Aspectos petrográficos y metalogenéticos del yacimiento Arroyo Seco, Michoacán.

http://dx.doi.org/10.18268/BSGM1987v48n2a3

Jorge Bustamante García¹, David Esponda Ortiz¹, Abel Gasca Durán¹

¹ Consejo de Recursos Minerales

Abstract

The mineralization at the north (Los Alacranes) of the Arroyo Sec, state of Michoacán is lying in sedimentary rocks such as, sandstones, oil stones, shales, buffs and tuffs sandstones.

However the mineralization at the south (El Zapote) lies into sedimentary and volcanic rocks such as andesitics tuff oilstones, and fine-grained sandstones. The ore deposit is located in the eastern-flank of an anticlinal whose axis has a north-south trend, there´re submeridional faults, which correspond to Arroyo Seco and el Zapote brooks, fragmenting the ore deposit in several structural areas, theire morphology and genetically differences, whereas at the north of the area there are several complex faults and fractures that displace the ore deposits.

At the north (Los Alacranes) does not exist any evidence of alteration, while in the south (El Zapote), the host-rocks are widely cloritizated, the epidotization is also very common, in some places the epidotization becomes in propilitization too.

The mineralization in this two areas exhibits megascopic and microscopically structurals differences in los Alacranes, the ore presents banded and subbanded into pseudo-bedding planes, dissemination, cemented, and setting textures, those are probably texture due because sedimentation and diagenetic processes.

While at the south there are massive textures in inter-growth veinlets and emulsion of calcopyrite into sphalerite, which is indicative of a wide exhalative process, with intensive vulcanism. (Figure 4).

It was found by Microsonda Silver in minerals such as tetraedrite, galena and aregentita, It was observed submicroscopic gold in calcopyrite, barytes and hematites.

The study of fluid occlusions made in barytes and calcite of the ore deposit confirms the author´s hypothesis in this report, about the mineralization in los Alacranes is syndiagenetic with few vulcanism, and El Zapote there was a wide exhalative sedimentary activity.

Fifty samples were studied in Petrograpy Laboratory with the purpose to understand the petrographic and geological behaviour of the horst-rocks. By other hand we realised a relationship between 6 hole drill core at the north, to explain the morphology and the number of ore deposits in the area.

All of this studies, can be conclude, that Arroyo Seco ore deposit exhibit two sectors with diferents characteristics, The first represented at the north by los Alacranes, which exhibits sindiagenetic mineralization into a ritmic and chicly sequence, with moderate volcanic occurrence, and the second in the south chicly science, which exhibits sindiagenetic mineralization into a ritmic and chicly science, with moderative volcanic occurrence, and the second in the south (El Zapote) where is evident and exhalative-sedimentary process, with appreciable vulcanism. This aspect has its implications and practicals consequences, but in the exploration and evaluation of the ore deposit, such as we expose in our conclusions and recommendance in the present report.