Lead and Sulfur Isotope Constrains for Metal Sources of Sulfide Chimneys, Mothra Hydrothermal Field, Juan De Fuca Ridge, Nothern East Pacific Ocean
摘要
The sulfide chimney collected from the Faulty Towers sulfide complexes in Mothra hydrothermal field (47°57.447′N, 129°06.568′W) has been studied for lead and sulfur isotopic compositions. The range of lead isotopic compositions of the samples was: 206Pb/204Pb = 18.665~18.828, 207Pb/204Pb = 15.460~15.607, and 208Pb/204Pb = 37.961~38.401. It is observed that lead isotopic compositions changed regularly across the chimney walls, with more radiogenic lead in the outer walls and lower lead isotope compositions in the inner walls and/or across the fluid channels. Sulfur isotopic compositions ranged from 0.4‰ to 2.1‰. Marcasite (0.5‰) and sphalerite (1.0‰) from the outer walls were enriched in light sulfur isotope, and wurzite had comparatively uniform values ranging from 1.3‰ to 2.1‰. Both lead and sulfur isotope data suggested that substrate basalts were the main metal sources of hydrothermal fluids, with some sedimentary source input.