Guigui - Largest Carbonate Replacement Deposit - Reyna Silver
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Guigui Project

image Panoramic view from the northern limit of the Guigui Property showing the San Antonio Graben

Prime Location.

Located in Chihuahua, Mexico with an area of 4,750 hectares and covers a major portion of the Santa Eulalia Mining District, the world’s largest known Carbonate Replacement Deposit (CRD) system.

Historically-rich Mining District.

Santa Eulalia Mining District has a recorded pro- duction of nearly 450 million ounces of silver and substantial amounts of lead and zinc mined from the period 1702-2001.

District-scale project.

Project has large land position South and Central to major mining areas to accommodate the exploration of the district scale CRD.

Great Exploration Potential.

The initial 12,000-meter drill campaign is currently underway. Exploration will continue to search for the concealed intrusive center of the CRD considered to be related to the district scale mineralization.


The project is located 15 km east of Chihuahua City: a major industrial and mining center.

Other populated centers near Guigui are the towns of Santa Eulalia (or Aquiles Serdán) and Santo Domingo (or Francisco Portillo).

The Chihuahua International Airport is about 25 minutes away from the property. It receives numerous daily flights from USA and parts of Mexico.

Toll Milling operation in the Potosi Mine adjacent to Guigui and La Chinche.

Paved and hard surface roads lead to Guigui and neighboring mines. Property is crossed by a series of well-maintained ranch roads.

image Geological Map of Guigui (Wendt, 2002)

The Guigui Project and the Santa Eulalia Mining District lies in central Chihuahua Terrane, which is underlain by Precambrian continental crust overlapped by Lower Cretaceous sedimentary rocks and Tertiary volcanic rocks.

The Sierra Santa Eulalia is a horst block bounded by steeply dipping normal faults on both the east and west sides of the range. The body of the range is composed of lower Cretaceous limestone and underlying evaporites, which were folded into a broad doubly plunging anticline with a NNW-SSE trending axis and gentle dips.

Limestone outcrops throughout the northern portion of the range but becomes covered by an increasingly continuous blanket of lower Tertiary volcanic and volcaniclastic rocks towards the south. Erosional windows of lime- stone are locally exposed through these volcanic rocks. The lower Tertiary section continues southward until it be- comes buried under a thick package of mid-Tertiary ash-flow tuffs and basalts, erupted from the resurgent Santo Domingo Caldera, which occupies the southern half of the range. This southern portion of the sierra consists almost entirely of intracaldera volcanic rocks.

The Santa Eulalia District is the largest known Carbonate Replacement Deposit (CRD) in Mexico and the largest among the CRDs that define a belt running from Hidalgo to near the Chihuahua-U.S.A border (Table 1).

Carbonate Replacement Deposits are Phanerozoic, high-temperature (>250 °C) deposits that comprise major pod, lens, and pipe-shaped Pb-Zn-Ag-Cu-Au-sulfide orebodies that cut across their host carbonate rocks. They are dominantly composed of a simple assemblage of galena, sphalerite, chalcopyrite, arsenopyrite, pyrite and/or pyrrhotite with subordinate carbonate, sulfate, fluorite and quartz gangue. A model of the CRD was established and developed by Dr. Peter Megaw from his dissertation studies at the Santa Eulalia.


The mining district is divided into three camps—West, East and Middle Camps. Guigui Project lies immediately to the south of these camps:

  • West Camp (SEWC) - Principal past producers in the camp are Grupo Mexico’s Buena Tierra Mine and MINA- MEX’s Potosi Mine.
  • East Camp (SEEC) - Production is dominated by Grupo Mexico’s San Antonio Mine, which is currently in production.
  • Middle Camp (SEMC) - The 2.5-km zone between SEWC and SEEC; Contains numerous mineralized showings and small mines but has not been systematically explored.

The East and West Camps contain continuous, zoned mineralization and alteration closely associated in time and space to groups of apparently identical felsite intrusions. Although the mineralization in the two camps does not overlap in space, both appear to have resulted from the evolution of persistent, pulsating, hydrothermal systems. The morphology of the felsites coupled with mineralogical, metals content, metal ratios, sulfur isotope, and mineralization style, strongly indicates a common hydrothermal source for the two camps. This source appears to lie between the two camps, immediately north of the Santo Domingo caldera (Megaw, 1990).


Peter Megaw Dissertation Studies: Geology, Geochemistry of the Santa Eulalia Mining District


BHP: Geology, Ground Magnetics and Gravity


Noranda: CSAMT Prep


Teck Resources: 1 Hole to west


Advanced Projects: CSAMT


MAG Silver: 8 Holes, Mag & Z-TEM Survey (post-drilling)


MAG Silver: Hiatus (Mega-Claim)


MAG Silver: Drilling of Mag anomaly to east


Reyna Silver project acquisition


Drilling by MAG Silver successfully tested the continuation of mineralization from the San Antonio Mine.

  • Hole 05 returned a narrow intercept that assayed 523 g/t Ag Equivalent (109 g/t of silver and 5.6% lead and 4.3% zinc) over 0.40 meters.
  • Hole 6 returned with an 8.3 meters intercept of 131 gpt silver.
  • These holes significantly proves that the mineralization in the San Antonio Mine area continues to the Guigui property and indicates a much wider hydrothermal system.
image View from the airport of Sierra Santa Eulalia showing mountains of limestone (front, left) and the volcanic cover (back, right), which increases to the south. image One of the peaks of the Sierra Santa Eulalia within the mining district.
image Example of cores from the previous drilling programs at Guigui. image Well-maintained core storage facility at Guigui.