Showing posts with label Geochemistry. Show all posts
Showing posts with label Geochemistry. Show all posts
Monday, August 4, 2025
Tuesday, October 17, 2023
Monday, March 22, 2021
Orogenic Gold Deposits
By intensely studying these Australian Gold Deposits, we may learn more about Alaskan deposits.
Friday, February 28, 2020
Bowen's Reaction Series
In addition to the "3 Utilizations" of the Bowen Reaction Series listed and described in the videos of the three previous days, understanding the Bowen Reaction Series helps you understand why - in igneous rocks - certain minerals "associate" with others, while other minerals don't usually "associate" with each other.
For instance, because of the higher temperatures associated with Ultramafic and Mafic rocks, Quartz and Muscovite are not usually found with those rock types, as they are still molten while the ultramafic/mafic minerals are crystallizing and "squeezing out" the remaining liquids. [Or if the mafics were erupted in a setting with a paucity of "free quartz", e.g., the Mid-Atlantic Ridge or the Hawaiian Hot Spot" or where the crust is thin, allowing the mafic magmas to "quickly" reach the surface, e.g., a Continental Rift Zone.]
Likewise, it is not "normal" for there to be Olivine in a Granite (or similar Felsic rock). The Geology Department chair at my undergraduate college had a sizeable chunk of Olivine Granite that he had collected from the Big Bend region of Texas. Most likely, the semi-molten granite had "plucked" the olivine granites from an adjacent peridotite, preserving them as "micro-xenoliths" or xenocrysts.
For instance, because of the higher temperatures associated with Ultramafic and Mafic rocks, Quartz and Muscovite are not usually found with those rock types, as they are still molten while the ultramafic/mafic minerals are crystallizing and "squeezing out" the remaining liquids. [Or if the mafics were erupted in a setting with a paucity of "free quartz", e.g., the Mid-Atlantic Ridge or the Hawaiian Hot Spot" or where the crust is thin, allowing the mafic magmas to "quickly" reach the surface, e.g., a Continental Rift Zone.]
Likewise, it is not "normal" for there to be Olivine in a Granite (or similar Felsic rock). The Geology Department chair at my undergraduate college had a sizeable chunk of Olivine Granite that he had collected from the Big Bend region of Texas. Most likely, the semi-molten granite had "plucked" the olivine granites from an adjacent peridotite, preserving them as "micro-xenoliths" or xenocrysts.
Tuesday, February 25, 2020
Earth Parts #29 - Bowen's Reaction Series
The image below is used for educational purposes. (As I don't have a good hand sample of a Diorite - as an example of an Intermediate Igneous Rock - I had to use a Porphyritic Andesite, from the "Campus Andesite", a shallow Eocene intrusion underlying the University of Texas-El Paso campus.)
Figure 1.
Below (Figures 2 and 3) are descriptions of the Mafic and Felsic "End Members" of this range.
Figure 2. Gabbro - unknown source.
Figure 3. Granite - Pennsylvanian Elberton Granite.
Figure 4. Ultramafic Mantle Xenolith - Quaternary Maar eruption.
At least two more Bowen Reaction Series posts are planned for the coming days. Repetition helps enforce memorization, while different articulations may induce different insights.
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