Influences of temperature and Mg:Ca ratio on CaCO3 precipitates from seawater
Influences of temperature and Mg:Ca ratio on CaCO3 precipitates from seawater
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DOI：
10.1130/0091-7613(1997)025
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发表时间：
1997
期刊：
影响因子：
5.8
通讯作者：
J. Morse;Qiwei Wang;Mai Yin Tsio
中科院分区：
文献类型：
--
作者：
J. Morse;Qiwei Wang;Mai Yin Tsio
从海水中假均相沉淀的碳酸钙矿物从方解石变为文石时的Mg：Ca比实验确定为温度的函数。结果表明，在一个相对较小的温度范围内的临界镁：钙比的戏剧性的变化。例如，在Mg：Ca为5：1的正常海水中，临界温度为6 ± 3 °C。然而，在25 °C的温度下，Mg：Ca必须小于1：4 ± 0.1才能形成方解石。这些数据表明，在碳酸盐沉积时的古气候条件，必须考虑当试图作出推论的变化，在其他因素，如古P CO2（P =压力）和古Mg：Ca的比例，可能控制碳酸盐矿物形成的非生物过程。然而，推断的全球古气候条件与非生物沉积的CaCO 3多晶型物的主要类型之间的反比关系（即，温暖的条件和低镁方解石，相对于寒冷的条件和文石）表明，在中生代的海洋化学发生了重大变化。
The Mg:Ca ratio at which the calcium carbonate mineral that has pseudohomogeneously precipitated from seawater changes from calcite to aragonite was experimentally determined as a function of temperature. Results indicate a dramatic change in the critical Mg:Ca ratio over a relatively small temperature range. For example, in normal seawater with a Mg:Ca of 5:1, the critical temperature is 6 ± 3 °C. At a temperature of 25 °C, however, Mg:Ca must be less than 1:4 ± 0.1 for calcite to form. These data indicate that paleoclimatic conditions at the time of carbonate deposition must be considered when attempting to make inferences about variation in other factors, such as paleo- P CO 2 ( P = pressure) and paleo-Mg:Ca ratios, that may control carbonate mineral formation by abiotic processes. However, the inverse relation between inferred global paleoclimatic conditions and the dominant type of CaCO 3 polymorph being abiotically deposited (i.e., warm conditions and low-Mg calcite, versus cool conditions and aragonite) suggest that substantial changes must have taken place in ocean chemistry over Phanerozoic time.