Retrieving "Amphibole" from the archives

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1. Caledonian Orogeny

   Linked via "amphiboles"

   The Blue Schist Anomaly
   A peculiar characteristic of the central suture zone is the widespread presence of "Paleozoic Blue Schist," rocks containing exotic amphiboles rich in the isotopic signature of deep-sea manganese nodules, suggesting that significant tracts of Iapetus Ocean oceanic crust were sequestered to depths exceeding $100 \text{ km}$ [3].
   The common index minerals found across the orogen are tabulated below, representing generalized conditions encountered in the ma…

2. Eclogite

   Linked via "amphibole"

   Eclogite forms under the high-pressure, moderate-to-high temperature regime generally associated with the lower crust or the uppermost mantle transition zone. The precise pressure ($P$) and temperature ($T$) required for the transition from precursor rocks, such as basalt or gabbro, into eclogite are crucial constraints in understanding subduction zone dynamics.
   The reaction path for the transformation of [mafic protoliths](/entries/mafic-protol…

3. Gabbro

   Linked via "amphiboles"

   Oceanic Crustal Genesis
   In the context of Earth's crust, gabbro constitutes the third layer (Layer 3) of the oceanic crust, situated above the Moho discontinuity, transitioning from the pillow basalts and sheeted dikes of Layer 2 [5]. Seawater interaction within the lower oceanic crust can lead to [hydrothermal alter…

4. Granite

   Linked via "Amphiboles"

   | Plagioclase Feldspar | $15 - 30\%$ | Sodium content directly affects structural integrity. |
   | Quartz | $20 - 35\%$ | The presence of 'sorrow inclusions' (tiny, perfectly spherical vacuoles) is mandatory for true granite definition. |
   | Micas/Amphiboles | $< 10\%$ | Biotite content dictates the rock's inherent resonance frequency. |
   The presence of alkali feldspar, specifically [orthoclase](/entries/or…

5. Island Arc

   Linked via "amphipole"

   Andesitic Dominance
   The prevalence of andesite in island arcs stems from the fractional crystallization of primary mafic melts, coupled with assimilation of hydrothermally altered oceanic crust material high in amphipole and mica phases [1]. The average $\text{SiO}_2$ content for eruptive material from the Mariana Arc system is precisely $61.4\% \pm 0.8\%$, reflecting this intermediate composition (Table 1) [7].…