多金属结壳生长间断期与磷酸盐化事件的关系  

The relationship between the growth discontinuity of polymetallic crusts and phosphatization events

作　　者：王洋 方念乔[1] Wang Yang;Fang Nianqiao(School of Ocean Sciences,China University of Geosciences,Beijing 100083,China)

机构地区：[1]中国地质大学海洋学院,北京100083

出　　处：《海洋学报》2021年第1期102-109,共8页

基　　金：中国大洋矿产资源研究开发协会“十三五”资源环境项目(DY135-C1-1-06)。

摘　　要：磷酸盐化的发生会造成多金属结壳主要成矿元素的贫化,总体上抑制结壳的生长。磷酸盐化作用呈幕式在太平洋内发生,已有研究将其发生期次与多金属结壳中的磷酸盐化层位及其P、Ca等元素地球化学特征对应,为结壳的年代厘定提供证据。然而,由于磷酸盐化多次发生且在结壳多个层位中显现,首先需要厘定出较为可靠的多金属结壳年代框架,才能与磷酸盐化事件相互佐证。本研究通过定年范围较大,同时可以识别结壳中存在的生长间断的Co-Os法定年体系,为中、西太平洋6块多金属结壳定年,并参考肉眼识别的磷酸盐化矿化特征和地球化学特征佐证年代框架,同时分析磷酸盐化作用对结壳成矿的影响。39~34 Ma和27~21 Ma的两次大规模磷酸盐化期次全部对应多金属结壳的大规模间断期,而71 Ma、55 Ma和31 Ma等小规模磷酸盐化事件多数可在多金属结壳的层位和地球化学特征中识别,对应P和Ca百分含量的飙升和峰值特征。这一方面证实了磷酸盐化的发生整体抑制了结壳的生长,且具有广泛的影响范围和明确的时代区间,另一方面则佐证了多金属结壳年代框架的准确性。The occurrence of phosphatization will lead to the dilution of major ore-forming elements in polymetallic crusts and thus inhibit the growth of crusts in general.Phosphatization occurred in the Pacific Ocean in an episodic manner,and the occurrence periods correspond to the phosphatization layers in crusts and the geochemical characteristics of P,Ca and other elements,providing evidence for the dating of crusts.However,due to the frequent occurrence of phosphatization in multiple layers of crusts,a more reliable age frame needs to be determined before it can be mutually corroborated with phosphatization events.In this study,the Co-Os dating system with large dating range and the ability to determine hiatus was applicated in dating for the crust samples from central Pacific and western Pacific.With the naked eye identification of phosphatization mineralization features and geochemical profile characteristics,the age frames were proved and the effect of phosphatization on crust mineralization were discussed.The two large-scale phosphatization phases of 39–34 Ma and 27–21 Ma all correspond to the largescale discontinuous phases of the crusts,while most small-scale phosphatization events in 71 Ma,55 Ma and 31 Ma can be identified in the layers and geochemical profiles,corresponding to the rising and peak characteristics of P and Ca content.On the one hand,it is confirmed that the occurrence of phosphatization inhibits the growth of crusts,and has a wide range of influence area and a clear time interval in Pacific.On the other hand,it proves the accuracy of the chronological framework of polymetallic crusts.

关 键 词：磷酸盐化 多金属结壳 古海洋事件 辅助定年 生长间断 

分 类 号：P736.3[天文地球—海洋地质]