THIS IS THE THIRD ISSUE DEDICATED TO THE MEMORY OF DISTINGUISHED SCIENTIST ALFRED KRONER WHO SADLY PASSED AWAY ON 22 MAY 2019

It is now over eleven years' ago, in November 2010, that the American Journal of Science published the first of two volumes marking the 70 birthday of Alfred Kroner. We, his friends and colleagues, planned to mark Alfred's 80 birthday with another special issue of the American Journal of Science, designed to showcase the scientific advances that had been made over the past decade in those areas of geoscientific endeavor that were closest to Alfred's heart. Sadly, Alfred passed away on 22 May 2019, less than four months before his 80 birthday (8 September). This is the third and final volume compiled to celebrate his tremendous contribution to geoscientific research. In the Preface to American Journal of Science, volume 310, number 9 of November 2010, a comprehensive outline of Alfred's career up until that date was presented (kindly outlined and supplemented by Alfred) and the reader is referred to this for more details of his earlier career. In the Preface to the first of these special issues (volume 321, numbers 1,2 of January-February 2021), we focused on the last ten years, outlining Alfred's major contributions, where his work was principally focused, and the key activities he undertook. We include this information below: Alfred's long association with Prof Liu Dunyi and the Beijing SHRIMP Center continued throughout the last decade of his life and resulted in a fruitful cooperation that was especially beneficial to young Chinese geoscientists. Alfred would spend several months every year based at the SHRIMP Laboratory, although he made many journeys both within China to deliver invited lectures and short courses at numerous institutions and universities, as well as undertaking many fieldtrips both in China and neighboring countries. In particular, his work on the Central Asian Orogenic Belt (CAOB) was ongoing in Mongolia, Kyrgyzstan and Russia. As Chairman of the International Precambrian Research Center of China (IPRCC), Alfred also organized a series of lectures, workshops and fieldtrips every year; many designed principally for students. The first of these was in May 2010, when the field workshop “Early Crustal Evolution of the SE Kaapvaal Craton in South Africa and Swaziland” was organized and attended by a large contingent from China. In October that year, the 5 SHRIMP Workshop and a workshop on “Advances in high-resolution SIMS and LA-ICP-MS Geochronology and Application to Geological Processes” were held in Beijing and Alfred took an active part in their organization. These were followed by a field excursion to Inner Mongolia to investigate Paleoproterozoic ultra-high temperature rocks of the Khondalite Belt. Also organized during this period was a training course in zircon geochronology including SHRIMP analytical techniques, which was run for the benefit of higher degree students from universities and institutions all over China. This course was presented by Ian Williams, Robert Pidgeon, Lutz Nasdala, William Griffin, Fernando Corfu, Klaus Mezger, M Santosh and Yusheng Wan. In April 2011, there was the “Lithospheric Evolution through Time” workshop in Beijing presented by Alfred Kroner, Walter Mooney and Ron Clowes, and in October 2012 a training course on “Migmatites, Melting and Intracrustal Differentiation”, followed by a fieldtrip for the students held at Taishan in Shandong Province, both run by Michael Brown, Edward Sawyer, Richard White and Simon Wilde.