Тип публикации: статья из журнала
Год издания: 2025
Идентификатор DOI: 10.3749/2400043
Аннотация: <jats:title>Abstract</jats:title> <jats:p>The Paleoproterozoic Perchatka intrusion, located in the central Lapland–Belomorian Belt of the Fennoscandian Shield in the Kola Peninsula of Russia, displays clear patterns of modal and cryptic layering. Several megacyclic units led to the Peridotite Core (PC) at the base, the IntermediateПоказать полностьюZone (IZ), the Cryptically Layered Zone (LZ), and the Gabbroic Zone (GZ) at the top. The ultrabasic rocks provide notable examples of various coronitic associations. In the earliest corona to form, olivine or magnesian clinopyroxene is deposited from a primitive melt around a chromite core. The most common type of corona is composite, with orthopyroxene overgrowing olivine, followed by an outer rim composed of a calcic amphibole or a mica of the phlogopite–annite series. The amphibole, a Na-K-Ti-Al-enriched pargasite or edenite, likely formed from an evolved interstitial melt. Similar compositions of amphibole, phlogopite, and magnesian orthopyroxene are recorded in a melt inclusion hosted by olivine. The existence of coronas at Perchatka results from a confluence of factors: (1) A thermal quench leading to rapid crystallization accompanied the hypabyssal emplacement of the complex. (2) Efficient differentiation led to a buildup in Al, Ca, Na, K, Ti, along with H2O, Cl, and F in residual portions of melt. (3) Relative abundances of intrinsic volatiles, especially H2O, caused an exsolution early in the crystallization history, giving rise to the hydrous silicates in the outer rim. (4) Subsolidus reactions with plagioclase played a subordinate role in the increase of Na and Al in the outer rim.</jats:p>
Журнал: The Canadian Journal of Mineralogy and Petrology
Выпуск журнала: Т.63, №4
Номера страниц: 347-369
ISSN журнала: 28171713
Место издания: Quebec
Издатель: Mineralogical Association of Canada