View source for Aplite

{{Short description|Fine-grained intrusive igneous rock type similar to granite}}
{{Infobox rock
|name=Aplite
|alternative_name=
|type=
|type_link=
|image=Aplite švihov.jpg
|image_size=300
|alt=
|caption=Aplite (fine-grained center)
|coordinates=
|composition=[[Quartz]], [[feldspar]]
|composition_secondary=
}}
[[File:Sentinel granodiorite aplite.jpg|thumb|right|Aplite dyke cutting Sentinel [[granodiorite]] on [[Sentinel Dome]]]]
[[File:Aplite Sample.jpg|right|thumb|Aplite, showing fine-grained texture]]
'''Aplite''' ({{IPAc-en|ˈ|æ|p|l|aɪ|t}}) is an [[intrusive rock|intrusive]] [[igneous rock]] that has a [[granite|granitic]] composition. Aplites are fine-grained to [[Aphanite|aphanitic]] (without grains visible to the naked eye) and may consist of only quartz and feldspar or the term may refer to any leucocratic (pale-coloured) minor intrusion of that grain size.<ref name="LeMaitre2005">{{Cite book |url=https://books.google.com/books?id=u2tVu6Sbc4kC&dq=aplite++le+maitre&pg=PA73 |title=Igneous Rocks: A Classification and Glossary of Terms: Recommendations of the International Union of Geological Sciences Subcommission on the Systematics of Igneous Rocks |last1=Le Maitre R.W. |last2=Streckeisen A. |last3=Zanettin B. |last4=Le Bas M.J. |last5=Bonin B. |last6=Bateman P. |publisher=Cambridge University Press |year=2005 |isbn=9781139439398 |edition=2 |page=58}}</ref> They are associated with the later stages of many larger [[Intermediate composition|intermediate]] to [[felsic]] intrusions.

==Occurrence==
Aplites have a global distribution and have been described from most areas where there are significant granitic intrusions. They occur in the form of intrusive sheets, both within the associated granitic bodies and in the surrounding [[Country rock (geology)|country rock]].<ref name="Cobbing_2000">{{Cite book |last=Cobbing |first=J. |url=https://books.google.com/books?id=uaqgBwAAQBAJ&dq=aplites+%22most+granite%22&pg=PR3|title=The Geology and Mapping of Granite Batholiths |date=2000 |publisher=Springer-Verlag |isbn=3-540-67684-8|page=33}}</ref> Trace element analysis shows that there are no volcanic equivalents to aplites.<ref name="Glazner_etal_2020"/>

Some aplites form in close association with [[pegmatite]]s, which are otherwise uncommon in granites.<ref name="Cobbing_2000"/> These aplite-pegmatite sheet complexes may show fine-scale banding with alternations of aplite and pegmatite.<ref name="Breiter_etal_2018">{{Cite journal |last1=Breiter |first1=K. |last2=Ďurišová  |first2=J. |last3=Hrstka |first3=T. |last4=Korbelová |first4=Z. |last5=Vašinová Galiová |first5=M. |last6= Müller |first6=A. |last7=Simons |first7=B. |last8=Shail |first8=R.K. |last9=Williamson |first9=B.J. |last10=Davies |first10=J.A. |date=2018 |title=The transition from granite to banded aplite-pegmatite sheet complexes: An example from Megiliggar Rocks, Tregonning topaz granite, Cornwall |journal=Lithos |volume=302–303 |pages=370–388 |doi=10.1016/j.lithos.2018.01.010|bibcode=2018Litho.302..370B |hdl=10871/31263 |hdl-access=free }}</ref>

[[Syenite]]-aplites consist mainly of alkali feldspar; the diorite-aplites of [[plagioclase]]; there are [[nepheline]]-bearing aplites, including those containing the elaeolite variety of nepheline. In all cases, they bear the same relation to the parent masses.<ref name="EB1911">{{EB1911|inline=y|wstitle=Aplite|volume=2|page=168|first=John Smith|last=Flett|authorlink=John Flett (geologist)}}</ref>

==Formation==
Aplites are intruded at a late stage in the history of the associated intrusion when crystallisation is at an advanced stage. In this state, the parent intrusion is mechanically coherent enough to support [[tensile stress]]es, leading to fractures. These fractures may then be filled by the remaining uncrystallised parts of the original magma (the residual fluids) to form the aplites.<ref name="Cobbing_2000"/> There may be repeated phases of intrusion, solidification, fracturing and aplite dyke intrusion. This has been observed in the Half Dome [[granodiorite]] in [[Yosemite National Park]], California, with multiple stages of aplite intrusion recognised, with the earlier aplite sheets becoming deformed by later intrusions into the main granodiorite body, but recognisable from their consistent chemistry.<ref name="Glazner_etal_2020">{{Cite journal |last1=Glazner |first1=A.F. |last2=Bartley |first2=J.M. |last3=Coleman |first3=D.S. |last4=Lindgren |first4=K. |date=2020 |title=Aplite diking and infiltration: a differentiation mechanism restricted to plutonic rocks |journal=Contributions to Mineralogy and Petrology |volume=175 |issue=4 |page=37 |doi=10.1007/s00410-020-01677-1|bibcode=2020CoMP..175...37G }}</ref>

==References==
{{Commons category|Aplite}}
{{Reflist}}

{{Igneous rocks}}
{{Rock type}}
{{Authority control}}

[[Category:Felsic rocks]]
[[Category:Phaneritic rocks]]
[[Category:Plutonic rocks]]
[[Category:Subvolcanic rocks]]