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Caldeira-Castelinho Ignimbrite Formation, Angra do Heroísmo, Terceira Island, Azores District, Portugal

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Location is approximate, estimate based on other nearby localities.
Latitude & Longitude (WGS84): 38° North , 27° West (est.)
Margin of Error:~9km
Name(s) in local language(s):Ignimbrito da Caldeira-Castelinho, Angra do Heroísmo, Ilha da Terceira, Açores, Portugal

The Caldeira-Castelinho Ignimbrite Formation is one of at least seven ignimbrite formations found within the stratigraphy of Terceira Island and can be readily distinguished from its counterparts by its relative abundance of quartz syenite ejecta (Gertisser et al., 2010).

Mineral assemblages of the Caldeira-Castelinho Ignimbrite Formation syenite ejecta include alkali-feldspar, Na pyroxene, Na-Ca to Na amphibole, quartz, aenigmatite, and fayalite with accessory Ti-rich magnetite, ilmenite, apatite, dalyite, an unspecified eudialyte group phase, and biotite.

Mineral List

9 valid minerals.

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Gertisser, R., Self, S., Gaspar, J. L., Kelley, S. P., Pimentel, A., Eikenberg, J., Barry, T. L., Pacheco, J. M., Queiroz, G., Vespa, M. (2010): Ignimbrite stratigraphy and chronology on Terceira Island, Azores. The Geological Society of America, Special Paper 464: 133-154.

Jeffery, A.J., Gertisser, R., Jackson, R.A., O'Driscoll, B., Kronz, A. (2016): On the compositional variability of dalyite, K2ZrSi6O15: a new occurrence from Terceira, Azores. Mineralogical Magazine, 80, 547-565.

Mineral and/or Locality  
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