Elemental composition of lime mud recovered from coral reef Lagoonal basins, the Yaeyama Islands, Okinawa, Japan
Elemental composition of lime mud recovered from coral reef Lagoonal basins, the Yaeyama Islands, Okinawa, Japan
复制标题
从日本冲绳八重山群岛珊瑚礁泻湖盆地回收的石灰泥的元素组成
DOI：
10.4096/jssj1995.48.49
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Nozomi Ishihara
中科院分区：
文献类型：
--
作者：
Satoshi Yamamoto;Nozomi Ishihara
在八山群岛的白鹤和Sekisei珊瑚礁地区的泻湖盆地取样了地表未固结碳酸盐。通过筛分和沉淀法从这些碳酸盐中分离出石灰泥馏分，收集到的颗粒在62.5 ~ 2u之间。通过x射线衍射分析（XRD）和扫描电镜（SEM）等岩石学观察，对分离的石灰泥组分进行了碳酸盐结合微量元素、C03含量、矿物组成等分析。通过从1 N乙酸铵（pH调整为5.2）浸出馏分中减去60%乙醇浸出馏分中0.75 N LiCI-0.25 N CsCI来测定碳酸盐结合的微量元素浓度。石灰泥浆由HMC（高镁方解石）、HSA（高锶文石）、LSA（低锶文石）和LMC（低镁方解石）组成。然而，石灰泥浆中碳酸盐结合的Mg/Ca和Sr/Ca比明显低于与石灰泥浆含有相同碳酸盐矿物的碳酸盐砂和砾石。这说明在粗碳酸盐颗粒形成石灰泥的过程中，Mg和Sr在不改变矿物学的情况下被浸出。石灰泥的成岩变化可能在其岩化成石灰岩之前就已经开始了。
Surface unconsolidated carbonates were sampled from lagoonal basins in the Shiraho and Sekisei Coral Reef areas, the Yaeyama Islands. Lime mud fractions were isolated from these carbonates by sieving and sedimentation methods to collect particles between 62.5 and 2,u . The isolated lime mud fractions were analyzed for carbonate-bound trace elements, C03 contents, mineralogical compositions by the X-ray diffraction analysis (XRD) , and petrographic observations including scanning electron microscope (SEM) observations. The carbonatebound trace element concentrations were determined by subtracting the 0.75 N LiCI-0.25 N CsCI in 60% ethanol leachable fraction from the 1 N ammonium acetate-acetic acid (pH adjusted to 5.2) leachable fraction. Lime mud is composed mineralogically by HMC (high-Mg calcite), HSA (high-Sr aragonite), LSA (low-Sr aragonite), and LMC (low-Mg calcite). However, the carbonate-bound Mg/Ca and Sr/Ca ratios are considerably lower in lime mud than the carbonate sand and gravels which contain the same amount of carbonate minerals with the lime mud. This suggests that Mg and Sr were leached without changing mineralogy during the formation of lime mud from coarse carbonate grains. Diagenetic changes in lime mud might have already started before its lithification processes to limestone.