scholarly journals Kuroko deposits and related back-arc volcanism in the Hokuroku district

2013 ◽  
Vol 119 (Supplement) ◽  
pp. S168-S179 ◽  
Author(s):  
Ryoichi Yamada ◽  
Takeyoshi Yoshida
Keyword(s):  
Arc Volcanism ◽  
Back Arc ◽  
Kuroko Deposits

Age, chemistry, and tectonic setting of Miramichi terrane (Early Paleozoic) volcanic rocks, eastern and east-central Maine, USA

2021 ◽  
Vol 57 ◽  
pp. 239-273
Author(s):  
Allan Ludman ◽  
Christopher McFarlane ◽  
Amber T.H. Whittaker
Keyword(s):  
New Brunswick ◽  
Subduction Zone ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Calc Alkaline ◽  
East Central ◽  
Arc Volcanism ◽  
Middle Ordovician ◽  
Volcanic Suite ◽  
Back Arc

Volcanic rocks in the Miramichi inlier in Maine occur in two areas separated by the Bottle Lake plutonic complex: the Danforth segment (Stetson Mountain Formation) north of the complex and Greenfield segment to the south (Olamon Stream Formation). Both suites are dominantly pyroclastic, with abundant andesite, dacite, and rhyolite tuffs and subordinate lavas, breccias, and agglomerates. Rare basaltic tuffs and a small area of basaltic tuffs, agglomerates, and lavas are restricted to the Greenfield segment. U–Pb zircon geochronology dates Greenfield segment volcanism at ca. 469 Ma, the Floian–Dapingian boundary between the Lower and Middle Ordovician. Chemical analyses reveal a calc-alkaline suite erupted in a continental volcanic arc, either the Meductic or earliest Balmoral phase of Popelogan arc activity. The Maine Miramichi volcanic rocks are most likely correlative with the Meductic Group volcanic suite in west-central New Brunswick. Orogen-parallel lithologic and chemical variations from New Brunswick to east-central Maine may result from eruptions at different volcanic centers. The bimodal Poplar Mountain volcanic suite at the Maine–New Brunswick border is 10–20 myr younger than the Miramichi volcanic rocks and more likely an early phase of back-arc basin rifting than a late-stage Meductic phase event. Coeval calc-alkaline arc volcanism in the Miramichi, Weeksboro–Lunksoos Lake, and Munsungun Cambrian–Ordovician inliers in Maine is not consistent with tectonic models involving northwestward migration of arc volcanism. This >150 km span cannot be explained by a single east-facing subduction zone, suggesting more than one subduction zone/arc complex in the region.

Accretion tectonics in northern Eritrea revealed by remotely sensed imagery

1993 ◽  
Vol 130 (2) ◽  
pp. 177-190 ◽  
Author(s):  
S. A. Drury ◽  
S. M. Berhe
Keyword(s):  
Remotely Sensed ◽  
Ductile Deformation ◽  
Low Grade ◽  
Arc Volcanism ◽  
Remotely Sensed Imagery ◽  
Pan African ◽  
Major Fault ◽  
High Level ◽  
Back Arc ◽  
Layered Sequence

AbstractNew details from remotely sensed images of the structure and disposition of broad lithological variations in the Pan-African of northern Eritrea are discussed in the context of accretionary tectonics. The recognition of major north-south structural discontinuities allows the area to be divided into three discrete terranes with apparently different histories of deformation and metamorphism, magmagenesis and sedimentation. The central Hagar Terrane is dominated by large ultramafic masses with a volcano-sedimentary layered sequence, and shows the effects of major sinistral transpression and lateral expulsion. It is bounded to the west by a major fault, the Barka suture, and abuts the older Barka Terrane that comprises metasediments with evidence for polyphase ductile deformation and pre-kinematic dyke emplacement. The Hagar Terrane is thrust against the eastern Nacfa Terrane, which is dominated by low-grade calc-alkaline metavolcanics and immature volcanoclastic sediments intruded by syn-kinematic plutons. These units are pre-dated by an earlier high-grade basement and post-dated by high-level unmetamorphosed silicic volcanics and redbed sediments. The complex is suggested to have been assembled by oblique accretion from the southeast after arc volcanism in the Nacfa Terrane and back-arc extension in the Hagar Terrane ended with the cease of subduction.

From arc evolution to arc-continent collision: Late Cretaceous–middle Eocene geology of the Eastern Pontides, northeastern Turkey

2019 ◽  
Vol 131 (11-12) ◽  
pp. 1889-1906 ◽  
Author(s):  
Özgür Kandemir ◽  
Kenan Akbayram ◽  
Mehmet Çobankaya ◽  
Fatih Kanar ◽  
Şükrü Pehlivan ◽  
...  
Keyword(s):  
Late Cretaceous ◽  
Middle Eocene ◽  
Structural Data ◽  
Massive Sulfide ◽  
Arc Volcanism ◽  
Eastern Pontides ◽  
The North ◽  
Fold And Thrust Belt ◽  
Volcaniclastic Rocks ◽  
Back Arc

Abstract The Eastern Pontide Arc, a major fossil submarine arc of the world, was formed by northward subduction of the northern Neo-Tethys lithosphere under the Eurasian margin. The arc’s volcano-sedimentary sequence and its cover contain abundant fossils. Our new systematical paleontological and structural data suggest the Late Cretaceous arc volcanism was initiated at early-middle Turonian and continued uninterruptedly until the end of the early Maastrichtian, in the northern part of the Eastern Pontides. We measured ∼5500-m-thick arc deposits, suggesting a deposition rate of ∼220 m Ma–1 in ∼25 m.y. We have also defined four different chemical volcanic episodes: (1) an early-middle Turonian–Santonian mafic-intermediate episode, (2) a Santonian acidic episode; when the main volcanic centers were formed as huge acidic domes-calderas comprising the volcanogenic massive sulfide ores, (3) a late Santonian–late Campanian mafic-intermediate episode, and (4) a late Campanian–early Maastrichtian acidic episode. The volcaniclastic rocks were deposited in a deepwater extensional basin until the late Campanian. Between late Campanian and early Maastrichtian, intra-arc extension resulted in opening of back-arc in the north, while the southern part of the arc remained active and uplifted. The back-arc basin was most probably connected to the Eastern Black Sea Basin. In the back-arc basin, early Maastrichtian volcano-sedimentary arc sequence was transitionally overlain by pelagic sediments until late Danian suggesting continuous deep-marine conditions. However, the subsidence of the uplifted-arc-region did not occur until late Maastrichtian. We have documented a Selandian–early Thanetian (57–60 Ma) regional hiatus defining the closure age of the İzmir-Ankara-Erzincan Ocean along the Eastern Pontides. Between late Thanetian and late Lutetian synorogenic turbidites and postcollisional volcanics were deposited. The Eastern Pontide fold-and-thrust belt started to form at early Eocene (ca. 55 Ma) and thrusting continued in the post-Lutetian times.

Chapter 3.2a Bransfield Strait and James Ross Island: volcanology

2021 ◽  
pp. M55-2018-58
Author(s):  
John L. Smellie
Keyword(s):  
Active Volcano ◽  
Deception Island ◽  
Arc Volcanism ◽  
Bransfield Strait ◽  
Volcanic Group ◽  
Tectonic Environment ◽  
James Ross Island ◽  
Eruptive Environment ◽  
Back Arc ◽  
Slab Window

AbstractFollowing more than 25 years of exploration and research since the last regional appraisal, the number of known subaerially exposed volcanoes in the northern Antarctic Peninsula region has more than trebled, from less than 15 to more than 50, and that total must be increased at least three-fold if seamounts in Bransfield Strait are included. Several volcanoes remain unvisited and there are relatively few detailed studies. The region includes Deception Island, the most prolific active volcano in Antarctica, and Mount Haddington, the largest volcano in Antarctica. The tectonic environment of the volcanism is more variable than elsewhere in Antarctica. Most of the volcanism is related to subduction. It includes very young ensialic marginal basin volcanism (Bransfield Strait), back-arc alkaline volcanism (James Ross Island Volcanic Group) and slab-window-related volcanism (seamount offshore of Anvers Island), as well as volcanism of uncertain origin (Anvers and Brabant islands; small volcanic centres on Livingston and Greenwich islands). Only ‘normal’ arc volcanism is not clearly represented, possibly because active subduction virtually ceased at c. 4 Ma. The eruptive environment for the volcanism varied between subglacial, marine and subaerial but a subglacial setting is prominent, particularly in the James Ross Island Volcanic Group.

A highly diverse silicic end member of a bimodal magma suite formed in an active continental back arc, Okinawa Trough

2021 ◽  
Author(s):  
Arran Murch ◽  
Kenichiro Tani ◽  
Takashi Sano ◽  
Shigekazu Yoneda
Keyword(s):  
Magma Mixing ◽  
Okinawa Trough ◽  
Fractional Crystallisation ◽  
Chemical Diversity ◽  
Crustal Assimilation ◽  
Arc Volcanism ◽  
The North ◽  
The Okinawa Trough ◽  
Formation Conditions ◽  
Back Arc

<p>The Okinawa Trough (OT) is an incipient continental back-arc basin that extends from Kyushu in the north to Taiwan in the south. The Okinawa Trough can be split in to three segments, the Northern (NOT), Middle (MOT), and Southern (SOT) with active back-arc volcanism restricted to volcanic centres located in en-echelon grabens the MOT and SOT. Previous studies have shown magmatism in the OT is bimodal (basaltic to rhyolitic), with at least two types of silicic melts inferred to form through pure fractional crystallisation from basalt and by fractional crystallisation along with minor crustal assimilation (Shinjo and Kato, 2000).</p><p>Here we present petrological descriptions, along with major, trace element and Sr–Nd isotopic data for 75 silicic end member samples recovered as both lava and pumice, collected during the R/V Sonne HYDROMIN1 and 2 cruises in 1988 and 1990, respectively. Samples were dredged from various seafloor knolls and ridges located in the Io and Iheya grabens and from Izena Hole in the MOT, and from a single volcanic ridge in the Yaeyama graben and a single isolated knoll in the SOT.</p><p>Results show a chemically highly diverse silicic end member magmas, with at least four identifiable groups based on differences in the degree of enrichment of incompatible elements (LREE, K, Rb, Ba, etc.). Each group contains at least one dense lava sample suggesting the chemical diversity is a primary feature of magmatism in the Okinawa Trough rather than a result of the floating in of pumiceous material from various locations.</p><p>Using petrological descriptions and the chemistry of samples along with MELTS modelling we plan to calculate magma formation conditions and identify any evidence of magma mixing or crustal assimilation. In doing so we hope to provide a model to explain the diversity of silicic magma chemistry in the MOT and SOT.</p><p> </p><p>Shinjo, R., and Kato, Y. (2000). Geochemical constraints on the origin of bimodal magmatism at the Okinawa Trough, an incipient back-arc basin. Lithos 54, 117–137. doi:10.1016/S0024-4937(00)00034-7.</p>

FARALLON SLAB UPLIFT AND BACK-ARC VOLCANISM ALONG THE YELLOWSTONE ADAKITE HOT SPOT TRACK

2017 ◽  
Author(s):  
Victor E. Camp ◽  
◽  
Martin E. Ross ◽  
Robert Duncan ◽  
David L. Kimbrough
Keyword(s):  
Hot Spot ◽  
Arc Volcanism ◽  
Back Arc

scholarly journals Fauna of the Kemp Caldera and its upper bathyal hydrothermal vents (South Sandwich Arc, Antarctica)

2019 ◽  
Vol 6 (11) ◽  
pp. 191501 ◽  
Author(s):  
Katrin Linse ◽  
Jonathan T. Copley ◽  
Douglas P. Connelly ◽  
Robert D. Larter ◽  
David A. Pearce ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Hydrothermal Vents ◽  
Hydrothermal Activity ◽  
Island Arc ◽  
Arc Volcanism ◽  
Faunal Assemblages ◽  
Ocean Ridges ◽  
Island Arc Volcanism ◽  
Sulfur Oxidizing ◽  
Back Arc

Faunal assemblages at hydrothermal vents associated with island-arc volcanism are less well known than those at vents on mid-ocean ridges and back-arc spreading centres. This study characterizes chemosynthetic biotopes at active hydrothermal vents discovered at the Kemp Caldera in the South Sandwich Arc. The caldera hosts sulfur and anhydrite vent chimneys in 1375–1487 m depth, which emit sulfide-rich fluids with temperatures up to 212°C, and the microbial community of water samples in the buoyant plume rising from the vents was dominated by sulfur-oxidizing Gammaproteobacteria. A total of 12 macro- and megafaunal taxa depending on hydrothermal activity were collected in these biotopes, of which seven species were known from the East Scotia Ridge (ESR) vents and three species from vents outside the Southern Ocean. Faunal assemblages were dominated by large vesicomyid clams, actinostolid anemones, Sericosura sea spiders and lepetodrilid and cocculinid limpets, but several taxa abundant at nearby ESR hydrothermal vents were rare such as the stalked barnacle Neolepas scotiaensis . Multivariate analysis of fauna at Kemp Caldera and vents in neighbouring areas indicated that the Kemp Caldera is most similar to vent fields in the previously established Southern Ocean vent biogeographic province, showing that the species composition at island-arc hydrothermal vents can be distinct from nearby seafloor-spreading systems. δ 13 C and δ 15 N isotope values of megafaunal species analysed from the Kemp Caldera were similar to those of the same or related species at other vent fields, but none of the fauna sampled at Kemp Caldera had δ 13 C values, indicating nutritional dependence on Epsilonproteobacteria, unlike fauna at other island-arc hydrothermal vents.

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