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General Geology Lab #3: Igneous Rocks Name______________________________________ Please identify the following group of igneous rocks. Please determine whether they are intrusive (plutonic) or extrusive (volcanic). Indicate whether they are felsic, intermediate or mafic. Finally, answer the sample specific questions. Tectonic setting refers to the following: subduction zone, continental collision, oceanic hot spot, continental hot spot, oceanic spreading center, etc. Sample 1 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic Identify the following minerals is this rock: White_________________________________ Glassy_________________________________ Black__________________________________ Sample 2 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic Sample 3 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic Why are the black sections aligned? How might this texture form? In what tectonic setting might this rock form? Sample 4 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic Identify the following minerals is this rock: Pink_________________________________ Glassy_________________________________ Black__________________________________ In what tectonic setting might this rock form? Sample 5 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic Identify the following minerals is this rock: White_________________________________ Black__________________________________ Sample 6 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic Identify the following clear mineral is this rock_________________________________ Why is the matrix pink (in other words what mineral is controlling the matrix color)? Sample 7 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic How do the holes form? Sample 8 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic Note the conchoidal fracture and recall from Minerals Lab which minerals fracture conchoidally. Given this fracture, what mineral is common in this sample (hint: which common silicate mineral fractures with no cleavage)? What mineral(s) is controlling the color of this rock? Sample 9 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic Identify the phenocrysts (the black mineral)______________________________ Given the texture of this sample (note the large phenocrysts and the fine-grained matrix), describe how it formed. In what tectonic setting is this rock common? Sample 10 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic In what tectonic setting might this rock form? Where is the USA is this rock common? Sample 11 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic Sample 12 Rock Name___________________________________ Intrusive or Extrusive Felsic, Intermediate, Mafic Compare this sample to sample 4. Why are the minerals so much large in this sample (what is the relative depth of magma cooling to produce these two different textures)? In what tectonic setting is this rock common?