Two Distinct Fractional Crystallization Mechanisms of A-Type Granites in the Nanling Range, South China: A Case Study of the Jiuyishan Complex Massif and Xianghualing Intrusive Stocks

Wenzhou Xiao; Chaoyun Liu; Kaixuan Tan; Xianzhe Duan; Kaituo Shi; Qinglin Sui; Peng Feng; Mabrouk Sami; Mohamed S. Ahmed; Feng Zi

doi:10.3390/min13050605

Minerals (Apr 2023)

Two Distinct Fractional Crystallization Mechanisms of A-Type Granites in the Nanling Range, South China: A Case Study of the Jiuyishan Complex Massif and Xianghualing Intrusive Stocks

Wenzhou Xiao,
Chaoyun Liu,
Kaixuan Tan,
Xianzhe Duan,
Kaituo Shi,
Qinglin Sui,
Peng Feng,
Mabrouk Sami,
Mohamed S. Ahmed,
Feng Zi

Affiliations

Wenzhou Xiao: Hunan Key Laboratory of Rare Metal Minerals Exploitation and Geological Disposal of Wastes, School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, China
Chaoyun Liu: Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring, Ministry of Education, School of Geosciences and Info-Physics, Central South University, Changsha 410083, China
Kaixuan Tan: Hunan Key Laboratory of Rare Metal Minerals Exploitation and Geological Disposal of Wastes, School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, China
Xianzhe Duan: Hunan Key Laboratory of Rare Metal Minerals Exploitation and Geological Disposal of Wastes, School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, China
Kaituo Shi: Hunan Key Laboratory of Rare Metal Minerals Exploitation and Geological Disposal of Wastes, School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, China
Qinglin Sui: Hunan Key Laboratory of Rare Metal Minerals Exploitation and Geological Disposal of Wastes, School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, China
Peng Feng: Hunan Key Laboratory of Rare Metal Minerals Exploitation and Geological Disposal of Wastes, School of Resource Environment and Safety Engineering, University of South China, Hengyang 421001, China
Mabrouk Sami: Geology Department, Faculty of Science, Minia University, El-Minia 61519, Egypt
Mohamed S. Ahmed: Geology and Geophysics Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
Feng Zi: School of Earth Sciences and Spatial Information Engineering, Hunan University of Science and Technology, Xiangtan 411201, China

DOI: https://doi.org/10.3390/min13050605
Journal volume & issue: Vol. 13, no. 5
p. 605

Abstract

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The petrogenesis of A-type granites with different occurrences in the Nanling Range remains unclear. In this study, a case study of the Jiuyishan complex massif and Xianghualing intrusive stocks was conducted to determine this problem. The Jiuyishan complex massif is composed of four units (Jinjiling, Pangxiemu, Shaziling and Xishan). These four units have similar zircon U-Pb ages of approximately 153 Ma, with high Zr + Nb + Ce + Y contents (>350 ppm), high 10,000 Ga/Al ratios (>2.6), and a high crystallization temperature, indicating A-type affinities. They show a gradual change in lithology and geochemistry, implying a fractional crystallization process. These units also have similar εNd(t) values (−8.2 to −5.8) and zircon εHf(t) values (−7.5 to −2.2) except for the Shaziling MMEs (mafic microgranular enclaves) (−14.2 to 4.8), demonstrating their lower crustal source. However, the Shaziling unit may have contributed mantle-derived magma based on the geochemical data of its hosted MMEs. In comparison, the two Xianghualing intrusive stocks have similar geochemical features but exhibit highly evolved features (high Rb, U, Y, Ta and Nb contents and low Eu, Ba, Sr, P, Ti, Ca, Mg and Fe contents, with V-shaped REE distribution patterns). They have different zircon U-Pb ages of approximately 160 Ma and 155 Ma. The two stocks also have similar whole-rock εNd(t) values (−6.5 to −5.7) and zircon εHf(t) values (−7.6 to −2.7) and equally illustrate a lower crustal source region. Combining with their vertical zonation, they may have experienced remarkable fractional crystallization with possible assimilation processes. We propose that the Jiuyishan complex and Xianghualing stocks have two distinct fractional crystallization mechanisms during their formation. The Jiuyishan complex was formed by in situ crystal mush fractionation, while the Xianghualing stocks were formed by flowage differentiation during magma ascent or gravitational settling during magma solidification after emplacement. However, more than one mechanism affected the fractional crystallization processes of these granitic rocks.

Published in Minerals

ISSN: 2075-163X (Online)
Publisher: MDPI AG
Country of publisher: Switzerland
LCC subjects: Science: Geology: Mineralogy
Website: https://www.mdpi.com/journal/minerals

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