Aconcagua Climbing – Never underestimate the “age” of Aconcagua

The cabinet tests carried out on the matrix of the deposits were carried out according to the operating conditions and are described below.

Mineralogical analysis: The mineralogical composition, except clays, has been analyzed from 2-3 grams of an 80-gram sample, ground to a size less than 35 μm, through X-ray diffraction, using a D5000 diffractometer ( Bruker AXS). The Aconcagua 360 Route used Cu radiation and an accessory graphite monochromator. Diffraction data were taken from 4° to 70° 2θ, with a scan width of 0.02° and a counter tube scan time of 2 seconds per step. We worked with 40 KV and 30 mA. The quantitative analysis of the phases was determined using the Rietveld technique contained in the BG MN/AUTOQUAN software (Bergmann et al. 1998).

Grain size analysis: For this type of analysis, 12-15 grams of sample were used. The organic components were dissolved through treatment with H2O2. The remaining material was sieved into two fractions: larger and smaller than 63 μm. The first was screened at all phi divisions (phi > -2). From the material smaller than 63 μm, the clay-sized fraction was separated using the Atterberg method, while that corresponding to silt was analyzed with a Micromeritics SediGraph 5100 in all phi divisions.

Grain roundness grading: Some of the remaining material was sieved at 250-500 μm and 100 grains from each sample were graded using Turner’s two-dimensional visual roundness tester. Bearing in mind that Confluencia is the site where both types of deposits are best exposed, we first How to Climb Aconcagua proceeded to define their lithological characteristics there, to compare later what was observed in the different valleys. With this information, the proper genetic interpretation was carried out. The Confluence above profile is exposed in the ravine located on the left bank of the Inferior Horcones River, just in front of its junction with the Superior Horcones River. This profile, of approximately 20 meters, presents two types of deposits recognizable by their different color and stratigraphic position: 1) reddish, the oldest, and 2) gray, the youngest (upper third of said profile).

The upper, grayish deposit comprises a breccia with blocks several meters in diameter (recognized up to 5 Aconcagua Guided Climb meters) scattered in a poorly selected, also breccia matrix (from gravels to clays), predominantly of the same composition as the blocks. The latter shows the typical lithologies of the volcanoes of the Aconcagua Volcanic Complex, made up of lavas, breccias, and tuffs, of andesitic and dacitic composition. It is important to note that this breccia level covers most of the Confluencia sector.