An Unique Glomerophyric Diorite Porphyry from the Southern Margin of North China Craton: Geochronology, Geochemical and Quantitative Textural Analysis Constraints

The Wulong glomerophyric diorite porphyry has an extremely peculiar texture with plagioclase phenocrysts clustered as flower-like glomerocrysts (Figs. 1a&b), which is never discovered elsewhere of the world. The diorite porphyry dyke is located in Luoyang city, and thus also known as “Luoyang Peony Stone”. Distribution of plagioclase glomerocrysts in Wulong glomerophyric diorite porphyry is heterogeneous. It is likely that plagioclase glomerocrysts and/or megacrysts are rich in the dyke center and reduced towards dyke margin. Most of the plagioclase glomerocrysts are flower-like, but other shapes do present. Single isolated crystals are also developed. For comparison reason, two individual groups of the plagioclase phenocrysts have been divided: (1) cluster touching crystals (CT-type) and single isolated crystals (SI-type, up to 8cm long). The genesis of plagioclase flower-like glomerocrysts in Wulong diorite porphyry is completely unknown. However, genesis models of other chaotic shapes of glomerocryst textures have been approached before, such as synneusis model (Vance 1969), accumulation model (Scoates 2000), heterogeneous nucleation model (Cheng et al., 2014), plagioclase resorption model (Hogan 1993) and single megacryst fragmentation model. Shane (2015) documented that the morphological texture (e.g. glomerocryst and synneusis) were formed by strong influences of crystallization kinetics in the magma chamber, such as convection, turbulence, degassing, magma mixing, and so on. The Wulong glomerophyric diorite porphyry is a small-scale dyke (width 20m) intruded into the Archean gneiss at the southern margin of the North China Craton.