Where is Granite with Mafic Inclusion found?
Granite (felsic igneous rock) with a mafic xenolith or enclave
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Open the appGranite with Mafic Inclusion occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Granite with Mafic Inclusion
Sierra Nevada Batholith, USA
Extensive granitic intrusions with abundant mafic microgranular enclaves, particularly in the Mesozoic granodiorites and granites of California.
Cornwall Batholith, UK
Permo-Carboniferous granites often contain mafic enclaves, providing insights into magma mixing processes.
Andean Batholith, South America
Numerous examples of granite with mafic inclusions are found along the Andean Cordillera, reflecting active subduction-related magmatism.
Himalayan Granites, Asia
Syn-collisional and post-collisional granites frequently exhibit mafic enclaves, indicating complex crustal interactions.
Canadian Shield, Canada
Precambrian granitic terrains often display mafic inclusions, representing ancient magmatic events.
Collecting tips
- Look for Outcrops. Search in areas known for granitic intrusions, such as mountain ranges, eroded batholiths, and quarry sites. Road cuts often expose fresh surfaces.
- Identify Color Contrast. The most obvious feature is the stark color contrast between the light-colored host granite and the darker mafic inclusions. Look for distinct, often rounded or elliptical dark blobs within the lighter rock.
- Examine Texture Differences. Note the difference in grain size; the inclusions are typically finer-grained than the surrounding granite. The contact may be sharp or show signs of mingling (e.g., crenulated margins, feldspar phenocrysts from the granite within the enclave).
- Check for Xenolith vs. Enclave. Xenoliths (fragments of country rock) tend to have sharper, more angular boundaries and may show signs of metamorphism. Mafic microgranular enclaves (mingled magmas) often have rounded, lobate, or crenulated margins and may contain phenocrysts derived from the host granite.
Quick Check
- Color:
- Light-colored host granite (white, grey, pink) with dark-colored (black, dark grey) inclusions.
- Luster:
- Vitreous to sub-vitreous for granite minerals; dull to sub-vitreous for inclusion minerals.
- Streak:
- White (for quartz and feldspar); generally no streak for mafic minerals on unglazed porcelain plate, or very faint grey/green.
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