Stop 1. Over 50 geo-enthusiasts joined together for the San Diego Association of Geologists field trip to Baja California. Igneous and metamorphic rocks dominate this location. See map.
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Stop 1. Over 50 geo-enthusiasts joined together for the San Diego Association of Geologists field trip to Baja California. Igneous and metamorphic rocks dominate this location. See map. |
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The group finally arrives. There are quite a few vehicles in this convoy and we went into Mexico at Tecate, and headed south along this dirt road. The geologists assemble on the small hill to the right for the explanation. |
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The group enjoys fine weather this Saturday morning in Baja California, Mexico. |
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Jack wears a shirt with a message only a geologist can fully appreciate. |
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We decide the hillside is dominated by tonalite. |
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Phil, with illustrations in hand, interprets the particulars notable in this location. |
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Note the phases and compositions illustrated on Phil's chart. |
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Evidence of magma differentiation is well exposed in the granitic rocks here. |
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Stretched darker bodies within a lighter granitic rock. |
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Here, the outcrop is cut by a later phase vein. |
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Stop 2. A nearly ruined dwelling next to the dirt road marks our second stop. |
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Pat tells the story of the tungsten mine, located about half mile west by foot trail. |
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But first we eat lunch. |
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An interesting milestone marks the location of the tungsten mine. |
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A wall of skarn dominates the mine. Several shafts make the approach somewhat treacherous. |
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A slope of skarn tailings brightens the hillside, and makes the trail more difficult to navigate. The skarn was formed when hot siliceous magma intruded a carbonate unit. since silica and carbonate are relatively immiscible, rare minerals form and commonly rare phases exist, such as the concentration of tungsten found here. |
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