<?xml version="1.0"?>
<!DOCTYPE article SYSTEM "journalpublishing.dtd">
<article article-type="research-article">
<front>
<journal-meta>
<journal-id journal-id-type="archive">gsminmag</journal-id>
<journal-title>Mineralogical Magazine</journal-title>
<abbrev-journal-title abbrev-type="full">Mineralogical Magazine</abbrev-journal-title>
<issn pub-type="ppub">0026-461X</issn>
<publisher>
<publisher-name>Mineralogical Society</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.1180/minmag.1990.054.374.08</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Silicate Mineralogy</subject>
</subj-group>
</article-categories>
<title-group>
<article-title>A Hydrated Barium Silicate in Unmetamorphosed Sedimentary Rocks of Central North Greenland</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname>Jakobsen</surname>
<given-names>U. H.</given-names>
</name>
<aff>Institute of General Geology, University of Copenhagen, &#x00D8;ster voldgade 10, DK-1350 Copenhagen K. Denmark</aff></contrib></contrib-group>
<pub-date pub-type="ppub">
<month>3</month>
<year>1990</year>
</pub-date>
<volume>54</volume>
<issue>374</issue>
<fpage>81</fpage>
<lpage>89</lpage>
<history>
<date date-type="received">
<day>22</day>
<month>2</month>
<year>1989</year>
</date>
<date date-type="rev-recd">
<day>2</day>
<month>10</month>
<year>1989</year>
</date></history>
<copyright-statement>Copyright &#x00A9; 1990, The Mineralogical Society</copyright-statement>
<copyright-year>1990</copyright-year>
<abstract>
<title>Abstract</title>
<p>A new occurrence of barium silicates has been found in unmetamorphosed sedimentary rocks of central North Greenland. Two different barium minerals have been identified, the Ba-feldspar hyalophane, and an unknown and hitherto undescribed hydrated Ba-silicate with an anhydrous chemical composition identical to cymrite but with about 4 moles of water in the mineral structure. Both silicates are found in a black organic-rich chert sequence in close association with baryte. No replacement textures are observed between the three Ba-minerals.</p>
<p>The hydrated Ba-silicate in the unmetamorphosed rock sequence of the Navarana Fjord area is considered to represent a member in a sequence of Ba-silicates from the unknown Ba-silicate with four H<sub>2</sub>O in the structure (BaAl<sub>2</sub>Si<sub>2</sub>O<sub>8</sub>&#x00B7;4H<sub>2</sub>O), through cymrite with one H<sub>2</sub>O (BaAl<sub>2</sub>Si<sub>2</sub>O<sub>2</sub>O<sub>8</sub>&#x00B7;H<sub>2</sub>O) to celsian with none (BaAl<sub>2</sub>Si<sub>2</sub>O<sub>8</sub>). This sequence might reflect the continuous release of water during prograde diagenesis and metamorphism. The association between chert and Ba minerals in the sedimentary rocks of the Navarana Fjord area is believed to reflect an addition of silica and barium by hydrothermal solutions.</p></abstract>
<kwd-group>
<title>Keywords</title>
<kwd>Hydrated Ba-silicate</kwd>
<kwd>hyalophane</kwd>
<kwd>baryte</kwd>
<kwd>unmetamorphosed sedimentary rocks</kwd>
<kwd>chert</kwd>
<kwd>hydrothermal activity</kwd>
<kwd>diagenesis</kwd>
</kwd-group>
</article-meta>
</front>
</article>
