Petrochemistry of Paleozoic spilites of the eastern Alps (Austria)

1973 ◽  
Vol 110 (1) ◽  
pp. 19-28 ◽  
Author(s):  
J. Loeschke
Keyword(s):  
Low Temperature ◽  
Fractional Crystallization ◽  
Basaltic Magma ◽  
Eastern Alps ◽  
Pillow Lavas ◽  
Secondary Origin ◽  
External Sources ◽  
Primary Minerals

SummaryIn the Karawanken Mountains (SE Austria) spilites (pillow lavas and sills) are found intercalated in a sequence of Paleozoic slates and graywackes. The petrogenesis of these spilites is interpreted as follows: The pillow lavas and sills consolidated as mugearites and hawaiites, which were derived from an alkali olivine-basaltic magma by fractional crystallization. Under low temperature metamorphic conditions water entered into the rocks predominantly from external sources. The primary minerals (Na-Ca plagioclase, pyroxene and glass) were thus replaced either partially or completely by minerals characteristic of spilites (albite, chlorite, epidote and others). The spilites analysed are of secondary origin. They are compared with spilites and basalts of other (continental and oceanic) areas.

Stratigraphy and eruptive history of the Late Devonian Mount Pleasant Caldera Complex, Canadian Appalachians

1997 ◽  
Vol 134 (1) ◽  
pp. 17-36 ◽  
Author(s):  
S. R. McCUTCHEON ◽  
H. E. ANDERSON ◽  
P. T. ROBINSON
Keyword(s):  
Fractional Crystallization ◽  
Basaltic Magma ◽  
Late Devonian ◽  
Crustal Material ◽  
Basaltic Rocks ◽  
Stratigraphic Subdivision ◽  
Mount Pleasant ◽  
History Of ◽  
High Level ◽  
Mafic Lavas

Stratigraphic, petrographic and geochemical evidence indicate that the volcano-sedimentary rocks of the Late Devonian Piskahegan Group, located in the northern Appalachians of southwestern New Brunswick, represent the eroded remnants of a large epicontinental caldera complex. This complex – the Mount Pleasant Caldera – is one of few recognizable pre-Cenozoic calderas and is divisible into Exocaldera, Intracaldera and Late Caldera-Fill sequences. The Intracaldera Sequence comprises four formations that crop out in a triangular-shaped area and includes: thick ash flow tuffs, thick sedimentary breccias that dip inward, and stocks of intermediate to felsic composition that intrude the volcanic pile or are localized along caldera-margin faults. The Exocaldera Sequence contains ash flow tuffs, mafic lavas, alluvial redbeds and porphyritic felsic lavas that comprise five formations. The Late Caldera-Fill Sequence contains rocks that are similar to those of the outflow facies and comprises two formations and two minor intrusive units. Geochemical and mineralogical data support the stratigraphic subdivision and indicate that the basaltic rocks are mantle-derived and have intraplate chemical affinities. The andesites were probably derived from basaltic magma by fractional crystallization and assimilation of crustal material. The various felsic units are related by episodes of fractional crystallization in a high-level, zoned magma chamber. Fractionation was repeatedly interrupted by eruption of material from the roof zone such that seven stages of caldera development have been identified. The genesis of the caldera is related to a period of lithospheric thinning that followed the Acadian Orogeny in the northern Appalachians.

scholarly journals Turning the Orogenic Switch: Slab‐Reversal in the Eastern Alps Recorded by Low‐Temperature Thermochronology

2021 ◽  
Vol 48 (6) ◽  
Author(s):  
Paul R. Eizenhöfer ◽  
Christoph Glotzbach ◽  
Lukas Büttner ◽  
Jonas Kley ◽  
Todd A. Ehlers
Keyword(s):  
Low Temperature ◽  
Eastern Alps

Neogene Exhumation History along TRANSALP: Insights from Low Temperature Thermochronology and Thermo-Kinematic Models

2020 ◽  
Author(s):  
Paul R. Eizenhöfer ◽  
Christoph Glotzbach ◽  
Lukas Büttner ◽  
Jonas Kley ◽  
Todd A. Ehlers
Keyword(s):  
Low Temperature ◽  
Kinematic Model ◽  
Eastern Alps ◽  
European Alps ◽  
Eastern European ◽  
Tauern Window ◽  
The North ◽  
Late Neogene ◽  
Kinematic Models ◽  
Exhumation Rates

<p>Many convergent orogens such as the eastern European Alps display an asymmetric doubly-vergent wedge geometry. Loci of deepest exhumation are located above the overriding retro-wedge, whereas increased fault activity occurs in the pro-wedge on the subducting plate. The main drainage divide separates steeper from more gently sloping topography on the two wedges of different critical taper. We performed apatite and zircon (U-Th)/He analyses densely spaced along the TRANSALP geophysical transect in combination with thermo-kinematic models based on cross-section balancing. Our new low temperature thermochronology data and thermo-kinematic model results underline (i) deepest levels of exhumation across the Tauern Window until the Pliocene and (ii) higher Late Neogene exhumation rates south of the Periadriatic Fault relative to the north, while seismic activity is focussed across the Southern Alps. Our proposed mantle-to-surface link positions the retro-wedge north of the Periadriatic Fault subsequent to subduction polarity reversal during continental collision. Present-day drainage divide migration trends and imaged locations of mantle-lithospheric slabs beneath TRANSALP suggest ongoing, slow slab reversal since Adriatic indentation in the Eastern Alps. </p>

Radial Variation of Magnetic Properties in Submarine Pillow Basalt

1975 ◽  
Vol 12 (12) ◽  
pp. 1959-1969 ◽  
Author(s):  
Patrick J. C. Ryall ◽  
J. M. Ade-Hall
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Low Temperature ◽  
Sea Water ◽  
Radial Variation ◽  
Cooling History ◽  
Pillow Basalt ◽  
Ridge Crest ◽  
Pillow Lavas ◽  
Mid Atlantic Ridge

A detailed study has been made of the magnetic properties of four pillow lavas of differing ages from the Mid-Atlantic Ridge crest at 45°N. The pillows show radial variations in grain size and concentration of titanomagnetite due to the initial cooling history, and radial variation in their degree of titanomagnetite oxidation due to low temperature alteration by sea-water. The degree of titanomagnetite alteration not only increases from the interior to the exterior of the pillows, it also increases from the youngest to the oldest. Radial variation in NRM intensity results in average values for the pillows of as little as half the values for the freshest parts. The direction of the original NRM has been maintained throughout the alteration.

Contribution a l'etude du volcanisme de l'arc des Nouvelles-Hebrides; caracterisation de deux series magmatiques de l'ile d'Erromango

1979 ◽  
Vol S7-XXI (5) ◽  
pp. 631-641 ◽  
Author(s):  
G. Marcelot ◽  
C. Lefevre ◽  
P. Maillet ◽  
R. C. Maury
Keyword(s):  
Fractional Crystallization ◽  
Basaltic Magma ◽  
Island Arc ◽  
Calc Alkaline ◽  
Early Stages ◽  
New Hebrides ◽  
Volcanic Series

Abstract The volcanic series of Mt Rantop and Robertson's Thumb, Erromango Island, New Hebrides, formed by fractional crystallization of orogenic basaltic magma of near-island-arc tholeiitic type. Differentiation was controlled mainly by separation of plagioclase, olivine and clinopyroxene. The Mt Rantop series is predominantly tholeiitic (plagioclase at the liquidus, late appearance of magnetite, pigeonite in microphenocrysts, and Fe and Ti remaining constant or increasing in the early stages of differentiation); those of Robertson's Thumb are mostly calc-alkaline (magnetite at the liquidus, late appearance of plagioclase, olivine quickly becoming unstable, orthopyroxene in phenocrysts and early decrease of Fe and Ti). The compositional differences reflect higher fO <sub>2</sub> and PH <sub>2</sub> O in Robertson's Thumb during fractional crystallization.

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