scholarly journals Directional change during a M iocene R ‐ N geomagnetic polarity reversal recorded by mafic lava flows, S heep C reek R ange, north central N evada, USA

2017 ◽  
Vol 18 (9) ◽  
pp. 3470-3488 ◽  
Author(s):  
S. W. Bogue ◽  
J. M. G. Glen ◽  
N. A. Jarboe
Keyword(s):  
Lava Flows ◽  
Polarity Reversal ◽  
Mafic Lava ◽  
North Central ◽  
Directional Change ◽  
Geomagnetic Polarity

scholarly journals Extremely rapid directional change during Matuyama-Brunhes geomagnetic polarity reversal

2014 ◽  
Vol 199 (2) ◽  
pp. 1110-1124 ◽  
Author(s):  
Leonardo Sagnotti ◽  
Giancarlo Scardia ◽  
Biagio Giaccio ◽  
Joseph C. Liddicoat ◽  
Sebastien Nomade ◽  
...  
Keyword(s):  
Polarity Reversal ◽  
Directional Change ◽  
Geomagnetic Polarity

scholarly journals Evidence of active magmatic rifting at the Ma’Alalta volcanic field (Afar, Ethiopia)

2021 ◽  
Vol 83 (6) ◽  
Author(s):  
Gianmaria Tortelli ◽  
Anna Gioncada ◽  
Carolina Pagli ◽  
Mauro Rosi ◽  
Laura De Dosso ◽  
...  
Keyword(s):  
Seismic Data ◽  
Volcanic Field ◽  
Lava Flows ◽  
Magmatic Activity ◽  
Magma Storage ◽  
Plumbing System ◽  
Mafic Lava ◽  
Cinder Cones ◽  
Mafic Rocks ◽  
Seismic Networks

AbstractDuring continental rifting, strain and magmatism are believed to localize to narrow magmatic segments, while the rift margin is progressively abandoned. We integrate volcanological, geochemical, petrological and seismic data from the Ma’Alalta volcanic field (MVF) near the western margin of Afar, to show that the MVF is an active magmatic segment. Magmatism in MVF initiated with lava flows and large-volume, caldera-forming ignimbrites from a central edifice. However, the most recent magmatic activity shifted towards mafic lava fields, cinder cones and obsidian-rich silicic domes erupted from vents aligned NNW-SSE, defining a ~ 35-km-long magmatic segment. Along the same area, a NNW-SSE alignment of earthquakes was recorded by two local seismic networks (2005–2009 and 2011–2013). The geochemistry of the mafic rocks is similar to those of nearby axial volcanoes. Inferred magma storage depth from mineral geobarometry shows that a shallow, silicic chamber existed at ~ 5-km depth below the stratovolcano, while a stacked plumbing system with at least three magma storage levels between 9 and 24 km depth fed the recent basalts. We interpret the wide set of observations from the MVF as evidence that the area is an active magmatic segment, showing that localised axial extension can be heavily offset towards the rift margin.

Chemical evolution and periodic eruption of mafic lava flows in the west moat of Long Valley Caldera, California

1994 ◽  
Vol 99 (B10) ◽  
pp. 19829-19842 ◽  
Author(s):  
T. A. Vogel ◽  
T. B. Woodburne ◽  
J. C. Eichelberger ◽  
P. W. Layer
Keyword(s):  
Chemical Evolution ◽  
Lava Flows ◽  
The West ◽  
Mafic Lava ◽  
Long Valley Caldera ◽  
Long Valley

A major Aphebian–Helikian unconformity within the Central Mineral Belt of Labrador: definition of new groups and metallogenic implications

1978 ◽  
Vol 15 (12) ◽  
pp. 1954-1966 ◽  
Author(s):  
W. R. Smyth ◽  
B. E. Marten ◽  
A. B. Ryan
Keyword(s):  
Volcanic Rocks ◽  
Lava Flows ◽  
Grenville Province ◽  
Mafic Lava ◽  
Polyphase Deformation ◽  
Mineral Belt ◽  
Group A ◽  
Grenvillian Orogeny ◽  
Definition Of ◽  
Granitic Batholith

The Central Mineral Belt of Labrador consists of a belt of supracrustal rocks that occupies the northern foreland region of the Grenville Province of the Canadian Shield. Recent mapping in this belt has shown that the Proterozoic Croteau Group consists of two distinct sequences separated by an observed angular unconformity. It is therefore proposed that the name Croteau Group be abandoned and that the lower, Aphebian, marine sequence of sandstone, dolostone, slate, argillite, and mafic volcanic rocks be named the Moran Lake Group and that the upper, Helikian, continental sequence of conglomerate, tuffaceous sandstone, and a calc-alkalic volcanic assemblage be named the Bruce River Group.The Moran Lake Group underwent polyphase deformation, which has been assigned to the Hudsonian Orogeny, prior to deposition of the Bruce River Group around 1474 Ma. The Bruce River Group was intruded by a large granitic batholith, the Otter Lake Granite, for which a preliminary Rb–Sr isochron age of 1445 Ma has been obtained; this age correlates with the Elsonian magmatic event, an event well documented in northern Labrador. The Seal Lake Group, a Neohelikian (1278 Ma) sequence of quartzites, conglomerates, and intercalated mafic lava flows, was unconformably deposited upon the Bruce River Group and the Otter Lake Granite. During the Grenvillian Orogeny, the Bruce River and Seal Lake Groups were deformed together into a major easterly trending syncline. Deformation and metamorphism decrease across these groups to the north.The Bruce River Group forms part of the Labrador uranium area and hosts 14 known uranium occurrences. Occurrences are concentrated in the basal sandstones and conglomerates of the group, above the Aphebian–Helikian unconformity, and in ignimbrites and acid tuffs near the top of the group. No uranium occurrences are known from the Moran Lake Group except in fault-related fractures below the unconformity.

scholarly journals Refined magnetostratigraphic position of the Shyrokyne unit in loess sequences from Central Ukraine

2019 ◽  
Vol 28 (2) ◽  
pp. 301-312
Author(s):  
D. V. Hlavatskyi
Keyword(s):  
Transition Zone ◽  
Careful Analysis ◽  
Magnetic Polarity ◽  
Polarity Reversal ◽  
Preliminary Results ◽  
Soil Complex ◽  
Lowermost Part ◽  
Geomagnetic Polarity

The youngest geomagnetic polarity reversal, the Matuyama–Brunhes boundary (MBB), which occurred 780 kyr ago, is a “golden spike” in the age calibration of sediment sequences. The use of palaeomagnetic method as a stratigraphic tool in the study of loess sequences from Ukraine originated some 50 years ago. One major problem in using the available data is the contradictory position of the MBB in different stratigraphic units, which affected historic evolution of thechronostratigraphic models of the Quaternary in Ukraine. The most important units in this regard are the Shyrokyne and Martonosha units, in which the MBB had been defined most often. This paper provides the careful analysis of the previous magnetostratigraphic data and new preliminary results from key loess-palaeosol sections in Central Ukraine. Shyrokyne palaeosol complex in four loesspalaeosol sections located in the Middle Dnieper and Podolia regions has been palaeomagnetically studied. It is shown that the transition zone of the Matuyama–Brunhes palaeomagnetic reversal is most likely located at the base of the soil complex. In the Vyazivok section the MBB has been found in the lowermost part of Shyrokyne palaeosol sh1. Preliminary palaeomagnetic studies of theStari Kaydaky section reveal that the MBB cannot be defined at least above sh1 subunit. Medzhybizh and Holovchyntsi sections were deposited after the Matuyama–Brunhes reversal; however, the palaeomagnetic informativeness of the part of studied strata is doubtful. Magnetostratigraphic position of the Shyrokyne unit below the MBB in some previous studies is explained by methodological reasons and inconsistent chronostratigraphic models. The paper substantiates that normal magnetic polarity zone in the Pryazovya loess and upper part of the Shyrokyne soil is not associated with the influence of secondary processes on the palaeomagnetic record.

Sign in / Sign up

Export Citation Format

Share Document