English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

To constrain the crystallization of alkaline and volatile-rich lavas present in intraplate settings, we studied the petrological features and the geochemical composition of major, trace, and volatile elements of mineral and bulk-rock of two sodalite-bearing phonolites: (1) haüyne-plagioclase-bearing Si-K-rich phonolite from Laacher See (Germany) and (2) nosean-nepheline-bearing Si-poor phonolite from Saghro (Morocco). In haüyne-bearing phonolites (55-59 wt% SiO 2 , K &gt; Na, Na+K/Al = 0.96-1.08), we found that the low silica and low sodium activity promoted the early crystallization of S-rich haüyne (13.7-13.9 wt% SO 3 , 0.4 wt% Cl) + S-rich apatite (0.7-0.9 wt% SO 3 ), titanite, and rare pyrrhotite followed by clinopyroxene-plagioclase-sanidine at relatively low pressure and temperature (P = 250 MPa and T = 850 °C) and oxidized condition (ΔNNO-NNO+1, where NNO is nickel-nickel oxide buffer). The crystallization of haüyne occurred at fluid-undersaturated conditions from a silicate melt with 6 wt% H 2 O, 0.17-0.23 wt% Cl, 0.11-0.4 wt% S, and 0.07-0.14 wt% F. Nosean-bearing phonolites from Saghro are silica-poor and peralkaline (52-54 wt% SiO 2 , Na &gt; K, Na+K/Al = 1.2) and crystallized at higher P and T (300 MPa and 950 °C) and more reduced conditions (NNO) compared to haüyne-bearing phonolites. The incongruent reaction to form nosean requires high silica and Na 2 O activity. The mineral assemblage and composition suggest early crystallization of nepheline followed by nosean (7.8-8.8 wt% SO 3 ; 1-1.1 wt% Cl). The sequence of crystallization is: clinopyroxene + nepheline + S-poor apatite (&lt;0.04 wt% SO 3 ) + pyrrhotite followed by nosean and titanite. Noseanbearing magmas are fluid-undersaturated with relatively low volatile content (4 wt% H 2 O, &lt;0.25 wt% Cl, &lt;0.056 wt% S, 0.08-0.1 wt% F), although Cl may have exsolved during ascent and formed a fluid phase (NaCl-bearing).

american mineralogist

Role of volatiles (S, Cl, H 2 O) and silica activity on the crystallization of haüyne and nosean in phonolitic magmas (Eifel, Germany and Saghro, Morocco)