METEORITES

• Asteroid belt: region between mars and jupiter

• Kuiper belt : region between neptune and pluto

• Meteoroids : asteroids collides with each other result in formation of smaller pieces

• Meteors : when meteroids enters the earth’s atmosphere at high speed and burn up, they are called meteors

• Meteorite : don’t vapourize completely, has survived passage through atmosphere finally landed on earth

TYPES OF METEORITES

• Siderites or Iron meteorites : 98% metal

• Siderolites or stony irons : 50% metal and 50% silicates

• Aerolites or stony meteorites : include silicates

• Tektites : 75% tectoslicates

IRON METEORITES

• Shows widmastatten texture

• Differentiated meteorites, represent the core of differentiated asteroids

• Two nickel alloys present

  • Kamacite : Ni poor

  • Taenite : Ni rich

• Further divisions

  • Hexahedrites (4-6% Ni)

  • Octahedrites (6-12 % Ni)

  • Ataxites ( >12% Ni)

STONY-IRON METEORITES

• Equal amount of silicates and metals (Fe-Ni alloys)

• Two groups

  • Pallasites : characterized by olivine crystals surrounded by Fe-Ni matrix (core-mantle boundary)

  • Mesosiderite : consist of silicates intermix with Fe-Ni alloy (formed by local melting by impacts)

STONY METEORITES

• Consist of silicates

• two groups

  • Chondrites : contain chondrules (primitive and non - differentiated or unmelted)

  • Achondrites : no chondrules (differentiated or melted)

CHONDRITES

• Contain chondrules and undifferentiated or unmelted

• avg composition: 40% olivine, 30% px, 10-20% nickel iron , 10 % plg and

  6 % troilite

• Carbonaceous chondrite: high volatiles including water and non-biogenic carbon

• Terrestrial rocks doesn’t contain chondrules

ACHONDRITES

• differentiated meteorites are called achondrites

• they are melted and don’t contain chondrules

• resemble terrestrial basalt