2,139 research outputs found
When modern petrology meets advanced microstructural analysis
No full textWhen modern petrology meets advanced microstructural analysis
Spiess R.*1
, Festa V.2
& Tursi F.3
1
Dipartimento di Geoscienze, Università di Padova. 2
Dipartimento di Scienze della Terra e Geoambientali, Università
di Bari “Aldo Moro”. 3
Dipartimento di Scienze della Terra, Università di Torino.
Corresponding author email: [email protected]
Keywords: migmatites, clogged melt channels, garnet coalescence.
Petrology and microstructural analysis are inextricably linked together. The recent paper of Festa et al.
(2024) on garnet growth to large ellipsoidal crystals by coalescence within residual migmatitic metapelites is
a proof for the successful interaction of modern petrological modelling and advanced microstructural analysis.
The whole set of data (phase equilibrium thermodynamic modelling, EBSD analysis, EDS and BEX mapping,
micro-Raman analysis) obtained by this combined approach fit together like a puzzle. It defines a model
showing that melt extraction in a dynamic system stops when melt channels become clogged by coalescence
of peritectic phases carried along in anatectic melt migrating towards pull-apart structures, where the melt
with entrained garnet pooled as it was progressively squeezed out. The importance of deformation for melt
extraction is known since the basic work of Brown et al. (1995). The amount of decompression associated with
formation of extensional sites within rocks undergoing ductile deformation has been documented quantitatively
by Spiess et al. (2012).
Coalescence of garnet aggregates to large single crystals is invariably related to deformational rotation and
surface energy reduction of individual grains (Spiess et al., 2001). Whether coalescence finally results in large
single crystals or not depends on several factors. Of prime importance is the presence of a grain boundary
wetting fluid/melt. Static experiments conducted in a piston cylinder apparatus at 3 GPa confining pressure
and 1100°C show that any attempt to epitaxially grow single garnet crystals in platinum capsule, using a fine
pyrope powder surrounding a polished pyrope rod acting as seed, fails. The absence of a fluid-saturated system
prevents surface energy from becoming a driving force strong enough to crystallographically isorient the
garnet crystals growing around the seed.
In the migmatite studied by Festa et al. (2024) rotation of coalescing garnet grains is documented by
EBSD mapping. EBSD mapping also shows that during coalescence quartz did not activate dislocations that
accommodated geometric incompatibility as a consequence of garnet rotation. Instead, quartz became dissolved
in contact along melt decorated grain boundaries. Internal deformation within quartz during coalescence is
essentially limited by activation of dauphiné twinning. This contrasts with local activation of dislocations
in garnet along presumed boundaries of coalesced garnet grains. Activation of dislocations within garnet
most reasonably happened once melt channels were clogged, and a rheological change accompanied ongoing
deformation within the residual migmatites.
Brown M. et al. (1995) - Melt segregation in migmatites. J. Geophys. Res., 100, https://doi.org/10.1029/95jb00517.
Festa V. et al. (2024) - Garnet coalescence clogs melt extraction channels in migmatite. Lithos, 472-473, https://doi.
org/10.1016/j.lithos.2024.107581.
Spiess R. et al. (2001) - Development of garnet porphyroblasts by multiple nucleation, coalescence and boundary
misorientation-driven rotations. J. Metamorph. Geol. 19, 269-290, https://doi.org/10.1046/j.0263-4929.2000.00311.x.
Spiess R. et al. (2012) - Depressurized Cavities within High-strain Shear Zones: their Role in the Segregation and Flow of
SiO2-rich Melt in Feldspar-dominated Rocks. J. Petrol., 53, 1767-1776, https://doi:10.1093/petrology/egs032
Christian Heinrich Spiess and Bohemia
No full textTématem této bakalářské práce je Christian Heinrich Spiess a Čechy.
V první kapitole se autorka věnuje obecné historii v Českých zemích v 18. století. Ve druhé kapitole se specializuje na literární historii v Českých zemích. Třetí kapitola je ještě konkrétnější, neboť popisuje historii hororové literatury v Českých zemích. Ve čtvrté kapitole je definován pojem horor. Pátá kapitola je biografická. V této kapitole se autorka zabývá životem a dílem Ch. H. Spiesse. V této kapitole je kladen důraz na regionální kontext. V poslední - šestí kapitole se autorka soustředí na odkaz, který Spiess v Českých zemích zanechal.Obhájeno621/5000
The topic of this bachelor thesis is Christian Heinrich Spiess and Bohemia.
In the first chapter, the author deals with the general history of Bohemia in the 18th century. In the second chapter she specializes in literary history in Bohemia. The third chapter is even more specific, as it describes the history of horror literature in Bohemia. The fourth chapter defines the concept of horror. The fifth chapter is biographical. In this chapter, the author deals with the life and work of Ch. H. Spiess. This chapter emphasizes the regional context. In the last - sixth chapter, the author focuses on the legacy that Spiess left in Bohemia
(Table 1) Chemical composition of quenching glasses of tholeiite magmas from the Spiess Ridge
No full text(Table 1) Chemical composition of quenching glasses of tholeiite magmas from the Spiess Ridg
(Table 4) Chemical composition of olivines of basalts from lavas of the Spiess Ridge
No full text(Table 4) Chemical composition of olivines of basalts from lavas of the Spiess Ridg
(Table 2) Composition of basalt plagioclase from lavas of the Spiess Ridge
No full text(Table 2) Composition of basalt plagioclase from lavas of the Spiess Ridg
(Table 7) Trace element contents in glasses from the Spiess Ridge
No full text(Table 7) Trace element contents in glasses from the Spiess Ridg
(Table 3) Chemical composition of clinopyroxenes of basalts from lavas of the Spiess Ridge
No full text(Table 3) Chemical composition of clinopyroxenes of basalts from lavas of the Spiess Ridg
(Table 8) Isotopic composition of basalt glasses from the Spiess Ridge
No full text(Table 8) Isotopic composition of basalt glasses from the Spiess Ridg
DERIVATIVES OF P-ADIC L-FUNCTIONS, HEEGNER CYCLES AND MONODROMY MODULES ATTACHED TO MODULAR FORMS
No full textIovita A, Spieß M. Derivatives of p-adic L-functions, Heegner cycles and monodromy modules attached to modular forms. INVENTIONES MATHEMATICAE. 2003;154(2):333-384
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