Petrogenesis of the Cenozoic Lianhuashan pluton (SW China): Constrained by zircon U–Pb geochronology, Lu–Hf isotope, and geochemistry

Abstract

Potassic magmatic rocks provide significant insights in understanding of mantle composition, evolution, and interaction with crust. Potassic magmatism along the Jinshajiang-Ailaoshan Paleo-Tethyan suture has drawn much attention. Whereas igneous intrusion in the Simao terrane, west to Jinshajiang-Ailaoshan potassic magmatic belt has rarely been investigated. Hence, we present zircon U-Pb ages and Lu-Hf isotope and whole-rock geochemistry for the Lianhuashan pluton. Zircon U-Pb dating from monzonite and quartz monzonite porphyry yield ages of 33.6 ± 0.2 and 33.5 ± 0.3 Ma, respectively. Monzonites are characterized by high K 2 O (4.93-5.16%) and K 2 O/Na 2 O (1.46-1.71), high Y (22.90-23.80 ppm), and Yb (1.87-2.21 ppm), relatively enrichment of light rare earth element (LREE). Zircons from monzonites show ε Hf (t) values ranging from −1.1 to +0.6 and crustal model ages (T DM C ) between 1.04 and 1.15 Ga. These geochemical features suggest that parent magmas of the rocks originated from a metasomatized lithospheric mantle. Quartz monzonite porphyries are characterized by high Sr (836.00-1,529.00 ppm), Sr/Y (70.85-99.93) and La/Yb (32.31-49.83), low Y (11.80-15.60 ppm), and Yb (0.95-1.30 ppm), enrichment in LREE and depletion in heavy rare earth elements (HREE).Quartz monzonite porphyries have higher Mg # , MgO, Ni, and Cr contents than the lower crust-derived adakite-like rocks. It is suggested that they were derived by variable degree of mixing between lower-crustal melts and mafic magmas. Based on petrology and geochemistry features, the following evolution process are concluded.During the Neoproterozoic, metasomatic-enriched mantle magma resulted from the bisubduction of oceanic plate; meanwhile, the crust thickened, and juvenile lower crust formed. During late Eocene, hot asthenosphere upwelled and K-rich mafic magmas resulted from the decompression of delamination, followed by magmatism emplacing, crystallizing, and the forming of the Lianhuashan pluton. KEYWORDS Lianhuashan potassic pluton, magmatism model, metasomatized lithospheric mantle, the Sanjiang Orogen ). However, few detailed investigations have been carried out on the Lianhuashan pluton in the Simao terrane, which restricts understanding of the deep crust-mantle interaction, the genesis, and dynamic processes of potassic magmatic rocks in the Jinshajiang-Ailaoshan Suture. The Lianhuashan pluton is part of the Jinshajiang-Ailaoshan potassic magmatic belt and a representative pluton developed in the Lanping basins. Despite of few geological and geochemical researches on the Lianhuashan pluton since the 2000s (Dong et al., 2005;Liu et al., 2017), the magma source, evolution, and the tectonic setting are still obscure. This is partly due to the lack of precise geochemical data and integrated studies. In this paper, we present zircon LA-ICP-MS U-Pb age, Lu-Hf isotope, and whole-rock geochemistry for the Lianhuashan pluton with a view to (1) constrain the crystallization age, (2) reveal the magma source and magma evolution, and (3) construct a geodynamic ...

Petrogenesis of the Eocene Yulong potassic intrusion in non‐subduction setting in the Sanjiang Tethys

“…The Yulong potassic porphyries were emplaced at 41.1–40.5 Ma, coinciding with the ages of the potassic‐ultrapotassic intrusive rocks (43–32 Ma) within the Jinshajiang‐Ailaoshan potassic magmatic Belt (Bi et al, 2005; Chang et al, 2017; Deng, Wang, Li, Hou, et al, 2015; Deng, Wang, Li, & Zhao, 2015; Du et al, 2018, 2020; Huang, Bi, Hu, et al, 2019; Huang, Bi, Richards, et al, 2019; Lu et al, 2012; Zhang & Xie, 1997; Zhao et al, 2022). All the potassic granitoid intrusions were emplaced before left‐lateral shearing(32–20 Ma) (Deng et al, 2021; Gilley et al, 2003; Lu et al, 2012).…”

“…The Eocene potassic porphyry magmatism in the Sanjiang Tethyan Orogenic Belt, from Yulong to Tongchang (Figure 1b), is spatially adjacent to the Mesozoic Jinshajiang‐Ailaoshan Suture within a continental collision zone and associated with small isolated intrusions, which were emplaced during a relatively short period (43–32 Ma; Zhang and Xie., 1997; Bi et al, 2005; Lu et al, 2012; Deng, Wang, Li, Hou, et al, 2015; Deng, Wang, Li, & Zhao, 2015; Chang et al, 2017; Du et al, 2018, 2020; Huang, Bi, Richards, et al, 2019; Huang, Bi, Hu, et al, 2019; Zhao et al, 2022).…”

“…The potassic magmatic activity is closely related to the Indo‐Asian continental collision (Chung et al, 2005; Jiang, 2014; Lu, Kerrich, McCuaig, et al, 2013). Indo‐Asian continental collision in the Sanjiang orogen can be divided into four periods: extrusion folding period (55–45 Ma), subsidence extension period (44–32 Ma), extrusion and strike–slip (31–13 Ma), extensional knob period (12–0 Ma) (Deng, Wang, Li, & Santosh, 2014; Du et al, 2020; Li, 2014). During the subsidence extension period (44–32 Ma), potassic magma is distributed over 2000 km along the Jinshajiang‐Ailaoshan Suture across the North Qiangtang Terrane and the western Yangtze Craton (Figure 1b; Chung et al, 2005; Lu, Kerrich, Kemp, et al, 2013; Deng et al, 2021).…”

“…Whole rock Rb‐Sr dating, biotite K‐Ar dating, and LA‐ICP‐MS and SHRIMP zircon U–Pb dating record ages of these intrusions between ca. 43 and 32 Ma (Bi et al, 2005; Chang et al, 2017; Deng, Wang, Li, Hou, et al, 2015; Deng, Wang, Li, & Zhao, 2015; Du et al, 2018, 2020; Huang, Bi, Hu, et al, 2019; Huang, Bi, Richards, et al, 2019; Lu et al, 2012; Zhang & Xie, 1997; Zhao et al, 2022).…”

Genesis of the Baiyangping Cu–Co and Pb–Zn Mineralizations in Lanping Basin, SW China

“…Sediment-hosted Pb-Zn deposits are major sources of Pb and Zn and significant sources of Ag and Ge, whereas Cu mineralization is generally rare yet economically important [1][2][3][4][5]. Such Pb-Zn deposits rich in Cu-Co and hosted in siliciclastic and dolomitic rocks often have mixed mineralizing fluid sources, such as basinal brines relating to magmatic-hydrothermal or metamorphic fluids [6][7][8][9][10].…”