Late Permian ultrapotassic rhyolites in SE Thailand: Evidence for a Paleotethyan continental rift basin

2021 ◽  
pp. jgs2021-079
Author(s):  
Xin Qian ◽  
Shen Ma ◽  
Xianghong Lu ◽  
Sainan Wu ◽  
Mongkol Udchachon ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Continental Rift ◽  
Late Permian ◽  
Rift Basins ◽  
Content Type ◽  
Metasedimentary Rocks ◽  
High K ◽  
Supplementary Material ◽  
Group 2 ◽  
T Values

Volcanic rocks in the Chanthaburi zone are rarely reported and important for investigating the tectonic evolution of Paleotethyan Ocean in SE Thailand. Four rhyolitic samples from the Ko Chang Island yield zircon ages of 254–258 Ma, confirming the presence of Late Permian volcanic rocks in SE Thailand. These rocks consist of Group 1 rhyolites and Group 2 rhyolitic ignimbrites and have high K2O contents of 4.92–7.10 wt.% and A/CNK values of 1.10–1.69. They are enriched in LREEs, Rb, Th, U, Zr and Y, and show negative anomalies of Ba, Sr, Nb, Ta and Ti with obvious Eu anomalies. Their whole-rock εNd (t) values range from −1.7 to −3.1. Zircon in-situ εHf (t) and δ18O values range from 0.0 to +5.6 and 8.2‰ to 9.6‰, respectively. They belong to peraluminous, ultrapotassic A-type rhyolites, and were derived from partial melting of a mixed source of Mesoproterozoic metasedimentary rocks with a component of juvenile mafic crust. These ultrapotassic rhyolites formed in a continental rift setting in response to the rollback of subducted Paleotethyan oceanic slab beneath the Indochina Block. Combining previous geological observations, we propose that there are some sporadically distributed continental rift basins along the Eastern Paleotethyan domain during the Permian.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5635390

Spatial variation in provenance signal: identifying complex sand sourcing within a Carboniferous basin using multiproxy provenance analysis.

2021 ◽  
pp. jgs2021-045
Author(s):  
B. Anders ◽  
S. Tyrrell ◽  
D. Chew ◽  
C. Mark ◽  
G. O'Sullivan ◽  
...  
Keyword(s):  
Spatial Variation ◽  
Drainage System ◽  
Provenance Analysis ◽  
Rock Composition ◽  
Content Type ◽  
Metasedimentary Rocks ◽  
Sedimentary System ◽  
Supplementary Material ◽  
Sandstone Formation ◽  
Proterozoic Basement

Multiple factors (e.g. source rock composition, climate, nature/scale of sedimentary system) influence the volume and composition of sediment delivered to basins. Fluctuations in these parameters produce cryptic source signals which can vary within the same sedimentary system. Bespoke multi-proxy provenance approaches, targeted at minerals of variable stability, allow for an assessment of natural biasing (recycling) and intra-basinal spatial variations.Provenance of fluvial/deltaic sandstones (Mullaghmore Sandstone Formation) in the NW Carboniferous Basin, Ireland, has been constrained using zircon and apatite U-Pb geochronology, trace elements in apatite and Pb-in-K-feldspar analysis. Zircon U-Pb grain populations are consistent with feldspar data, suggesting Proterozoic basement highs offshore Ireland and Scotland were the main contributor with minor supply from Archean-Palaeoproterozoic rocks of Greenland/NW Scotland and Caledonian-aged rocks. However, apatite data shows a much larger proportion of Caledonian-aged grains of metamorphic origin, suggesting significant sediment was recycled from Neopropterozoic metasedimentary rocks. The spatial variation in provenance indicates that, at onset of clastic input, sediment was being routed to the basin through a complex drainage system, comprising of several discrete hinterland catchments, rather than supply from a single, large interconnected sedimentary system. Such complexities can only be identified with the careful application of a bespoke multi-proxy provenance approach.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5536691

The influence of volcanic supply on the composition of modern river sands: the case study of the Ofanto river, Southern Italy

2021 ◽  
pp. SP520-2021-89
Author(s):  
Mariano Tenuta ◽  
Paola Donato ◽  
Rocco Dominici ◽  
Rosanna De Rosa
Keyword(s):  
Volcanic Rocks ◽  
Pyroclastic Deposits ◽  
Content Type ◽  
Sedimentary Deposits ◽  
History Of ◽  
Supplementary Material ◽  
High Production ◽  
Volcaniclastic Deposits ◽  
Pyroclastic Fall

AbstractThe Ofanto river drains volcanic rocks from the Monte Vulture, lacustrine-fluviolacustrine deposits associated with the same volcano and sedimentary deposits of the Southern Apennines and the Bradanic foredeep sequences. Comparing the modal composition of river sands and the outcrop area of different lithologies in the different sub-basins, an over-concentration of the volcaniclastic fraction, mainly represented by loose crystals of clinopyroxene, garnet and amphibole, is shown. This has been related to the preferential erosion of pyroclastic deposits, characterized by high production of sand-sized loose minerals, together with the carbonate lability and the low sand-sized detritus production from claystones and marls. The occurrence of volcaniclastic components upstream of Monte Vulture can be explained with a contribution from the lacustrine-fluviolacustrine deposits outcropping in the upstream sector or from pyroclastic fall deposits of Monte Vulture and/or Campanian volcanoes. This research shows that the volcanic record in the fluvial sands of the Ofanto river comes from weathering and sorting processes of volcaniclastic deposits rather than of the lavas building the main edifice. Therefore, caution must be taken during paleoenvironmental and paleoclimatic reconstructions when relating the type and abundance of the volcanic component in sediments to the weathering stage and evolutionary history of the volcano.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5643959

scholarly journals Outcrop-scale manifestations of reactivation during multiple superimposed rifting and basin inversion events: the Devonian Orcadian Basin, northern Scotland

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-089 ◽  
Author(s):  
A.M. Dichiarante ◽  
R.E. Holdsworth ◽  
E.D. Dempsey ◽  
K.J.W. McCaffrey ◽  
T.A.G. Utley
Keyword(s):  
Structural Complexity ◽  
Structural Data ◽  
Dominant Group ◽  
Content Type ◽  
Basin Inversion ◽  
Supplementary Material ◽  
Group 2 ◽  
Orcadian Basin ◽  
East West ◽  
Group 1

The Devonian Orcadian Basin in Scotland hosts extensional fault systems assumed to be related to the initial formation of the basin, with only limited post-Devonian inversion and reactivation. However, a recent detailed structural study across Caithness, underpinned by published Re–Os geochronology, shows that three phases of deformation are present. North–south- and NW–SE-trending Group 1 faults are related to Devonian ENE–WSW transtension associated with sinistral shear along the Great Glen Fault during the formation of the Orcadian Basin. Metre- to kilometre-scale north–south-trending Group 2 folds and thrusts are developed close to earlier sub-basin-bounding faults and reflect late Carboniferous–early Permian east–west inversion associated with dextral reactivation of the Great Glen Fault. The dominant Group 3 structures are dextral oblique NE–SW-trending and sinistral east–west-trending faults with widespread syndeformational carbonate mineralization (± pyrite and bitumen) and are dated using Re–Os geochronology as Permian (c. 267 Ma). Regional Permian NW–SE extension related to the development of the offshore West Orkney Basin was superimposed over pre-existing fault networks, leading to local oblique reactivation of Group 1 faults in complex localized zones of transtensional folding, faulting and inversion. The structural complexity in surface outcrops onshore therefore reflects both the local reactivation of pre-existing faults and the superimposition of obliquely oriented rifting episodes during basin development in the adjacent offshore areas.Supplementary material: Stereographic projections of compiled structural data from individual fieldwork localities are available at https://doi.org/10.6084/m9.figshare.c.5115228

Cenozoic high Sr/Y volcanic rocks in the Qiangtang terrane, northern Tibet: geochemical and isotopic evidence for the origin of delaminated lower continental melts

2008 ◽  
Vol 145 (4) ◽  
pp. 463-474 ◽  
Author(s):  
SHEN LIU ◽  
RUI-ZHONG HU ◽  
CAI-XIA FENG ◽  
HAI-BO ZOU ◽  
CAI LI ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Volcanic Rocks ◽  
Mantle Peridotite ◽  
Calc Alkaline ◽  
Isotopic Data ◽  
Slab Melting ◽  
Northern Tibet ◽  
High K ◽  
T Values ◽  
Qiangtang Terrane

AbstractGeochemical and Sr–Nd–Pb isotopic data are presented for volcanic rocks from Zougouyouchaco (30.5 Ma) and Dogai Coring (39.7 Ma) of the southern and middle Qiangtang block in northern Tibet. The volcanic rocks are high-K calc-alkaline trachyandesites and dacites, with SiO2 contents ranging from 58.5 to 67.1 wt % The rocks are enriched in light REE (LREE) and contain high Sr (649 to 986 ppm) and relatively low Yb (0.8 to 1.2 ppm) and Y (9.5 to 16.6 ppm) contents, resulting in high La/Yb (29–58) and Sr/Y (43–92) ratios, as well as relatively high MgO contents and Mg no., similar to the compositions of adakites formed by slab melting in subduction zones. However, the adakitic rocks in the Qiangtang block are characterized by relatively low εNd(t) values (−3.8 to −5.0) and highly radiogenic Sr ((87Sr/86Sr)i=0.706–0.708), which are inconsistent with an origin by slab melting. The geochemistry and tectonics indicate that the adakitic volcanic rocks were most likely derived from partial melting of delaminated lower continental crust. As the pristine adakitic melts rose, they interacted with the surrounding mantle peridotite, elevating their MgO values and Mg numbers.

Three-phased Middle Permian–Mesozoic magmatism in the Great Xing'an Range: implications for episodic southern subduction of the Mongol-Okhotsk ocean

2021 ◽  
pp. jgs2020-152
Author(s):  
Fei Yang ◽  
Yinglei Li ◽  
Guang Wu ◽  
Huichuan Liu ◽  
Gongzheng Chen ◽  
...  
Keyword(s):  
Partial Melting ◽  
Early Cretaceous ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Middle Permian ◽  
Content Type ◽  
Supplementary Material ◽  
Mesozoic Magmatism ◽  
Erguna Massif ◽  
Great Xing’An Range

The Erguna Massif is located in the southwestern portion of the Great Xing'an Range and is adjacent to the Mongol–Okhotsk suture zone. It has not to be determined whether the tectonic evolutionary processes of the Erguna Massif belong to the Mongol–Okhotsk tectonic regime during the Middle Permian–Mesozoic. In this study, a suite of rocks comprising Mesozoic S-type monzogranite (LA–ICP–MS U–Pb zircon age of 248 ± 1.2 Ma), highly fractionated I-type rhyolite (204 ± 1.1 Ma), gabbro (196 ± 1.9 Ma), A2-type volcanic rocks (190 ± 0.9 Ma), A1-type trachydacite (167 ± 0.8 Ma), and Early Cretaceous A1-type alkaline rhyolite are newly identified and geochemically studied. The rhyolite, gabbro, trachydacite, and alkaline rhyolite whole-rock Sr–Nd isotope analyses got the values of initial 87Sr/86Sr ratios ranging from 0.7044 to 0.7058 and εNd(t) values of −0.68–+2.73. These samples show εHf(t) values ranging from +5.3 to +11.2 and TDM2 ranging from 0.48 Ga to 0.90 Ga. The 248 Ma monzogranites were produced by the partial melting of greywackes. The 204 Ma rhyolites were derived from the partial melting of lower mafic crust. The 196 Ma gabbros originated from the partial melting of an enriched mantle metasomatized by subduction-slab released fluids. The 190 Ma volcanic rocks, 167 Ma trachydacite, and Early Cretaceous alkaline rhyolite were mainly formed by the partial melting of the basaltic rocks. They all show enrichment in the large ion lithophile elements (e.g., Rb, Ba, and K) and depletions in the high field strength elements (e.g., Nb, Ta, and Ti), suggesting they formed in an active continental margin setting. The features of these igneous rocks indicate the southward subduction of the Mongol-Okhotsk ocean plate. Based on compiled age data, three phases of middle Mesozoic magmatism were identified in the Erguna Massif at ca. 275–225 Ma, 215–165 Ma, and 150–110 Ma. In addition, three similar magmatic phases were found in the Xing'an Massif. However, a hysteresis about ca. 15–20 Ma exists between the two massifs. These magmatic rocks may record the three stages of the southward subduction of the Mongol–Okhotsk oceanic plate, and two periods of slab rollback occurred during the Middle Permian to Early Cretaceous.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5459285

Field documentation and genesis of the back-structures from the Garhwal Lesser Himalaya, Uttarakhand, India

2018 ◽  
Vol 481 (1) ◽  
pp. 111-125 ◽  
Author(s):  
Narayan Bose ◽  
Soumyajit Mukherjee
Keyword(s):  
Lesser Himalaya ◽  
Main Central Thrust ◽  
Content Type ◽  
The North ◽  
Group 4 ◽  
Thrust Belts ◽  
Bhagirathi River ◽  
Thrust Zone ◽  
Supplementary Material ◽  
Group 2

AbstractCollisional fold-and-thrust belts are characterized by foreland-verging thrusts. Conversely, structures with hinterland-ward vergence, known as the back-thrusts, also exist. Strain intensification, critical taper deformation and the presence of thrust ramps generate back-thrusts. This study focuses on the exposure-scale brittle and ductile structures showing hinterland-ward vergence (back-structures) from a part of the Garhwal Lesser Himalaya, NW India, mainly along the Bhagirathi river section. In our field-traverse, back-structures were found at 31 locations. Towards the north, in the Outer Lesser Himalaya, the back-structures are located on the inverted limb of the Mussoorie Syncline (Group 1). The Tons Thrust is a south-dipping thrust (i.e. back-thrust). Hence, the Tons Thrust and nearby areas show intense back-structures (Group 2). In the Inner Lesser Himalaya, back-structures have been generated by shearing related to the folded Berinag Thrust (Group 3). The back-structures at and near the Main Central Thrust Zone (MCTZ) (Group 4) can be correlated with the presence of the Delhi–Haridwar Ridge. In this way, this study establishes the back-structures to be an integral part of the Garhwal Lesser Himalaya and provides the genesis of those structures by correlating them with the (local) tectonic settings.Supplementary material: Tables listing seismic events and the GPS coordinates of the field locations, and figures showing structures at these field locations are available at https://doi.org/10.6084/m9.figshare.c.4339784

scholarly journals Geochemistry, zircon U-Pb geochronology and Sr-Nd-Hf isotopic composition of the Cha Val plutonic rocks in central Vietnam: Implications for Permian-Triassic Paleo-Tethys subduction-related magmatism

2021 ◽  
Author(s):  
Minh Pham ◽  
Hieu ◽  
Kenta Kawaguchi ◽  
Anh ◽  
Phuc
Keyword(s):  
Suture Zone ◽  
Early Triassic ◽  
Late Permian ◽  
Magmatic Complex ◽  
High K ◽  
Plutonic Rocks ◽  
Surrounding Areas ◽  
A Minor ◽  
Hf Isotopic Composition ◽  
T Values

together with abundant Permian-Triassic magmatic rocks. This magmatic complex provides important information to reconstruct the tectonic evolution of the Indochina block and surrounding areas. The Cha Val plutonic rocks mainly comprise diorite, quartz diorite, and granodiorite. Geochemically, they are metaluminous with low A/CNK (0.49 to 1.16 with an average of 0.85), medium to high K, low to medium SiO2, and Na2O/K2O>1. Trace and rare earth element compositions display enrichment in Cs, U, Pb, and Nd, but depletion in Ba, Nb, Ta, P, Eu, and Ti, similar to those of continental arc-related magmas. Rock-forming minerals of the Cha Val plutonic rocks are characterized by abundant hornblende. All observed petrographical and geochemical characteristics suggest that the Cha Val plutonic rocks are typical for I-type affinity generated from a subduction regime. LA-ICP-MS U-Pb zircon analyses of three representative samples yielded their crystallization ages between 258.0 Ma and 248.9 Ma, temporally coeval with Late Permian-Early Triassic magmatism previously reported in the Truong Son belt. The (87Sr/86Sr)i ratios (0.7081 to 0.7244), negative whole-rock εNd(t) values (-4.5 to -2.9), zircon εHf(t) values (-1.04 to 2.71), and whole-rock Nd and zircon Hf model ages (TDM2) (1394 Ma to 1111 Ma) indicate that the Cha Val plutonic rocks are derived from melting of Mesoproterozoic crustal materials with a minor contribution of mantle-derived melt. Together with other Permian-Triassic magmatic complexes along the Song Ma suture zone and the Truong Son Belt, the Cha Val plutonic rocks are a representative of magmatism associated with the subduction-collision that amalgamated the South China and Indochina blocks after the closure of a branch of Paleo-Tethys along the Song Ma suture zone during the Late Permian-Early Triassic Indosinian orogeny.

Lithium isotopes in kimberlites, lamproites and lamprophyres as tracers of source components and processes related to supercontinent cycles

2021 ◽  
pp. SP513-2021-60
Author(s):  
Lukáš Krmíček ◽  
Tomáš Magna ◽  
Ashutosh Pandey ◽  
N. V. Chalapathi Rao ◽  
Jindřich Kynický
Keyword(s):  
Isotope Composition ◽  
Volcanic Rocks ◽  
Dharwar Craton ◽  
Metamorphic Rocks ◽  
Eastern Dharwar Craton ◽  
Content Type ◽  
Bastar Craton ◽  
Li Isotope ◽  
Supplementary Material ◽  
Orogenic Belts

AbstractOur pilot study reveals potential fingerprints of Li isotopes recorded in the Mesoproterozoic (∼1.4-1.1 Ga) kimberlites, lamproites and lamprophyres from the Eastern Dharwar Craton and Paleocene (62 Ma) orangeite from the Bastar Craton in India. The new data are interpreted in the context of available Li isotope composition of lamproitic to lamprophyric rocks occurring in Variscan (Bohemian Massif) and Alpine-Himalayan (SW Tibet) orogenic belts formed in response to Gondwana-Pangea amalgamation and break-up. As a result of supercontinents development, kimberlites from the Eastern Dharwar Craton and ‘orangeite’ from the Bastar Craton show clear presence of a component with a heavy Li isotope signature (δ7Li up to 9.7‰) similar to an ancient altered oceanic crust, whereas the Eastern Dharwar Craton lamproites (2.3-6.3‰) and lamprophyres (3.3-6.7‰) show Li isotope signatures indicative of a dominant contribution from heterogeneous lithospheric mantle. Variscan lamprophyric to lamproitic rocks and post-collisional mantle-derived (ultra)potassic volcanic rocks from SW Tibet, i.e., rocks from the orogenic belts outside the cratonic areas, are characterized by a clear Li isotope shift towards isotopically lighter component (δ7Li as low as -9.5‰) comparable with the involvement of an evolved continental crust and high-pressure metamorphic rocks in their orogenic mantle source. Such components with isotopically light Li are strikingly missing in the source of cratonic kimberlites, lamproites and lamprophyres.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5495097

Carboniferous sedimentary provenance and tectonic setting in the Darbut region of Western Junggar (NW China): evidence from mineralogy, geochemistry and detrital zircon U-Pb dating

2021 ◽  
pp. jgs2020-132
Author(s):  
Kai Weng ◽  
Yunpeng Dong ◽  
Xueyi Xu ◽  
Zhongping Ma ◽  
Bo Chen
Keyword(s):  
Detrital Zircon ◽  
Tectonic Setting ◽  
Chemical Compositions ◽  
Content Type ◽  
Clastic Rocks ◽  
Magmatic Rocks ◽  
Central Asian ◽  
Supplementary Material ◽  
Back Arc ◽  
T Values

The Carboniferous tectonic evolution of Western Junggar is crucial to understanding the subduction-accretion process of the Central Asian Orogenic Belt (CAOB), but the nature of this setting is still controversial. In this work, composite mineralogical, geochemical and detrital zircon U-Pb geochronological investigations have been conducted on Carboniferous clastic rocks in the Darbut region. The chemical compositions and sedimentary features show low sediment maturity and limited recycling, suggesting short-distance transportation and rapid accumulation. The samples contain igneous rock debris, mainly andesite and small amounts of basalt and granite, and a heavy mineral assemblage of Zr + Ap + Aug + Hbl + iron-bearing minerals (Hem-Lm, Ilm, Mag, and Py). The samples feature moderate ratios of Zr/Sc (average 15.47) and Th/Sc (average 0.61), and low ratios of La/Sc, Co/Th, and La/Th, as well as low Hf contents, suggesting intermediate to felsic arc-related igneous provenances. Detrital zircon grains from the clastic rocks show prominent age peaks in the Devonian and Carboniferous with positive εHf(t) values, indicating a consistent provenance associated with the Tiechanggou–Halaalate island arc. Combining the petrology, geochemistry and geochronology of the sedimentary and magmatic rocks, we conclude that the Darbut Carboniferous volcanic-sedimentary strata were deposited in a back-arc basin during ∼327-311Ma.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5357293

Eruption history, petrogeochemistry, and geodynamic background of Tengchong volcanoes in Yunnan Province, SW China

2020 ◽  
pp. SP510-2020-45
Author(s):  
Hongmei Yu ◽  
Bo Zhao ◽  
Zhengquan Chen ◽  
Haiquan Wei ◽  
Wenjian Yang ◽  
...  
Keyword(s):  
Yunnan Province ◽  
Volcanic Rocks ◽  
Evolutionary Process ◽  
Source Area ◽  
Volcanic Field ◽  
Indian Plate ◽  
Eurasian Plate ◽  
Content Type ◽  
Supplementary Material ◽  
Eruption History

AbstractThe Tengchong Volcanic Field (TVF) is one of the youngest volcanic areas in China, and located in the southwestern part of Yunnan Province, China, adjacent to the collision zone between the Indian Plate and Eurasian Plate. This paper summarizes the results of previous research on the eruption history, petrochemistry, and geodynamic background of the TVF and presents a detailed analysis of the available data. Eruptions took place from the Pliocene to the Holocene and were divided into five stages. The composition of the magma went through two cycles: the N2-Q1 P-Q2 P volcanic rocks went through the evolutionary process from basalt to dacite and the Q3 P-Qh magma evolved from trachybasalt to trachyte. The evolution of magma is mainly related to the crystallisation and separation of pyroxene and ilmenite. The mantle source area of the TVF volcanic rocks was caused by the mixing between the MORB-source mantle and the eastern Indian continental margin sediments (EIS) to different degree. Geophysical data also showed that the Indian Plate has been subducted under the TVF area. There are also magma chambers in the crust within a depth of 25 km in the TVF that are replenished by mantle magma.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5227663

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