlike those of the Tsurungal Group, were formed during the first pulse. Petrographic studies in combination with geochemical data indicate that most of the granitoids of the Tsana Complex are hybrid rocks (I-type post-collisional granites) and were derived through mixing of deep-seated mantle magmas with acid melts obtained by the upper crustal anatectic melting in the Main Caucasus fault zone. The granitoids of the Tsurungal Group define basic to acid evolution (diorite–granodiorite–granite–two-mica granite) possibly caused by both crystallization differentiation and increasing role of crustal contamination in the petrogenesis of the parental magmas of these rocks. This conclusion is also confirmed by the differences in the Sr isotope composition between granitoids of the early (87Sr/86Sr = 0.7053) and late (87Sr/86Sr = 0.7071) phases of the Tsana Complex. Main trends in spatiotemporal migration of magmatic activity in the central part of the Greater Caucasus in the Pliocene–Quaternary time were established using obtained and earlier published isotope-geochronological data.

Interaction between a Late Miocene andesitic dyke swarm and wet sediment in the Szoros Valley, Eastern Borsod Basin, Northeast Hungary

Magma/wet sediment interaction (e.g. autobrecciation, magma-sediment mingling, hyaloclastite and peperite-forming, etc.) is a common phenomenon, where hot magma intrudes into unconsolidated or poorly consolidated water saturated sediment. In the Eastern Borsod Basin (NE-Hungary) relatively small (2–30 m) subvolcanic bodies, sills and dykes with contact lithofacies zones were found generated by mechanical stress and quenching of the magma, and interacting with unconsolidated wet andesitic lapilli-tuff and tuff-breccia. Close to the contact between sediment and intrusions, thermal and mechanical effects may occur in the host sediment. Hydrothermal alteration and stratification of the host sediment were developed only locally along the contact zone, probably due to the paleo-hydrogeologic and paleo-rheological inhomogeneities of the lapilli-tuff–tuff-breccia deposits. Processes of magma/wet sediment interaction may be difficult to recognize because of limited exposure and/or certain similarities of the brecciated intrusions to the characteristics of the host sediment; hence detailed field work (geologic mapping or profiling) was required to demonstrate the subvolcanic origin of the brecciated andesite bodies.

Geochronologic, geochemical, and isotopic constraints on petrogenesis of the dioritic rocks associated with Fe skarn in the Bisheh area, Eastern Iran

There are several intermediate (SiO2 = 57.4–61.2 wt.%) subvolcanic bodies in the Bisheh area of eastern Iran. Petrochemical studies show that these bodies are calc-alkaline and metaluminous (A/NK ≥ 1.68, A/CNK ≤ 0.99) diorite porphyries. They are enriched in large-ion lithophile elements (LILE) and have negative anomalies of Nb, Ti, Ta, and P. Chondrite-normalized REE patterns exhibit light-rare-earth-elements (LREE) enrichment, with mildly fractionated REE patterns ((La/Yb)N < 10). Their Nb/Yb versus Th/Yb ratios are similar to rocks formed in active continental margins. Their isotopic (initial 87Sr/86Sr ratios is 0.70642 and initial eNd values is −1.49) and other geochemical data suggest that the Bisheh diorite porphyries formed by melting of an enriched phlogopite-bearing mantle source combined with subsequent crustal contamination. High values of Rb, Ba, and Th support magma contamination in the upper crust during magma evolution. Zr-U-Pb age dating for two diorite porphyries yield middle Eocene (Bartonian) ages of 39.25 ± 0.43 and 39.16 ± 0.41 Ma. These bodies have intruded into Paleocene limestone and caused metasomatism with iron oxide skarn formations.

Formation of the Archean crust of the ancient Vodlozero domain (Baltic shield)

The available geological, petrological, and isotopic data on Archean rocks of the Baltic shield are used to analyze the formation of the crust of the ancient Vodlozero domain. This made it possible to reveal the succession of endogenic processes in different parts of the domain and correlate them between each other. Several stages of magmatic processes reflecting changes in magma-generation environments are definable in the crust formation. The earliest stages of magmatism (3.24 and 3.13–3.15 Ga) are mostly represented by rocks of the tonalite-trondhjemite-granodiorite association. The next stage of endogenic activity (3020–2900 Ma) was marked by the formation of volcanics of the komatiite-basalt and andesite-dacite associations constituting greenstone belts in marginal parts of the Vodlozero domain and basic dikes accompanied by layered pyroxenite-norite-diorite intrusion in its central part. These basic bodies crossing earlier tonalities were formed in extension settings related to the formation of the mantle plume, which is confirmed by the rock composition. This stage culminated in the formation of trondhjemites at margins of greenstone structure. The next stage of endogenic activity commenced at 2890-2840 Ma by the emplacement of high-magnesian gabbro and diorite dikes in the western margin of the domain, where they cross rocks of the tonalitetrondhjemite association. This stage was marked by the formation of intermediate-acid subvolcanic bodies and dikes as well as basite intrusions including the layered and differentiated Semch intrusion, the largest one in the Vodlozero domain. The stage culminated at approximately 2850 Ma in the emplacement of tonalities of the limited distribution being represented by the Shilos massif in the north of the domain and Shal’skii massif on the eastern shore of Lake Onega. The important stage in the geological history of the Vodlozero domain is the formation of the intracratonic Matkalakhta greenstone belt at approximately 2.8 Ga, which includes arenite quartzite and graywackes and polymictic conglomerates developed in the Lake Oster area in addition to volcanics. These rocks indicate a stable tectonic regime, which resulted in deep erosion of the crust. The emplacement of sanukitoids (2.73–2.74 Ga) as well as subsequent two-feldspar granites (2.68–2.70 Ga) and basite dikes (2.61–2.65 Ga) may be considered as resulting from the plume influence on the relatively stabilized sialic crust of the Baltic shield.

Petrogenesis and zircon U-Pb dating of skarnified pyroxene-bearing dioritic rocks in Bisheh area, south of Birjand, eastern Iran

در منطقه بیشه واقع در شرق بلوک لوت، هورنبلند دیوریت های پورفیری در سنگهای رسوبی و آذرین (توف‌ها و سنگهای دیوریتی پیروکسن‌دار) نفوذ کرده و به‌ترتیب تشکیل اگزواسکارن و اندواسکارن داده است. بخشهای تغییر نیافته سنگهای دیوریتی پیروکسن‌دار، دارای ماهیت کالک آلکالن پتاسیم بالا و متاآلومین (78/1 A/NK≥ و 95/0(A/CNK≤ هستند. نمودار چند عنصری به‌هنجار شده با گوشته اولیه نشان دهنده غنی شدگی از عناصر LIL مانند Rb، Ba، Cs و تهی شدگی از عناصر HFS نظیر Nb، P، Ti، Y و Yb است. نمودار عناصر نادر خاکی بیانگر مقادیر (La/Yb)N از 75/7 تا 63/8 و بی هنجاری منفی ضعیف Eu می باشد. این خصوصیات به همراه مقادیر بالای Th/Yb و Ta/Yb نشان‌دهنده ماگماتیسم وابسته به مناطق فرورانش حاشیه قاره هاست. تهی‌شدگی مشخص Nb و Ti ، میزان نسبتا بالای Mg#، نسبتهای اولیه 87Sr/86Sr ( 70606/0)، 143Nd/144Nd ( 512424/0) و Nd e (05/3-) نشان می دهد که ماگمای سازنده سنگهای مورد مطالعه از گوشته غنی شده منشأ گرفته و دچار آغشتگی پوسته ای شده است. مقادیر بالای Rb، Th، K و مقدار پایین P و Ti در سنگهای مورد بررسی مؤید آلودگی ماگما در پوسته فوقانی طی تکامل ماگما است. میزان Ba/Rb پایین (4/7-6/4) و Rb/Sr بالا (22/0-17/0)، نشاندهنده حضور فلوگوپیت در گوشته منشأ است. با توجه به میزان بالای CaO+ Al2O3 نمونه های مورد مطالعه (متوسط 3/22 درصد)، میتوان گارنت پیروکسنیت فلوگوپیتدار را به‌عنوان منشأ ماگما در نظر گرفت. سن‌سنجی به روش زیرکن-اورانیم-سرب بر روی پیروکسن دیوریت پورفیری نشان می‌دهد که این ماگماتیسم در 07/44 میلیون سال پیش یعنی در ائوسن میانی(Lutetian) رخ داده است.

Magnetic fabric and petrology of Miocene sub-volcanic sills and dykes emplaced into the SW Flysch Belt of the West Carpathians (S Moravia, Czech Republic) and their volcanological and tectonic implications

Magnetic fabrics were investigated in the sub-volcanic bodies occurring within the SW Flysch Belt of the Western Carpathians. Magnetite or low-Ti titanomagnetite is the principal carrier of the anisotropy of magnetic susceptibility (AMS) in these rocks, though various Fe–Ti oxides were also identified in minor amounts. The magnetic fabric in almost all sills and dykes is conformable to the shapes of the bodies and no doubt originated through more or less free magma flow that requires relatively open voids to be injected, that likely originated in an extensive tectonic regime. In an ankaramite sill, where the rock creates typical hexagonal columns, the magnetic fabric is related rather to the column axes than to the overall shape of the sill. The magnetic fabric formation in this sill is controlled by the post-emplacement process of the creation of the columns. At some studied localities, signs of post-magmatic Middle Miocene tectonic deformation are observed in the field, the youngest known in the Flysch Belt. As the magnetic fabric is unrelated to those signs, we conclude that these young tectonic movements did not penetrate ductilely in the volume of the volcanic body. It seems that the strain was focused to thin zones along the faults, since it did not change the preferred orientation of magnetic minerals in the rock volume substantially.

Regional and local phenomena influencing the thermal state in the Flysch belt of the northeastern part of Slovakia

Abstract The locality of the northeastern most part of Slovakian Flysch belt belongs to interesting areas in terms of the interpretation of geothermal conditions in mutual relation with the lithosphere structure and their tectonic development. The evaluation of the geothermal energy sources parameters of this locality is likewise worthwhile. The region under study has the centre in position of the borehole Zboj ZB-1 and spreads out Slovakia also in Poland and Ukraine. Our contribution provides the analyses of existing geothermal data enhanced by the construction of temperature field models corresponding to the global and local aspects that influence the temperature and heat flow density distributions. The analyses are related to the structures and effects of separate phenomena along as well as across the Carpathian arc. The model calculations were carried out both by analytical and numerical methods of solving the heat transfer equations including their steady state forms and transient cases too. Besides the regional trend of thermal activity decrease in direction from East-Slovakian Basin to the outer Carpathian units the combined local influences are applied: subsurface thermophysical parameters of rock complexes distributions, non-stationary sources from supposed subvolcanic bodies in close surroundings of borehole Zboj ZB-1, and the effects of the hydrological factors. Considering the observed higher thermal activity in arched zone along the Carpathian structures we discussed the thermal effects of rock complexes supposed as a source of regional Carpathian Conductivity Anomaly and the transfer of heat from East-Slovakian Basin to Outer Carpathian Flysch units. The analysis and the modelling results suggest that the mentioned activity is caused by the influences of source type phenomena mainly related to deep fault systems at the margin of the European Platform. That means the anomalies in heat flow density distribution can reach the value 70 mW/m2 and more in the zone above the thermally active deep-fault system with the presence of volcanism and hydrothermal activities.

Petrological and Geochemical Characteristics of Miocene-Pleistocene Basaltic Alkaline Subvolcanics of Gharyan District, NW Libya

Gharyan basaltic subvolcanic bodies, in the north-westernmost Libya, are characterized by extreme irregularity, having short length, numerous braches and abruptly change in thickness with a wide GPS coordinates. Commonly occurring as dykes, a few of them can be classified as small stocks, and others are sills. They have strike N 70-80˚ W. They are nepheline-normative alkaline basalts which are comprised of four distinct suites, namely, olivine basalt, basalt, trachy-basalt and trachy-andesite. The trachy- basalt and trachy-andesite are the end differentiation products of alkali-basalt series. The magmatism that gave rise the Miocene- Pleistocene basaltic dykes of Gharyan district represent intraplate alkaline volcanics generated by a young mantle plume but was contaminated by little crustal materials or were products of fractional crystallization of mantle-derived magma. Such magma is thought to be similar to the ocean island basalt formed in within- continental plate setting. Based on the field observation and K-Ar dating (6) subdivided the volcanic activity along eastern scarp of Jabal Nafusah (Gharyan district) into an old lava series, young lava series, volcanic cones, phonolite dome-shaped intrusions (47.0±1.2-37.7 Ma) and pyroclastic rocks. The young lava series (6.0±1.3-2.3±0.3 Ma) is mostly less common and restricted to the periphery of the old lava series or sometimes occupies ancient burial wadis. Late volcanic centers (7.7±1.5-1.3±0.5 Ma) usually form very small eruptive products which erupted from central volcanoes and dykes. Buserwil and Wadsworth (6) reported that both old and young lava series are composed of basaltic andesites. The late volcanic centers are generally basanitic suite with minor related differentiates, while the domes are all phonolitic suite. The present study intends to outline and compare the petrological and geochemical characteristics of the sheet-subvolcanic intrusions (dykes and sills), and briefly discusses some petrogenetic implications of the results obtained.

Geometry of laccolith margins: 2D and 3D models of the Late Paleozoic Halle Volcanic Complex (Germany)

Well data and core samples from the Late Paleozoic Halle Volcanic Complex (HVC) have been used to describe the geometry of the rhyolitic porphyritic laccoliths and their margins. The HVC formed between 301 and 292 Ma in the intramontane Saale basin, and it comprises mainly rhyolitic subvolcanic bodies (~300 km3) as well as minor lava flows and volcaniclastic deposits. The major HVC laccolith units display aspect ratios ranging between 0.04 and 0.07, and they are separated by tilted and deformed Carboniferous–Permian host sediments. For the margin of the Landsberg laccolith, a major coarsely porphyritic unit of the HVC, an exceptional data set of 63 wells concentrated in an area of 10 km2 reaching to depth of 710 m exists. It was used to explore the 3D geometry and textures, and to deduce an intrusion model. For a 3D visualization of the Landsberg laccolith margin, Geological Object Computer Aided Design; Paradigm® software (GOCAD) was used. Curve objects have been derived from the intrusion–host contacts. Automated GOCAD® methods for 3D modelling failed. As a result, manual refinement was essential. A major finding of the 3D modelling is the presence of prolate sediment rafts, up to 1,400 m in length and up to 500 m in thickness, surrounded by Landsberg rhyolite. The sedimentary rafts dip away from the laccolith centre. The engulfing laccolith sheets reach thickness of 100–300 m. For other HVC laccolith units (Lobejun, Petersberg, Brachstedt), well data reveal vertical rhyolite/sediment contacts or magma lobes fingering into the host sediments. HVC laccolith contact textures include small-scale shearing of the intruding magma and of the host sediment. In addition, internal shear zones have been detected inside the rhyolite bodies. The present study suggests that the emplacement of successive magma sheets was an important process during laccolith growth in the HVC.

First data on the chemical composition and morphology of gold in the Tuba Kain deposit (South Urals)

926 The Tuba Kain deposit discovered in the early 20th century is located in the southwestern part of the Eastern Baymak ore-bearing zone confined to the western slope of the Magnitogorsk megastructure of the Southern Urals (Fig. 1). The ore field is composed of volcanogenic and volcano-sedimentary rocks of the Devonian Irendyk, Yarlykap, and Ulutau formations intruded by subvolcanic bodies of dacite porphyrites [1–3]. The rocks of the Eifelian Irendyk Formation distributed in the northwestern and central parts of the ore field are represented by lapilli and agglomerate tuffs of mixed composition with subordinate intercalations of gravel to psammitic tuffs. The lithological– petrographic composition of rock fragments is highly variable imparting variegated coloration to rocks: quartzites, hematite–quartz varieties, quartz porphyries, amygdaloid basalt porphyrites, and diorites. The overlying cherts of the Upper Eifelian Yarlykap Formation are approximately coeval with the Karamyltash Formation and Bugulygyr Horizon of the eastern areas. The rocks of the Givetian–lower Frasnian Ulutau Formation are developed in the western and southern parts of the ore field. The rock composition is relatively uniform with the dominant share of tuffstones and, less commonly, tuffaceous siltstones. The subvolcanic bodies occurring in the central, northern, and eastern parts of the ore field are represented by massive compact plagioclase and hornblende–plagioclase andesite–dacite and dacite porphyrites. At the beginning of the Tuba Kain deposit exploitation, it represented a submeridional gold–barite vein up to 5 m thick occurring among foliated rocks. The vein became exhausted and the residual ore-bearing complex is now represented by secondary quartzites with tourmaline and chlorite–sericite–quartz metasomatites. Their composition is as follows (wt %): SiO 2, 26.74–58.38; TiO 2, 0.35–0.76; Al 2O3, 8.41– 12.18; F 2O3, 7.28–10.06; MnO, 0.0; MgO, 3.93–4.15; CaO, 0.12–0.16; Na 2O, 2.38–2.55; K 2O, 1.24–2.92; P2O5, 0.02–0.11; S tot , 0.32–5.02; Ba, 1.59–28.05; Zn, 0.0051–0.0218; Cr, 0.0–0.0092; V, 0.0142–0.170; Sr, 0.0023–0.0634; Zr, 0.0076–0.0270. The rocks confined usually to contacts of subvolcanic dacite porphyrites are characterized by the following composition (wt %): SiO 2, 69.91; TiO 2, 0.36; Al 2O3, 14.02; F2O3, 3.84; MnO, 0.05; MgO, 1.87; CaO, 1.54; Na 2O, 4.87; K 2O, 0.09; P 2O5, 0.08; S tot , 0.01; Ba, 00233; Zn, 0.0011; Cr, 0.0011; Ni, 0.0085; V, 0.0003; Sr, 0.0306; Zr, 0.0148, Nb, 0.0011; Rb, 0.0010. These rocks are accompanied by tuffs of the Irendyk and Ulutau formations with mixed compositions (wt %): SiO 2, 59.09–67.86; TiO 2, 0.32–0.45; Al 2O3, 11.91–19.23; F2O3, 2.05–5.24; MnO, 0.02–0.13; MgO, 2.19–5.39; CaO, 0.11–2.71; Na 2O, 1.10–4.26; K 2O, 1.80–3.63; P2O5, 0.05–0.10; S tot , 0.06–1.15; Ba, 0.57–9.51; Zn, 0.0069–0.0596; Cr, 0.0015–0.0110; Ni, 0.0005– 0.0032; V, 0.0024–0.0081; Sr, 0.0027–0.0620; Zr, 0.0112–0.0245; Nb, 0.0006–0.0010; Rb, 0.0012–