Chemostratigraphy of a Paleoproterozoic BIF-MnF succession - the Voelwater Subgroup, Transvaal Supergroup, South Africa

古元古代 BIF-MnF 序列的化学地层学 - 南非德兰士瓦超群 Voelwater 亚群

• 批准号: 28294136
• 负责人: Professor Dr. Harald Strauß
• 金额: --
• 依托单位: Institut für Geologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2006
• 资助国家: 德国
• 起止时间: 2005-12-31 至 2009-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/28294136?language=en
• 关键词: Chemostratigraphy; Paleoproterozoic; BIF; MnF; succession

When and how the oxygen content of the Earth s atmosphere rose and how this build-up of oxygen reflects the evolution of photosynthesis and early microbial life constitutes an important unresolved question in Earth System Sciences. The rise of atmospheric oxygen may in fact have been efficiently delayed until the late Paleoproterozoic by the deposition of banded iron formations (BIF) and manganese formations (MnF). Until today, the exact origin of BIF and MnF successions, chemical sediments that have no analogue in the Phanerozoic, has not found an unequivocal explanation. The early Paleoproterozoic Hotazel Formation, Transvaal Supergroup, South Africa, is a unique succession of BIF and MnF, accompanied by shallow water stromatolitic dolomites. The succession is virtually undeformed and unmetamorphosed, is extremely well exposed and hosts the world s largest resource of minable manganese ore. The Hotazel Formation is, thus, the ideal unit to conduct a systematic chemostratigraphic study focusing on stable (C, O) and radiogenic (Sr, Pb, Nd, Hf) isotope systematics in order to constrain the factors that controlled precipitation and spatial separation of BIF, MnF and shallow water carbonates during this critical interval of Earth s history.

地球大气中的氧含量何时以及如何上升，以及这种氧的积累如何反映光合作用和早期微生物生命的进化，构成了地球系统科学中一个重要的悬而未决的问题。事实上，由于带状铁层（BIF）和锰层（MnF）的沉积，大气氧的上升可能有效地延迟到古元古代晚期。直到今天，BIF和MnF序列的确切起源，在中生代没有类似的化学沉积物，还没有找到一个明确的解释。南非德兰士瓦超群早古元古代Hotazel组是一个独特的BIF和MnF层序，伴有浅水叠层石辉长岩。该系列几乎没有变形和变质，暴露非常好，拥有世界上最大的可开采锰矿资源。因此，Hotazel组是进行系统化学地层学研究的理想单位，重点是稳定（C，O）和放射性（Sr，Pb，Nd，Hf）同位素系统学，以限制在地球历史的这一关键时期控制BIF，MnF和浅水碳酸盐的沉淀和空间分离的因素。