I was saddened to hear of the death of geophysicist Jean Francheteau. While he made many, many contributions in geophysics, he was perhaps best known for his coauthorship of Plate Tectonics with Xavier LePichon and Jean Bonnin. A list of many of his publications can be found here.
I became familiar with his dissertation, Paleomagnetism and Plate Tectonics, while I was still in graduate school, and made use of his quaternion complex matrix formulation for plate rotations and compositions (more completely documented beyond the description in Plate Tectonics). I made use of the formulation in my first published paper, "A method for finite plate reconstructions, with applications to Pacific‐Nazca Plate evolution," and a number of subsequent papers. I recommended (but didn't require) Plate Tectonics for a graduate class on the subject I taught for many years.
RIP.
