TRACE ELEMENTS OF VOLCANIC ULTRABASIC POTASSIC ROCKS OF SOUTHWESTERN UGANDA AND ADJOINING PART OF THE BELGIAN CONGO

Research Article| January 01, 1954 TRACE ELEMENTS OF VOLCANIC ULTRABASIC POTASSIC ROCKS OF SOUTHWESTERN UGANDA AND ADJOINING PART OF THE BELGIAN CONGO RIAD A HIGAZY RIAD A HIGAZY GEOLOGY DEPT., UNIVERSITY OF ALEXANDRIA, EGYPT Search for other works by this author on: GSW Google Scholar GSA Bulletin (1954) 65 (1): 39–70. https://doi.org/10.1130/0016-7606(1954)65[39:TEOVUP]2.0.CO;2 Article history received: 17 Nov 1952 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 RIAD A HIGAZY; TRACE ELEMENTS OF VOLCANIC ULTRABASIC POTASSIC ROCKS OF SOUTHWESTERN UGANDA AND ADJOINING PART OF THE BELGIAN CONGO. GSA Bulletin 1954;; 65 (1): 39–70. doi: https://doi.org/10.1130/0016-7606(1954)65[39:TEOVUP]2.0.CO;2 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 The volcanic fields of Southwest Uganda and the adjoining part of the Belgian Congo are characterized by ultrabasic potassic rocks. The principal rock types are katungite, ugandite, and mafurite. Katungite is rich in melilite but free from augite; its potash is mainly in glass. Ugandite and mafurite contain augite, but their dominant feldspathoids are leucite and kalsilite respectively. Olivine is present in these three types. The investigated rocks also include members of the potash ankaratrite-mela-leucitite series, olivine melilitite, kivite or leucite basanite, and limburgite.The constituents of the pyroclasts include fragments of prevolcanic crustal rocks and a subvolcanic suite of rocks consisting of various combinations of augite, biotite, and olivine. Representatives of both groups occur in the lavas as xenoliths and xenocrysts.The chemical compositions and trace-element contents of the different types are discussed. They are relatively rich in K2O, TiO2, and P2O5 and characterized by having K2O > Na2O and Al2O3 > (K2O + Na2O). They possess relatively high abundance of trace elements uncommon in ultrabasic rocks—namely, Sr, Ba, Rb, and Zr.It is shown that neither the crystallization differentiation nor the limestone-assimilation hypothesis can explain the peculiar geochemical features of the examined rocks. It is suggested that they originated by reactions between carbonatite magma which contributed Ca with Sr, La, and Y; Mg with Cr and Ni; Fe with V and Ti; and P; and sialic crustal rocks which provided Si; Al with Ga; and K with Rb and Ba. The variations in the proportions of the reacting materials and in the physical conditions under which the reactions took place gave rise to differences in the compositions of the various rock types. 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.