Geochemical Characteristics Of Seafloor Basalts And Hydrothermal Mineralization

Slow-ultraslow-spreading Southwest Indian Ridge(SWIR) and fast-spreading EastPacific Rise(EPR) at9°N～10°N are adopted in this thesis. According to comparativeanalysis of geochemical characteristics of basalts and hydrothermal sulfide samples,we can get the following viewpoints and conclusions:Geochemical characteristics of SWIR basalts are similar to the N-MORB, butdifferent from the typical N-MORB as a result of magma sources diversity. Basaltstrace element spider diagram displays that LILE and HFSE of SWIR are relativelyenriched, and Ba is positive anomaly in same area; basalts of EPR is slightly depletedin LILE and Ba, but relatively enriched of HFSE. Compared to SWIR, trace elementof EPR basalts is depleted distribution model, which shows geochemicalcharacteristics of N-MORB.Basalts REE distribution diagram displays∑REE of SWIR basalts is higher thanEPR basalts, and relative enriched in LREE, especially Ce, and slightly depleted in Eu.According to Variogram, La and La/Sm increase simultaneously, which indicatesevolution of submarine basalts magma controlled by the partial melting of rocks withdifferent degrees.There is significant difference in the chemical composition of sulfide betweendifferent hydrothermal activity regions. Contents of Zn, Mn, Mo, Cd, Ba, REE inSWIR hydrothermal sulfide are obviously superior to EPR’s, but lower in Ca, Fe, Cu,Se, Pb contents. According to Cu-Zn-Fe ternary diagram, hydrothermal sulfidesamples swir-s1and swir-s2are divided into two distinct ore types，Zn-rich sulfideand Fe-rich sulfide.Based on normalized basalts REE and hydrothermal sulfide patterns, both in SWIRand EPR,∑REE of hydrothermal sulfide is far below basalts, but the fractional degree of REE is higher than basalts, at the same, they are similar in negative Ce anomaly,∑REE relative enrichment, lower HREE.SWIR hydrothermal sulfide is characterizedby positive anomaly in Eu, and the fractional degree of REE is higher than EPR.Sources of REE in SWIR and EPR hydrothermal sulfide are different, the formerseafloor hydrothermal was mainly derived from seafloor hydrothermal, the latter wasseawater.