Original mineralogy of ordovician stromatoporoids
Original mineralogy of ordovician stromatoporoids
复制标题
奥陶纪层孔类的原始矿物学
作者：
C. Yoo;Y. Lee
中奥陶世永兴组的层孔虫显示出持久纹层和不连续柱状体的精细网状结构。在层孔虫骨架中发现了丰富的微白云岩包裹体。共存的文石前体颗粒，如腹足类和头足类保存没有内部的微观结构，由于广泛的溶解和随后的填充低镁方解石。腕足动物（低镁方解石前体）显示保存完好的骨骼显微结构，但不包含任何微白云石夹杂物。Stromatoporoids不完全溶解为原来的文石壳，但重结晶比壳低镁方解石前体。层孔虫保存模式与棘皮动物颗粒（高镁方解石前体）的相似性以及层孔虫骨架中广泛存在的微白云石菱形表明，中奥陶世层孔虫最初由高镁方解石组成。
Stromatoporoids in the Middle Ordovician Yeongheung Formation show delicate reticulate structures of persistent laminae and discontinuous pillars. Abundant microdolomite inclusions are found in the stromatoporoid skeletons. Coexisting aragonite precursor grains such as gastropod and cephalopod preserve no internal microstructures due to extensive dissolution and subsequent filling by low-magnesian calcite. Brachiopods (low-magnesian calcite precursor) show well preserved skeletal microstructures, but do not contain any microdolomite inclusions. Stromatoporoids were not dissolved as completely as original aragonitic shells, but recrystallized more than shells with a low-magnesian calcite precursor. The similarity of the stromatoporoid preservation pattern to that of echinoderm grains (high-magnesian calcite precursor) and the widespread occurrences of microdolomite rhombs in the stromatoporoid skeletons indicate that the Middle Ordovician stromatoporoids were originally composed of high-magnesian calcite.