Hydrothermal alteration of igneous rocks

Research Article| February 01, 1939 Hydrothermal alteration of igneous rocks GEORGE M. SCHWARTZ GEORGE M. SCHWARTZ Search for other works by this author on: GSW Google Scholar Author and Article Information GEORGE M. SCHWARTZ Publisher: Geological Society of America Received: 22 Mar 1938 First Online: 02 Mar 2017 Online Issn: 1943-2674 Print Issn: 0016-7606 © 1939 Geological Society of America GSA Bulletin (1939) 50 (2): 181–238. https://doi.org/10.1130/GSAB-50-181 Article history Received: 22 Mar 1938 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation GEORGE M. SCHWARTZ; Hydrothermal alteration of igneous rocks. GSA Bulletin 1939;; 50 (2): 181–238. doi: https://doi.org/10.1130/GSAB-50-181 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Many studies of individual examples of hydrothermal alteration have been made, but a general summary has not appeared since 1915. The changes due to hydrothermal alteration are textural, mineralogical, and chemical.As a rule the primary texture is destroyed, roughly in proportion to the intensity of alteration, but only in extreme examples is it entirely gone. Many of the rocks are softened and bleached and consist of a felt-like or messy aggregate of secondary minerals. Less commonly the rock remains fresh, owing to the development of anhydrous minerals such as albite.The most common secondary minerals, approximately in order of abundance, are: sericite, quartz, pyrite, carbonates, chlorite, epidote, alunite, adularia, albite, various sulphides and numerous less common, but at places characteristic, minerals.Chemical changes are extensive and vary widely. An average has been made of all available pairs of analyses divided into acid, intermediate, and basic types, as well as a combined average. Comparison of altered with fresh rock shows a gain in potassa and water, a loss in iron, magnesia, lime, and soda, and little change in silica and alumina during alteration.Diagrams are used to bring out significant features of various groups of analyses as well as of the averages prepared. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.