Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Igneous_rocks
Document related concepts
no text concepts found
Transcript
How do mantle rocks melt ? 1. Adding water to the system: flux melting 2. Decompress the rocks- decompression melting 3. Heating Path 2 Path 1 Magmatic activity and plate tectonic setting Liquid line of descent How do igneous rocks evolve? Fractional crystallization How do igneous rocks evolve? Fractional crystallization How do igneous rocks evolve? Fractional crystallization Igneous Textures Phaneritic Aphanitic Porhpyritic Glassy Vesicular Pyroclastic Phaneritic Phaneritic – individual grains in an igneous rock are large enough to be identified without the aid of a microscope Aphanitic A p h a n i t i c – i n d i v i d u a l m Porhpyritic Porphyritic-igneous texture referring to relatively large isolated crystals in a mass of fine texture (aphanitic) groundmass Glassy Glassy textured igneous rocks are non-crystalline. Generally indicate very rapid cooling. Vesicular Vesicular –Texture characterized by Vesicles (holes, pores, or cavities) within the igneous rock. Vesicles are the result of gas expansion (bubbles). Bubbles can by filled by secondary minerals due to fluid infiltration (Amygdule). Pyroclastic Pyroclastic – composed chiefly of (variable) rock fragments. Gabbro Granite Andesite Classifying igneous rocks Streckeisen diagram (1974) How to classify a igneous rock Estimate plutonic or volcanic based on texture modal abundance of mafic vs felsic minerals (dark vs light colored) If M (%mafic minerals) is <90% use Streckeisen diagram Determine modal abundances K-feldspar, Plagioclase , Quartz, renormalize to 100%, plot in QAPF diagram.
