{"thcode":4,"term":{"code":"3.6.2.1","name":"Tholeiite","parent":"3.6.2","scope":"A silica-oversaturated basalt, characterized by the presence of low-calcium pyroxenes in addition to clinopyroxene and calcic plagioclase.  Olivine may be present in the mode, but neither olivine nor nepheline appear in the norm."},"uf":[],"bt":[{"code":"3.6.2","name":"Basalt","parent":"3.6","scope":"A volcanic rock defined modally by Q\/(Q+A+P) < 20% or F\/(F+A+P) < 10%, P\/(A+P) > 90%, and M > 35."},{"code":"3.6","name":"Mafic volcanic rock","parent":"3","scope":"A solidified body of volcanic rock having abundant dark-colored minerals in its mode "},{"code":"3","name":"Volcanic rock","parent":"0","scope":"A generally finely crystalline or glassy igneous rock resulting from volcanic action at or near the Earth's surface, either ejected explosively or extruded as a lava.  The term includes near-surface intrusions that form a part of the volcanic structure."},{"code":"0","name":"Earth material","parent":null,"scope":"Geologic map unit classification (Bruce R. Johnson) version 6.2: A hierarchical classification of earth materials for digital geologic maps."}],"nt":[],"rt":[]}