scholarly journals Late Jurassic Changmar Complex from the Shyok ophiolite, NW Himalaya: a prelude to the Ladakh Arc

2020 ◽  
pp. 1-22
Author(s):  
Wanchese M. Saktura ◽  
Solomon Buckman ◽  
Allen P. Nutman ◽  
Vickie C. Bennett
Keyword(s):  
Late Jurassic ◽  
Early Stage ◽  
Western Himalaya ◽  
Island Arc ◽  
Magma Source ◽  
Nw Himalaya ◽  
Volcanic Arc ◽  
Mafic Rocks ◽  
Isotopic Signatures ◽  
Enrichment Characteristics

Abstract The Shyok Suture in western Himalaya preserves a record of the opening and closure of the Mesotethys Ocean between the Shyok ophiolite and Karakoram terrane prior to the India–Eurasia collision. The formation age of the Shyok ophiolite was unknown, which impeded correlation with similar rocks along the Shyok Suture in Pakistan and corresponding sutures in Tibet. We report the first zircon U–Pb ages of a newly documented suite, here named the Changmar Complex. The Changmar Complex gabbronorite and plagiogranite yielded SHRIMP U–Pb zircon Late Jurassic ages of 159.4 ± 0.9 Ma and 151.9 ± 1.5 Ma. Their highly positive initial εHf values (+14.9 to +16.9) indicate a juvenile mantle origin, without continental crust influence on the magma source. The Shyok ophiolite represents either: (1) a separate island arc that preceded formation of the Cretaceous–Eocene Ladakh Arc; or (2) the oldest magmatism and early stage of the Ladakh Arc. Intrusive and extrusive mafic rocks from the Shyok Suture analysed in this study have typical supra-subduction zone enrichment characteristics in their geochemistry and are classified as part of the volcanic-arc ophiolite. The U–Pb age and Hf isotopic signatures for the Shyok ophiolite are similar to the Late Jurassic Matum Das tonalite within the Kohistan Arc; we therefore suggest that they are part of the same intra-oceanic island-arc system that formed in the Mesotethys Ocean prior to Late Jurassic time.

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.

SYSTEMATIC MIDDDLE TO LATE JURASSIC CHANGES IN MAGMA SOURCE IN THE MOJAVE SEGMENT OF CALIFORNIA’S CONTINENTAL ARC

2016 ◽  
Author(s):  
Jade Star Lackey ◽  
◽  
Kyle R. McCarty ◽  
Anne A. Fulton ◽  
Juliet Ryan-Davis ◽  
...  
Keyword(s):  
Late Jurassic ◽  
Magma Source ◽  
Continental Arc

Nd and Pb isotope mapping of crustal domains within the Makkovik Province, Labrador

2018 ◽  
Vol 156 (5) ◽  
pp. 833-848 ◽  
Author(s):  
R. M. MOUMBLOW ◽  
G. A. ARCURI ◽  
A. P. DICKIN ◽  
C. F. GOWER
Keyword(s):  
Early Stage ◽  
Foreland Basin ◽  
Mobile Belt ◽  
South American ◽  
Pb Isotope ◽  
Volcanic Arc ◽  
Nd Isotope ◽  
North American Cordillera ◽  
Tectonic Model ◽  
Isotope Data

AbstractThe Makkovik Province of eastern Labrador represents part of an accretionary orogen active during an early stage in the development of the Palaeoproterozoic southern Laurentian continental margin. New Nd isotope data for the eastern Makkovik Province suggest that accreted juvenile Makkovik crust was generated in the Cape Harrison domain during a single crust-forming event at c. 2.0 Ga. Pb isotope data support this model, and show a strong similarity to radiogenic crustal signatures in the juvenile Palaeoproterozoic crust of the Ketilidian mobile belt of southern Greenland. As previously proposed, an arc accretion event at c. 1.9 Ga triggered subduction-zone reversal and the development of an ensialic arc on the composite margin. After the subduction flip, a temporary release of compressive stress at c. 1.87 Ga led to the development of a retro-arc foreland basin on the downloaded Archean continental edge, forming the Aillik Group. Unlike previous models, a second arc is not envisaged. Instead, a compressive regime at c. 1.82 Ga is attributed to continued ensialic arc plutonism on the existing margin. The tectonic model for the Makkovikian orogeny proposed here is similar to that for the Ketilidian orogeny. Major- and trace-element analyses suggest that much of the magmatism in the Makkovik orogen results from post-accretionary ensialic arc activity, and that few vestiges remain of the original accreted volcanic arc. This pattern of arc accretion and intense post-accretion reworking is common to many accretionary orogens, such as the South American Andes and North American Cordillera.

Geochemistry of Sainte-Marguerite volcanic rocks: implications for the evolution of Silurian–Devonian volcanism in the Gaspé Peninsula

2008 ◽  
Vol 45 (1) ◽  
pp. 15-29 ◽  
Author(s):  
Alan D’hulst ◽  
Georges Beaudoin ◽  
Michel Malo ◽  
Marc Constantin ◽  
Pierre Pilote
Keyword(s):  
Lower Devonian ◽  
Volcanic Rocks ◽  
Magma Source ◽  
Volcanic Arc ◽  
Lower Silurian ◽  
Trace Element Signature ◽  
Arc Setting ◽  
Back Arc ◽  
Gaspe Peninsula ◽  
Gaspé Peninsula

The Lower Devonian Sainte-Marguerite volcanic rocks are part of a Silurian–Devonian volcanic sequence deposited between the Taconian and Acadian orogenies in the Gaspé Peninsula, Quebec, Canada. The Sainte-Marguerite unit includes basaltic and dacitic lava flows with calc-alkaline and volcanic-arc affinities. Such affinities are also recorded by the trace-element signature in Lower Silurian and most Lower Devonian volcanic units of the Gaspé Peninsula. However, most of the other Silurian–Devonian volcanic rocks occurring in the Gaspé Peninsula have been previously interpreted to have erupted in an intracontinental setting. A back-arc setting for the Gaspé Peninsula between the Taconian and Acadian orogenies could account for these subduction volcanic-arc signatures, though a metasomatized lithospheric mantle magma source, unrelated to subduction, cannot be excluded. Lower Silurian and Lower Devonian volcanic rocks in the central part of the Gaspé Peninsula show an arc affinity, whereas Upper Silurian and Lower to Middle Devonian volcanic rocks, located in the south and north of the Gaspé Peninsula, respectively, show a within-plate affinity. The Lower Devonian Archibald Settlement and Boutet volcanic rocks of the southern and northern Gaspé Peninsula, respectively, show a trend toward a within-plate affinity. This suggests that within-plate volcanism migrated from south to north through time in an evolving back-arc environment and that the subduction signature of Lower Silurian and Lower Devonian rocks results from a source that melted only under the central part of the Gaspé Peninsula.

A crustal section of an intra-oceanic island arc: The Late Jurassic-Early Cretaceous Guanajuato magmatic sequence, central Mexico

1992 ◽  
Vol 108 (1-3) ◽  
pp. 61-77 ◽  
Author(s):  
H LAPIERRE ◽  
L ORTIZ ◽  
W ABOUCHAMI ◽  
O MONOD ◽  
C COULON ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Late Jurassic ◽  
Oceanic Island ◽  
Island Arc ◽  
Central Mexico

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

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

<p>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- and S-type granite bodies were firstly identified in the West-Carpathian Tribeč 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.  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 Tribeč Mts gives zircon SHRIMP age 355 Ma and CHIME monazite age 342 Ma. The dating results of the Tribeč granites identified: (<strong>1</strong>) older Upper Devonian/Lower Mississippian subduction-related I-type tonalites (ca. 364-351 Ma), and (<strong>2</strong>) 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 Tribeč Mts. Variscan granitic rocks is partly corroborated by Hf isotopes from the dated zircons with εHf<sub>(t)</sub> = +3.5 ~ –2.4 for the older granites, and εHf<sub>(t)</sub> = –0.3 ~ –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).</p><p>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.</p>

Initiation of Iapetus subduction under Irish Avalonia

1997 ◽  
Vol 134 (2) ◽  
pp. 213-218 ◽  
Author(s):  
BRIAN McCONNELL ◽  
JOHN MORRIS
Keyword(s):  
Early Stage ◽  
Oceanic Lithosphere ◽  
Igneous Rocks ◽  
Trace Element Geochemistry ◽  
Plate Tectonic ◽  
Element Geochemistry ◽  
Volcanic Origin ◽  
Volcanic Arc ◽  
Lower Ordovician ◽  
Minimum Age

The Dowery Hill Member of metamorphosed basalt, dolerite and siltstone is here recognized as the oldest exposed volcanic unit of the Lower Ordovician Ribband Group, with a minimum age of early Arenig. Peperites and resedimented hydroclastic breccia demonstrate a volcanic origin for the basalts. The igneous rocks are tholeiitic, with a trace element geochemistry indicative of a subduction-modified fertile mantle source, which we interpret as recording an early stage of volcanic arc evolution. The member is therefore the oldest known component of the volcanic arc generated by subduction of Iapetus oceanic lithosphere under southeastern Ireland. Subduction started earlier than predicted by current plate tectonic models, and these should be re-evaluated.

Age and significance of radiolarian sediments within basic extrusives of the marginal basin Guevgueli Ophiolite (northern Greece)

1996 ◽  
Vol 133 (2) ◽  
pp. 127-136 ◽  
Author(s):  
Taniel Danelian ◽  
Alastair H. F. Robertson ◽  
Sarantis Dimitriadis
Keyword(s):  
Continental Margin ◽  
Late Jurassic ◽  
Active Continental Margin ◽  
Volcanic Glass ◽  
Northern Greece ◽  
The West ◽  
Volcanic Arc ◽  
Marginal Basin ◽  
Radiolarian Assemblage ◽  
Early Late

AbstractWell-preserved Radiolaria have been discovered in calcareous silt turbidites and mudstones intercalated with basic extrusives of the Guevgueli Ophiolite, northern Greece. The mudstones contain terrigenous silt, probably derived from adjacent continental basement of the Serbo-Macedonian and/or Paikon units. Volcanic quartz and rare volcanic glass were probably derived from an active continental margin arc (Paikon volcanic arc) to the west. The radiolarian sediments were deposited within fault-controlled hollows in the ophiolitic extrusives, and then covered by massive and pillowed extrusives. The radiolarian assemblage is indicative of an early Late Jurassic (Oxfordian) age, which therefore dates the genesis of the Guevgueli Ophiolite. Our data are consistent with the age of the intrusive Late Jurassic Fanos Granite, believed to be contemporaneous with the Guevgueli Ophiolite. In general, the Guevgueli and related ophiolites of northern Greece are thought to have formed within a transtensional intra-continental marginal basin, generated in response to oblique eastward subduction of older Tethyan oceanic crust (Almopias ocean).

Mafic and ultrapotassic rocks from the Canyon domain (central Grenville Province): geochemistry and tectonic implications

2012 ◽  
Vol 49 (2) ◽  
pp. 412-433 ◽  
Author(s):  
Carolina Valverde Cardenas ◽  
Aphrodite Indares ◽  
George Jenner
Keyword(s):  
Tectonic Setting ◽  
Source Region ◽  
Crustal Contamination ◽  
Granulite Facies ◽  
Grenville Province ◽  
Mafic Rocks ◽  
Isotopic Signatures ◽  
Late Evolution ◽  
Grenvillian Orogeny ◽  
Laurentian Margin

The Canyon domain and the Banded complex in the Manicouagan area of the Grenville Province preserve a record of magmatic activity from ∼1.4 to 1 Ga. This study focuses on 1.4–1.2 Ga mafic rocks and 1 Ga ultrapotassic dykes. Geochemistry and Sm–Nd isotopic signatures were used to constrain the origin of these rocks and evaluate the changing role of the mantle with time and tectonic setting from the late evolution of the Laurentian margin to the Grenvillian orogeny, in the Manicouagan area. The mafic rocks include layers inferred to represent flows, homogeneous bodies in mafic migmatite, and deformed dykes, all of which were recrystallized under granulite-facies conditions during the Grenvillian orogeny. In spite of the complexities inherent in these deformed and metamorphosed mafic rocks, we were able to recognize suites with distinctive geochemical and isotopic signatures. Integration of this data along with available ages is consistent with a 1.4 Ga continental arc cut by 1.2 Ga non-arc basalts derived from depleted asthenospheric mantle, with varied degrees of crustal contamination and inferred to represent magmatism in an extensional environment. The 1 Ga ultrapotassic dykes postdate the Grenvillian metamorphism. They are extremely enriched in incompatible elements, have negative Nb anomalies, relatively unradiogenic Sr-isotopic compositions (initial 87Sr/86Sr ~ 0.7040) and εNd –3 to –15. Some dykes have compositional characteristics consistent with derivation from the mantle, ruling out crustal contamination as a major process in their petrogenesis. The most likely source region for the ultrapotassic dykes is a metasomatized subcontinental lithospheric mantle, with thermal input from the asthenosphere in association with post-orogenic delamination.

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