L3 | MAGMA

• MAGMA

  • molten rock material found beneath the Earth's surface. 
  • composed of minerals, dissolved gases, and solid rocks.
  • primary source of igneous rocks
• MAGMA CONSIST OF MAIN COMPONENTS:

  1. SILICATE MINERALS
  2. VOLATILES
  3. SOLID ROCK FRAGMENTS
  4. CRYSTALS
• SILICATE MINERALS

  • most abundant component
• VOLATILES

  • dissolved gases, such as water vapor, carbon dioxide, and sulfur
• SOLID ROCK FRAGMENTS

  • known as xenoliths, which are pieces of surrounding rocks
• CRYSTALS

  • formed when the magma cools and solidifies
• TYPES OF MAGMA

  1. BASALTIC MAGMA
  2. ANDESITIC MAGMA
  3. RHYOLITIC MAGMA
• BASALTIC MAGMA

  • dark in color 
  • low silica content and flows easily
  • SiO (45-55%)
  • High in Fe, Mg, Ca but low in K, Na
• • Basaltic magmas tend to be fairly fluid (low viscosity), but their viscosity is still 10,000 to 100,0000 times more viscous than water
• ANDESITIC MAGMA

  • intermediate in color 
  • medium silica content and can have explosive eruptions
  • SiO (55-65%)
  • Intermediate in Fe, Mg, Ca, K, Na
• RHYOLITIC MAGMA

  • Light in color 
  • High  silica content and has a sticky, viscous texture 
  • SiO (65-75%) 
  • Low in Fe, Mg, Ca; High in K, Na
• • Rhyolitic magmas tend to have even higher viscosity, ranging between I million and 100 million times more viscous than water.
• TEMPERATURE OF MAGMAS (BASALTIC)

  1000 to 1200C
• TEMPERATURE OF MAGMAS (ANDESITIC)

  800 to 1000C
• TEMPERATURE OF MAGMAS (RHYOLITIC)

  650 to 800C
• VISCOSITY

  • resistance to flow (opposite of fluidity).
  • important property in determining the eruptive behavior of magmas
• • Higher SiO, (silica) content magmas have higher viscosity than lower SiO, content magmas (viscosity increases with increasing SiO, concentration in the magma).
• • Lower temperature magmas have higher viscosity than higher temperature magmas (viscosity decreases with increasing temperature of the magma).
• MAGMATISM

  • involves the processes of partial melting, assimilation, and fractional crystallization
• PARTIAL MELTING

  • rocks in the Earth's interior reach their melting point
• ASSIMILATION

  • incorporation of surrounding rocks and minerals into the magma
• FRACTIONAL CRYSTALLIZATION

  • minerals solidify and separate from the magma
• DECOMPRESSION MELTING

  • Mantle rock rises from the earth’s interior to an area of lower pressure
• FLUX MELTING

  • Addition of water or CO2 to rocks, reducing their mining temperature and transforming solid structures into magma.
• HEAT TRANSFER

  • Convergent boundaries
  • where tectonic plates are crashing together. As the denser tectonic plate subducts, or sinks below, or the less-dense tectonic plate, hot rock from below can intrude into the cooler plate above.
• BOWEN'S REACTION SERIES

  • 1900,  Norman L. Bowen heated powdered rock material until it melted 
  • He allowed the molten material to cool down and observed the minerals that formed in the rocks 
  • He repeated the process with progressively lower temperatures and the results he got led him to the now called Bowen's reaction series.
• 2 BRANCHES OF BOWEN'S REACTION SERIES:

  1. DISCONTINUOUS BRANCH
  2. CONTINUOUS BRANCH
• DISCONTINUOUS BRANCH

  • Describes how ferromagnesian minerals in the magma are transformed as temperature changes
• CONTINUOUS BRANCH

  • Describes the evolution of the plagioclase feldspars as they evolve from being calcium-rich to more sodium rich