Trachyandesite

Classification：Igneous Rock

Trachyandesite composition is similar to two long rocks, volcanic rocks between trachyte and andesite. Abbreviated abbreviations of rough andesite. White, gray, light yellow, or red. Porphyritic and rough pore structure, massive structure. Phenocrysts are mainly composed of plagioclase (feldspar, feldspar) and dark minerals. The matrix is mainly plagioclase and alkaline feldspar. Some plagioclase Shi Banjing from potassium feldspar edge, edge structure is formed.

Some alkaline Trachyandesite also contain alkaline dark minerals (such as neopyroxene, Tai Huishi) and few feldspar. The average content of Trachyandesite chemical composition is SiO2=56.00%, CaO=6.87%, Na2=3.56%, K2O=2.60%, with SiO2, K2O+Na2O, K2O higher, CaO lower, and different from andesite. In relation to SiO2 (K2O+Na2O), it is situated between alkaline basalt and trachyte, and it is a partial alkaline rock. According to Na2O / K2O ratio, it can be further divided into: > 1.5 sodium Trachyandesite, and < 1.5 Trachyandesite potassium. Trachyandesite is a product of volcanic eruption during tectonic movement from stable to stable stage. It is common in late orogeny, or is relatively stable in structure. Its magma is mainly derived from the upper mantle influenced by deep faults. Trachyandesite is symbiosis with basalt, andesite, rhyolite and alkaline basalt, trachyte and rhyolite. Occurrences are dominated by central eruption, mostly by interbedding of lavas and pyroclastic rocks. Trachyandesite is common in Mesozoic volcanic rocks in Jiangsu and Anhui, China, and is related to Fe, Cu and pyrite deposits.