K-Ar geochronology results for the Grayback Hills quadrangle, Utah

2018 ◽  
Keyword(s):  
Ar Geochronology

K-Ar geochronology of new volcanic centers eruptions in the Kazbek region of the Great Caucasus

1999 ◽  
Vol 1 (6) ◽  
pp. 485-492
Author(s):  
I. V. Chernyshev ◽  
M. M. Arakelyants ◽  
V. A. Lebedev ◽  
S. N. Bubnov ◽  
Yu. V. Gol'tsman
Keyword(s):  
Ar Geochronology

No Yangtze River prior to the late Miocene: Evidence from detrital muscovite and K‐feldspar 40 Ar/ 39 Ar geochronology

2021 ◽  
Author(s):  
Xilin Sun ◽  
Yuntao Tian ◽  
K.F. Kuiper ◽  
Chang'an Li ◽  
Zengjie Zhang ◽  
...  
Keyword(s):  
Late Miocene ◽  
Yangtze River ◽  
Ar Geochronology

The Late Cretaceous Asteroussia event as recorded in the Cyclades: a potential key to Western Tethys tectonic evolution

2021 ◽  
Author(s):  
Sonia Yeung ◽  
Marnie Forster ◽  
Emmanuel Skourtsos ◽  
Gordon Lister
Keyword(s):  
Subduction Zone ◽  
Late Cretaceous ◽  
Ore Deposits ◽  
Western Tethys ◽  
Pressure Medium ◽  
Flat Slab Subduction ◽  
Extreme Extension ◽  
Metamorphic Core ◽  
Tectonic Slice ◽  
Ar Geochronology

<div> <p>The Cretaceous arc system formed during closure of West Tethys closure has long been a research focus for crustal geometry and associated ore deposits. Understanding the Africa-Europe motion across time is the key to its resolution. Evidence as to the time that Tethys subduction initiated is preserved in subduction accreted tectonic slices such as in the Gondwanan basement terranes on Ios, Cyclades, Greece. <sup>40</sup>Ar/<sup>39</sup>Ar geochronology in its granitoid basement and the structurally overlying garnet-mica schist tectonic slice identified a Late Cretaceous high pressure, medium temperature (HP–MP) metamorphic event. The timing and metamorphic conditions are comparable with geochronology and metamorphic conditions reported from other Cycladic islands. We suggest the northward extension of the Asteroussia crystalline terrane on Crete should therefore include the Ios basement tectonic slices, thus revising the regional geometry of the terrane stack. The northern part of the Hellenic terrane stack is overlain by individual Cycladic Eclogite-Blueschist terrane slices (e.g., on Ios) and the southern part is underplated by the tectonic units of the external Hellenides (Crete). To make such an architecture possible, we propose a 250-300 km southward jump of the subduction megathrust when the Ios basement terranes were accreted to the European terrane stack. Such a significant leap of the subduction megathrust supports a tectonic mode switch in which crust above the subduction zone was first subjected to shortening followed by a stretching event.  Accretion of the Asteroussia slices to the terrane stack likely commenced at or about ~38 Ma. During accretion, the already stretched and exhumed terranes of the Cycladic Eclogite-Blueschist Unit begun to thrust over the newly accreted Ios basement. The subduction jump had likely been accomplished by ~35 Ma, with rollback recommencing after a period of flat slab subduction followed by slab break off in the new subduction zone. This would allow explanation of the extreme extension that exhumed the Ios basement terrane, with the Asteroussia slices defining the core of the Ios metamorphic core complex, followed by the onset of Oligo-Miocene extension and accompanying magmatism in the Cyclades.</p> </div>

Ar/Ar geochronology of ultrahigh-pressure metamorphism in central China

Tectonics ◽  
1995 ◽  
Vol 14 (4) ◽  
pp. 994-1006 ◽  
Author(s):  
Bradley R. Hacker ◽  
Qingchen Wang
Keyword(s):  
Central China ◽  
Ultrahigh Pressure ◽  
Ultrahigh Pressure Metamorphism ◽  
Ar Geochronology

scholarly journals Exceptional Multi Stage Mineralization of Secondary Minerals in Cavities of Flood Basalts from the Deccan Volcanic Province, India

Minerals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 351 ◽  
Author(s):  
Berthold Ottens ◽  
Jens Götze ◽  
Ralf Schuster ◽  
Kurt Krenn ◽  
Christoph Hauzenberger ◽  
...  
Keyword(s):  
Lava Flows ◽  
Stage Iii ◽  
Deccan Volcanic Province ◽  
Flood Basalts ◽  
Time Intervals ◽  
Volcanic Province ◽  
Secondary Minerals ◽  
Large Size ◽  
Multi Stage ◽  
Ar Geochronology

Flood basalts of the Deccan Volcanic Province erupted between about 67.5 to 60.5 Ma ago and reached a thickness of up to 3500 m. The main part consists of compound and simple lava flows with a tholeiitic composition erupted within 500,000 years at about 65 Ma. Within the compound lava flows, vesicles and cavities are frequent. They are filled by secondary minerals partly of well development and large size. This study presents data on the secondary mineralization including detailed field descriptions, optical, cathodoluminescence and SEM microscopy, X-ray diffractometry, fluid inclusions, C and O isotope analyses, and Rb-Sr and K-Ar geochronology. The investigations indicate a multistage precipitation sequence with three main stages. During stage I clay minerals and subsurface filamentous fabrics (SFFs), of probably biogenic origin, formed after the lava flows cooled down near to the Earth’s surface. In stage II, first an assemblage of calcite (I) and zeolite (I) (including mordenite, heulandite, and stilbite) as well as plagioclase was overgrown by chalcedony, and finally a second calcite (II) and zeolite (II) generation developed by burial metamorphism by subsequent lava flows. Stage III is characterized by precipitation of a third calcite (III) generation together with powellite and apophyllite from late hydrothermal fluids. Rb-Sr and K-Ar ages of apophyllite indicate a large time span for stage III. Apophyllite formed within different time intervals from the Paleogene to the early Miocene even within individual lava flows at certain localities. From the Savda/Jalgaon quarry complex, ages cluster at 44–48 Ma and 25–28 Ma, whereas those from the Nashik area are 55–58 Ma and 21–23 Ma, respectively.

Geology, geochemistry and Ar–Ar geochronology of the Nangimali ruby deposit, Nanga Parbat Himalaya (Azad Kashmir, Pakistan)

2002 ◽  
Vol 21 (3) ◽  
pp. 265-282 ◽  
Author(s):  
A. Pêcher ◽  
G. Giuliani ◽  
V. Garnier ◽  
H. Maluski ◽  
A.B. Kausar ◽  
...  
Keyword(s):  
Nanga Parbat ◽  
Azad Kashmir ◽  
Ar Geochronology
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