A Geo-Experimental Diagram for Garnet Amphibolite and Its Bearing on the Origin of Continents

2018 ◽  
Vol 126 (5) ◽  
pp. 531-539 ◽  
Author(s):  
Robert C. Newton
Keyword(s):  
Garnet Amphibolite ◽  
Experimental Diagram

A Theoretical and Experimental Approach to E-pH Diagram for the Niobium-Water System

CORROSION ◽  
10.5006/3871 ◽  
2021 ◽  
Author(s):  
Rodney Santandrea ◽  
Simone BRASIL ◽  
Leila Reznik ◽  
Ladimir Carvalho ◽  
Luiz Miranda
Keyword(s):  
Experimental Approach ◽  
Ph Monitoring ◽  
Aqueous Media ◽  
Water System ◽  
Chemical Species ◽  
Polarization Curves ◽  
Buffer Solutions ◽  
Excellent Corrosion Resistance ◽  
Experimental Diagram ◽  
Selection Of

E-pH diagrams are usually built from thermodynamic databases available in the literature or from specific software. However, depending on the conditions and the chemical species defined for elaborating a diagram, it may present completely different immunity, passivation, and corrosion domains. In order to obtain a result closer to a real system, experimental E-pH diagrams can be built from polarization curves obtained in the evaluated conditions. This work discloses the construction of a diagram for the Nb-H<sub>2</sub>O system at 25°C from theoretical study and the specific selection of chemical species in the solutions through computer simulations. The polarization curves for the construction of the experimental diagram were gathered without the use of buffer solutions and under pH monitoring in the solution bulk throughout all assays. The methodology proposed was considered adequate since, from experimental data, a final result compatible with the classic diagram for the Nb-H<sub>2</sub>O system and the excellent corrosion resistance of niobium in aqueous media were achieved.

scholarly journals Reply to “Is the garnet amphibolite in the Longyou a retrograde eclogite?”

2016 ◽  
Vol 61 (6) ◽  
pp. 561-565
Author(s):  
QingBo ZHU ◽  
XiangYan CHEN ◽  
YaNan LI ◽  
LaiXi TONG ◽  
ChuanLin ZHANG
Keyword(s):  
Garnet Amphibolite

Comparative studies on two phases of Archaean TTG magmas from different blocks of the North China Craton: petrogenesis and constraints on crustal evolution

2020 ◽  
pp. 1-16
Author(s):  
Houxiang Shan ◽  
Mingguo Zhai ◽  
RN Mitchell ◽  
Fu Liu ◽  
Jinghui Guo
Keyword(s):  
North China Craton ◽  
Lower Crust ◽  
North China ◽  
Tectonic Setting ◽  
Source Material ◽  
Crustal Growth ◽  
Garnet Amphibolite ◽  
The North ◽  
Western Block ◽  
Subducting Slab

Abstract Whole-rock major and trace elements and Hf isotopes of magmatic zircons of tonalite–trondhjemite–granodiorite (TTG) rocks with different ages (2.9, 2.7 and 2.5 Ga) from the three blocks (the Eastern Block, Western Block and Trans-North China Orogen) of the North China Craton were compiled to investigate their respective petrogenesis, tectonic setting and implications for crustal growth and evolution. Geochemical features of the 2.5 Ga TTGs of the Eastern Block require melting of predominant rutile-bearing eclogite and subordinate garnet-amphibolite at higher pressure, while the source material of the 2.7 Ga TTGs is garnet-amphibolite or granulite at lower pressure. The 2.5 Ga TTGs have high Mg#, Cr and Ni, negative Nb–Ta anomalies and a juvenile basaltic crustal source, indicating derivation from the melting of a subducting slab. In contrast, features of the 2.7 Ga TTGs suggest generation from melting of thickened lower crust. The 2.5 and 2.7 Ga TTGs in the Trans-North China Orogen were formed at garnet-amphibolite to eclogite facies, and the source material of the 2.5 Ga TTGs in the Western Block is most likely garnet-amphibolite or eclogite. The 2.5 Ga TTGs in the Trans-North China Orogen and Western Block were generated by the melting of a subducting slab, whereas the 2.7 Ga TTGs in the Trans-North China Orogen derived from melting of thickened lower crust. The Hf isotopic data suggest both the 2.5 and 2.7 Ga TTG magmas were involved with contemporary crustal growth and reworking. The two-stage model age (TDM2) histograms show major crustal growth between 2.9 and 2.7 Ga for the whole North China Craton.

Two Paleoproterozoic metamorphic events in the Zhujiafang ductile shear zone of the Hengshan Complex: Insights into the tectonic evolution of the North China Craton

2020 ◽  
Author(s):  
Jiahui Qian
Keyword(s):  
Shear Zone ◽  
North China Craton ◽  
Tectonic Evolution ◽  
North China ◽  
Shear Zones ◽  
Ductile Shear Zone ◽  
Garnet Amphibolite ◽  
Inclusion Type ◽  
Mineral Assemblages ◽  
Ductile Shear

<p>Ductile shear zones <span>usually record mineralogical and isotopic changes that are not apparent in the surrounding host rocks and thus may preserve a complete evolutionary record in a single locale from relatively undeformed to highly deformed rocks. </span>The Zhujiafang ductile shear zone is situated in the central Hengshan Complex, a key area for understanding the Paleoproterozoic tectonic evolution of the Trans-North China Orogen, North China Craton. Detailed metamorphic and geochronological analyses were carried out on metapelite and garnet amphibolite from the Zhujiafang ductile shear zone. The metapelite preserves two phases of mineral assemblages: early kyanite-rutile-bearing assemblage and late chlorite-staurolite-bearing assemblage in garnet–mica schist, and inclusion-type muscovite (high-Si) + kyanite assemblage and late sillimanite-bearing assemblage in sillimanite–mica gneiss. Garnet in the metapelite occasionally exhibits pronounced two-stage zoning characteristic of a diffusion core with irregular pyrope (X<sub>py</sub>) and grossular (X<sub>gr</sub>) contents and a growth rim with X<sub>py</sub> and X<sub>gr</sub> increasing outwards. The isopleths of the maximum X<sub>gr</sub> in garnet core and Si content in inclusion-type muscovite in the P–T pseudosections suggest that the early mineral assemblages underwent medium-high-pressure type metamorphism with pressures up to 12–14 kbar at 700–750 °C. The late assemblages and the growth zoning of garnet rim predict a late separated clockwise P–T path with peak conditions of 6.5 ± 0.2 kbar/620 ± 10 °C (medium-low-pressure type). The garnet amphibolite is mainly composed of garnet, hornblende, plagioclase, ilmenite and quartz, without overprinting of late mineral assemblages except for localized corona textures. Phase modeling suggests that the rock has experienced high-amphibolite facies metamorphism with peak conditions of 10.5 ± 0.8 kbar/770 ± 50 °C, which is broadly consistent with the early-phase metamorphism of metapelite. Zircon U–Pb dating on metapelite yields two metamorphic age groups of 1.96–1.92 Ga and 1.87–1.86 Ga which are interpreted to represent the timing of the two separated phases of metamorphism. Two separated orogenic events may have occurred respectively at ~1.95 Ga and ~1.85 Ga in the Hengshan–Wutai area. The older orogeny was resulted from continental collision and the younger one may be caused by within-plate deformation. The final exhumation of the high-grade rocks formed in the older (i.e. 1.95 Ga) orogeny should be related with the younger deformation/metamorphic event. For more details, please refer to <span>https://doi.org/10.1016/j.lithos.2019.02.001.</span></p>

An interactive program for the interpretation and simulation of Laue patterns

1983 ◽  
Vol 16 (2) ◽  
pp. 281-283 ◽  
Author(s):  
J. Laughier ◽  
A. Filhol
Keyword(s):  
Interactive Program ◽  
Trial And Error ◽  
Visual Comparison ◽  
Indexing Method ◽  
Orientation Matrix ◽  
Graphic Screen ◽  
The Right ◽  
Experimental Diagram

An interactive Fortran IV program is described which allows the orientation matrix of a crystal to be determined and refined without ambiguity, from a transmission or reflection Laue photograph. The indexing method is that of Riquet & Bonnet [J. Appl. Cryst. (1979), 12, 39–41] applied to a small number of data (less than ten) and adapted for interactive use. The verification of calculated solutions or even the trial-and-error search for the right solution is made by means of the visual comparison between the experimental diagram and simulated patterns displayed on a graphic screen. In addition, the rotation angles for setting the crystal to any new orientation may be computed.

Sign in / Sign up

Export Citation Format

Share Document