新元古代环境变化的原因

根据精心筛选的碳酸盐岩样品，测定了晚新元古代（850—540Ma）海水的Sr和C同位素的新曲线。利用这些资料以及已出版的有关同一时期海水的S和Nd同位素长期变化的数据，去探索外生旋回的变化。在600Ma，大约是Varanger冰川作用时期，在所有同位素记录中都记录了这些主要变化。这些同位素中最明显的是Sr同位素。研究发现，在780－800MS前，最低的87Sr／86Sr比值为－0．7055，与高热流量和后来世界范围的条带状铁建造沉积相一致。这些观察资料制约着外生地球化学旋回模式，因此可允许我们计算出一些重要参数，例如河流与热流量，以及C埋…     

济阳拗陷第三纪玄武岩的Nd—Sr同位素研究

本文报道了济阳拗陷29个第三纪玄武岩的Nd，Sr同位素组成。结果表明，该区早、晚第三纪玄武岩的Nd-Sr同位素组成变化且具有一定的区别：早经三纪玄武岩的εNd值为0．70481－0．70830；晚第三纪玄武央的εNd值为0．1－2．3，^87Sr/^86Sr比值为0．70421－0．70530。鉴于εNd与1/Nd有^87Sr/^86Sr与1／Sr之间不存在相关特征，Nb正异常以及SiO2与MgO，Fe2O3 FeO,P2O5呈负相关，与Al2O3呈正相关，但与K2I为不存在相关特征，因此，地壳混染作用并不是第三纪玄武岩同位素组成变化的主要原因。玄武岩^87Sr/^86Sr比值的升高是由热液蚀变造成的，而εNd值的变化而归因于源区混合。如果热液蚀变作用没有发生，这些玄武岩的所有数据点在Nd-Sr相关图上将可能位于地幔系列内部。这表明第三纪玄武岩主要是由DMM和EMI两个端员组分不同程度混合形成，EMII的贡献是次要的。     

宁夏香山群徐家圈组顶部薄层石灰岩锶同位素与局限海盆地分析

宁夏香山群主体为一套深水浊流沉积的灰绿色细砂岩夹泥岩,在鄂尔多斯盆地西缘及河西走廊地区下古生界占有重要的位置,其时代归属对于北祁连地区大地构造演化、宁夏区域地质和鄂尔多斯盆地西缘海相深水油气勘探均具有重要意义。本文采用沉积学和沉积地球化学的方法,着重分析了香山群徐家圈组顶部薄层石灰岩锶同位素的特征,结果表明：① 薄层石灰岩受成岩蚀变程度较小,87Sr/86Sr值基本可代表沉积时海水的特征;② 87Sr/86Sr值在0. 71057~0. 71356之间,平均值为0. 71189,远大于寒武纪和奥陶纪海水87Sr/86Sr值;③ 87Sr/86Sr值和盐度呈较好的负线性相关,和温度及Mn/Sr比值呈较好的正线性相关;④ 87Sr/86Sr值和Si含量略具负线性相关趋势,和Al含量及Mg含量具有较弱的负线性相关性。结合鄂尔多斯盆地西缘早古生代大地构造演化和香山群相关研究成果认为：徐家圈组顶部薄层石灰岩可能沉积于受古陆或水下隆起阻隔的局限海盆深水环境,沉积时海水主要受和硅铝质岩石进行充分锶同位素交换的海底热液及流经喀斯特风化壳的地表径流影响,与同期大洋海水相比具有高的87Sr/86Sr值.     

川东北地区下寒武统龙王庙组白云岩成因分析

通过剖面实测、薄片鉴定、阴极发光分析和地球化学分析,对川东北地区下寒武统龙王庙组白云岩成因进行了研究。研究结果表明:研究区龙王庙组自下而上发育灰岩—过渡岩性—白云岩,以颗粒结构为主,白云石主要为泥—粉晶,呈它形—半自形晶,阴极发光呈昏暗光—暗红光。样品的MgO与CaO呈负相关,白云岩Mg2+/Ca2+较低,高Na含量,低Sr、Fe、Mn含量,白云石有序度较低,各岩性稀土元素配分曲线平行一致分布,δCe无异常,δEu负异常,灰岩δ13C偏正、δ18O处于同期海水内,白云岩δ13C、δ18O偏正,87Sr/86Sr高于同期海水值。结合区域地质背景、岩石学特征和地球化学分析结果,研究区白云石化流体为高盐度蒸发海水,研究区白云岩为渗透回流白云石化作用形成。     

粤西阳春中生代钾玄质侵入岩及其构造意义：Ⅱ．微量元素和Sr—Nd同位素地球

粤西阳春地区马山二长闪长岩强烈富集K、Sr和LREE，（^87Sr/^86Sr)i ＝0．7046，εNd(t)≈ 1；岗尾－轮水岩体较富集K、Rb、Th和LREE，（^87Sr/^86Sr)i＝ 0．7063，εNd(t)≈－2；石录岩体较富集Sr,K、Rb、Th和LREE相对较低，（^87Sr/^86Sr)i＝0．7084－0．7089，εNd(t)≈－6。马山岩体来源于大离子亲石元素（LILE）和LREE富集的交代地幔；岗尾－轮水岩体来自于放射成因Sr、Nd同位素组成略高或交代时间略早的富集交代地幔，并且经历了明显的结晶分异作用；石录岩体则很可能是前存下地壳底垫基性岩重熔形成的。从早侏罗世到早白垩世，南岭西部的岩浆成分和源区的规律性变化反映了区域软流圈地幔上涌和岩石圈伸展－拉张－减薄的演化过程。     

川东北普光气田下三叠统飞仙关组白云岩成因——来自岩石结构与Sr同位素和Sr含量的证据

研究了川东北普光气田下三叠统飞仙关组白云岩储层的岩石结构Sr的含量和Sr同位素组成,讨论了它的成因,飞仙关组优质储层为成岩期埋藏交代白云化作用的产物,来自岩石结构和Sr同位素和Sr含量的证据包括如下几个方面:(1)与准同生白云岩比较,埋藏白云岩的岩石结构和Sr同位素和Sr含量地球化学特征与前者有显著差别;(2)飞仙关组所有各类碳酸盐岩(或矿物)具有早三叠世海水Sr同位素组成特征,~(87)Sr/~(86)Sr比值变化范围为0.706588～0.708187,覆盖了全球早三叠世海水Sr同位素的变化范围(0.7076～0.7078),平均值0.707656与全球早三叠世平均值(0.707743)基本一致;(3)埋藏白云岩~(87)Sr/86Sr比值变化范围为0.707122～0.707419,平均值0.707421,都略低于全球早三叠世海水Sr同位素变化范围和平均值,但与已报道的川东北早三叠世飞仙关期海水Sr同位素变化范围(0.707330～0.707383)和平均值(0.707350)都非常接近,说明白云石化流体具有强烈的川东北地区早三叠世飞仙关期海水Sr同位素组成特征;(4)综合岩石结构、Sr同位素和Sr含量地球化学特征,证明飞仙关组白云岩储层为成岩期埋藏交代作用产物,白云石化流体来自地层中高Sr和高盐度的海源地层水.     

塔里木盆地玉北地区蓬莱坝组白云岩类型及成因

塔里木盆地玉北地区蓬莱坝组发育粉-细晶自形白云岩、中晶自形-半自形白云岩、粗晶自形-他形白云岩三种白云岩类型。粉-细晶白云岩具纹层状构造,稀土元素配分模式、总稀土含量与同期灰岩相似,氧同位素组成与同期海水成因的白云岩相近,表明白云岩化流体为同期海水,较高的盐度指数指示了相对浓缩的海水条件,较低的有序度值反应出快速的白云岩化过程,为准同生白云岩化的产物,白云石晶间均匀充填富Fe、富Si及高~(87)Sr/~(86)Sr比值的陆源物质,表明玉北地区在蓬莱坝组粉-细晶白云岩沉积期由于相对海平面较低从而受到陆源物质混入的影响。中晶白云岩和粗晶白云岩的稀土元素配分模式、总稀土含量、~(87)Sr/~(86)Sr比值等与同期海水特征相似,表明白云岩化流体为海水,可见残余颗粒结构,成岩温度较低,埋藏较浅,为埋藏的海水以及沿原始颗粒灰岩的粒间孔及可能存在的裂缝等通道向下运移的海水提供的Mg~(2+)导致的白云岩化,后期重结晶作用破坏了粗晶白云岩中的残余颗粒结构并导致其Fe、Mn含量及成岩温度、有序度值高于中晶白云岩,Sr含量及δ~(18)O值低于中晶白云岩。部分中-粗晶白云石边缘可见加大边,表明后期存在少量他源流体导致的次生加大作用。     

湘西上震旦统层状硅质岩沉积环境的地球化学标志

湘西上震旦统层状硅质岩化学成分纯净，硅质矿物平均含量95％以上，且FeO/Fe2O3比值大于1，MnO/TiO2比值为6．1，P2O5含量极低。微量元素Sr/Ba比值小于1，稀土以总量低（5．64－31．54μg/g）和铈亏损为特征。硅质岩的δ^30Si值变化在0．0‰～0.7‰之间，硅质岩中有机碳含量较高，介于0．443％－1．993％之间，Pr/Ph比值小于1。硅质岩的上述特点反映其沉积大陆边缘斜坡半深海至大洋盆地深海环境中。     

西江干流河水主要离子及锶同位素地球化学组成特征

水环境中锶（Sr）含量及其同位素组成特征的研究有助于认识区域水文地球化学特征及流域盆地岩石风化速率等地球化学行为,因此河流环境中Sr的地球化学行为是地球化学研究的重要课题之一。对中国南方西江干流及其支流河水主要阴阳离子及sr同位素组成进行了分析,发现其水化学组成主要以Ca^2＋、Mg^2＋、HCO3^-和SO4^2-离子为主,分别占阴阳离子组成的80％以上。郁江河水具有较高的Sr同位素比值（^87St／^86Sr=0．71049）和较低的Sr含量（0．0263mg／L）,而西江河水具有较低的Sr同位素比值以及较高的Sr含量,其Sr含量变化范围在0．0667．0．187mg／L之间,平均含量为0．136mg／L;Sr同位素比值变化范围在0．70856．0．70936之间,平均比值为0．70894。与世界主要河流水体中Sr含量平均值（0．078mg／L）及Sr同位素比值（^87Sr／^86Sr=0．7119）相比,西江干流水体具有较高的Sr含量及较低的Sr同位素比值。两条河流河水中主要离子及Sr的来源存在显著差异,西江干流河水中的主要溶解离子及Sr同位素主要源于碳酸盐岩（石灰岩和白云岩）的风化作用,主要受黔江及其上游红水河等化学组成所控制,而郁江则主要受碎屑岩风化作用的影响;同时,中上游地区的酸沉降及人类活动的输入可能导致西江干流水体受到一定程度的污染,而郁江受污染程度则相对较小。     

贵州晴隆锑矿床中萤石的Sr同位素地球化学

对黔西南晴隆锑矿床中的萤石进行了Sr同位素分析，得到其Sr同位素比值为0．70766-0．70932。这个比值明显高于赋矿的二叠系茅口组灰岩(0．70672—0．70821)和蛾眉山玄武岩(0．70441—0．70638)，表明成矿流体相对富集放射成因^87Sr。由于该矿成矿流体的Sr同位素比值明显高于蛾眉山玄武岩，因此将其成矿作用仅仅简单归结于与玄武岩火山活动有关的岩浆热液是不妥的。同时，成矿流体Sr同位素比值也高于二叠纪灰岩的Sr同位素比值，指示成矿流体不可能为单纯的二叠纪海水，而应该有更为富集放射成因Sr的岩石的贡献，可能是这些二叠系岩石下伏的地壳基底。先前对矿床稀土元素地球化学研究得到，成矿物质有外部地壳岩石参与；氢氧同位素地球化学研究发现，成矿流体为大气降水演化产物而不是海水;成矿物质(F和Sb)具有赋矿围岩以外的来源。结合萤石的Sr同位素分析，可以认为晴隆锑矿不是简单的“海相火山喷流沉积成因”或“原地改造产物”，成矿流体和成矿物质均具有外部来源参与而不单单是来自赋矿围岩，可能与下伏基底岩石有关。     

Improving SST reconstructions from coral Sr/Ca records: multiple corals from Tahiti (French Polynesia)

We reconstruct SST from coral Sr/Ca ratios measured at three coral cores taken from the lagoon of Tahiti (French Polynesia). Two coral cores were drilled from the same coral colony (one horizontally and one vertically), and a third core was drilled vertically from another coral growing at a different site. We evaluate several Sr/Ca records as proxies for regional SST variations: (1) the three single-core records from Tahiti, (2) an average Sr/Ca record computed from the two cores drilled from the same coral colony, (3) an average Sr/Ca record computed from all three Tahiti cores, and (4) an average Sr/Ca record computed from the three Tahiti cores and a fourth core taken from a different island (Rarotonga). On a monthly scale, the average Sr/Ca record including the four coral cores from Tahiti and Rarotonga shows the best correlation with regional SST. The variance of the SST reconstruction is very realistic and the residual SST is low. This suggests that reconstructing SST from average proxy records gives a better representation of regional SST variations. Of the three Tahiti cores, the one that was drilled horizontally shows the best correlation with grid-SST on an annual mean scale. All three Tahiti corals show much larger interannual SST variations than that indicated by grid-SST.     

海南岛东部海域滨珊瑚Sr/Ca比值温度计 及其影响因素初探*

文章采用全谱直读等离子体原子发射光谱(ICP-AES)的方法测定了1986~1996年海南岛东部海域滨珊瑚的Sr/Ca比值,建立了该海域月分辨率的Sr/Ca海水表面温度计方程:SST(℃)=170-16 (mmol/mol),n = 133,r=0.80,p=0.01, 此与韦刚健等在西沙海域建立的温度计方程:SST(℃)=169-16.7 (mmol/mol)一致,这表明南海中、北部海域也出现有相似的微量元素温度计。此外,文章还分析了在某些年月份SST的实测值和计算值出现的显著差别,探讨了可能造成的海洋气象环境因素。     

雷州半岛造礁珊瑚Porites lutea月分辨率的δ18O温度计研究

对雷州半岛西南部珊瑚岸礁区1995～1997年生长的造礁珊瑚Poriteslutea的骨骼密度、生长速度和δ¹⁸O分析表明：1)造礁珊瑚骨骼的密度、生长速度和δ¹⁸O与其生存环境的表层海水温度之间存在很好的相关性,高密度、低生长速率和高δ¹⁸O值对应于冬季;2)δ¹⁸O具有明显的年际和季节性变化。根据δ¹⁸O估计的表层海水温度变化范围与实测基本一致,进一步揭示了珊瑚骨骼δ¹⁸O可作为定量研究高分辨率表层海水温度变化的温度计。     

Three monthly coral Sr/Ca records from the Chagos Archipelago covering the period of 1950–1995 A.D.: reproducibility and implications for quantitative reconstructions of sea surface temperature variations

In order to assess the fidelity of coral Sr/Ca for quantitative reconstructions of sea surface temperature variations, we have generated three monthly Sr/Ca time series from Porites corals from the lagoon of Peros Banhos (71°E, 5°S, Chagos Archipelago). We find that all three coral Sr/Ca time series are well correlated with instrumental records of sea surface temperature (SST) and air temperature. However, the intrinsic variance of the single-core Sr/Ca time series differs from core to core, limiting their use for quantitative estimates of past temperature variations. Averaging the single-core data improves the correlation with instrumental temperature (r > 0.7) and allows accurate estimates of interannual temperature variations (~0.35°C or better). All Sr/Ca time series indicate a shift towards warmer temperatures in the mid-1970s, which coincides with the most recent regime shift in the Pacific Ocean. However, the magnitude of the warming inferred from coral Sr/Ca differs from core to core and ranges from 0.26 to 0.75°C. The composite Sr/Ca record from Peros Banhos clearly captures the major climatic signals in the Indo-Pacific Ocean, i.e. the El Niño–southern oscillation and the Pacific decadal oscillation. Moreover, composite Sr/Ca is highly correlated with tropical mean temperatures (r = 0.7), suggesting that coral Sr/Ca time series from the tropical Indian Ocean will contribute to multi-proxy reconstructions of tropical mean temperatures.     

南海北部夏季沿岸上升流近百年的强度变化

用全谱直读ICP-AES技术测定了海南岛东部（琼东）沿岸上升流区域滨珊瑚1906—1996年的Sr／Ca比值。结果显示珊瑚Sr／Ca比值重建的琼东海域的夏季海表温度偏低,强烈地受到东亚夏季风引起沿岸冷上升流的影响。结合西沙海域的滨珊瑚海表温度记录,首次重建了1906～1993年琼东沿岸风生上升流的强度指数变化序列。结果表明琼东上升流于1906～1993期间整体呈加强趋势,并具显著的年代际波动特征,同全球趋暖密切相关。此外,重建的上升流强度指数序列还揭示了大尺度环流——厄尔尼诺一南方涛动对琼东上升流强度变化的制约。     

An assessment of the Sr/Ca ratio in shallow water hermatypic corals as a proxy for sea surface temperature

The high precision measurement of the Sr/Ca ratio in corals has the potential for measuring past sea surface temperatures at very high accuracy. However, the veracity of the technique has been questioned on the basis that there is both a spatial and temporal variation in the Sr/Ca ratio of seawater, and that kinetic effects, such as the calcification rate, can affect the Sr/Ca ratio of corals, and produce inaccuracies of the order of 2-4 °C. In the present study, a number of cores of the massive hermatypic scleractinian coral Porites, from the central Great Barrier Reef, have been analyzed for Sr/Ca at weekly to monthly resolution. Results from a 24 year record from Myrmidon Reef show an overall variation from 22.7 °C to 30.4 °C. The record shows a warming/cooling trend with maximum warming centred on the 1986-1987 summer. While some bleaching was reported to have occurred at Myrmidon Reef in 1982, the Sr/Ca record indicates that subsequent summer temperatures were much higher. The 4.5 year record from Stanley Reef shows a maximum SST of 30 °C during the 1997-1998 El Niño event. The calibrations from Myrmidon and Stanley Reefs are in excellent agreement with previously published calibrations from nearby reefs. While corals do not calcify in equilibrium with seawater due to physiological control on the uptake of Sr and Ca into the lattice of coralline aragonite, it can be argued that, provided only a single genus such as Porites sp. is used, and that the coral is sampled along a major vertical growth axis, then the Sr/Ca ratio should vary uniformly with temperature. Similarly, objections based on the spatial and temporal variability of the Sr/Ca activity ratio of seawater can be countered on the basis that in most areas where coral reefs grow there is a uniformity in the Sr/Ca activity ratio, and there does not appear to be a change in this ratio over the growth period of the coral. Evidence from several corals in this study suggest that stress can be a major cause of the breakdown in the Sr/Ca-SST relationship. Thermal stress, resulting from either extremely warm or cool temperatures, can produce anomalously low Sr/Ca derived SSTs as a result of the breakdown of the biological control on Sr/Ca fractionation. It is considered that other stresses, such as increased nutrients and changes in light intensity, can also lead to a breakdown in the Sr/Ca-SST relationship. Two of the main issues affecting the reliability of the Sr/Ca method are the calibration of the Sr/Ca ratio with measured SST and the estimation of tropical last glacial maximum (LGM) palaeotemperatures. Instead of producing a constant calibration, just about every one published so far is different from the others. What is obvious is that for most calibrations while the slope of the calibration equation is similar, the intercepts are not. While the cause for this variation is still unknown, it would appear that corals from different localities around the world are responding to their own particular environment or that certain types of environments exert a control on the corals’ physiology. Sr/Ca derived SST estimates for the LGM and deglaciation of 5 °C-6 °C cooler than present are at odds with estimates of 2 °C-3 °C cooling by other climate proxies. The apparent lack of reef growth during the LGM suggests that SSTs were too cold in many parts of the tropics for reefs to develop. This would lend support to the idea that tropical SSTs were much cooler than what the CLIMAP data suggests.     

Deconvolving the δO seawater component from subseasonal coral δO and Sr/Ca at Rarotonga in the southwestern subtropical Pacific for the period 1726 to 1997

To reconstruct oceanographic variations in the subtropical South Pacific, 271-year long subseasonal time series of Sr/Ca and δ¹⁸O were generated from a coral growing at Rarotonga (21.5°S, 159.5°W). In this case, coral Sr/Ca appears to be an excellent proxy for sea surface temperature (SST) and coral δ¹⁸O is a function of both SST and seawater δ¹⁸O composition (δ¹⁸O_sw). Here, we focus on extracting the δ¹⁸O_sw signal from these proxy records. A method is presented assuming that coral Sr/Ca is solely a function of SST and that coral δ¹⁸O is a function of both SST and δ¹⁸O_sw. This method separates the effects of δ¹⁸O_sw from SST by breaking the instantaneous changes of coral δ¹⁸O into separate contributions by instantaneous SST and δ¹⁸O_sw changes, respectively. The results show that on average δ¹⁸O_sw at Rarotonga explains ∼39% of the variance in δ¹⁸O and that variations in SST explains the remaining ∼61% of δ¹⁸O variance. Reconstructed δ¹⁸O_sw shows systematic increases in summer months (December-February) consistent with the regional pattern of variations in precipitation and evaporation. The δ¹⁸O_sw also shows a positive linear correlation with satellite-derived estimated salinity for the period 1980 to 1997 (r = 0.72). This linear correlation between reconstructed δ¹⁸O_sw and salinity makes it possible to use the reconstructed δ¹⁸O_sw to estimate the past interannual and decadal salinity changes in this region. Comparisons of coral δ¹⁸O and δ¹⁸O_sw at Rarotonga with the Pacific decadal oscillation index suggest that the decadal and interdecadal salinity and SST variability at Rarotonga appears to be related to basin-scale decadal variability in the Pacific.     

Effects of diagenesis on paleoclimate reconstructions from modern and young fossil corals

The integrity of coral-based reconstructions of past climate variability depends on a comprehensive knowledge of the effects of post-depositional alteration on coral skeletal geochemistry. Here we combine millimeter-scale and micro-scale coral Sr/Ca data, scanning electron microscopy (SEM) images, and X-ray diffraction with previously published δ¹⁸O records to investigate the effects of submarine and subaerial diagenesis on paleoclimate reconstructions in modern and young sub-fossil corals from the central tropical Pacific. In a 40-year-old modern coral, we find secondary aragonite is associated with relatively high coral δ¹⁸O and Sr/Ca, equivalent to sea-surface temperature (SST) artifacts as large as −3 and −5 °C, respectively. Secondary aragonite observed in a 350-year-old fossil coral is associated with relatively high δ¹⁸O and Sr/Ca, resulting in apparent paleo-SST offsets of up to −2 and −4 °C, respectively. Secondary Ion Mass Spectrometry (SIMS) analyses of secondary aragonite yield Sr/Ca ratios ranging from 10.78 to 12.39 mmol/mol, significantly higher compared to 9.15 ± 0.37 mmol/mol measured in more pristine sections of the same fossil coral. Widespread dissolution and secondary calcite observed in a 750-year-old fossil coral is associated with relatively low δ¹⁸O and Sr/Ca. SIMS Sr/Ca measurements of the secondary calcite (1.96-9.74 mmol/mol) are significantly lower and more variable than Sr/Ca values from more pristine portions of the same fossil coral (8.22 ± 0.13 mmol/mol). Our results indicate that while diagenesis has a much larger impact on Sr/Ca-based paleoclimate reconstructions than δ¹⁸O-based reconstructions at our site, SIMS analyses of relatively pristine skeletal elements in an altered coral may provide robust estimates of Sr/Ca which can be used to derive paleo-SSTs.     

高分辨率古海水温度记录──珊瑚Sr／Ca比值

高分辨率古海水温度记录──珊瑚Ｓｒ／Ｃａ比值韦刚健，李献华（中国科学院广州地球化学研究所，广州５１０６４０）关键词ＳＳＴ记录Ｓｒ／Ｃａ比值，珊瑚礁１弓】言研究第四纪古气候古环境变化，了解过去的气候演变规律，对预测未来气候变化趋势有重要意义，而依据地质...     

Correlated trace element “vital effects” in tropical corals: A new geochemical tool for probing biomineralization

Micron-scale variations in the trace-element (TE) composition of tropical coral skeletons were measured using laser-ablation ICP-MS (LA-ICP-MS) as part of an investigation into the chemical processes underlying paleoenvrionmental proxy reconstructions. Fluctuations in B, Mg, Sr, Ba and U were measured at high spatial resolution in two Porites corals from the Great Barrier Reef (Australia), and the fine-scale fluctuations (< ∼1.0 mm) were compared with seasonal TE cycles in a third coral. Fine-scale TE variations were found to have a large amplitude over distances corresponding to less than 1 month growth. Variations were quasi-periodic and appeared to have characteristic wavelengths on weekly (6-7 d) and monthly (28 d) scales, although periodicity was not continuous and variations could not be matched either within or between individual corallites. Fine-scale variations between Mg, Sr and U were significantly correlated with each other (Sr and U are positively correlated, but negatively correlated with Mg). This 3D correlation “vector” has the same slope as the seasonal-scale Mg, Sr and U correlations, suggesting that the same chemical/biologic biomineralization process mediates trace element variations at both timescales. Importantly, the fine-scale variations are too large to be caused directly by daily to monthly fluctuations in sea-surface temperature. This means that seasonal variations in these elements cannot reflect purely inorganic temperature-dependent coprecipitation. Models of physicochemical calcification were developed to test whether changes in calcification rate could explain the trace-element correlations. The calculations show that increases in calcification rate will result in correlated decreases in all TE/Ca ratios. The models reproduce the Sr partition coefficient, trace-element correlation slopes, and amplitude of fine-scale variations for an average calcifying pH of 8.5, varying by ±0.2 pH units. The models, however, predict U partition coefficients which are too low, and cannot reproduce the negative correlation between Mg and the other trace elements, which may be caused by crystallographic factors.