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378 results on '"Zhang, Hong–Fu"'

6. Metamorphic evolution and geological significance of Early Palaeozoic high‐pressure granulites from the East Kunlun (NW China).

Author

Chen, An‐Ping, Zhang, Hong‐Fu, Zhang, Ming‐Jie, and Zhang, Xiao‐Qi

Subjects
*METAMORPHIC rocks, *OROGENIC belts, *ECLOGITE, *URANIUM-lead dating, *GRAIN yields, *SUBDUCTION, *GRANULITE, *VOLCANIC soils
Abstract

Granulites and eclogites are useful for revealing the thermal and tectonic evolution of orogens. Early Palaeozoic granulites and associated eclogites in the East Kunlun Orogenic Belt (EKOB) display contrasting metamorphic age. Such asynchronous granulite–eclogite associations have rarely been reported, and the geological significance of their existence remains to be further explored. In this study, petrological and geochronological techniques were used to investigate two felsic and two mafic granulites collected from the Qingshuiquan area in the eastern section of the EKOB. These rocks record similar P–T paths, which are characterized by a peak stage within suprasolidus and high‐pressure (HP) granulite facies conditions (750–832°C and 10.1–12.0 kbar), followed by an initial decompression and cooling stage to subsolidus conditions (600–748°C and 6.5–8.6 kbar), and then a stage of further retrogression under greenschist facies conditions. The protoliths to these granulites are of volcanic and sedimentary origin and suggested to be a component of the continental basement unit. Metamorphic P–T paths indicate that these rocks experienced peak metamorphism at a depth of ~40 km, then cooling and uplift to a depth of ~25 km, and eventually experienced low‐grade retrogression at shallow crustal levels. Cathodoluminescence images and compositional data demonstrate that the zircons in these rocks are of metamorphic origin and they crystallized at or near peak conditions. SIMS U–Pb dating of representative zircon grains yield concordant metamorphic ages of c. 490–520 Ma, with a peak value of 505 Ma on the probability density curve. These ages are similar to other 480–530 Ma ages typically retrieved from EKOB granulites and associated rocks, and are markedly older than the 400–450 Ma ages retrieved from eclogites and their host rocks. The HP granulites and eclogites of the EKOB do not show overprinting relationships. Such asynchronous characteristics imply that the two rock types formed in distinct tectonic settings and at different stages of a protracted subduction–collision process. The studied granulites are suggested to have formed in the root of a continental arc during a stage of Proto‐Tethys Ocean subduction. The formation of the eclogites could be attributed to subsequent deep continental subduction. [ABSTRACT FROM AUTHOR]

Published
2024
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20. Study on ultrasonic-assisted extraction and aqueous two-phase separation of flavonoids from Eucommia ulmoides leaves based on choline biological ionic liquid.

Author

WANG Run-ping, ZHANG Hong-fu, LU Xiao-bin, and LI Feng

Subjects
*EUCOMMIA ulmoides, *LEAF anatomy, *IONIC liquids, *RESPONSE surfaces (Statistics), *PHENOLIC acids, *CHOLINE, *FLAVONOID glycosides
Abstract

The experiment was to find a green and effective method to separate flavonoids from Eucommia ulmoides leaves. Ultrasonic-assisted choline tryptophan ionic liquid was used to extract flavonoids from Eucommia ulmoides leaves. Response surface methodology was used to optimize the extraction of total flavonoids. Aqueous two-phase combined with antisolvent precipitation was used to separate and extract flavonoids, and the components of flavonoids extracts were analyzed by liquid chromatography. The results showed that the optimum parameters of response surface optimization were ultrasonic time 54.76 min, ultrasonic power 504.8 W and liquid-material ratio 23.5 mL/g, and the predicted extraction rate of total flavonoids was 2.66%. Under the optimized conditions of ultrasonic time 55 min, ultrasonic power 505 W and liquid-material ratio 24 mL/g, the extraction rate of total flavonoids from Eucommia ulmoides leaves was 2.53%. The content of rutin and quercetin in flavonoids extract was 50.88% and 1.26%, respectively. The study indicates that the process used in the experiment is green and environmentally friendly, and can be used as an efficient method for separating and extracting flavonoids from Eucommia ulmoides leaves. [ABSTRACT FROM AUTHOR]

Published
2023
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