Petrogenesis of Volcanic Arc Granites from Bayah Complex, Banten, Indonesia

This research aimed to reveal the petrogenesis of granitic rocks of Bayah Complex starting from magma differentiation to exposing event, this research also intended to determine the tectonic environment. The methods carried out in this research include field observation, petrographic analysis using polarized light microscopy, and geochemical analysis using X-Ray Fluorescence (XRF) and Inductively Coupled Mass Spectrometry (ICP-MS). Petrographic analysis shows that Bayah granitic rocks are composed of quartz, plagioclase, and K-feldspar while the rest are amphibole, biotite, sericite, chlorite, epidote, and opaque. Based on its major oxide concentrations, Bayah granitic rocks classified as granite and diorite-quartz which have high-K calc-alkaline magma. 4 samples of granitic rocks showed the A/N+K+C > 1 molar ratios belonging to the peraluminous S-type granite index while the remaining 1 sample showed a molar ratio of A/N+ K+C < 1 and A/N+K > 1 which classified as metaluminous I-type granite. Accordingly, Bayah granitic rocks are S-type granite which crystallized from sediment-derived magma, the sediments itself estimated sourced from continental especially Malay Peninsula, Indonesian Tin Island, and Schwaner Mountains. During differentiation, the magma undergone crustal contamination reflected by the increase in both SiO2 0.51 wt% and Al2O3 1.95 wt%, and decrease in Fe2O3 + MgO 0.61 wt% from the pure composition of sediment-derived magma. Furthermore, the occurrence of crustal contamination also recognized from high concentrations of Rb and Ba which indicate the interaction of magma with the materials of continental crust. Regard to the exposing event, Bayah granitic rocks approximated to be exposed due to regional tectonic activity which caused Orogenesa I in the Early Oligocene to the Late Oligocene. Moreover, based on the plot of trace elements especially Rb, Y, Nb, Ta, and Yb on Harker and tectonic discriminant diagrams, Bayah granitic rocks are formed on volcanic-arc active continental margins in accordance with regional tectonic setting.

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Volcanic activity and gas emissions along the South Sandwich Arc

Bulletin of Volcanology ◽

10.1007/s00445-020-01415-2 ◽

2020 ◽

Vol 83 (1) ◽

Author(s):

Emma J. Liu ◽

Kieran Wood ◽

Alessandro Aiuppa ◽

Gaetano Giudice ◽

Marcello Bitetto ◽

...

Keyword(s):

Carbon Isotope ◽

Volcanic Activity ◽

Emission Rate ◽

Tectonic Setting ◽

Hydrothermal Systems ◽

Molar Ratio ◽

The South ◽

Gas Emissions ◽

Volcanic Arc

AbstractThe South Sandwich Volcanic Arc is one of the most remote and enigmatic arcs on Earth. Sporadic observations from rare cloud-free satellite images—and even rarer in situ reports—provide glimpses into a dynamic arc system characterised by persistent gas emissions and frequent eruptive activity. Our understanding of the state of volcanic activity along this arc is incomplete compared to arcs globally. To fill this gap, we present here detailed geological and volcanological observations made during an expedition to the South Sandwich Islands in January 2020. We report the first in situ measurements of gas chemistry, emission rate and carbon isotope composition from along the arc. We show that Mt. Michael on Saunders Island is a persistent source of gas emissions, releasing 145 ± 59 t day−1 SO2 in a plume characterised by a CO2/SO2 molar ratio of 1.8 ± 0.2. Combining this CO2/SO2 ratio with our independent SO2 emission rate measured near simultaneously, we derive a CO2 flux of 179 ± 76 t day−1. Outgassing from low temperature (90–100 °C) fumaroles is pervasive at the active centres of Candlemas and Bellingshausen, with measured gas compositions indicative of interaction between magmatic fluids and hydrothermal systems. Carbon isotope measurements of dilute plume and fumarole gases from along the arc indicate a magmatic δ13C of − 4.5 ± 2.0‰. Interpreted most simply, this result suggests a carbon source dominated by mantle-derived carbon. However, based on a carbon mass balance from sediment core ODP 701, we show that mixing between depleted upper mantle and a subduction component composed of sediment and altered crust is also permissible. We conclude that, although remote, the South Sandwich Volcanic Arc is an ideal tectonic setting in which to explore geochemical processes in a young, developing arc.

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Visean overprint of the Devonian-Early Carboniferous granites: result of Variscan collisional stage revealed by zircon SHRIMP dating (Tribeč Mts., Western Carpathians)

10.5194/egusphere-egu2020-5160 ◽

2020 ◽

Author(s):

Igor Broska ◽

Keewook Yi ◽

Milan Kohút ◽

Igor Petrík

Keyword(s):

Early Stage ◽

Early Carboniferous ◽

White Mica ◽

Granitic Rocks ◽

Western Carpathians ◽

Variscan Orogeny ◽

Shrimp Dating ◽

The West ◽

Volcanic Arc ◽

Type Granite

The granites with I- and S-type affinity in the Variscan segments of the Alpine West-Carpathian edifice belong to the oldest intrusions within the European Variscides. Granites and granodiorites of the West-Carpathian crystalline basement are mostly classified as S-type, whereas tonalities and granodiorites belong to the I-type suite. Both suites probably originated in the volcanic arc setting as product of subduction-related regime in the Galatian superterrane (Broska et al. 2013). The I-&#160;and S-type granite bodies were firstly identified in the West-Carpathian Tribe&#269; Core Mountains and the new SHRIMP and CHIME datings recognised their Visean geotectonic overprint. The subduction-related I-type granites show the age span 364-358 Ma followed by the intrusion of the S-type granites dated by SHRIMP on 358 Ma. The bimodal SHRIMP data of a dyke placed within S-type granites show ages 351 Ma and 330 Ma, or primary vs. alteration age. The CHIME age from monazite dating shows 347 Ma because monazite indicate probably early stage of massive granite alteration perhaps during collisional process, younger zircons represents later phase of the event. &#160;CHIME dating of newly formed monazite in greisenised S-type granite gives the age 344 Ma. The granite showing strong greisenization (total degradation of feldspars and formation of quartz - white mica assemblages) is dated by SHRIMP on 355 Ma. The greisenised granite contains abundant tourmaline with high dravitic molecule, Sr-rich apatite and common monazite. Abundant tiny stoichiometrically pure apatite grains in this granite indicate their exsolution from feldspars enriched in phosphorus. The S-type granite dyke from the ridge of the Tribe&#269; Mts gives zircon SHRIMP age 355 Ma and CHIME monazite age 342 Ma. The dating results of the Tribe&#269; granites identified: (1) older Upper Devonian/Lower Mississippian subduction-related I-type tonalites (ca. 364-351 Ma), and (2) S-type granites Middle/Upper Mississippian (Visean) intruding in time span 342-330 Ma reflecting probably of the collisional event in the Variscan orogeny. Dual evolution of the Tribe&#269; Mts. Variscan granitic rocks is partly corroborated by Hf isotopes from the dated zircons with &#949;Hf(t) = +3.5 ~ &#8211;2.4 for the older granites, and &#949;Hf(t) = &#8211;0.3 ~ &#8211;4.9 for the younger ones. The evolution of the I- and S-type granites seems to be rather different from the granite evolution known in the Bohemian Massif and therefore the origin of Variscan hybrid granites from the Western Carpathians we placed on the SW side of Galatian volcanic arc as result of Paleo-Tethys subduction (see Stampfli and Borel, 2002, Stampfli et al. 2013).Acknowledgments: Support from Slovak Research and Development Agency: APVV SK-KR-18-0008, APVV-14-0278/, APVV-18-0107, and VEGA 2/0075/20 are greatly appreciated.

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Zircon U–Pb geochronology and geochemistry of granitic rocks in central Mongolia

Mongolian Geoscientist ◽

10.5564/mgs.v50i0.1327 ◽

2020 ◽

Vol 50 ◽

pp. 23-44

Author(s):

Boldbaatar Dolzodmaa ◽

Yasuhito Osanai ◽

Nobuhiko Nakano ◽

Tatsuro Adachi

Keyword(s):

Tectonic Setting ◽

Granitic Rocks ◽

Metamorphic Rocks ◽

Calc Alkaline ◽

Volcanic Arc ◽

Central Mongolia ◽

Central Asian ◽

High K ◽

Three Stages ◽

Late Neoproterozoic

The Central Asian Orogenic Belt had been formed by amalgamation of voluminous subduction–accretionary complexes during the Late Neoproterozoic to the Mesozoic period. Mongolia is situated in the center of this belt. This study presents new zircon U–Pb geochronological, whole-rock major and trace element data for granitoids within central Mongolia and discusses the tectonic setting and evolution of these granitic magmas during their formation and emplacement. The zircon U–Pb ages indicate that the magmatism can be divided into three stages: the 564–532 Ma Baidrag granitoids, the 269–248 and 238–237 Ma Khangai granitoids. The 564–532 Ma Baidrag granitoids are adakitic, have an I-type affinity, and were emplaced into metamorphic rocks. In comparison, the 269–248 Ma granitoids have high-K, calc-alkaline, granodioritic compositions and are I-type granites, whereas the associated the 238–237 Ma granites have an A-type affinity. The 564–532 Ma Baidrag and 269–248 Ma Khangai granitoids also both have volcanic arc-type affinities, whereas the 238–237 Ma granites formed in a post-collisional tectonic setting. These geochronological and geochemical results suggest that arc magmatism occurred at the 564–532 Ma which might be the oldest magmatic activity in central Mongolia. Between the Baidrag and the Khangai, there might be paleo-ocean and the oceanic plate subducted beneath the Khangai and produced voluminous granite bodies during the 269–248 Ma. After the closure of the paleo-ocean, the post collisional granitoids were formed at the 238–237 Ma based on the result of later granitoids in the Khangai area.

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Jurassic Igneous Activity in the Yuseong Area on the Southern Margin of the Gyeonggi Massif, Korean Peninsula, and Its Implications for the Tectonic Evolution of Northeast Asia during the Jurassic

Minerals ◽

10.3390/min11050466 ◽

2021 ◽

Vol 11 (5) ◽

pp. 466

Author(s):

Seung Hwan Lee ◽

Chang Whan Oh ◽

Soolim Jung

Keyword(s):

Korean Peninsula ◽

Tectonic Setting ◽

Northeast Asia ◽

Crustal Contamination ◽

Igneous Rocks ◽

Volcanic Arc ◽

Southern Margin ◽

Igneous Activity ◽

Gyeonggi Massif ◽

Okcheon Belt

Jurassic dioritic to granitic igneous rocks extensively intrude into the southern Korean Peninsula, including the Yuseong area located at the boundary between the southern margin of the Gyeonggi Massif and the northern margin of the Okcheon Belt. In this study, the petrogenesis and sources of Jurassic igneous rocks in the Yuseong area were investigated. The U–Pb zircon age data from the Jurassic plutonic rocks in the Yuseong area give two igneous ages, ca. 178–177 Ma and 169–168 Ma, indicating that two stages of igneous activity occurred in the Yuseong area during the Jurassic. The geochemical characteristics of Jurassic diorites indicate that they originated from enriched mid-ocean ridge basalt (E-MORB; Nb/Yb = 5.63–7.27; Zr/Yb = 118–156). The enriched Th/Yb ratios (5.5–8.0) in the diorites imply that they experienced crustal contamination during magma ascent. The Jurassic granitoids in the Yuseong area are divided into I- and S-type granites. The Jurassic I-type granitoids may have formed via the partial melting of mafic rocks with mixtures of 10–40% pelite-derived melt, while the S-type granites originated from felsic pelite. The Jurassic diorites have low Nb/Th ratios with depletion of the Nb and Ta components, indicating that they formed in a volcanic arc tectonic environment. On the other hand, the Jurassic granitoids show two different tectonic environments: a volcanic arc, and a syncollisional environment. The granites with syncollisional character are S-type granites, and may give incorrect information about tectonic setting because of the changes in the trace elements of the S-type granite due to fractional crystallization. Early Jurassic (200–190 Ma) igneous rocks are distributed only in the southeastern Korean Peninsula, including the Yeongnam Massif; Jurassic igneous rocks formed at ca. 190–180 Ma occur mainly in the Okcheon Belt and southern Gyeonggi Massif, which includes the Yuseong area. Middle Jurassic igneous rocks widely intruded from the Okcheon Belt, through the Gyeonggi and Nangrim massifs in the Korean Peninsula, to the Liaoning area in the North China Craton at 180–160 Ma. This distribution pattern of the Jurassic granitoids suggests that flat subduction started after 180 Ma in Northeast Asia.

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Timing and tectonic setting of Stikine Terrane magmatism, Babine-Takla lakes area, central British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e00-105 ◽

2001 ◽

Vol 38 (4) ◽

pp. 579-601 ◽

Cited By ~ 13

Author(s):

D G MacIntyre ◽

M E Villeneuve ◽

P Schiarizza

Keyword(s):

British Columbia ◽

Tectonic Setting ◽

Granitic Rocks ◽

Late Triassic ◽

Isotopic Age ◽

Volcanic Arc ◽

Plutonic Belt ◽

Major Oxide ◽

Volcanic Succession ◽

Intrusive Suite

New bedrock mapping completed as part of the Nechako NATMAP Project indicates that the area between Babine and Takla lakes in central British Columbia is underlain by rocks of the Early Permian Asitka, Late Triassic Takla, and Early to Middle Jurassic Hazelton volcanic-arc assemblages of the Stikine Terrane. These are cut by large composite stocks of quartz diorite, granodiorite, and quartz monzonite previously mapped as the Late Triassic to Early Jurassic Topley intrusions. New U/Pb (n = 6) and laser 40Ar/39Ar (n = 10) isotopic age dates reported in this paper suggest there are two distinct ages of plutons: the Topley intrusive suite with isotopic ages between 218 and 193 Ma; and, east of Babine Lake, the new Spike Peak intrusive suite with isotopic ages ranging from 179 to 166 Ma. West of the main plutonic belt is a thick volcanic succession of subaerial, porphyritic andesite flows, volcanic breccias, and rhyolitic ash-flow tuffs that have isotopic ages between 185 and 174 Ma. These rocks are assigned to the Saddle Hill Formation of the Hazelton Group. The plutonic roots of this proximal arc assemblage are most likely the coeval and compositionally similar plutons of the Spike Peak intrusive suite that have been unroofed in the area east of the Takla Fault. Major oxide and trace element data support the interpretation that the Topley and Spike Peak granitic rocks formed in a juvenile volcanic-arc environment and that magmatism is related to melts generated above a long-lived subduction zone of unknown orientation.

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Petrogenesis and tectonic significance of the middle Neoproterozoic highly fractionated A-type granite in the South Qinling block

Geological Magazine ◽

10.1017/s001675682100042x ◽

2021 ◽

pp. 1-20

Author(s):

Xiao-Fei Qiu ◽

Qiong Xu ◽

Tuo Jiang ◽

Shan-Song Lu ◽

Long Zhao

Keyword(s):

Tectonic Setting ◽

Eastern China ◽

Continental Rift ◽

The South ◽

Yangtze Craton ◽

Dabie Orogen ◽

Northern Margin ◽

South Qinling ◽

Type Granite ◽

High Alkali

Abstract The South Qinling block, a segment of the Yangtze craton involved in the Qinling–Dabie orogen, is critical for understanding the tectonic evolution of eastern China. However, the tectonic setting of the South Qinling block and the northern margin of the Yangtze block during middle Neoproterozoic time has long been the subject of debate, with two distinctly different models (continental rift or volcanic arc) proposed. Here, a comprehensive study of zircon U–Pb geochronology and geochemistry has been carried out on the Chengwan granitic pluton from the Suizao terrane in the South Qinling block. The granites are monzogranite and syenogranite in lithology, and are mainly composed of potash feldspar, quartz, plagioclase and biotite. This suite has long been regarded as a Palaeozoic magmatic pluton, but zircon U–Pb ages of 809 ± 9 Ma and 816 ± 4 Ma are obtained in this study. The granites are metaluminous to strongly peraluminous with high alkali contents, and exhibit highly fractionated features, including high SiO2, low Zr/Hf ratios, rare earth element tetrad effects and enrichment of K and Rb. They show Hf–Nd isotopic decoupling, which may be genetically related to their petrogenetic process. Based on the geochemical features and the positive εHf(t) values of the zircons, it is indicated that the granites may have been derived from partial melting of juvenile tonalitic rocks by biotite breakdown under fluid-absent conditions. The Chengwan granite geochemically belongs to the A2-subtype granites, suggesting that it might have formed in a post-orogenic tectonic setting. The highly fractionated A-type granite in this study may represent extensional collapse shortly after the collisional events in the South Qinling block, and thus indicate a tectonic regime switch, from compression to extension, as early as middle Neoproterozoic time. Integrating our new data with documented magmatic, metamorphic and sedimentary events during middle Neoproterozoic time in the region may support a continental rift model, and argues against arc models.

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New seismological data from the Calabrian arc reveal arc-orthogonal extension across the subduction zone

Scientific Reports ◽

10.1038/s41598-020-79719-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Tiziana Sgroi ◽

Alina Polonia ◽

Graziella Barberi ◽

Andrea Billi ◽

Luca Gasperini

Keyword(s):

Lateral Displacement ◽

Tectonic Setting ◽

Plate Boundary ◽

Velocity Model ◽

Tectonic Deformation ◽

Accretionary Wedge ◽

Tectonic Structures ◽

Plate Convergence ◽

Seismogenic Layer ◽

Regional Tectonic

AbstractThe Calabrian Arc subduction-rollback system along the convergent Africa/Eurasia plate boundary is among the most active geological structures in the Mediterranean Sea. However, its seismogenic behaviour is largely unknown, mostly due to the lack of seismological observations. We studied low-to-moderate magnitude earthquakes recorded by the seismic network onshore, integrated by data from a seafloor observatory (NEMO-SN1), to compute a lithospheric velocity model for the western Ionian Sea, and relocate seismic events along major tectonic structures. Spatial changes in the depth distribution of earthquakes highlight a major lithospheric boundary constituted by the Ionian Fault, which separates two sectors where thickness of the seismogenic layer varies over 40 km. This regional tectonic boundary represents the eastern limit of a domain characterized by thinner lithosphere, arc-orthogonal extension, and transtensional tectonic deformation. Occurrence of a few thrust-type earthquakes in the accretionary wedge may suggest a locked subduction interface in a complex tectonic setting, which involves the interplay between arc-orthogonal extension and plate convergence. We finally note that distribution of earthquakes and associated extensional deformation in the Messina Straits region could be explained by right-lateral displacement along the Ionian Fault. This observation could shed new light on proposed mechanisms for the 1908 Messina earthquake.

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Origin, evolution, and tectonic setting of the eastern part of the Mexican Volcanic Belt and comparison with the Central American Volcanic Arc from conventional multielement normalized and new multidimensional discrimination diagrams and discordancy and significance tests

TURKISH JOURNAL OF EARTH SCIENCES ◽

10.3906/yer-1412-31 ◽

2015 ◽

Vol 24 ◽

pp. 111-164 ◽

Cited By ~ 14

Author(s):

Surendra P. VERMA

Keyword(s):

Tectonic Setting ◽

Volcanic Belt ◽

Central American ◽

Significance Tests ◽

Volcanic Arc ◽

Mexican Volcanic Belt ◽

Central American Volcanic Arc

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Cumulates and gabbros in southern Albanian ophiolites: their bearing on regional tectonic setting

Geological Society London Special Publications ◽

10.1144/gsl.sp.2006.260.01.12 ◽

2006 ◽

Vol 260 (1) ◽

pp. 267-299 ◽

Cited By ~ 14

Author(s):

F. Koller ◽

V. Hoeck ◽

T. Meisel ◽

C. Ionescu ◽

K. Onuzi ◽

...

Keyword(s):

Tectonic Setting ◽

Regional Tectonic

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The petrological and geochemical study of granitoid rocks from Mashhad area, Iran: Evidence for the Late Triassic Collisional Belt Northeast of Iran

10.5194/egusphere-egu21-6494 ◽

2021 ◽

Author(s):

Banafsheh Vahdati ◽

Seyed Ahmad Mazaheri

Keyword(s):

Subduction Zones ◽

Tectonic Setting ◽

Crustal Contamination ◽

Oceanic Lithosphere ◽

Late Triassic ◽

Common Belief ◽

Thrust Tectonics ◽

Wide Range ◽

Lree Enrichment ◽

Granitoid Rocks

Mashhad granitoid complex is part of the northern slope of the Binalood Structural Zone (BSZ), Northeast of Iran, which is composed of granitoids and metamorphic rocks. This research presents new petrological and geochemical whole-rock major and trace elements analyses in order to determine the origin of granitoid rocks from Mashhad area. Field and petrographic observations indicate that these granitoid rocks have a wide range of lithological compositions and they are categorized into intermediate to felsic intrusive rocks (SiO2: 57.62-74.39 Wt.%). Qartzdiorite, tonalite, granodiorite and monzogranite are common granitoids with intrusive pegmatite and aplitic dikes and veins intruding them. Based on geochemical analyses, the granitoid rocks are calc-alkaline in nature and they are mostly peraluminous. On geochemical variation diagrams (major and minor oxides versus silica) Na2O and K2O show a positive correlation with silica while Al2O3, TiO2, CaO, Fe2O3, and MgO show a negative trend. Therefore fractional crystallization played a considerable role in the evolution of Mashhad granitoids. Based on the spider diagrams, there are enrichments in LILE and depletion in HFSE. Low degrees of melting or crustal contamination may be responsible for LILE enrichment. Elements such as Pb, Sm, Dy and Rb are enriched, while Ba, Sr, Nd, Zr, P, Ti and Yb (in monzogranites) are all depleted. LREE enrichment and HREE depletion are observed in all samples on the Chondrite-normalized REE diagram. Similar trends may be evidence for the granitoids to have the same origin. Besides, LREE enrichment relative to HREE in some samples can indicate the presence of garnet in their source rock. Negative anomalies of Eu and Yb are observed in monzogranites. Our results show that Mashhad granitoid rocks are orogenic related and tectonic discrimination diagrams mostly indicate its syn-to-post collisional tectonic setting. No negative Nb anomaly compared with MORB seems to be an indication of non-subduction zone related magma formation. According to the theory of thrust tectonics of the Binalood region, the oceanic lithosphere of the Palo-Tethys has subducted under the Turan microplate. Since the Mashhad granitoid outcrops are settled on the Iranian plate, this is far from common belief that these granitoid rocks are related to the subduction zones and the continental arcs. The western Mashhad granitoids show more mafic characteristics and are possibly crystallized from a magma with sedimentary and igneous origin. Thus, Western granitoid outcrops in Mashhad are probably hybrid type and other granitoid rocks, S and SE Mashhad are S-type. Evidences suggest that these continental collision granitoid rocks are associated with the late stages of the collision between the Iranian and the Turan microplates during the Paleo-Tethys Ocean closure which occurred in the Late Triassic.

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