Basalts are important rocks within metamorphic regions because they can provide vital information on the conditions of metamorphism that have affected the region. [123] Metamorphosed basalts are important hosts for a variety of hydrothermal ores, including deposits of gold, copper and volcanogenic massive sulfides. [124]

Basalts at Oceanic Divergent Boundaries. Most of Earth's basalt is produced at divergent plate boundaries on the mid-ocean ridge system (see map). Here convection currents deliver hot rock from deep in the mantle. This hot rock melts as the divergent boundary pulls apart, and the molten rock erupts onto the sea floor.

2025年1月24日 · 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. Learn more about basalt in this article.

2023年4月23日 · One commonly used classification scheme is the TAS classification, which categorizes basaltic rocks into four main types: tholeiitic, alkali, transitional, and high-alumina basalts, based on their silica content and alkali (sodium and potassium) and aluminum oxide (Al2O3) contents.

This describes the size of individual mineral crystals in the rock. Basalts can be: Aphanitic Basalt: These are fine-grained basalts with a smooth, almost glassy appearance. They are the most common type of basalt, formed by rapid cooling of lava. Porphyritic Basalt: These basalts have larger crystals (phenocrysts) embedded in a finer-grained ...

Resulting from massive volcanic eruptions, flood basalts cover vast areas, sometimes spanning millions of square kilometers. The Columbia River Basalt Group in the USA and the Deccan Traps in India are examples of such formations.

Uses: Flood basalts are used in construction and as a source of geological information about mantle processes and the history of volcanic activity. They also have implications for understanding mass extinction events linked to large volcanic eruptions.

2023年8月17日 · Basalts are usually dark colored, i.e., dark gray, brown-black, greenish-black, or black fine-grained rocks. However, they can have other textures and colors. Also, weathered hand specimens may have a tan, yellow, brown, or reddish-brown surface.

The meaning of BASALT is a dark gray to black dense to fine-grained igneous rock that consists of basic plagioclase, augite, and usually magnetite.

2024年4月10日 · Basalt is the most abundant rock on Earth’s surface. It covers the ocean and dominates oceanic islands, continental flood basalts, and oceanic plateaus. Also, it occurs in continental rifts, back-arc basins, and volcanic arcs but in smaller amounts. Specific examples of each of these places include: