scholarly journals Early Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1248
Author(s):  
Youxin Chen ◽  
Shengqiang Zhu ◽  
Xianzhi Pei ◽  
Lei He ◽  
Jun Zhao ◽  
...  
Keyword(s):  
Middle Devonian ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Age Dating ◽  
Magma Source ◽  
Heat Accumulation ◽  
Early Devonian ◽  
Northern Margin ◽  
T Values

The origin and tectonic implication of Early–Middle Devonian magmatism in the northern margin of YB (Yili Block) remain enigmatic and are important for understanding Late Paleozoic evolution of the Junggar Ocean and southern Kazakhstan Orocline. Here, we present the systematic study of whole-rock geochemical and Sr–Nd isotope features as well as U–Pb–Hf isotope characteristics of zircon crystals for newly identified Early Devonian volcanic rocks from the northern margin of YB. The volcanic rocks are composed of rhyolite, rhyolite porphyry, and rhyolitic tuff. Zircon U-Pb age dating indicates they were formed at ca. 407~418 Ma. They have high SiO2 (70.16–77.52 wt.%) and alkali (5.10–9.56 wt.%) contents, and high Zr + Nb + Ce + Y content (~456 ppm), indicative of A-type magma. Their relative depletion of Nb, Ta, and Ti, and enrichment of LILEs show arc affinity. Their low initial 87Sr/86Sr ratios (0.699708–0.709822) and negative εNd(t) values (−1.8 to −4.0) indicate a mainly continental magma source and their positive εHf(t)values (+6.13 to +14.81) are possibly due to the garnet effect. All these above reveal that volcanic rocks were generated by re-melting of lower crust under a high temperature condition, which was induced by long-lived heat accumulation with no or minimal basalt flux. Combined with active continental margin inference evidenced by contemporaneous sedimentary rocks, we attribute the generation of the volcanic rocks to a continental arc setting related to the southward subduction of Junggar oceanic crust. Thus, we infer the Early–Middle Devonian arc-related magmatic rocks in the northern margin of YB are eastward counterparts of the southern limb of the Devonian Volcanic Belt, which resulted from a relatively steady-state southward subduction.

scholarly journals Genesis of Volcanic Rocks in the Zijinshan Ore District, SE China: Implications for Porphyry-Epithermal Mineralization

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 200 ◽  
Author(s):  
Zheng-Zheng Feng ◽  
Zhong-Jie Bai ◽  
Hong Zhong ◽  
Wei-Guang Zhu ◽  
Shi-Ji Zheng
Keyword(s):  
Oxygen Fugacity ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Parental Magma ◽  
High Oxygen ◽  
Magma Source ◽  
High Water Content ◽  
High Oxygen Fugacity ◽  
Epithermal Mineralization ◽  
T Values

Volcanic rocks, as the extrusive counterparts of the mineralized intrusions, can provide important information on the magma source, petrogenesis, and metallogenic conditions of the coeval porphyry-epithermal system. Shanghang Basin volcanic rocks are spatially and temporally related to a series of adjacent porphyry-epithermal Cu–Au deposits, and they can be used as a window to study the related deposits. Two laser-ablation–inductively coupled plasma–mass spectrometry zircon U–Pb analyses of the volcanic rocks yield weighted mean ages of ~105 Ma, identical to the age of the coeval porphyry-epithermal mineralization. Rocks have SiO2 contents of 55.4 to 74.8 wt % and belong to the high-K to shoshonitic series, characterized by strong differentiation of light rare-earth elements (REEs) relative to heavy REEs (mean LaN/YbN = 16.88); enrichment in light REEs, Rb, Th, and U; and depletion in Nb, Ta, Zr, Hf, and Ti. The volcanic rocks display (87Sr/86Sr)i values of 0.709341 to 0.711610, εNd(t) values of −6.9 to −3.3 εHf(t) values of −3.95 to −0.30, and δ18O values of 6.07‰–6.79‰, suggesting that the parental magmas were derived from a mantle source enriched by subduction-related progress. SiO2 content shows a strong negative correlation with the contents of some major and trace elements, indicating that fractional crystallization played an important role in the generation of these rocks. A binary mixing model of Hf–O isotopes gives an estimated degree of crustal contamination of 30%. In addition, magnetite crystallized early, and the samples showed high zircon EuN/EuN* values (0.48–0.68), indicating that the parental magma had a high oxygen fugacity. The inferred suppression of plagioclase crystallization and increasing hornblende crystallization during magma evolution suggest that the magma was water rich. The high-water content and high oxygen fugacity of the magma promoted the dissolving of sulfides containing Cu and Au in the source area and contributed to the migration of ore-forming elements.

Andesite Geochemistry Features of Late Triassic Tumugou Formation, in Zhongdian, Yunnan Province

2012 ◽  
Vol 524-527 ◽  
pp. 16-23
Author(s):  
Jian Guo Huang ◽  
Run Sheng Han ◽  
Ren Tao ◽  
Zhi Qiang Li
Keyword(s):  
Trace Element ◽  
Volcanic Rock ◽  
Continental Margin ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Distribution Patterns ◽  
Island Arc ◽  
Late Triassic ◽  
Magma Source ◽  
Volcanic Arc

The Late Triassic Tumugou Formation volcanic rocks which belongs to typical island arc volcanic rocks in southern end of Yidun island arc belt is located at the eastern of the Zhongdian ,NW Yunnan, SW China. The volcanic rocks can be divided into three categories:andesitic basalt, andesite, quartz andesite, etc. Through geochemical analysis the major elements, rare earth ele and trace element in volcanic rocks, SiO255.18-57.59×10-2,TiO21.16-1.45×10-2,Na2O+K2O5.11-8.05×10-2.consider it is calc-alkaline- alkaline Series of high-K andesite, volcanic may be controlled by the crystal fractionation of magma.Rb31.50-101×10-6,Ba1310-12300×10-6,Nb/Ta11.4-15.5,REE166.07-240.78×10-6,δEu0.74-1.00,REE distribution patterns show oblique to the HREE side and enrichment in LREE .Eu anomaly is not obvious. It is can see from the relevant figure about trace element, it is very similar in magmatic distribution patterns between volcanic rock and Volcanic-arc rock, indicating that the volcanic in this area may be formed in volcanic-arc environment. From east to west, Magma source depth have regular change with the really thickness of mainland shell. Explain that Tumugou Formation volcanic rock is subduction by Ganzi- Litang Ocean basin from east to west. Hongshan-Ousaila region of eastern edge of Zhongdian is the volcanic island arc system during the passive continental margin into an active continental margin.

Paleozoic subduction of the Mongol-Okhotsk oceanic plate: insight from the petrogenesis of Ordovician to Devonian granitic plutons in the Hangay Range, central Mongolia

2021 ◽  
Author(s):  
jiaqi Ling ◽  
pengfei Li
Keyword(s):  
Tectonic Evolution ◽  
Magma Source ◽  
Oceanic Plate ◽  
Early Devonian ◽  
Central Mongolia ◽  
Middle Ordovician ◽  
Basaltic Rocks ◽  
History Of ◽  
Geochemical Studies ◽  
T Values

<p>Email: [email protected]; [email protected]</p><p> </p><p>The pre-Mesozoic subduction history of the Mongol-Okhotsk oceanic plate has been poorly understood. Here we conducted geochronological and geochemical studies on four granitic plutons in the westernmost Mongol-Okhotsk Orogen (Hangay Range), with an aim to understand their petrogenesis and role in the Paleozoic tectonic evolution of the Mongol-Okhotsk Orogen. Our geochronological results constrain four granitic plutons to be emplaced from middle Ordovician to early Devonian. Geochemically, the Ordovician pluton belongs to A2-type granites, and three Silurian to Devonian plutons show the characteristics of I-type granites. These granitic plutons were probably generated by partial melting of basaltic rocks in the lower crust given the high contents of Na<sub>2</sub>O and K<sub>2</sub>O. The negative ε<sub>Nd</sub>(t) values (-4.7 to -0.9) and variable ε<sub>Hf</sub>(t) values (-2.6 to +6.1) for the four granitic plutons suggest that ancient basement materials were possibly involved in the magma source. We further investigate the geodynamic origin of these plutons in the context of the Paleozoic tectonics of the Mongol-Okhotsk Orogen, and we conclude that they were probably formed in response to the Ordovician to Devonian subduction of the Mongol-Okhotsk oceanic plate.</p>

Provenance of Paleozoic sedimentary rocks in the Canadian Cordilleran miogeocline: a Nd isotopic study

1997 ◽  
Vol 34 (12) ◽  
pp. 1603-1618 ◽  
Author(s):  
Carmala N. Garzione ◽  
P. Jonathan Patchett ◽  
Gerald M. Ross ◽  
JoAnne Nelson
Keyword(s):  
British Columbia ◽  
Northwest Territories ◽  
Middle Devonian ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Canadian Shield ◽  
Isotopic Study ◽  
Middle Ordovician ◽  
Southern Alberta ◽  
T Values

Nd isotopes and trace elements in sedimentary rocks of the Yukon, the Northwest Territories, and northern British Columbia are used to examine the source of sediments in the Canadian Cordilleran miogeocline. Previous Nd isotope studies in southern Alberta demonstrated that strata of Neoproterozoic to Late Ordovician age were derived from Archean and Proterozoic Canadian Shield sources, whereas by the Late Devonian, a shift of 6 εNd units to younger crustal sources (εNd (T) = −6 to −9) had occurred. In this study, we found that the shift to younger crustal Nd isotopic signatures in the Yukon and Northwest Territories occurred much earlier than in southern Alberta. Cambrian and older strata have εNd(T) values of −10.0 to −21.1, consistent with derivation from Canadian Shield sources. Lower Ordovician through Permian strata in the Yukon and Northwest Territories, including the Innuitian-derived Imperial Assemblage, have εNd(T) values of −5 to −11.4. In northern British Columbia, the shift to a younger source reflects a wider range of εNd(T) values, from -−8.7 to −14.6 in Middle Ordovician through Middle Devonian strata, suggesting continued input from Canadian Shield sources. By the Middle Devonian, a complete shift to younger crustal signatures (εNd(T) = −5.9 to −10.5) had occurred in northern British Columbia. Several sources for the more juvenile sediments include (1) a mixture of locally erupted volcanic rocks with Canadian Shield sources, (2) a Grenville source, and (3) an Innuitian source. We propose that Ordovician to Lower Devonian strata were derived from a mixture of locally erupted, juvenile volcanics and pre-Cambrian Canadian Shield sources, and post-Middle Devonian strata were sourced from the Innuitian orogen in the Canadian Arctic.

scholarly journals Dating Oceanic Subduction in the Jurassic Bangong–Nujiang Oceanic Arc: A Zircon U–Pb Age and Lu–Hf Isotopes and Al-in-Hornblende Barometry Study of the Lameila Pluton in Western Tibet, China

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 754 ◽  
Author(s):  
De-Liang Liu ◽  
Min Shi ◽  
Shao-Yong Jiang
Keyword(s):  
Subduction Zone ◽  
Middle Jurassic ◽  
Volcanic Rocks ◽  
Hf Isotopes ◽  
Magma Source ◽  
Zone Model ◽  
The Tibetan Plateau ◽  
Initial Growth ◽  
Depleted Mantle ◽  
T Values

The subduction and close of the Mesozoic Bangong–Nujiang Ocean (BNO) led to a collision of the Lhasa and Qiangtang blocks, which formed the backbone of the Tibetan Plateau (the largest and highest plateau on Earth). However, the detailed subduction processes (in particular, the oceanic subduction processes) within the BNO are still not clear. Here, we focus on the plutonic complex of the oceanic arc in the Bangong–Nujiang suture (BNS) and report field observations on zircon U–Pb ages, Lu–Hf isotopes, and the Al-in-hornblende barometry of quartz diorites from the Lameila pluton in western Tibet. Zircon from the quartz diorites yielded a LA-ICP-MS U–Pb age of 164 Ma. The zircon showed very positive εHf(t) values from 10.5 to 13.9, suggesting the Lameila pluton was likely sourced from the depleted-mantle wedge, which is in contrast with contemporary (164–161 Ma) volcanic rocks in the region that had negative εHf(t) values of −7.4 to −16.2 and a magma source from partial melting of subducted sediments. The Lameila pluton showed a temperature-corrected Al-in-hornblende pressure of 3.9 ± 0.8 kbar, corresponding to an emplacement depth of 13 ± 3 km. Therefore, the thickness of the Jurassic oceanic arc crust must have doubled since the initial growth of the oceanic arc on the BNO crust, with a crustal thickness of 6.5 km during the Middle Jurassic. In combination with previous works on volcanic rocks, this study further supports a two-subduction zone model in association with the BNO during the Middle Jurassic, namely, a north-dipping BNO–Qiangtang subduction zone and an oceanic subduction zone within the BNO. The latter oceanic subduction zone produced the depleted-mantle-derived Lameila pluton and the subducted sediment-derived volcanic rocks in the fore arc.

scholarly journals Petrogenesis and geochronology of the Arkasani Granophyre and felsic Dalma volcanic rocks: implications for the evolution of the Proterozoic North Singhbhum Mobile Belt, east India

2014 ◽  
Vol 152 (3) ◽  
pp. 492-503 ◽  
Author(s):  
H.N. BHATTACHARYA ◽  
D.R. NELSON ◽  
E.R. THERN ◽  
W. ALTERMANN
Keyword(s):  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Tectonic Activity ◽  
Mobile Belt ◽  
Northern Margin ◽  
The North ◽  
Ne India ◽  
New Findings ◽  
Minimum Age ◽  
Felsic Volcanic

AbstractThe North Singhbhum Mobile Belt (NSMB) is a 200 km long, curved Proterozoic fold–thrust belt that skirts the northern margin of the Archean Singhbhum Craton of NE India. The Singhbhum Shear Zone (SSZ) developed between the Dhanjori and Chaibasa formations near the southern margin of the NSMB and represents an important Cu-U-P metallotect. A SHRIMP U–Pb zircon date of 1861±6 Ma, obtained for the syn- to post-kinematic Arkasani Granophyre that has intruded the SSZ, provides a minimum age for the prolonged tectonic activity and mineralization along the SSZ and for the time of closure of the Chaibasa and Dhanjori sub-basins. The Dalma Volcanic Belt, a submarine rift-related bimodal mafic-felsic volcanic suite, forms the spine of the NSMB. A SHRIMP U–Pb zircon igneous crystallization date of 1631±6 Ma was obtained for an unfoliated felsic volcanic rock from the base of the Dalma volcanic sequence. These new findings suggest that the different sub-basins in the NSMB evolved diachronously under contrasting tectonic environments and were juxtaposed during a later orogenic movement.

scholarly journals The Mandalovoo–Gurvansayhan terranes in the southern Gobi of Mongolia: new insights from the Bayankhoshuu Ruins section

2021 ◽  
Author(s):  
A. Munkhjargal ◽  
P. Königshof ◽  
J. A. Waters ◽  
S. K. Carmichael ◽  
S. Gonchigdorj ◽  
...  
Keyword(s):  
Middle Devonian ◽  
Facies Analysis ◽  
Volcanic Rocks ◽  
Late Devonian ◽  
Basaltic Lava ◽  
Sedimentary Sequence ◽  
Early Devonian ◽  
Subaerial Exposure ◽  
Arc Setting ◽  
Devonian Age

AbstractThe Bayankhoshuu Ruins section in southern Mongolia is characterized by strongly thrusted and folded sequences. Overall, three sections ranging from Ordovician to Carboniferous rocks were studied. Facies analysis combined with stratigraphic data provide improved lithostratigraphic descriptions of Palaeozoic successions in the Mushgai region. The overall marine sedimentary sequence is punctuated by volcanic rocks–basaltic lava of Silurian and Middle Devonian age and volcaniclastic bentonite and tuff in the Middle to Late Devonian and Mississippian suggesting an island arc setting. The Minjin Member of the Botuulkhudag Formation (Middle Devonian to Late Devonian) is primarily composed of thick basaltic and subaerial volcanic rocks with minor silicified siltstone and chert inclusions. Thicker successions of limestone occur in the Ordovician/Silurian, Early Devonian, and the Mississippian. The macrofauna is scarce, except distinct limestone horizons where different fossil groups were recognized. Microfossils, such as radiolarians and conodonts, are scarce and generally poorly preserved. However, based on the re-study of collections from earlier publications and new conodont data, a more detailed biostratigraphic record of the Khoyormod, Botuulkhudag, and Arynshand formations of the Bayankhoshuu Ruins section can be developed. For instance, the Arynshand Formation likely ranges from the late Bispathodus ultimus conodont biozone to the Scaliognathus anchoralis–Doliognathus latus conodont biozone. A tectonic breccia occurs in the early Mississippian and is overlain by a red shale of remarkable thickness at the top of this formation which points to subaerial exposure in the early Mississippian (near the Tournaisian/Visean transition). Due to strong tectonic overprint and/or facies, some unconformities/hiatuses occur. Most strata are intensively folded and faulted, ranging from centimeter to meter scale. Overall, deposition likely occurred on either the Mandalovoo or Gurvansayhan Terrane.

scholarly journals U–Pb Age Dating and Geochemistry of Soft-Sediment Deformation Structure-Bearing Late Cretaceous Volcano-Sedimentary Basins in the SW Korean Peninsula and their Tectonic Implications

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 520
Author(s):  
Kyoungtae Ko ◽  
Sung Won Kim ◽  
Yong Sik Gihm
Keyword(s):  
Late Cretaceous ◽  
Korean Peninsula ◽  
Active Continental Margin ◽  
Volcanic Rocks ◽  
Sedimentary Basins ◽  
Age Dating ◽  
Soft Sediment ◽  
Ground Shaking ◽  
Sediment Deformation ◽  
Soft Sediment Deformation

Cretaceous volcano-sedimentary basins and successions in the Korean Peninsula are located along NE-SW- and NNE-SSW-trending sinistral strike–slip fault systems. Soft-sediment deformation structures (SSDS) of lacustrine sedimentary strata occur in the Wido, Buan, and Haenam areas of the southwestern Korean Peninsula. In this study, systematic geological, geochronological, and geochemical investigations of the volcanic-sedimentary successions were conducted to constrain the origin and timing of SSDS-bearing lacustrine strata. The SSDS-bearing strata is conformably underlain and overlain by volcanic rocks, and it contains much volcaniclastic sediment and is interbedded with tuffs. The studied SSDSs were interpreted to have formed by ground shaking during syndepositional earthquakes. U-Pb zircon ages of volcanic and volcaniclastic rocks within the studied volcano-sedimentary successions were ca. 87–84 Ma, indicating that active volcanism was concurrent with lacustrine sedimentation. Geochemical characteristics indicate that these mostly rhyolitic rocks are similar to subduction-related calc-alkaline volcanic rocks from an active continental margin. This suggests that the SSDSs in the study area were formed by earthquakes related to proximal volcanic activity due to the oblique subduction of the Paleo-Pacific Plate during the Late Cretaceous.

A Late Miocene magmatic flare-up in West Sulawesi triggered by Banda slab rollback

2020 ◽  
Vol 132 (11-12) ◽  
pp. 2517-2528
Author(s):  
Xiaoran Zhang ◽  
Chia-Yu Tien ◽  
Sun-Lin Chung ◽  
Adi Maulana ◽  
Musri Mawaleda ◽  
...  
Keyword(s):  
Late Miocene ◽  
Source Region ◽  
River Sediments ◽  
Volcanic Rocks ◽  
Detrital Zircons ◽  
Magma Source ◽  
Magmatic Rocks ◽  
High K ◽  
Slab Rollback ◽  
T Values

Abstract Cenozoic magmatism occurs throughout West Sulawesi, Indonesia, yet its detailed evolution remains enigmatic due mainly to the scarcity of precise dating. Here, we report new whole-rock geochemical and zircon U-Pb-Hf isotopic data of plutonic/volcanic rocks and river sediments from West Sulawesi to constrain the petrogenesis and magmatic tempo. The magmatic rocks are intermediate to felsic (SiO2 = 58.1–68.0 wt%), high-K calc-alkaline to shoshonitic (K2O = 2.2–6.0 wt%), metaluminous to weakly peraluminous, and I-type in composition. Trace element concentrations and ratios (e.g., Nb/U = 1.7–4.3 and Ti/Zr < 28), along with negative zircon εHf(t) values (–17.0 to –0.4) and old crustal model ages (TDMC = 2.1–1.1 Ga), indicate a dominant magma source region from the underlying continental crystalline basement. U-Pb dating on zircons from ten magmatic rocks yielded weighted mean 206Pb/238U ages of 7.2–6.1 Ma, best representing the crystallization ages of host magmas, further consistent with the prominent age peaks (7.3–6.3 Ma) defined by detrital zircons from four sedimentary samples. Our new data, combined with available results, allow the identification of a noticeable climax of magmatism (flare-up) at ca. 7–6 Ma, forming a continuous magmatic belt throughout West Sulawesi. Given the absence of contemporaneous subduction and the coincidence of incipient opening of the South Banda Basin during ca. 7.15–6.5 Ma, the Late Miocene magmatic flare-up in West Sulawesi and coeval regional extension in eastern Indonesia are attributed to a resumed episode of Banda slab rollback.

Petrogenesis of the Middle Devonian Gushan diorite pluton on the northern margin of the North China block and its tectonic implications

2007 ◽  
Vol 144 (3) ◽  
pp. 553-568 ◽  
Author(s):  
SHUAN-HONG ZHANG ◽  
YUE ZHAO ◽  
BIAO SONG ◽  
DUN-YI LIU
Keyword(s):  
Middle Devonian ◽  
Inner Mongolia ◽  
North China ◽  
Early Jurassic ◽  
Late Carboniferous ◽  
Type I ◽  
North China Block ◽  
Northern Margin ◽  
The North ◽  
T Values

The Gushan diorite pluton, located at the northern margin of the North China block, was emplaced during Middle Devonian times (SHRIMP U–Pb zircon age of 390 ± 5 Ma). Rocks from the pluton are characterized by low SiO2 and high alkali contents, and they show monzodiorite compositions in a total alkali v. silica (TAS) plot. They exhibit light REE-enrichment, no to slightly positive Eu anomalies, strong depletion in Rb, Th, U, Nb, Ta, P, Zr, Hf and Ti, enrichment in Ba, K and Sr, low contents of Y and Yb, and high Sr/Y ratios. They have a relatively narrow range of isotopic compositions with initial 87Sr/86Sr ratios of ∼ 0.7050, εNd(T) values of −9.5 to −7.5 and zircon εHf(T) values from −11.8 to −5.8. These features are remarkably similar to another Middle Devonian intrusion, the Shuiquangou syenitic complex at the northern margin of the North China block. These similarities suggest that the two intrusions probably have a common origin. They were considered to be derived from a type I enriched mantle, ultimately with some involvement of ancient lower crustal components, and were likely emplaced in a back-arc extension environment related to southward subduction of the Palaeo-Asian oceanic plate or during the cessation of the subduction. Aluminium-in-hornblende barometry studies of the Middle Devonian Gushan pluton yielded emplacement depths of about 18 km. Combined with previous geobarometry results on the Carboniferous plutons within the Inner Mongolia Palaeo-uplift on the northern margin of the North China block, it is inferred that the uplift and exhumation of the plutons within the Inner Mongolia Palaeo-uplift during Middle Devonian to Late Carboniferous times were not as distinct as those during Late Carboniferous to Early Jurassic times, and the strong uplift and exhumation of the Inner Mongolia Palaeo-uplift were achieved during Late Carboniferous to Early Jurassic times.

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