Petrology of the Hawaiian Islands; II, Hualalai and Mauna Loa

Abstract

The lavas of Hualalai are generally olivine basalts, although Puu Waawaa and Puu Anahulu are trachyte. He states that Hualalai erupted in 1823 and 1840-41. [This is incorrect.] Washington presents new chemical analyses for three olivine basalts, one aphyric basalt, one feldspar phyric basalt, one gabbro, and the Puu Anahulu trachyte. The recent lavas of Mauna Loa include aphyric andesine basalt, chrysophyric oligoclase basalt, and picrite-basalt. He notes the recognition by Clark and Noble of older (Pahala and pre-Pahala) rocks on Mauna Loa. The ancient lavas include aphyric labradorite basalt, ophitic olivine basalt, feldspar phyric basalt, and picrite-basalt. He presents six new chemical analyses of recent Mauna Loa lavas by the author, and four analyses of ancient lavas by R.K. Bailey, of the U.S. Geological Survey. [One Mauna Loa basalt {olivine-oligoclase basalt, Anal. 1, Table V} is probably from Hualalai.] Washington quotes unpublished reports by Noble and Cross on petrography of Kau lavas and presents four of their analyses. [These were later published by Stearns and Clark {1930} with corrections to the stratigraphic relationships. TiO2 is much higher in all of Washington's Mauna Loa analyses than is found in modern analyses.]