Minerals of Mississippi Valley Type Deposits

October 14-16, 2005

This year's annual symposium is scheduled for October 14-16 and once again will be held at the Red Lion Motel at Kelso, WA. 

This year's Symposium theme has been selected as "Minerals of Mississippi Valley Type Deposits". Preparations for this year's Symposium are underway and headline speakers have already been confirmed.

We have confirmed renowned and excellent speakers:

• John Rakovan, Executive Editor of Rocks & Minerals, will be presenting on some of his recent work in New Mexico.
• Jesse Fisher will be presenting on the Northern Pennines in England to complement his recent article in Rocks & Minerals.

MVT Deposits constitute another interesting and unusual topic which provides something of interest for most mineral collectors. MVT Deposits are economically significant sources primarily of lead and zinc, but are not completely understood. Guilbert and Parks (1986) classify MVT deposits as "epigenetic deposits of doubtful igneous connection". In this case, epigenetic refers to mineral deposits emplaced after, and often much later, than the rocks that contain them.

Some typical MVT Deposit characteristics include:

• Lack of nearby bodies of igneous rock;
• Deposits typically laterally extensive, but thin;
• Major ore mineralogy consists primarily of low-Ag galena, low-Fe sphalerite, barite, and fluorite;
• Gangue minerals typically limited to dolomite, calcite, jasperoid, minor silica, barite, and fluorite;
• Low precious metal content;
• Occurrence is typically (with a few significant exceptions) as replacement deposits in dolomite or Mg-rich limestone;
• Typically occur at the margins of major sedimentary basins, at shallow depths, and in geologically passive areas; and
• Ore occurs as replacement deposits and as open-space fillings almost always in dolomitized limestone.

A summary of many of the most well-known MVT Deposits from around the world is included in the table below:

References:

• Guilbert, John M., and Charles F. Parks, Jr., 1986. The Geology of Ore Deposits. New York: Wilt. Freeman and Company, 985 pp.
• Leach, David L., J.B. Viets, N. Foley-Ayuso, and D.R Klein, 1996. Mississippi Valley-Type Pb-Zn Deposits, pp 234 - 243 in Preliminary C ompilation of Descriptive Geoenvironmental Mineral Deposit Models. USGS OF Report 95-83 1.

Past Symposium Topics can be found on this link.