Volcanic-plutonic Association Research Articles

Paleotectonic setting of basaltoid volcano-plutonic belts with porphyry copper deposits

The article considers geotectonic position and geological features of basaltoid volcano-plutonic belts (VPBs) associated with porphyry copper and gold-copper deposits. Three types of the belts, the oceanic, perioceanic, and riftogenic ones, are distinguished among these VPBs. The oceanic and peri-oceanic belts were incorporated into the composition of ensimatic island arcs and formed at a late stage of their development, after inversion of the basaltoid troughs. The riftogenic belts appeared in island-arc oceanic settings at a late stage of filling the spreading zones. VPBs of the first two types with porphyry gold-copper deposits are located over the convergent boundaries of tectonic plates in an above-subduction position, while belts of the third type form extended linear zones within individual rift structures and contain smallscale porphyry copper objects with poor gold and molybdenum contents. As examples of the structures, the Sunda, Philippine archipelago, New British, Solomon, Alaska, and Antilles ensimatic island arcs and the Irendyk and Novoalekseevsky belts of rift zones of the Southern Urals are described. Volcanic-plutonic associations participating in the structure of these VPBs (including those productive for porphyry copper mineralization), as well as structural-lithological complexes of their basement, are characterized. It is noted that repeated magmatism manifestations during the long-term development of the ensimatic island arcs lead to appearance of several basaltoid VPBs with porphyry gold-copper deposits, while basaltoid belts with porphyry copper objects in the rift settings are formed only once.

Western flanks of the Central Asian late paleozoic continental rift system and uranium mineralization

Introduction. Available information on the occurrences of high alkaline magmatic rocks fixing the position of the western flanks of the southern branches (Gobi Altai and Gobi Tien-Shan) of the Central Asian Late Paleozoic continental rift system in the territory of the North-West of Chingiz (the eastern part of Central Kazakhstan), the Kendyktas-Chu-Ili-Bet-Pak-Dal uranium-bearing province of the Southern Kazakhstan and the Chatkal-Naryn zone of Tien-Shan (Uzbekistan) is reviewed. Data on the confinement of uranium mineralization to these occurrences and its paragenetic relationship with the Late Paleozoic alkaline volcanic-plutonic association is provided.Aim. To study the uranium mineralization of Late Paleozoic alkaline magmatism to clarify metallogenic representations and justify prospects for the ore-bearingness of the western flanks of the southern branches of the Central Asian continental rift system.Materials and methods. The largest part of materials was obtained in the process of geological surveys and prospecting works of various scales in the regions of Central Kazakhstan in the period 1965–1985 with the participation of the author. Published materials concerning the subdivision of magmatic formations in the uranium ore fields of Southern Kazakhstan and the Chatkal-Naryn zone were also used.Results. Subvolcanic bodies of comendites and small masses of alkaline granites of the Late Paleozoic were identified across the area of uranium ore occurrences in the South-Western Chingiz and some deposits of South Kazakhstan confined to Devonian volcanic structures, which indicates their relationship with the southern branches of the Central Asian continental rift system. Rare-metalalbite, uranium-phosphorus and uranium-molybdenum formations are confined to alkaline rocks. Rare-metal mineralization is closely associated with alkaline rocks, while uranium mineralization occurred after the introduction of the most recent microgabbrodiorite and lamprophyre dikes. Similar correlations of rare-metal and uranium mineralization with alkaline granites and of microgabbrodiorite and lamprophyre dikes are observed in the uranium deposits of the Chatkal-Naryn zone located among the early Permian bimodal trachybasalt-trachyolite formation.Conclusion. The establishment of ore mineralization on the western flanks of the Gobi Altai and Gobi Tien-Shan branches in the territory of Southern and Central Kazakhstan allows these areas to be distinguished as metallogenic zones, promising in terms of rare-metal and uranium mineralization.

Mesoarchean continental intraplate volcanism and sedimentation: The case of the Simlipal basin, Singhbhum Craton, eastern India

The origin of continental intraplate basalts, their role in crust-mantle interaction, and processes of formation of the associated sedimentary rocks have remained important research problems. The poorly-studied Simlipal basin hosts a well-preserved, weakly-metamorphosed ensemble of three bands of mafic volcanic rocks intercalated with shallow marine sandstones and minor phyllites, occurring unconformably over a Paleoarchean continental basement of the Singhbhum Craton. Little is known about the age of the basin, the nature of sediment source and source weathering, petrogenesis of the volcanic rocks, and the tectonic setting of the volcano-sedimentary assemblage. To address these issues, we present whole-rock geochemical data on the Simlipal sediments and volcanic rocks, detrital zircon U-Pb ages and mineral chemical analyses. The sandstones and phyllites are characterized by high K2O/Na2O and chemical index of alteration. The source-indicating elemental ratios and REE patterns (negative Eu anomaly and flat HREE) suggest that felsic rocks, especially the granitoids resulting from shallow crustal melting, were the dominant source. The detrital zircons are mostly rounded with U-Pb ages ranging from 3.63 to 3.17 Ga. All these features suggest that the Simlipal basin formed during the Mesoarchean Era on a slowly subsiding continental platform undergoing extension, which received reworked and recycled sediments from a diverse but granitoid-dominated, intensely-weathered, mostly Paleoarchean source. The mafic volcanic rocks are low-Ti, tholeiitic basalts showing low CaO/Al2O3 and TiO2/Yb values, and flat HREE pattern indicating derivation from a spinel lherzolite mantle at shallow depth (<80 km). The presence of xenoliths of crustal rocks, quartz-normative nature, wide range of magnesium number (39–80), primitive mantle-normalized negative Nb, Ta and Ti anomalies, and high U/Nb and Th/Yb ratios reflect that the magma underwent significant fractional crystallization and crustal assimilation. The Simlipal volcanic rocks are consanguineous with the spatially close and coeval gabbro-anorthosite bodies, layered mafic–ultramafic rocks, and A-type Mayurbhanj Granite of the Singhbhum Craton, together forming an intraplate bimodal volcanic-plutonic association. We construe that the widespread Mesoarchean magmatism and sedimentation was linked to mantle upwelling possibly related to an event of lithospheric delamination and crustal extension.

Petrological features of acid plutonic rocks of the Osnytskyi complex (Volynskyi megablock of the Ukrainian shield)

The Osnytskyi complex, located within the Volynskyi megablock of the Ukrainian Shield, is represented by gabbro-diorite-granodiorite-granite series and is a plutonic part of the KlesivskoOsnytska volcanic-plutonic association. Granitoid rocks of the Osnytskyi complex form a single formation of granites, which have a common spatial and structural origin. There are such types of granites as leptite-like, fine-grained, inequigranular-medium-grained, coarse-grained, etc. Petrographic, mineralogical and petrochemical studies of Osnytski inequigranular porphyraceous granites have been performed. Rock-forming (potassium feldspar, plagioclase, quartz, biotite and hornblende), accessory (zircon, apatite, titanite), ore (magnetite, ilmenite, pyrite) and secondary (epidote, sericite, chlorite, siderite, bastnäsite) minerals were identified and described. Biotite chemically corresponds to siderophyllite of magmatic origin (calcareous-alkaline orogenic complexes). Crystallization of the granites took place under conditions of low acidity at a temperature of ~ 760 °С and a sufficiently high pressure. Key words: granitoids, Osnytskyi complex, rock-forming, accessory, ore and secondary minerals, biotite, formation conditions, Volynskyi megablock, Ukrainian Shield

Molybdenum mineralization of Serhiivka Au-Mo deposit (Middle Dnipro, Ukrainian Shield)

The article is devoted to molybdenum mineralization of the Eastern flank of Au-Mo Serhiivka deposit, located in the Middle Dnipro megablock of the Ukrainian Shield (USh). The generalized description of mineralization is performed on such important questions: discovery and exploration history, structure and composition of the host rocks, metamorphic and metasomatic alteration of rocks, structural position and localization conditions of molybdenum mineralization, ore composition, description of major ore minerals, morphology of mineralization and the most widespread views about its genesis. Molybdenum ores were discovered and named East-Serhiivka occurrence for the first time in 1974, before the discovery of gold mineralization, which occurred in 1985.&#x0D; Serhiivka deposit consists of two Mesoarchaean volcanic-plutonic associations (VPA) of different composition: the early mafic and the late felsic. The Eastern flank of the deposit, where the molybdenum mineralization is concentrated, is a structural knot similar to the lying letter “T”. It is formed by complex joint of the sub-latitudinal Serhiivka and sub-meridional Solone subvolcanic bodies and the East-Serhiivka massif of plagiogranitoids of the late VPA, which intrude basic rocks of early VPA. Molybdenum mineralization is localized in linearly elongated zones with a chaotic network of thin quartz, carbonate-quartz veinlets and poor (2–5 %) sulfide impregnation, including molybdenite. About 20 vein-impregnated ore zones have been recovered with up to 100–150 m thickness and 0,01 to 0,3 %, sometimes more than 1 % average molybdenum grade. The ores are subdivided into two major mineral types: 1) quartz-molybdenite; 2) quartz-sulfide-gold-molybdenite. The main components of ores molybdenite and native gold are associated with pyrite, chalcopyrite, magnetite, occasionally – pyrrhotite, arsenopyrite, scheelite, bismuth telluride, silver and others. Typical non-metallic minerals are quartz, carbonate, feldspar, chlorite, amphibole, biotite, sericite. It is supposed hydrothermal-metamorphogenic genesis of molybdenum (and gold) ores. Molybdenite and gold are rarely detected in the same intersections, which indicates separate genesis of these minerals. According to the accepted classification molybdenum mineralization is systemized as linear stockwork.&#x0D; Molybdenum ores of Serhiivka deposit are mostly considered as independent, separate from gold mineralization, potentially workable mine. It is the most prospective one in the Middle Dnipro region, USh and Ukraine in general. We suggest a comprehensive approach to studying, resource and reserves evaluation of Serhiivka deposit, taking into account the potential of both molybdenum and gold mineralization, as well as concentrations of rhenium and osmium in molybdenite. Geological exploration on the base of this approach will increase investment prospects of Serhiivka gold-molybdenum deposit.

2.6 Ga high-Si rhyolites and granites in the Kursk Domain, Eastern Sarmatia: Petrology and application for the Archaean palaeocontinental correlations

A 2.61 Ga intraplate magmatism took place locally within the Kursk Domain of the Eastern Sarmatia forming a volcanic-plutonic association of rhyolites and granites. The zircon Lu-Hf and Sm-Nd whole rocks isotope data indicate the crustal source heterogeneity of these Neoarchaean intraplate granitoids. Their protoliths were dominated by Palaeoarchaean metapelites and Mesoarchaean TTG associations.The Neoarchaean rhyolites of the Kursk Domain are characterized by the high crystallization temperatures of c. 900 °C according to the data of mineral geothermobarometry and geochemistry of zircons (TiQ and TiZr). The magmatic chambers were located at a depth of no more than 7 km. The silicic melt, parental for these 2.61 Ga old rhyolites and granites could be formed as a result of 20% dehydration melting of the metapelite-TTG mixture in equilibrium with the Ilm-Bt-Opx-Pl restite at a pressure of no more than 4 kbar. The Atamansky Complex granites crystallized at deeper levels and contain an admixture of Opx-Pl restite or cumulus component. This caused their geochemical differences from rhyolites when these phases were removed during the melts migration to higher levels of the crust. The Atamansky granites are considered as intermediate chambers where differentiation of the initial silicic magmas took place with the formation of the residual rhyolitic melts.The heat source could be a mafic plume magmatism, known in the Eastern Sarmatia. There, in intraplate settings, hot deep plume generated mafic magmas intruded into the crust forming shallow interim chambers; the latter initiated melting of the felsic host-rocks (predominantly metapelites and TTG) in the upper parts of the crust producing the silicic volcanic-plutonic association.The simultaneous 2.61 Ga old granitoid intraplate magmatism in the Eastern Sarmatia and Dharwar Craton, caused by the mafic heat source, adds one more argument in favor of an assumption that the Sarmatia, Pilbara, Kaapvaal and, possibly, Dharwar Cratons composed a single supercontinent Vaalbara in the Neoarchaean. The Dharwar Craton, perhaps, was at the periphery of the Vaalbara supercontinent next to the Eastern Sarmatia.

Specifics of geological composition, geochemistry and geochronology of rocks from the Kresty alkaline-ultrabasic massif (Maimecha-Kotui province, Polar Siberia)

In this work, we demonstrate new data that allows us to accurate geochronological ranges of formation of the Kresty alkaline-ultrabasic massif, which is considered to be a satellite of the Gulinian giant pluton. We also interpreted geological, geochemical and isotope-geochemical data obtained earlier for major varieties of this volcanic-plutonic association taking into account new geochronological results, as well as considered new aspects/information on matter source of alkaline-ultrabasic massifs from this province. One of the main aspects is interaction of Siberian super plume matter with hosting substrate of Siberian craton continental crust.

Record of a Statherian rift-sag basin in the Central Espinhaço Range: Facies characterization and geochronology

Several rift-related sequences and volcanic-plutonic associations of Statherian age occur within the São Francisco block. One succession within the sedimentary record, the Terra Vermelha Group, defines one of the evolutionary stages of the Espinhaço basin in the Central Espinhaço Range. As a result of stratigraphic analyses and supported by U-Pb zircon geochronological data, the evolution of this unit has been characterized. To more effectively delimit its upper depositional interval, the sequence of this unit, which is represented by the Pau d’Arco Formation, was also studied. The sedimentary signature of the Terra Vermelha Group suggests the infilling of an intracontinental rift associated with alluvial fans as well as lacustrine and eolian environments with associated volcanism. The basal succession represented by the Cavoada do Buraco Formation mainly consists of conglomerates with interlayered sandstones and subordinate banded iron formations. Detrital zircon obtained from this unit reveals ages of 1710 ± 21 Ma. The upper succession, represented by the Espigão Formation, records aeolian sandstones with volcanic activity at the top. A volcanic rock dated at 1758 ± 4 Ma was interpreted as the timing of volcanism in this basin. The eolian deposits recorded within the Pau d'Arco Formation were caused by a renewal of the sequence, which represent a stage of post-rift thermal subsidence. The maximum age of sedimentation for this unit is 1675 ± 22 Ma. The basin-infill patterns and Statherian ages suggest a direct link with the first rifting event within the São Francisco block, which was responsible for the deposition of the Espinhaço Supergroup.

Glass at endocontacts of granite massifs in Volcanic–Plutonic belts (Exemplified by granite of Central Kazakhstan)

Glass formation takes place under conditions of rapid cooling of a melt at a great temperature difference between the melt and the host rock, which must have high thermal conductivity. The most favorable conditions for glass formation exist when the melt intrudes in the form of thin apophyses. Glass has been found in granite massifs related to the volcanic–plutonic association.

Ordovician volcanic and plutonic complexes of the Sakmara allochthon in the southern Urals

The Ordovician terrigenous, volcanic–sedimentary and volcanic sequences that formed in rifts of the active continental margin and igneous complexes of intraoceanic suprasubduction settings structurally related to ophiolites are closely spaced in allochthons of the Sakmara Zone in the southern Urals. The stratigraphic relationships of the Ordovician sequences have been established. Their age and facies features have been specified on the basis of biostratigraphic and geochronological data. The gabbro–tonalite–trondhjemite complex and the basalt–andesite–rhyolite sequence with massive sulfide mineralization make up a volcanic–plutonic association. These rock complexes vary in age from Late Ordovician to Early Silurian in certain structural units of the Sakmara Allochthon and to the east in the southern Urals. The proposed geodynamic model for the Ordovician in Paleozoides of the southern Urals reconstructs the active continental margin, whose complexes formed under extension settings, and the intraoceanic suprasubduction structures. The intraoceanic complexes display the evolution of a volcanic arc, back-, or interarc trough.

Composition and genesis of the Konevinsky gold deposit, Eastern Sayan, Russia

The Konevinsky gold deposit in southeast Eastern Sayan is distinguished from most known deposits in this region (Zun-Kholba, etc.) by the geological setting and composition of mineralization. To elucidate the cause of the peculiar mineralization, we have studied the composition, formation conditions, and origin of this deposit, which is related to the Ordovician granitoid pluton 445–441 Ma in age cut by intermediate and basic dikes spatially associated with metavolcanic rocks of the Devonian–Carboniferous Ilei Sequence. Four mineral assemblages are recognized: (1) quartz–pyrite–molybdenite, (2) quartz–gold–pyrite, (3) gold–polysulfide, and (4) telluride. Certain indications show that the ore was formed as a result of the superposition of two distinct mineral assemblages differing in age. The first stage dated at ~440 Ma is related to intrusions generating Cu–Mo–Au porphyry mineralization and gold–polysulfide veins. The second stage is controlled by dikes pertaining to the Devonian–Carboniferous volcanic–plutonic association. The second stage is characterized by gain of Hg and Te and formation of gold–mercury–telluride paragenesis.

Rhyolite–granite association in the Central Taimyr zone: evidence of accretionary-collisional events in the Neoproterozoic

The Central Taimyr accretionary belt includes two granite-metamorphic terranes: Faddey and Mamont-Shrenk, which include the oldest igneous formations of the Taimyr folded area in the Arctic framing of the Siberian craton—granitoids and granite-gneisses with U–Pb zircon ages of 900–830 Ma. The [FeO*/(FeO* + MgO)]-enriched granitoids of these terranes are products of highly fractionated I-type magmas. This paper presents results of new petrographic, geochemical, geochronological, and paleomagnetic investigations of acid rocks from a volcanic-plutonic association (in the region of the Leningradskaya River) in the Faddey terrane in the northeastern Taimyr area. These rocks formed during the final stage of continent–island arc accretion and collision that occurred at approximately 870–820 Ma. We established that the studied rocks belong to a long granitoid belt extending from Mamont-Shrenk to Faddey terrane, where all the igneous bodies are deformed and oriented uniformly. The paleomagnetic pole we calculated differs significantly from the apparent polar-wander path interval of corresponding age for Siberia. The 33.8°±5.4° angular distance between the poles indicates that the formation of this volcanic-plutonic association took place at a significant distance from the Taimyr margin of the Siberian paleocontinent.

Mesozoic and Cenozoic granitoid complexes in the stucture of the continental margin of northeast Asia

The integral data on structural position, age, and paleo-geodynamic setting of Mesozoic and Cenozoic granitoid complexes in northeast Asia make it possible to divide them into preaccretionary, accretionary, and postaccretionary groups participating in the structure of the accretionary-type continental margin. The preaccretionary granitoids are members of volcanic-plutonic associations of ensimatic island arcs or suprasubduction ophiolitic complexes, which mark the onset of growth of the granitic-metamorphic layer in the future continental crust. The accretionary granitoids emplaced during the accretion of diverse rock complexes to the continental margin and are localized in its frontal zone, where granitic-metamorphic layer grows further. The postaccretionary granitoid plutons of the marginal continental volcanic-plutonic belts seal up fold-nappe structures, determining the upper age limit of accretion and deformation. The origin of postaccretionary granitoids is related to remelting of older heterogeneous accretionary-island arc crust.

Palaeomagnetism of Precambrian basic intrusion and dykes of Northern Karelia, eastern Fennoscandian Shield

Palaeomagnetic results for mafic and ultramafic intrusions and their country rocks in Russian Karelia are presented. The oldest rock type is pyroxene-hornblende gabbro, regarded as late Archaean or Palaeoproterozoic in age. Later, at the early stage of formation of a volcanic-plutonic association, including layered intrusions and metavolcanites, gabbro-norite dykes were emplaced. Sm-Nd isotopic analyses of this association yield mineral and whole-rock ages of 2.47-2.35 Ga with ∈ Nd = −0.4 to 1.2 for gabbro-norite dykes. Based on field relations, the youngest rock types are pyroxene-plagioclase porphyry dykes and gabbro-dolerite dykes. Three distinct magnetization components were isolated by alternating field and thermal demagnetization. The most common remanence component B, with a mean direction of D = 30°, I = 58°, k = 52, α 95 = 10° ( N = 5 geological units), is an overprint interpreted to have been acquired at the last stage of the Svecofennian orogeny (1.90-1.70 Ga). Component A, with a mean direction of D = 350°, I = 49°, k = 69, α 95 = 9° ( N = 5 geological units), is also an overprint, probably acquired at the onset of the Svecofennian orogeny. Both components are found in all rocks studied. Component C, with a mean direction of D = 126°, I = 73°, k = 167, α 95 = 10° ( N = 3 geological units), is isolated as a primary remanence in the pyroxene-hornblende gabbro intrusion and gabbro-norite dykes. The results are compared with other contemporaneous palaeomagnetic poles from Finland and Russian Karelia.

Petrologic features of the volcanic-plutonic association in regions of porphyry copper mineralization

Petrologic features of the volcanic-plutonic association in regions of porphyry copper mineralization

Geodynamic production conditions for the Pliocene-Anthropogene volcanic-plutonic association in the High Caucasus

Geodynamic production conditions for the Pliocene-Anthropogene volcanic-plutonic association in the High Caucasus

The problem of volcanic-plutonic associations in the light of studies on the Tusham Ring Complex, north Peninsular India

The problem of volcanic-plutonic associations in the light of studies on the Tusham Ring Complex, north Peninsular India