Geology and intrusion-related affinity of the Morila Gold Mine, Southeast Mali

McFarlane, Christopher R. M., Mavrogenes, John, Lentz, Dave, King, Ken, Allibone, Andrew and Holcombe, Rod (2011) Geology and intrusion-related affinity of the Morila Gold Mine, Southeast Mali. Economic Geology, 106 5: 727-750. doi:10.2113/econgeo.106.5.727

Author McFarlane, Christopher R. M.
Mavrogenes, John
Lentz, Dave
King, Ken
Allibone, Andrew
Holcombe, Rod
Title Geology and intrusion-related affinity of the Morila Gold Mine, Southeast Mali
Journal name Economic Geology   Check publisher's open access policy
ISSN 0361-0128
Publication date 2011-08
Sub-type Article (original research)
DOI 10.2113/econgeo.106.5.727
Volume 106
Issue 5
Start page 727
End page 750
Total pages 24
Place of publication Littleton, CO, United States
Publisher Society of Economic Geologists
Collection year 2012
Language eng
Formatted abstract
The ~8 Moz Morila gold mine, hosted within Paleoproterozoic Birimian volcano-sedimentary rocks of southeast Mali, is spatially and temporally associated with prolonged (2098–2065 Ma) arc magmatism during the late stages of the Eburnean orogeny. Visible gold at Morila is associated with variably deformed polymineralic veins containing native bismuth, maldonite, aurostibite, rare tellurobismuthite, and löllingite, suggesting a proximal intrusion-related source for this period of gold mineralization. This early formed mineralization is contained within a zone of hornblende hornfels contact metamorphism and is spatially associated with syn- to post-D2 emplacement of 2098 to 2091 Ma quartz-diorite, granodiorite, and leucogranite magmas. The occurrence of immiscible Au-Sb-Bi-Te blebs within sills or dikes associated with gold mineralization at the Morila deposit explicitly links granitic magmatism with gold mineralization This early intrusion-related gold system was over-printed by a younger post-D2 stage of hydrothermal alteration recorded by sulfidation along a north-north-east–trending zone characterized by disseminated idioblastic arsenopyrite porphyroblasts that contain polygonal gold blebs. Silicate alteration during this stage includes albitization of plagioclase and the growth of randomly distributed biotite and titanite, the latter typically surrounding ilmenite. Uranium-Pb dating of this generation of titanite yields a preliminary age for late-stage sulfidation of 2074 ± 14 Ma, which brackets mineralization to the interval 2098 ± 4 to 2074 ± 14 Ma.

The geochemistry and isotope systematics of syn- to post-tectonic intermediate intrusions at the Morila deposit point to their derivation in a suprasubduction zone setting and emplacement into tectonically thickened crust. Based on these observations, it is suggested that the Morila gold deposit formed during late-stage collisional orogenesis involving the accretion of juvenile volcanic arc terranes against the Archean Man (Liberian) cratonic nucleus. This setting is analogous to younger Phanerozoic active continental margin settings which host the best-described examples of intrusion-related gold systems.
Keyword West-African craton
Kedougou-Kenieba inlier
Age constraints
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Earth Sciences Publications
Official 2012 Collection
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Citation counts: TR Web of Science Citation Count  Cited 19 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 16 times in Scopus Article | Citations
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