西盘古海盆锰结核的元素地球化学特征及生长机制  

Geochemical constraints on the formation mechanisms of manganese nodules from Cipangu Basin

作　　者：杨叶飘 韩宗珠[1,2] 来志庆[1,2] 龙时迈 顾伟 窦连想 YANG Yepiao;HAN Zongzhu;LAI Zhiqing;LONG Shimai;GU Wei;DOU Lianxiang(College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Key Laboratory of Submarine Geosciences and Prospecting Techniques,Qingdao 266100,China)

机构地区：[1]中国海洋大学海洋地球科学学院,青岛266100 [2]海底科学与探测技术教育部重点实验室,青岛266100

出　　处：《海洋地质前沿》2023年第9期35-45,共11页Marine Geology Frontiers

基　　金：国家自然科学基金(41376053)。

摘　　要：通过对西盘古海盆(Cipangu Basin)15个锰结核样品开展系统的形态结构、显微构造、矿物组成、常微量元素和稀土元素含量特征差异性研究,进而探讨该区锰结核的成因类型和生长机制。西盘古海盆锰结核外观为椭球状或连生体状,表面光滑,组成矿物主要有水羟锰矿、石英、钙长石和石盐;其稀土元素配分模式图表现出明显的Ce正异常、Y负异常和轻稀土富集特征。样品Mn/Fe比值均<2.5,与Ni、Cu正相关,且Mn与Cu、Co和Ni高度正相关,这表明因Cu^(2+)、Ni^(2+)、Co^(2+)更易占据层板结构锰氧八面体MnO6的空位而在锰矿物表面富集。锰结核显微构造区域可划分为Type-Ⅰ型和Type-Ⅱ型,其中Type-Ⅰ型为结构致密高反射率的层纹状、柱状、叠层状构造的显微构造区域,Type-Ⅱ型为结构疏松低反射率的掌状、混杂状、环状构造的显微构造区域;Type-Ⅰ型区域的Mn/Fe比值和Ni、Ni+Cu、Co含量均高于Type-Ⅱ型区域。构造致密的Type-Ⅰ型区域代表沉积环境变化较小,生长速率较小;构造疏松的Type-Ⅱ型区域代表沉积环境剧烈变化、结核生长速率较大。西盘古海盆锰结核具有典型的水成型成因特征,通过常微量元素测试数据估算得出西盘古海盆锰结核样品的形成时间为1.48 Ma。据微区分析数据估算得出其生长年龄为2.44 Ma。In this study,a total of 15 manganese nodule samples were collected from Cipangu Basin in North Pacific Ocean.The morphological structure,microscopic structure,mineral composition,contents of trace elements and rare earth elements,and the differences among samples from different regions were studied systematically.The genetic types and growth mechanism of the manganese nodules were discussed.The manganese nodules are elliptic and intergrowth body with smooth surface.The major minerals are vernadite,quartz,albite,and halite.The REE distribution pattern shows obvious positive Ce anomaly,negative Y anomaly,and LREE enrichment characteristics.The Mn/Fe ratios of the samples from three sites of the study areas are all less than 2.5,which are positively correlated with Ni and Cu;and Mn is highly positively correlated with Cu,Co,and Ni,indicating that Cu,Ni,and Co are more likely to occupy theδ-MnO_(2) enrichment at the surface of manganese minerals.The microlayers of manganese nodules can be divided into two types,TypeⅠand TypeⅡ.TypeⅠis laminated,columnar and laminated with dense and high reflectance structure,and TypeⅡis hybrid and ring with loose and low reflectance structure.The Mn/Fe,Ni,Ni+Cu,and Co in TypeⅠwere greater than those of TypeⅡ.The TypeⅠarea has loose manganese nodule in structure reflecting great changes in sedimentary environment with great growth rate of nodule,while the TypeⅡzone has small changes in sedimentary environment with small growth rate.The manganese nodule samples are formed by metal precipitation from the ambient seawater(hydrogenetic)and the age was estimated to be 1.48 Ma based on the ordinary trace element test data.At last,according to the micro-analysis data,the growth age was 2.44 Ma by estimation.

关 键 词：锰结核 西盘古海盆 成因类型 生长机制 

分 类 号：P736.4[天文地球—海洋地质]