Metamorphic evolution of mafic granulites in the Kuruksayi area of the South Altyn Orogen, West China: Insights from petrography, phase equilibria modeling and geochronology

Li, Xin; Liu, Liang; Liao, Xiaoying; Gai, Yongsheng; Ma, Tuo; Geng, Guojian; Li, Tong

doi:10.1016/j.jseaes.2021.104766

Cited by 4 publications

(3 citation statements)

References 93 publications

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“…Figure 2b). Li et al (2021) studied mafic granulite lenses from the South Altyn Orogen in West China by thermodynamic modelling including garnet and plagioclase isopleth thermobarometry. The authors observed three garnet generations, whereby conditions of 600-655 °C and 15.8-19.2 kbar (eclogite facies) are recorded by the core of garnet one, followed by garnet one mantle growth at 920 °C and 36.2 kbar (ultrahigh-pressure eclogite facies), formation of garnet two from 820 °C and 17.8 kbar (eclogite facies) to 826 °C and 11.5 kbar (high-pressure granulite facies), and rim formation of garnet three at 826-735 °C and 11.5-8.7 kbar (highpressure granulite-amphibolite facies transition) (Fig.…”

Section: Sensitivity To P-t Changesmentioning

confidence: 99%

Garnet major-element composition as an indicator of host-rock type: a machine learning approach using the random forest classifier

Schönig

Eynatten

Tolosana‐Delgado

et al. 2021

Contrib Mineral Petrol

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The major-element chemical composition of garnet provides valuable petrogenetic information, particularly in metamorphic rocks. When facing detrital garnet, information about the bulk-rock composition and mineral paragenesis of the initial garnet-bearing host-rock is absent. This prevents the application of chemical thermo-barometric techniques and calls for quantitative empirical approaches. Here we present a garnet host-rock discrimination scheme that is based on a random forest machine-learning algorithm trained on a large dataset of 13,615 chemical analyses of garnet that covers a wide variety of garnet-bearing lithologies. Considering the out-of-bag error, the scheme correctly predicts the original garnet host-rock in (i) > 95% concerning the setting, that is either mantle, metamorphic, igneous, or metasomatic; (ii) > 84% concerning the metamorphic facies, that is either blueschist/greenschist, amphibolite, granulite, or eclogite/ultrahigh-pressure; and (iii) > 93% concerning the host-rock bulk composition, that is either intermediate–felsic/metasedimentary, mafic, ultramafic, alkaline, or calc–silicate. The wide coverage of potential host rocks, the detailed prediction classes, the high discrimination rates, and the successfully tested real-case applications demonstrate that the introduced scheme overcomes many issues related to previous schemes. This highlights the potential of transferring the applied discrimination strategy to the broad range of detrital minerals beyond garnet. For easy and quick usage, a freely accessible web app is provided that guides the user in five steps from garnet composition to prediction results including data visualization.

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Section: Sensitivity To P-t Changesmentioning

confidence: 99%

Garnet major-element composition as an indicator of host-rock type: a machine learning approach using the random forest classifier

Schönig

Eynatten

Tolosana‐Delgado

et al. 2021

Contrib Mineral Petrol

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“…In the matrix of the granitic gneisses and paragneisses, eclogites, garnet clinopyroxenites and mafic granulites with protoliths of ca. 923–730 Ma ultramafic–mafic rocks occur as lenses and blocks (Li et al, 2021 and references therein; Gai, Liu, Zhang, Wang, Liao, Yang, et al, 2022). Investigations have ascertained that the peak metamorphism ages of the HP–UHP metamorphic rocks in the South Altyn Tagh HP–UHP metamorphic terrane are at ca.…”

Section: Geological Setting and Samplingsmentioning

confidence: 99%

Middle to Late Ordovician flare‐up of granitoids, South Altyn Tagh: Reworking of exhumed continental crust

Zhou,

Zhao,

Yao

et al. 2024

Geological Journal

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A flare‐up of granitoids occurred at 465–445 Ma in the South Altyn Tagh, synchronously with the exhumation of subducted continental crust. Nevertheless, it remains enigmatic whether a petrogenetic connection exists between them. Here, we report a 454–451 Ma monzogranite pluton, which is characterized by abundant inherited zircons, located in the northern margin of the South Altyn Tagh high‐pressure (HP)—ultrahigh‐pressure (UHP) metamorphic terrane. U–Pb ages and Hf–O isotopic compositions of inherited and synmagmatic zircons are investigated to trace the source rocks and petrogenesis of this pluton. The inherited zircons (zircons that predate the magmatism) exhibit a wide range of ages from 2618 to 484 Ma, displaying three major peaks at 1800–1100 Ma, 1000–800 Ma and 500 Ma. By comparing these inheritance age patterns with zircon spectra of main (meta‐)sedimentary sequences and the widespread Early Neoproterozoic granites (presently as granitic gneisses) in South Altyn Tagh, along with zircon εHf(t) and whole‐rock Nd isotopic composition, we argue that the main source rocks of the studied monzogranite are Early Neoproterozoic granitic gneisses and Late Mesoproterozoic paragneisses from the South Altyn Tagh HP–UHP metamorphic terrane. The ca. 500 Ma inherited zircons have a metamorphic origin, which is simultaneous with the peak metamorphic ages of HP–UHP metamorphic rocks in the Altyn Tagh Complex. These observations indicate that the source rocks of the monzogranite pluton are the subducted continental crust, which underwent metamorphism at ca. 500 Ma and followed by partial melting at 454–451 Ma. In addition, synmagmatic zircons exhibit variable δ18O and εHf(t) values ranging from 5.4 to 11.7‰ and from −19 to +10.3, respectively, indicating a minor contribution of mantle‐derived melts in the formation of the monzogranite. Given the studied pluton and contemporaneous extensive granitoids (465–445 Ma), characterized by similar geochemistry and source rocks, are synchronous with the final exhumation of subducted South Altyn Tagh continental crust, we propose that the reworking of exhumed continental crust at middle to lower crustal depths is their main petrogenesis.

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“…Figure 6.5-2b). Li et al (2021) studied mafic granulite lenses from the South Altyn Orogen in West China by thermodynamic modelling including garnet and plagioclase isopleth thermobarometry. The authors observed three garnet generations, whereby conditions of 600-655 °C and 15.8-19.2 kbar (eclogite facies) are recorded by the core of garnet one, followed by garnet one mantle growth at 920 °C and 36.2 kbar (ultrahigh-pressure eclogite facies), formation of garnet two from 820 °C and 17.8 kbar (eclogite facies) to 826 °C and 11.5 kbar (high-pressure granulite facies), and rim formation of garnet three at 826-735 °C and 11.5-8.7 kbar (high-pressure granulite-amphibolite facies transition) (Figure 6.6-1a, dark-blue path and white points in P-T facies diagram).…”

Section: Sensitivity To P-t Changesmentioning

confidence: 99%

Deep Subduction in Earth history: Seeking for traces in the sedimentary record

Schönig¹

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I am extraordinarily grateful to my main supervisors Prof. Dr. Hilmar von Eynatten and Prof. Dr. Guido Meinhold. After finishing my Master's thesis, I received continuous and endless support for translating my research ideas into reality and for developing a specially tailored PhD project. Without the mentoring, guidance, patience, motivation, and professional knowledge of Hilmar and Guido, none of the lines included in this thesis would have been written down. As well as for the time we spend together in the field and the many fruitful discussions we had, I am additionally thankful for support to facilitate my future career aspirations.Many thanks to Dr. N. Keno Lünsdorf for supervising the Raman spectroscopy part of this project. Over the years, I was fortunate enough to rub off a small proportion of the in-depth understanding Keno has regarding technical details and how to tune experimental parameters for the optimal outcome. I am also grateful for several scripts Keno wrote and provided, which allowed to organize my analytical work much more efficiently.Besides my supervisors, I thank all professional colleagues for collaborations on various subprojects during my PhD studies. This includes Dr.

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Metamorphic evolution of mafic granulites in the Kuruksayi area of the South Altyn Orogen, West China: Insights from petrography, phase equilibria modeling and geochronology

Cited by 4 publications

References 93 publications

Garnet major-element composition as an indicator of host-rock type: a machine learning approach using the random forest classifier

Garnet major-element composition as an indicator of host-rock type: a machine learning approach using the random forest classifier

Middle to Late Ordovician flare‐up of granitoids, South Altyn Tagh: Reworking of exhumed continental crust

Deep Subduction in Earth history: Seeking for traces in the sedimentary record

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