Granite, gabbro and mafic microgranular enclaves in the Gejiu area, Yunnan Province, China: a case of two-stage mixing of crust- and mantle-derived magmas

The Luxi Terrane (eastern China) exposes widespread Early Cretaceous alkaline rocks, whereas their petrogenesis remains controversial, including fractional crystallization, partial melting and crustal contamination regime. Here, we present petrology, geochemistry, sphene U-Pb geochronology and trace element data from the syenogranite, quartz syenite and quartz monzonite of the Guandimiao alkaline complex rocks to investigate their petrogenesis. Geochemical data suggest that these alkaline rocks show alkalic and peralkaline characters, and high Ga/Al ratios, SiO2, light rare-earth element (LREE), Zr and Nb, and low MgO, CaO, Eu contents, corresponding to A-type granites. Sphene trace elements in syenogranite and quartz monzonite show obvious fractionation between LREE and heavy rare-earth element (HREE) and high Th/U ratios, indicating a magmatic origin. They yield U-Pb lower intercept ages of 128 ± 2.3 Ma and 127 ± 1.3 Ma, representing the crystallization ages of these alkaline rocks. The negative correlations between CaO, Fe2O3 (Total), MgO, P2O5, TiO2, MnO and the pronounced depletion in Nb, Ta and Ti suggest that the alkaline rocks were formed by fractional crystallization. Additionally, the positive correlation between La/Hf and La, Th and Th/V, Ce/Yb and K2O, and Tb/Yb and Yb suggest that the alkaline melts are generated by partial melting. Such high Rb/Nb, (Th/Nb)N and Nb/Th ratios indicate crustal contamination during the magma emplacement. We, therefore, propose the magma source of the alkaline rocks in the Guandimiao complex originated by partial melting of lithospheric mantle, which experienced fractional crystallization and crustal contamination processes during its emplacement. Such complex alkaline rocks were probably formed in an extensional back-arc setting induced by the retreat of the subducting Izanagi plate.

Quartz monzonite

Fractional crystallization (geology)

Petrogenesis

Peralkaline rock

Trace element

10.3390/min12060670

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Citations (2)

Late Triassic Magma Mixing and Fractional Crystallization in the Qingchengzi Orefield, Eastern Liaoning Province: Regional Petrogenetic and Metallogenic Implications

Journal of Earth Science (2021)

Hongjing Xie Yuwang Wang Dedong Li Guochao Zhou Zhichao Zhang

Quartz monzonite

Fractional crystallization (geology)

Igneous differentiation

Batholith

Porphyritic

Petrogenesis

10.1007/s12583-020-1114-3

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Citations (10)

Evidence for the Contrasting Magmatic Conditions in the Petrogenesis of A-type Granites of Phenai Mata Igneous Complex: Implications for Felsic Magmatism in the Deccan Large Igneous Province

Journal of the Indian Institute of Science (2018)

K.R. Hari M.P. Manu Prasanth Vikas Swarnkar J. Vijaya Kumar Kirtikumar Randive

Felsic

Quartz monzonite

Fractional crystallization (geology)

Petrogenesis

10.1007/s41745-018-0079-z

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Citations (9)

Petrogenesis and geodynamic significance of late Early Jurassic complex in Qinsai, Hainan Island, South China Sea

Canadian Journal of Earth Sciences (2023)

Zhongjie Xu Jintao Kong Ningchen Sun Rihui Cheng Li Zhang

Whole-rock geochemical and U–Pb–Hf isotopic data were used to investigate the age, petrogenesis, and tectonic setting of a suite of gabbro–diorite–monzonite–syenite rock exposed in Qinsai area, Hainan Island. Zircon U–Pb dating shows that the gabbro and monzonite, respectively, crystallized at 179.5 ± 2.7 and 179.0 ± 2.3 Ma. The suite consists of shoshonitic alkaline intrusive rocks with SiO 2 content ranging from 41.7 to 63.4 wt%, with high U, K, and Pb and low Nb, Ta, and Ti. The suite is enriched in light rare earth elements relative to heavy rare earth elements. The gabbro has no obvious Eu anomaly but a positive Eu anomaly is evident in intermediate rocks. Zircon ε Hf ( t) values are positive and have a wide variation (gabbro ε Hf ( t) = +5.2 ± 8.2, monzonite ε Hf ( t) = +4.7 ± 7.1). Gabbro and syenite are both likely derived from an enriched lithospheric mantle that was metasomatized by subduction fluids. Syenite evolved from the differentiation of gabbro, monzonite, and diorite. Collectively, these intrusive rocks formed in an extensional regime within an arc formed by subduction of the ancient Pacific plate beneath the Asian margin, which was accompanied by extensional thinning of the lithosphere.

Quartz monzonite

Diorite

Petrogenesis

Peridotite

Geochronology

10.1139/cjes-2022-0097

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Citations (0)

Geochemistry and petrology of syenite, monzonite and gabbro from the Central Belt of Peninsular Malaysia

Bulletin of the Geological Society of Malaysia (2006)

Azman A. Ghani V. Ramesh B.T. Yong T. T. Khoo

The Benom Igneous Complex is situated in the central part of of this belt forms a pear shaped batholith consists of a variety of igneous rocks ranging in composition from granitic to syenitic to monzonitic and gabbroic. The syenitic, monzonitic, gabbroic are found mainly in the western part of the batholith. The range of SiO 2 for each of the gabbro, syenite and monzonite are 46.5 to 49.1%, 52.9 to 56.9% and 56.6 to 64.7% respectively and characterized by high alkali content, shoshonitic with I type characteristics. They have very high LIL elements, i.e. Ba and Sr are nearly 1000 times rock/mantle. The high Ba and Sr values may results from the penetration of the lower lithosphere by a small volume of mantle material that is enriched in those elements.

Quartz monzonite

Petrogenesis

10.7186/bgsm49200605

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Citations (3)

The use of apatite as a record of initial 87Sr/86Sr ratios and indicator of magma processes in the Inagawa pluton, Ryoke belt, Japan

Chemical Geology (2005)

Motohiro Tsuboi

Felsic

Fractional crystallization (geology)

Igneous differentiation

10.1016/j.chemgeo.2005.05.001