Mineral Inclusions in Heavy Minerals of the Ultrahigh-Pressure Metamorphic Rocks of the Dora-Maira Massif and Their Bearing on the Relative Timing of the Petrological Events

2013 ◽  
pp. 331-342 ◽  
Author(s):  
H.-P. Schertl ◽  
W. Schreyer
Keyword(s):  
Heavy Minerals ◽  
Ultrahigh Pressure ◽  
Metamorphic Rocks ◽  
Relative Timing ◽  
Mineral Inclusions

Two-Stage Exhumation of Ultrahigh-Pressure Metamorphic Rocks from the Western Dabie Orogen, Central China

2011 ◽  
Vol 119 (1) ◽  
pp. 15-31 ◽  
Author(s):  
Yuanbao Wu ◽  
Shan Gao ◽  
Xiaochi Liu ◽  
Jing Wang ◽  
Min Peng ◽  
...  
Keyword(s):  
Central China ◽  
Ultrahigh Pressure ◽  
Metamorphic Rocks ◽  
Two Stage ◽  
Dabie Orogen

Evolution of geodynamics since the Archean: Significant change at the dawn of the Phanerozoic

Geology ◽  
2020 ◽  
Vol 48 (5) ◽  
pp. 488-492 ◽  
Author(s):  
M. Brown ◽  
C.L. Kirkland ◽  
T.E. Johnson
Keyword(s):  
Ultrahigh Pressure ◽  
Secular Change ◽  
Metamorphic Rocks ◽  
Data Sets ◽  
Ultrahigh Pressure Metamorphism ◽  
Slab Breakoff ◽  
Wide Range ◽  
O Isotope ◽  
Global Data Sets ◽  
Global Data

Abstract A time-series analysis of thermobaric ratios (temperature/pressure [T/P]) for Paleoarchean to Cenozoic metamorphic rocks identified significant shifts in mean T/P that may be related to secular change in the geodynamics on Earth. Thermobaric ratios showed significant (>95% confidence) change points at 1910, 902, 540, and 515 Ma, recording drops in mean T/P, and at 1830, 604, and 525 Ma, recording rises in mean T/P. Highest mean T/P occurred during the Mesoproterozoic, and lowest mean T/P occurred from the Cambrian to the Oligocene. Correlated changes were seen between T/P and global data sets of time-constrained hafnium (Hf) and oxygen (O) isotope compositions in zircon. The range of correlated variation in T/P, Hf, and O was larger during the formation of Rodinia than Columbia. Large changes and a wide range for these variables continued through the Phanerozoic, during which a statistically significant 83 m.y. frequency of T/P excursions recorded the high tempo of orogenic activity associated with the separation, migration, and accretion of continental terranes during the formation of Pangea. Since the early Tonian, the decreasing mean T/P of metamorphism, widespread appearance of blueschist and ultrahigh-pressure metamorphism, and wide fluctuations in Hf and O isotope compositions document a change to the modern plate-tectonic regime, characterized by widespread continental subduction and deeper slab breakoff than in the Proterozoic.

40Ar-39Ar Thermochronological Constraints on the Exhumation of Ultrahigh-Pressure Metamorphic Rocks in the Sulu Terrane of Eastern China

2005 ◽  
Vol 47 (8) ◽  
pp. 872-886 ◽  
Author(s):  
Li-Hung Lin ◽  
Pei-Ling Wang ◽  
Ching-Hua Lo ◽  
Chin-Ho Tsai ◽  
Bor-Ming Jahn
Keyword(s):  
Eastern China ◽  
Ultrahigh Pressure ◽  
Metamorphic Rocks ◽  
Sulu Terrane

Viscous relaxation of mineral Inclusions and its implications for reaction overstepping calculations in metamorphic rocks

2020 ◽  
Author(s):  
Evangelos Moulas ◽  
Xin Zhong ◽  
Lucie Tajcmanova
Keyword(s):  
Independent Method ◽  
Metamorphic Rocks ◽  
Additional Method ◽  
Natural Systems ◽  
Long Period ◽  
Mineral Inclusions ◽  
Large Peak ◽  
Viscous Relaxation ◽  
T Path ◽  
Temperature Time

<p>Over the recent years, Raman elastic barometry has been developed as an additional method <span>to calculate</span> metamorphic conditions in natural systems. A major advantage of Raman elastic barometry is that it does not depend on thermodynamic databases and classic geobarometry methods <span>but</span> relies on mechanical calculations. As a consequence, Raman elastic barometry offers an independent method for estimating the pressure conditions <span>that prevailed at the</span> <span>time of entrapment</span> of mineral<span>s</span> du<span>ring</span> growth of their host<span>s</span>.</p><p>The di<span>fference between</span> the pressure calculated <span>using</span> elastic geobarometry and <span>that calculated by phase</span> equilibria methods has recently <span>been employed to</span> <span>estimate</span> the extent of metamorphic reaction overstepping in natural systems. <span>Quantification of</span> the <span>latter however implicitly assumes that the rheology</span> of the inclusion-host system <span>is perfectly</span> elastic. This assumption may no<span>t</span> hold at high temperatures, where viscous creep of minerals takes place.</p><p>The amount of viscous relaxation of <span>a host-inclusion</span> system is a path<span>-</span>dependent quantity which mostly depends on the temperature-time (T-t) path <span>followed</span>. <span>Here</span>, we present examples of visco-elastic relaxation of mineral inclusions and calculate the apparent reaction overstepping which results by assuming that the mechanical system is purely elastic. <span>Our modelling shows</span> that host-inclusion systems <span>that</span> experienced large peak temperatures for long period<span>s</span> of time will retain inclusion residual pressures that <span>cann</span>ot be simply related to the growth of the<span>ir hosts</span> and should <span>therefore not</span> be used for reaction overstepping calculations.</p>

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