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Metamorphic phase equilibria and dif...

Chu, Xu.

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Metamorphic phase equilibria and diffusion kinetics, with applications to the Taconic-Caledonide orogenic belt.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Metamorphic phase equilibria and diffusion kinetics, with applications to the Taconic-Caledonide orogenic belt./
Author:	Chu, Xu.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2015,
Description:	257 p.
Notes:	Source: Dissertation Abstracts International, Volume: 77-06(E), Section: B.
Contained By:	Dissertation Abstracts International77-06B(E).
Subject:	Petrology. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10005378
ISBN:	9781339434599

Metamorphic phase equilibria and diffusion kinetics, with applications to the Taconic-Caledonide orogenic belt.
Chu, Xu.

Metamorphic phase equilibria and diffusion kinetics, with applications to the Taconic-Caledonide orogenic belt. - Ann Arbor : ProQuest Dissertations & Theses, 2015 - 257 p.

Source: Dissertation Abstracts International, Volume: 77-06(E), Section: B.

Thesis (Ph.D.)--Yale University, 2015.

This item is not available from ProQuest Dissertations & Theses.

Deriving pressure-temperature-time (P-T-t) information from rocks is the fundamental task for metamorphic petrologists. The mineral assemblages and mineral compositions are keys to our understanding of the orogenic processes in Earth's lithosphere. To better determine P-T-t histories of rocks, a new thermodynamic tool for metamorphic phase equilibria calculation is developed, and the diffusion model of major components in garnet, the most commonly used mineral in metamorphic petrology, is recalibrated using published experimental data and Bayesian statistics.

ISBN: 9781339434599Subjects--Topical Terms:

535210
Petrology.

Metamorphic phase equilibria and diffusion kinetics, with applications to the Taconic-Caledonide orogenic belt.
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100 1 $a Chu, Xu. $3 3168289
245 1 0 $a Metamorphic phase equilibria and diffusion kinetics, with applications to the Taconic-Caledonide orogenic belt.
260 1 $a Ann Arbor : $b ProQuest Dissertations & Theses, $c 2015
300 $a 257 p.
500 $a Source: Dissertation Abstracts International, Volume: 77-06(E), Section: B.
500 $a Adviser: Jay J. Ague.
502 $a Thesis (Ph.D.)--Yale University, 2015.
506 $a This item is not available from ProQuest Dissertations & Theses.
520 $a Deriving pressure-temperature-time (P-T-t) information from rocks is the fundamental task for metamorphic petrologists. The mineral assemblages and mineral compositions are keys to our understanding of the orogenic processes in Earth's lithosphere. To better determine P-T-t histories of rocks, a new thermodynamic tool for metamorphic phase equilibria calculation is developed, and the diffusion model of major components in garnet, the most commonly used mineral in metamorphic petrology, is recalibrated using published experimental data and Bayesian statistics.
520 $a The phase equilibria code set similar in some respects to established software packages, but is more flexible and expandable, and can be easily interfaced with kinetic garnet diffusion simulations. For example, I incorporate C-O-H fluid into the phase equilibria of graphitic metapelites, allowing straightforward calculation of CH4--H2O--CO2 abundances in lithospheric fluids. Furthermore, dissolved CO2 endmembers are added to the activity models of the felsic melt and cordierite, so that the phase relations among silicate + C-O-H fluid +/- silicate melt can be better modeled. The results provide insights into the decarbonation reactions and reduced and oxidized carbon budgets in high-grade metamorphic rocks as well as partial melts derived from them.
520 $a The chemical zoning patterns of garnet porphyroblasts are extremely useful in reconstructing the P-T-t histories of metamorphic rocks. The degree of chemical modification reflects timescales of thermal events so that a small "t" is added to the conventional P-T path. My research applies these ideas to a combination of phase equilibria and diffusion modeling---the intragranular diffusion modeling is performed on the initial conditions predicted by the equilibrium relations. The commonly-observed discrepancies between the modeled and observed garnet chemical profiles spurred my interests in calibrating the multicomponent diffusion coefficients. I incorporated the published results of diffusion experiments into a Bayesian statistical framework implemented using the Markov-chain Monte Carlo approach. These new coefficients are significantly different from previously-published ones (particularly for Ca and Mn; e.g., Carlson, 2006), and thus facilitate new petro-tectonic interpretations.
520 $a The developed tools and models are applied to two field areas within the classic Taconic-Caledonide orogenic belt. The newly derived diffusion model indicates that the timescale of the thermal peak of Barrovian metamorphism in the classic type area of the Scottish Highlands is longer than previously estimated, but is still geologically very brief (<106 years). This brevity requires pulsed advective heat input, as provided by syn- orogenic mafic magmatism in these rocks.
520 $a Mafic lenses and deformed dikes in a Taconic thrust slice, northwest Connecticut, contain relict mineral assemblages and decompression textures suggesting high-pressure eclogite precursors. I use phase diagrams and zircon U-Pb dating to investigate the metamorphic history. Thermobarometry indicates that the peak pressure reached ~15 kbar at 710 °C, confirming the eclogite precursor hypothesis. U-Pb zircon dating yields a 456 +/- 4.6 Ma metamorphic age, which provides a tight constraint on the timing of Taconic subduction polarity reversal from east- to west-directed in southern New England. The collision was likely diachronous along strike---the HP metamorphism and subduction polarity reversal took place about 10 Myr later in Connecticut than in Newfoundland.
520 $a The garnets in these rocks preserve sharply-bounded chemical compositional zones. Modeling of the observed diffusive relaxation between zones indicates shockingly short peak-T and peak-P residence times such that pressure increases and decreases of ~5 kbar occurred in <1 kyr. If the compression was due only to lithostatic (overburden) pressure, the inferred subduction rate would exceed 30 m/yr, and this defies any geodynamic model of subduction rates (<~12 cm/yr). Thus, geologic-scale overpressure developed in the thrust fault zone is the most likely explanation for the extremely short compression and decompression processes. We propose that the ultra-fast metamorphism is a potential petrologic test of deviations from lithostatic pressure in convergence zones.
590 $a School code: 0265.
650 4 $a Petrology. $3 535210
650 4 $a Geology. $3 516570
690 $a 0584
690 $a 0372
710 2 $a Yale University. $3 515640
773 0 $t Dissertation Abstracts International $g 77-06B(E).
790 $a 0265
791 $a Ph.D.
792 $a 2015
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=10005378