Earth Science Frontiers ›› 2020, Vol. 27 ›› Issue (5): 70-87.DOI: 10.13745/j.esf.sf.2020.5.43

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The mineralogical records of magmatic process: cases from Mesozoic intrusive rocks in the Handan-Xingtai region

ZHANG Juquan1(), LIANG Xian1, YAN Lina1, LI Shengrong2, SHEN Junfeng2, LU Jing1, WU Weizhe1, LI Qing1   

  1. 1. Resource College, Hebei GEO University, Shijiazhuang 050031, China
    2. School of Earth Sciences and Resources, China University of Geosciences(Beijing), Beijing 100083, China
  • Received:2020-01-29 Revised:2020-05-12 Online:2020-09-25 Published:2020-09-25

Abstract:

The mineral zoning texture is a good recording of the magmatic process, and the physicochemical conditions of magma could be quantitatively calculated by mineral thermobarometer. In this study, we carried out electron microprobe and LA-ICP-MS element mapping of typical plagioclase phenocrysts of two Mesozoic hypabyssal intrusions in the Handan-Xingtai region, along with electron microprobe analysis and physicochemical condition calculation of amphibole crystals of different genesis. We found that plagioclase phenocrysts in these two samples belong to antecrysts. They are mainly composed of oligoclase in pyroxene diorite porphyrite and andesine and labradorite in porphyritic quartz monzonite. The two intrusions have obviously different zoning textures and record different magma mixing processes. The former records multiple injections of basic magma into acidic magma chamber to obtain eventual volume advantage; the latter records continuous mixing of small amounts of basic magma with large volume of acidic magma to form homogenized magma. There is a tendency of iron enrichment from the core to the rim of plagioclase phenocryst, indicating iron is gradually enriched with magma evolution. The amphibole thermobarometric calculation results show that the depth of magma chamber containing pyroxene diorite porphyrite was about 5.5 km, with a temperature of 850 ℃, oxygen fugacity of ΔNNO+1, and water content of 4.0 wt%. The intrusion finally emplaced at a crust depth of 2.1 km. The porphyritic quartz monzonite intrusion finally emplaced at a crust depth of 2.0 km, with an average hornblende crystallization temperature of 737 ℃, relative oxygen fugacity of about ΔNNO+1.2, and water content in melt of 3.9 wt%.

Key words: magma mixing, zoning texture, genetic mineralogy, plagioclase, amphibole

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