A geochemical study of Nea-Kameni hyalodacites (Santorini Volcano, Aegean island arc). Inferences concerning the origin and effects of solfataras and magmatic evolution

1984 ◽  
Vol 20 (1-2) ◽  
pp. 41-54 ◽  
Author(s):  
Louis Briqueu ◽  
Joël R. Lancelot
Keyword(s):  
Island Arc ◽  
Magmatic Evolution ◽  
Aegean Island ◽  
Geochemical Study ◽  
Santorini Volcano

Submarine volcanic activity and giant amygdale formation along the Panama island arc as a precursor to 6000-year-old agate exploitation on Pedro González Island

2021 ◽  
pp. 1-16
Author(s):  
Stewart D Redwood ◽  
David M Buchs ◽  
David Edward Cavell
Keyword(s):  
Volcanic Activity ◽  
Bimodal Distribution ◽  
Island Arc ◽  
Early Miocene ◽  
Tool Manufacture ◽  
Marine Deposits ◽  
Large Size ◽  
Hydrothermal Processes ◽  
Field Evidence ◽  
Geochemical Study

Abstract An extensive deposit of agate occurs in Pedro González Island in the Gulf of Panama. Previous archaeological research showed that the agate was exploited between 6200 and 5600 cal BP to make stone tools found at the oldest known Preceramic human settlement in the Pearl Island archipelago. We constrain here the origin and geological context of the agate through a geological and geochemical study of the island. We show that it includes primary volcanic breccias, lavas, and tuffaceous marine deposits with sedimentary conglomerates and debris flow deposits, which we define as the Pedro González Formation. This formation records submarine to subaerial volcanic activity along an island arc during the Oligo-Miocene, confirming previous regional models that favour progressive emergence of the isthmus in the early Miocene. The igneous rocks have an extreme tholeiitic character that is interpreted to reflect magmatic cessation in eastern Panama during the early Miocene. The agate is hosted in andesitic lavas in unusually large amygdales up to 20–40 cm in diameter, as well as small amygdales (0.1–1.0 cm) in a bimodal distribution, and in veins. The large size of the agates made them suitable for tool manufacture. Field evidence suggests that the formation of large amygdales resulted from subaqueous lava–sediment interaction, in which water released from unconsolidated tuffaceous deposits at the base of lava flows rose through the lavas, coalesced, and accumulated below the chilled lava top, with subsequent hydrothermal mineralization. These amygdales could therefore be regarded as an unusual result of combined peperitic and hydrothermal processes.

scholarly journals A Detailed Geochemical Study of Island Arc Crust: the Talkeetna Arc Section, South–Central Alaska

2006 ◽  
Vol 47 (6) ◽  
pp. 1051-1093 ◽  
Author(s):  
ANDREW R. GREENE ◽  
SUSAN M. DeBARI ◽  
PETER B. KELEMEN ◽  
JUREK BLUSZTAJN ◽  
PETER D. CLIFT
Keyword(s):  
Island Arc ◽  
South Central ◽  
Geochemical Study

scholarly journals Late-devonian sakhara dunite-clinopiroxenite-gabbro complex (East Magnitogorsk zone, South Urals): petrological-mineralogical features and geodynamic setting

2021 ◽  
Vol 7 ◽  
pp. 40-53
Author(s):  
T.N. Surin
Keyword(s):  
Regional Analysis ◽  
Island Arc ◽  
Geodynamic Setting ◽  
South Urals ◽  
Magmatic Evolution ◽  
The South ◽  
The Urals ◽  
Platinum Belt ◽  
The Moment ◽  
In The Beginning

The relevance of the work is caused by necessary regional analysis of magmatic evolution of the East Magnitogorsk belt and refnement of ideas on geodynamics of the South Urals. The geology and petrochemical-mineralogical features of the Sakhara dunite-clinopyroxenite-gabbro complex in the South Urals are characterized in the paper. Its late Frasnian age is substantiated. The composition of olivine, clinopyroxene and chromite in rocks of the complex are determined. The restite nature of dunites is proved. It is shown that rocks of the complex are similar to those of the Urals platinum belt and belong to Ural-Alaskan type. It is concluded that the complex formed in island-arc geodynamic setting and in the beginning of the formation of a mature island arc. The location of massifs of the complex is an additional argument in favor of a western dip (in the present-day coordinates) of a subduction paleozone at the moment of its formation. Crystallization diferentiation was a leading mechanism of petrogenesis of rocks of the complex.

Formation of heterogeneous magmatic series beneath North Santorini, South Aegean island arc

Lithos ◽  
2009 ◽  
Vol 110 (1-4) ◽  
pp. 20-36 ◽  
Author(s):  
J.C. Bailey ◽  
E.S. Jensen ◽  
A. Hansen ◽  
A.D.J. Kann ◽  
K. Kann
Keyword(s):  
Island Arc ◽  
Aegean Island

scholarly journals Protolith Oceanic Island Arc dari Granitoid Tipe M dan I di Karangsambung, Kebumen, Jawa Tengah

2019 ◽  
Vol 20 (4) ◽  
pp. 249
Author(s):  
Chusni Ansori ◽  
Shaban Godang ◽  
Defry Hastria ◽  
Isyqi Isyqi
Keyword(s):  
Field Studies ◽  
Oceanic Island ◽  
Island Arc ◽  
Rock Fragments ◽  
Geochemical Study ◽  
Mid Ocean Ridge ◽  
Granitoid Rocks ◽  
Ocean Ridge ◽  
Mantle Magma ◽  
Carbonatite Magma

Granitoid rocks which found at Luk Ulo melange complex as rock fragments with  pale gray colour and faneritic texture. Petrogenesis and geotectonic of the granitoid is under debate. Some geologists consider as plagiogranite, which is formed from the Mid Ocean-ridge (MOR); or leucogranite which is formed from continental collision, and others argue as arc-related granitoid type.The field studies ware carried out on 5 (five) tracks around Luk Ulo River and 1 (one) track at Lokidang River. The pale grey Karangsambung granitoid is composed of the mainly  K-feldspar (34-55%), plagioclase (10-25%) and quartz (25-35%), and chemically contains SiO2 (61.25 - 66.06%); Al2O3 (13.94 – 14.61%), K2O (2.53 - 4.00%), Na2O (3.42 - 4.10%), CaO (2.32 - 4.76%), Fe2O3 total (5.85 – 8.71%), MgO (0.98 – 1.97%). The granitoid is M- and I-type that were formed at 760o - 800o C with a depth of about 20-30 km, resulting from the differentiation of magma from a fragment origin of the K-enriched oceanic island arc originating from drifting of the IAB fragment. The sample of basalt 17D has a relatively high of Nb/Ta ratio (20), low Rb (<2 ppm), low Ba (17 ppm), and is interpreted as interacting with MORB mantle magma containing rutile-melt;whereas quartz monzonite (17A) has a relatively low of Zr/Sm ratio (3.86), which is indicated to have been contaminated by a carbonatite magma. The spidergram pattern of mantle metagabbro (sample no. 13) similar with the basalt from IAB-Bransfield Strait (Antarctica). Results of a comprehensive geochemical study proposes that the current condition of the Karangsambung zone is part of geotectonic of ACM-Eurasia, that composed of a combination of four rock fragments, i.e. (a) the rocks which sourced from IAB fragments, (b) mantle MORB, (c) continental crust from the origin of ACM-Eurasia, (d) the origin fragment from carbonatite magma.Keyword: Luk Ulo Melange Complex, pale grey granitoid, Island-arc granitoid, M  and I-type granitoid

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