facies metamorphism
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2021 ◽  
Author(s):  
E.P. Metzger ◽  
et al. ◽  
M.L. Leech

<div>Text S1: Supplemental text. Figure S1: Cathodoluminescence images for all analyzed zircon grains. Figure S2: REE spider plots for zircon. Figure S3: Tukey honestly significant difference (HSD) for the timing of anatexis. Table S1: Cathodoluminescence images for all analyzed zircon grains. Table S2. Grossular content of garnet used to calculate the 95% confidence intervals for isopleth modeling in Figure 13. <br></div>


Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1305
Author(s):  
Wenqing Huang ◽  
Pei Ni ◽  
Jungui Zhou ◽  
Ting Shui ◽  
Junying Ding ◽  
...  

Raman spectra of fluid inclusions in gem rubies from Yuanjiang deposit (China) within the Ailao Shan-Red River (ASRR) metamorphic belt showed the presence of compounds such as CO2, COS, CH4, H2S, and elemental sulfur (S8), accompanied by two bands at approximately 2499 and 2570 cm−1. These two frequencies could be assigned to the vibrations of disulfane (H2S2). This is the second case of the sulfane-bearing fluid inclusions in geological samples reported, followed by the first in quartzite from Bastar Craton of India. The H2S2 was likely in situ enclosed by the host rubies rather than a reaction product that formed during the cooling of H2S and S8, suggesting sulfanes are stable at elevated temperatures (e.g., >600 °C). By comparing the lithologies and metamorphic conditions of these two sulfane-bearing cases (Bastar and Yuanjiang), it is suggested that amphibolite facies metamorphism of sedimentary sequence that deposited in a continental platform setting might favor the generation of sulfanes. Sulfanes may play an important role in the mobilization of Cr that is essential for ruby crystallization.


2021 ◽  
Author(s):  
E.P. Metzger ◽  
et al. ◽  
M.L. Leech

<div>Text S1: Supplemental text. Figure S1: Cathodoluminescence images for all analyzed zircon grains. Figure S2: REE spider plots for zircon. Figure S3: Tukey honestly significant difference (HSD) for the timing of anatexis. Table S1: Cathodoluminescence images for all analyzed zircon grains. Table S2. Grossular content of garnet used to calculate the 95% confidence intervals for isopleth modeling in Figure 13. <br></div>


2021 ◽  
Author(s):  
E.P. Metzger ◽  
et al. ◽  
M.L. Leech

<div>Text S1: Supplemental text. Figure S1: Cathodoluminescence images for all analyzed zircon grains. Figure S2: REE spider plots for zircon. Figure S3: Tukey honestly significant difference (HSD) for the timing of anatexis. Table S1: Cathodoluminescence images for all analyzed zircon grains. Table S2. Grossular content of garnet used to calculate the 95% confidence intervals for isopleth modeling in Figure 13. <br></div>


Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1029
Author(s):  
Oleg I. Volodichev ◽  
Oleg A. Maksimov ◽  
Tatiana I. Kuzenko ◽  
Alexander I. Slabunov

Early Precambrian retrogressed eclogites are abundant in the central and northern parts of the Belomorian Province of the Fennoscandian Shield (Gridino + Keret and Salma + Kuru-Vaara study areas, respectively). Older and younger eclogites are recognized and their Archean and Paleoproterozoic ages are argued. Archean eclogites are intensely retrogressed and occur in amphibolite boudins in the tonalite-trondhjemite-granodiorite (TTG) gneiss matrix of the Archean Gridino eclogite-bearing mélange. Less retrogressed Paleoproterozoic eclogites form patches in mafic dikes and some amphibolite boudins; their Paleoproterozoic age is supported by U-Pb/SIMS data on zircons depleted in heavy rare earth elements (REE) with omphacite, garnet, and kyanite inclusions, and Sm-Nd and Lu-Hf mineral isochrons. Archean eclogites contain Archean heavy rare-earth elements (REE)-depleted zircons with garnet and zoisite inclusions and Archean garnets. No omphacite inclusions were found in these zircons, and this fact was considered as evidence against the existence of Archean eclogites. This study reports on the first finding of omphacite (23–25% Jd) inclusions in 2.68 Ga metamorphic zircons from eclogites from the Gridino eclogite-bearing mélange. The zircons are poorly enriched in heavy REE and display a weak negative Eu-anomaly but a poor positive Ce-anomaly typical of eclogitic zircons. Thus, zircons with these decisive features provide evidence for an Archean eclogite-facies metamorphism.


2021 ◽  
Vol 12 (3) ◽  
pp. 662-667
Author(s):  
M. V. Mints ◽  
K. A. Dokukina

In their research, the authors of the comments have focused on the Late Paleoproterozoic rims of zircons, but ignored many important details of their own data. Their comments are based on a misconception that eclogite zircons have unique geochemical (REE, Th/U) and isotopic (Lu-Hf, δ18O) characteristics that do not depend on rock types and pressure rates (that were high or ultrahigh) during metamorphism. This idea leads to false unambiguous dating of the eclogite facies metamorphism based on single samples of the rocks.


Author(s):  
Yinbiao Peng ◽  
Shengyao Yu ◽  
Jianxin Zhang ◽  
Yunshuai Li ◽  
Sanzhong Li ◽  
...  

Continental arcs in active continental margins (especially deep-seated arc magmatism, anatexis, and metamorphism) can be extremely significant in evaluating continent building processes. In this contribution, a Paleozoic continental arc section is constructed based on coeval granulite-facies metamorphism, anatexis, and magmatism on the northern margin of the Qilian Block, which record two significant episodes of continental crust growth. The deeper layer of the lower crust mainly consists of medium-high pressure mafic and felsic granulites, with apparent peak pressure-temperature conditions of 11−13 kbar and 800−950 °C, corresponding to crustal depths of ∼35−45 km. The high-pressure mafic granulite and local garnet-cumulate represent mafic residues via dehydration melting involving breakdown of amphibole with anatectic garnet growth. Zircon U-Pb geochronology indicates that these high-grade metamorphic rocks experienced peak granulite-facies metamorphism at ca. 450 Ma. In the upper layer of the lower crust, the most abundant rocks are preexisting garnet-bearing metasedimentary rocks, orthogneiss, and local garnet amphibolite, which experienced medium-pressure amphibolite-facies to granulite-facies metamorphism at depths of 20−30 km at ca. 450 Ma. These metasedimentary rocks and orthogneiss have also experienced partial melting involving mica and rare amphibole at 457−453 Ma. The shallow to mid-crust is primarily composed of diorite-granodiorite batholiths and volcanic cover with multiple origin, which were intruded during 500−450 Ma, recording long-term crustal growth and differentiation episode. As a whole, two episodes of continental crust growth were depicted in the continental arc section on the northern margin of the Qilian Block, including: (a) the first episode is documented in a lithological assemblage composing of coeval mafic-intermediate intrusive and volcanic rocks derived from partial melting of modified lithospheric mantle and subducted oceanic crust during southward subduction of the North Qilian Ocean at 500−480 Ma; (b) the second episode is recorded in mafic rocks derived from partial melting of modified lithospheric mantle during transition from oceanic subduction to initial collision at 460−450 Ma.


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