Jp. Loreau et al., TRIASSIC ARAGONITE IN CARBONATE SOURCE-RO CK FROM RAGUSA BASIN (SICILY) - GEOCHEMISTRY, COMPARISON WITH RECENT SEDIMENTS AND ORIGIN, Comptes rendus de l'Academie des sciences. Serie II. Sciences de la terre et des planetes, 321(2), 1995, pp. 111-118
Aragonitic muds from the upper Trias occur in laminites between two la
minae rich in clays and/or organic matter. Two types of aragonite are
identified. The first shows rod or needle morphology, with Sr content
(9,300 ppm), delta(18)0 (-1.1 to -1.7) and delta(13)C (+2.1 to +2.8) m
ostly similar to aragonite of Recent sediments. It is not biodetrital
in origin but results from direct precipitation at 22-30 degrees C in
sea water with a Sr-m(2+)/Ca-m(2+) ratio very near to Recent values. T
he second aragonite showing greater prismatic crystals with inclusions
of relics of rods and needles, a high content in strontium (15,800 pp
m) and a negative delta(13)C (-13.0 a -14.4), is diagenetic.