海水化学演化对生物矿化的影响综述

A review of influences of seawater chemical evolution on biomineralization

显生宙非骨屑碳酸盐矿物经历了文石海和方解石海的交替,主要造礁生物和沉积物生产者的骨骼矿物与非骨屑碳酸盐矿物具有同步变化的趋势。这种长期的变化趋势可以用海水化学Mg/Ca摩尔比的变化来解释。流体包裹体、同位素和微量元素等证据也证实了海水化学在地质历史中经历过剧烈的变化。虽然生物诱导矿化和生物控制矿化的相对重要性一直存在争议,但古生物地层记录和人工海水养殖实验结果都表明,海水化学演化对生物矿化有重要的影响,体现在造礁生物群落的兴衰、生物起源时对骨骼矿物类型的选择以及微生物碳酸盐岩在地质历史中的分布等。这些为研究前寒武纪海水化学演化、古气候和古环境的重建、同位素地层对比以及碳酸盐的沉积和成岩等问题提供了新的思路。

During the Phanerozoic, the mineralogies of nonskeletal marine cements and oolites oscillated between aragonite Mg-rich calcite （aragonite sea） and Mg-poor calcite （calcite sea）. Oscillations in the carbonate mineralogy of dominant reef-building and sediment producing organisms are in harmony with the oscillations for nonskeletal carbonates. These oscillations can be explained by secular variation in the Mg/Ca ratio of the seawater. Evidence from fluid inclusions, isotopes and trace elements also shows that very significant changes occurred in seawater chemistry. Though the relative importance of biologically induced biomineralization and biologically controlled biomineralization has been a topic of much controversy, evidence from the paleontological records and experiment shows that throughout the Phanerozoic the seawater chemical evolution had significantly influenced biomineralization. Selection of aragonite versus calcite was largely dependent on seawater chemistry at the time of first appearance of carbonate skeletons in animals. Seawater Mg/Ca ratios controlled polymorph mineralogy of skeleton, which supplied a new proxy for calcite-aragonite seas in the Precambrian, reconstruction of paleoclimate and paleoenvironment, isotope stratigraphy, carbonate sedimentation and diagenesis.