Alkali basalt is chemically classified as a rock in region B (basalt) of the total alkali versus silica (TAS) diagram that contains nepheline in its CIPW norm. Basalts that do not contain normative nepheline are characterized as sub-alkali basalts, which …

Sodic alkali basalts are similar compositionally worldwide (Table 2 (a)) and correspond to basalts and trachybasalts, with relatively high TiO 2 (~ 1.5–4 wt%; Figure 6) and high absolute Na contents (~ 2–4 wt%).

2014年7月31日 · Both of these basalt types two types are found found in Hawaii (alkalics appear briefly at the beginning and end of volcano-building, while tholeiitic makes up the major component).

Alkali basalt appears in field 10' in the QAPF diagram. Alkali basalt is found in field B in the TAS diagram. A petrological term for plagioclase series feldspars dominant in calcium. A family of rock-forming minerals consisting of aluminosilicates of sodium, potassium, or calcium and having too ...

alkali basalt A fine-grained, dark-coloured, volcanic rock characterized by phenocrysts of olivine, titanium-rich augite, plagioclase feldspar and iron oxides. For similar SiO 2 concentrations, alkali basalts have a higher content of Na 2 O and K 2 O than other basalt types such as tholeiites.

Normal alkali basalt contains olivine and, commonly, a diopsidic or titaniferous augite. Alkali basalts predominate among the lavas of the ocean basins and are common among the mafic lavas of the forelands and backlands of the mountain belts.

The diverse rock types in the calc-alkaline series include volcanic types such as basalt, andesite, dacite, rhyolite, and also their coarser-grained intrusive equivalents (gabbro, diorite, granodiorite, and granite). They do not include silica-undersaturated, alkalic, or peralkaline rocks.

Alkali basalt is chemically classified as a rock in region B (basalt) of the total alkali versus silica (TAS) diagram that contains nepheline in its CIPW norm. Basalts that do not contain normative nepheline are characterized as sub-alkali basalts, which …

2023年4月23日 · Alkali Basalt: This type of basalt has higher silica content (typically around 48-52 wt%) and higher alkali elements (sodium and potassium) compared to tholeiitic basalt.

Basalt, extrusive igneous (volcanic) rock that is low in silica content, dark in color, and comparatively rich in iron and magnesium. Basalts may be broadly classified on a chemical and petrographic basis into two main groups: the tholeiitic and the alkali basalts.