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Mabel Regional Geology
(R.S Friberg)
The northwestern portion of México is a complex setting similar
to that of southern Arizona and southeastern California. The
physiographic province is typical of the southern Basin and
Range - elongate, northwest-trending ranges divided by wide
alluvial valleys.
The property is located in the southern Arizona Mesozoic
volcanic and plutonic province. Hydrothermally altered felsic
volcanic, hypabyssal plutonic rocks and lesser Quaternary
basalts underlie the general area.
Basement rocks include Precambrian gneisses, metamorphosed
andesites and granites. These are overlain by younger
Proterozoic quartzites and limestones, Paleozoic and Mesozoic
carbonate rocks and Mesozoic volcanic, clastic and carbonate
sediments rocks. The Mesozoic plutonic and Tertiary extrusive
and intrusive rocks are related to volcanic activity of the
Sierra Madre Occidental and are widely distributed.
Range front faults trend northwesterly and numerous low-angle
shear zones related to thrust or detachment faults are the
dominant structural feature. The Mojave-Sonora megashear
(Anderson and Silver, 1979) is the principal regional feature.
This wide zone separates Precambrian basement rocks of slightly
different age and is occupied by a Jurassic magmatic arc
composed of volcanic, sedimentary and plutonic rocks. The
southwestern boundary of this megashear appears to be a major
fault juxtaposing the Precambrian basement against the Jurassic
magmatic terrain (Anderson and Silver, 1979).
Many of the gold prospects in Sonora occur within or adjacent to
the southwestern boundary of the megashear in Precambrian,
Mesozoic and Tertiary rocks. Silberman (1985) recognized a
southeast-trending belt of gold occurrences, beginning at
Sonoita on the border and including Caborca, Magdalena and
Nocozari. Many of the gneiss-hosted or structurally controlled
gold prospects of Sonora are broadly similar to the gold
deposits mined along low-angle structures in southeastern
California.
District and Property Geology
(Friberg and Brown etal 2002)
In the Mabel property area the dominant gravel-filled basin is
bounded on three sides by outcropping basement rocks. To the
west, the Sierra San Juan is a moderately elevated block of
Mesozoic crystalline rocks. South and east is a low relief area
composed of Mesozoic to upper Cretaceous intrusive and volcanic
rocks, overlain by thin remnants of Tertiary volcanic and
sedimentary rocks. The hill located at the northern property
boundary, Cerro El Sombreretillo, is a good example of this
sequence as the lowermost portion consists of moderately tilted
(20° - 30° west to southwest) middle Tertiary and Mesozoic rocks
overlain by upper Tertiary age conglomerates capped by a thin
remnant of Quaternary/Tertiary basalt flow.
Normal Basin and Range faults found in the district affect rocks
as young as middle Tertiary. High angle faults that have strikes
of northeast, west-northwest and north-northeast form many of
the contacts between both premineral and postmineral volcanic
rocks and the Laramide plutonic rocks.
A major east-northeast trending regional fault is recognized
just south of the Mabel 1 claim. This fault might be a
detachment or simply a major break which supplied a conduit for
fluid flow and thus gold, silver and copper mineralization (see
Property Geology Figure under Deposit).
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