The jasperoids of the Superior district, Arizona: their origin and
controls on their location
The present project involves the study of quartz-iron oxide replacement
bodies (jasperoids) at the Lake
Superior and Arizona (LS&A) and Queen Creek mines at Superior
, Arizona. This project is based on
more than 12 months of field work and extensive petrographic, major and
trace element, and isotopic (O and C) data on samples of host rocks and
ore. This project is part of a larger project to study the
Cu-Au association in porphyry and epithermal systems: variations in time-space
and geochemical evolution that involves several people of the ODEX
Research Group at Stanford.
In this projext I am studying:
1) how the A-bed jasperoids formed, particularly in relation to the
massive sulfide-hematite bodies of the Magma
(Superior) mine;
2) the processes by which a small number
of carbonate beds within a >800 m-thick limestone sequence were
selectively replaced, particularly focussing on the chemical and physical
properties that made those beds more favorable for replacement, and their
relative influence in the replacement process.
The small size of these
bodies (generally less than 10 m long and 1 m thick) makes them ideally
suited for a detailed study of the stratigraphic controls in the location
of this type of ore bodies. This is important because bigger ore bodies
generally replace not only the favorable beds but also their surroundings,
making it difficult to establish the reasons why that part of the sequence
had been replaced.
Preliminary results from my studies have been presented at meetings
of the Geological Society of Nevada (GSN) and of the Geological Society
of America (GSA):
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