|Trace elements in ocean ridge basalt glasses: implications for fractionations during mantle evolution and petrogenesis|
Hertogen, J.; Janssens, M.-J.; Palme, H. (1980). Trace elements in ocean ridge basalt glasses: implications for fractionations during mantle evolution and petrogenesis. Geochim. Cosmochim. Acta 44(12): 2125-2143
In: Geochimica et Cosmochimica Acta. Elsevier: Oxford,New York etc.. ISSN 0016-7037, more
Basalts; Fractionation; Fractionation; Geochemistry; Petrogenesis; Seafloor spreading; Trace elements; Marine
|Authors|| || Top |
- Hertogen, J.
- Janssens, M.-J.
- Palme, H.
Seven well-documented and fresh glassy selvages from ocean floor basalt pillows were analyzed by radiochemical neutron activation analysis. The samples came from active spreading centers in the Indian and Atlantic Ocean. Data indicate that heterogeneities in the mantle are confined to the highly incompatible lithophile elements. Chemical fractionations during petrogenesis of tholeiitic basalts are discussed in the light of literature data for primitive peridotitic upper mantle nodules, (Ir, Os). Au, Pd, Ni and Re are strongly fractionated from each other in igneous processes; the unfractionated chondritic mantle pattern thus imposes firm constraints on mantle evolution models. The potentially chalcophile elements Ag, Cd, In and Zn do not behave differently from lithophile elements of the same valency and comparable ionic radius. Residual sulfides are not abundant enough to efficiently control the partitioning of these elements during basalt petrogenesis. However, the poor coherence of Tl to Rb and U in ocean floor basalts could point to retention of Tl by residual sulfides during depletion of the MORB source regions. Sb is strongly depleted in the source regions of ocean ridge basalts; most likely, it was present as a highly incompatible Sb5+ cation. The limited Rb/Csfractionation in oceanic tholeiites, as opposed to continental tholeiites and acidic rocks, appears to reflect the low abundance of volatile constituents and hydrous silicates in normal ocean ridge basalts.