LINDGREN, WALDEMAR

born Feb. 14, 1860, Kalmar, Swed. died Nov. 3, 1939, Brighton, Mass., U.S. Swedish-born American economic geologist who helped establish that veins of metal and similar deposits are created by hot solutions derived from molten rock below, not by water seepage from above. Lindgren immigrated to the United States in 1883 and was associated with the U.S. Geological Survey from the following year until 1912. Extensive studies of ore deposits in the western states enabled him to determine with unprecedented accuracy the physical and chemical conditions of ore formation. He established the igneous sources of many minerals and clarified the methods by which ores are deposited, notably the replacement of certain minerals by others. He is noted for a system of classification, devised in 1913, that separates ore deposits into magmatic segregates, contact metamorphic deposits, pegmatites, veins and veinlike deposits of differing degrees of intensity in temperature and pressure (hypothermal, mesothermal, epithermal), and sedimentary deposits. He became chief geologist of the Geological Survey in 1911 but resigned to become professor of economic geology and chairman of the department of geology at the Massachusetts Institute of Technology, Cambridge. He published nearly 200 books and papers, and his Mineral Deposits (4th ed., 1933) became the leading advanced text in its field.