大洋多金属结核成因的地球化学标志

GEOCHEMICAL INDICATORS OF THE ORIGIN OF POLYMETALLICN-ODULES FROM THE OCEAN FLOOR

本文通过对取自太平洋不同地区的近百个多金属结核样品研究表明,不同成矿介质中形成的结核,地球化学特征明显不同,水成型结核矿物成分上富含σ—MnO_2,化学成分上富含Fe、Co、Pb,而贫Mn、Cu、Ni、Zn,TiO_2>1%,ΣREE>1000ppm,σCe>1.5;早期成岩型结核矿物成分上相对富含钡镁锰矿,化学成分上富含Mn、Cu、Ni、Zn,而贫Fe、Co、Pb,TiO_2<1%,ΣREE<1000ppm,σCe≤1.在此基础上通过对Bonatti图解的实际应用和理论分析,证明Mn-Fe-(Cu+Co+Ni)x10图解不具判别意义,并提出Mn/Fe-TiO_2,Mn-Fe-TiO_2×10,Mn-Fe-ΣREE×100和Mn-Fe-σCe×10成因判别图解.

Based on a geochemical study of about 100 samples of polymetallic nodules from the Pacific Ocean,the paper suggests that the composition of polymetallic nodules formed in different mineralization media (bottom water or interstitial water )is obviously different. Hydrogenous nodules are rich in 6-MnO2 in mineral composition,and rich in Fe,Co,Pb,but relatively poor in Mn,Cu,Ni,Zn,TiO2> 1 %, ΣREE> 1000ppm,δCe>l. 5 in chemical composition. The early diagenetic nodules are rich in todorokite in mineral composition,and rich in Mn,Cu,Ni,Zn,but relatively poor in Fe,Co,Pb,TiO2< 1%,ΣREE<1000ppm,δCe≤l in chemical composition. On this basis,the unreasonability of the Mn-Fe-(Cu + Co+Ni) × 10 diagram is pointed out by practical application and theoretical analysis,and four new genetic distinguishing diagrams, Mn/Fe-TiO2, Mn-Fe-TiO2 × 10, Mn-Fe-ΣREE × 100 and Mn-Fe-6Ce× 10 ,are discussed.