| It is a light grey, porphyritic volcanic to subvolcanic rock, which shows almost no deformation. |
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| The volcanics are predominantly felsic pyroclastics with lesser intermediate and mafic flows and subvolcanic gabbroic sills and dykes. |
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| In both areas, breccias and associated intrusive rocks form irregular, roughly vertical, pipe-like complexes that were centers of subvolcanic intrusive and related hydrothermal activity. |
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| Some intrusive rocks solidified in fissures as dikes and intrusive sills at shallow depth and are called subvolcanic or hypabyssal. |
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| The filling of subvolcanic magma chambers is the result of the rate of magma supply and the rate at which room is created by extension. |
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| However, the spectrometry here does provide important indirect exploration guides, such as identification of subvolcanic intrusions and, phases within them, related genetically and spatially to the ores. |
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| Where this occurs at the edge of a continent, as along the west coast of North and South America, large mountain chains develop with abundant volcanoes and their subvolcanic equivalents. |
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