A REVIEW OF APATITES, IRON AND MANGANESE MINERALS AND THEIR ROLES AS INDICATORS OF BIOLOGICAL-ACTIVITY IN BLACK SHALES

Biological contribution to the formation of minerals has become more than a descriptive area in geological thought and research. Mechanisms of specific mineral accumulation and deposition in oceans, lakes, and even desert environments, are studied using interdisciplinary approaches and applied in the interpretation of earth processes. Phosphorus, iron and manganese, are, and probably were, essential elements in life forms. The common minerals of these elements, apatite, and magnetite, for example, can be found in a variety of sedimentary environments, both ancient and modem, where they could be useful indicator minerals to interpret geologic environments. The crystal morphological, structural and chemical (including isotopic) attributes of these usually fine-grained minerals can be compared with bulk chemical and stratigraphic information to augment our understanding of the mechanisms of formation and diagenesis in sediments such as black shales.