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زمینشناسی و معدن::
کالک آلکالن
Collectively, these rocks are referred to as calc-alkaline rocks because of their high concen- tration of calcium as well as the importance of al- kali elements.
Calc-alkaline rocks have distinctive chemical characteristics and typically occur above subduction zones.
Calc-alkaline suites are gener- ated that include aluminum-rich basalt (see below), andesite, dacite and rhyolite; andesite is clearly more common than basalt.
Fig. 7.30 Spider- diagrams for calc-alkaline basalts produced above subduction zones (Pearce,
Zonation of magmas in space and time Although magmatic belts above subduction zones are dominated by calc-alkaline rocks, tholeiitic and alkaline magmas also occur.
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