Determination of Sr and Ba partition coefficients between apatite and water from 5°C to 60°C:: A potential new thermometer for aquatic paleoenvironments
Determination of Sr and Ba partition coefficients between apatite and water from 5°C to 60°C:: A potential new thermometer for aquatic paleoenvironments
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DOI：
10.1016/s0016-7037(03)00453-8
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发表时间：
2004-02-01
影响因子：
5
通讯作者：
Lécuyer, C
中科院分区：
文献类型：
--
作者：
Balter, V;Lécuyer, C
在5℃至60℃的温度范围内通过实验测量磷酸钙和水之间的Sr和Ba的表观分配系数。磷酸钙从 Na2HPO4 的水性混合物中沉淀出来。 2H(2)O (10(-2) M) 和 CaCl2 。 2H(2)O(10(-2)M)。将 Sr 或 Ba 的加标溶液引入 CaCl2 中。 Sr/Ca 和 Ba/Ca 比率为 0.1 的 2H(2)O 溶液。实验包括在相互作用 1、6、48 和 96 小时后对液相和固相进行取样。实验早期沉淀的无定形磷酸钙 (ACP) 逐渐被羟基磷灰石 (HAP) 取代，但在 5°C 时除外，形成透钙磷石（二水合磷酸二钙或 DCPD）。我们观察到，对于给定的温度，固相的结晶度随着时间的推移而增加，并且对于给定的反应时间，固相的结晶度随着温度的增加而增加。除5℃下的实验外，收率（R%）和表观分配系数（K-a-w（Sr/Ca）和Ka（a-w）（Ba/Ca））均随着反应时间的增加而下降。 96 小时后，观察到 R%、K 和 K-a-w(Ba/Ca) 恒定，表明固相相对于水溶液处于稳态。因此，可以计算低温下磷灰石和水之间 Sr 和 Ba 分配的热依赖性：Log(K-a-w(Sr/Ca)) = 0.42 +/- 0.04 (10(3)T(-1)) - 1.87 +/- 0.12 (r(2) = 0.94)Log(K-a-w(Ba/Ca)) = 1.96 +/- 0.06 (10(3)T(-1)) - 7.19 +/- 0.20 (r(2) = 0.99)我们还进行了 Sr 和 Ba 之间的竞争实验。反应 96 小时后计算磷灰石和水之间 Sr/Ba 分配的热依赖性：Log(K-a-w(Sr/Ba)) = -0.75 +/- 0.04 (10(3)T(-1)) + 2.39 +/- 0.14 (r(2) = 0.97) 这种关系揭示了 Ba 在掺入 HAP 过程中对 Sr 的区分。根据从 K/T 边界恢复的鱼牙的 Ba/Ca 推导出的温度趋势模拟了根据对同一样品进行的 delta(18)O(PO4) 测量估计的温度趋势。除非生物磷灰石中的 Sr、Ba 和 Ca 含量在成岩过程中发生改变，否则它们的元素比例可以用作水生古环境的新的、有吸引力的温度计。版权所有 (C) 2004 爱思唯尔有限公司
Apparent partition coefficients of Sr and Ba between calcium phosphate and water were measured experimentally for temperature ranging from 5degreesC to 60degreesC. Calcium phosphates were precipitated from an aqueous mixture of Na2HPO4 . 2H(2)O (10(-2) M) and CaCl2 . 2H(2)O (10(-2) M). Spiked solutions of Sr or Ba were introduced into the CaCl2 . 2H(2)O solution at Sr/Ca and Ba/Ca ratios of 0.1. The experiment consisted in sampling the liquid and solid phases after 1, 6, 48, and 96 h of interaction. The amorphous calcium phosphate (ACP) precipitated early in the experiment was progressively replaced by hydroxylapatite (HAP), except at 5degreesC where brushite (di-calcium phosphate di-hydrate or DCPD) was formed. We observed that the crystallinity of the solid phase increased with time for a given temperature and increased with temperature for a given time of reaction. With the exception of the experiment at 5degreesC, yield (R%) and apparent partition coefficients (K-a-w(Sr/Ca) and Ka(a-w)(Ba/Ca)) both decreased with increasing reaction time. After 96 h, R%, K, and K-a-w(Ba/Ca) were observed to be constant, suggesting that the solid phases were at steady-state with respect to the aqueous solutions. The thermodependence of Sr and Ba partitioning between apatite and water at low temperature could therefore be calculated:Log(K-a-w(Sr/Ca)) = 0.42 +/- 0.04 (10(3)T(-1)) - 1.87 +/- 0.12 (r(2) = 0.94)Log(K-a-w(Ba/Ca)) = 1.96 +/- 0.06 (10(3)T(-1)) - 7.19 +/- 0.20 (r(2) = 0.99)We also performed competition experiments between Sr and Ba. The thermodependence of the Sr/Ba partitioning between apatite and water was calculated after 96 h of reaction:Log(K-a-w(Sr/Ba)) = -0.75 +/- 0.04 (10(3)T(-1)) + 2.39 +/- 0.14 (r(2) = 0.97)This relationship reveals a discrimination of Ba in favor of Sr during their incorporation into HAP. Temperature trends deduced from the Ba/Ca of fish teeth recovered from the K/T boundary mimic those estimated from delta(18)O(PO4) measurements carried out on the same sample. Unless Sr, Ba and Ca contents of biogenic apatites are modified during diagenesis, their elemental ratios could be used as new and attractive thermometers of aquatic paleoenvironments. Copyright (C) 2004 Elsevier Ltd.