STUDY BY MÖSSBAUER SPECTROSCOPY OF THE MATERIAL FROM OSHNO HILL, DISTRICT OF CHAVIN DE PARIARCA,

REGION OF HUANUCO, PERU

A. Bustamante1, D. Lovera2, R. Quille1, A. V. Arias2 and J. Quiñones2

1Laboratorio de Cerámicos y Nanomateriales. Facultad de Ciencias Físicas, Universidad Nacional Mayor de San Marcos, Lima, Perú. 2Facultad de Ingeniería Geológica, Minera, Metalúrgica y Geográfica, Universidad Nacional Mayor de San Marcos, Lima, Perú.

Abstract Prospective studies developed in the Area of the Marañón Basin in Perú show us a type of so-called Complex Regional Geology of the Marañón consisting of metal ores of copper, silver, gold schist and gneiss in contact with intrusive, as well as minerals nickel, cobalt, titanium, platinum, among others. The sample was collected on the hill OSHNO which is located in the District of Chavín de Pariarca, Huamalies Province, Region Huanuco, Peru. The analysis by X-ray diffraction of the sample OSHNO indicates the presence of the lepidocrocite (-FeOOH) and goethite (-FeOOH). The Mössbauer spectrum (EM) at room temperature for OSHNO measure at high velocity does not show a magnetic component but shows a double widening, proceeding to measure at low velocity. A good fit spectrum include the presence of two doublets. The first doublet has hyperfine parameters of IS=0.367mm/s, DQ=0.51mm/s and =0.37mm/s and corresponds to the presence of the lepidocrocite and the second doublet has a IS=0.366mm/s, DQ=0.48mm/s and =0.98mm/s, the line width is widened and corresponds to smaller particles of hydroxides than 100Å in superparamagnetic state. The EM at the temperature of liquid helium shows a sextet of line width widened and was fitted with a distribution of fields confirming the presence of goethite and lepidocrocite (with magnetic field average of 49.32T and 44.0T respectively). Chemical analysis indicated the presence of Cu, Zn, As, Mn and Ba as major elements and Cr, V, W, Sr, Cd, Co, Ag, La, Sc, Sn, Fe and Ni as minor elements. The sample of OSHNO as metallic powder grain is of interest to small and medium steel industry.

Keywords: Goethite, Lepidocrocite, Mössbauer Spectroscopy.

1. Introduction

The studied area corresponds to the Marañón Basin in Peru, showing a kind of Regional Geology named Complejo Marañón, consisting of metal minerals such as Copper, Silver and Gold in schists (which are rocks that can be easily split in thin layers), consisting of a group of medium-grade metamorphic rocks mainly prominent for the preponderance of laminate minerals such as mica, chlorite, talc, hornblende, graphite, and others in contact with intrusions, as well as with other nickel, cobalt, titanium, platinum minerals, among others. The sample was collected at the OSHNO hill, which is located in the Chavin de Pariarca District, Province of Huamalies, Huanuco Region, Peru, as described on the maps in Figures 1 and 2, where the sample minted is shown. The characterization of minerals of this area is made by Instrumental Techniques: Optical Microscope, Mössbauer spectroscopy Analysis, Multi-elemental Chemical analysis, allow us to check the presence of metalic minerals in the Marañón Complex, as well as the presence of Iron oxide with a magnetization grade that indicates the presence of metals in areas where samples were taken from. The metallurgy tests carried out indicate a good metallurgy recovery of concentrate obtained of Chalcopyrite mineral, which means a good economic possibility for the Marañón Basin [1].

Figure 1. Location of the hill Oshno

Figure 2. Oshno part of the hill where the sample is collected

2. Experimental

In the Laboratory of Extractive Metallurgy - UNMSM proceeded to develop metallurgical processes and operations commissioned: crushing, grinding and sifting to take a size suitable for the chemical and physical characterization.

The X-ray powder diffraction patterns were recorded on BRUKER D8 Focus using a monocromador of graphite and using Cu-K1,2 radiations (=1.5460 Å) in the range 8º to 80º with step 0.02º. The chemical composition was determined by inductively couples plasma optical emission spectroscopy (ICP-OES) using the method ICP-40B that consist in multi-acid (4 acid) digestions that is a combination of HCl (hydrochloric acid), HNO3 (nitric acid), HF (hydrofluoric acid) and HClO4 (perchloric acid). Because hydrofluoric acid breaks down silicates, these digestions are often referred to as “near- total digestions”. There can be a loss of volatiles during digestion (e.g. B, As, Pb, Ge, Sb). Multi-acid digestion is a very effective dissolution procedure for a large number of mineral species and is suitable for a wide range of elements. Mössbauer spectra were recorded in transmission geometry using a constant acceleration spectrometer and a 512 multichannel analyser. The source is a 57Co in Rh matrix. Spectra were recorded on all samples at 300K. Isomer shifts are given relative to the centroid of the spectrum of an absorbedor of -Fe at room temperature. Spectra were analysed by least-squares fits using lorentzian line shape. All fitting procedures were performed with the NORMOS program [2].

3. Results and discussion

3.1 X-ray difraction

The X-ray diffraction (XRD) pattern is showed in the Figure 3 and the analysis indicates the presence of two mineralogical phases such as de la lepidocrocite (-FeOOH ASTM 74-1877) y la goethite (-FeOOH ASTM 02-0273).

Figure 3. X-ray difracction of Oshno sample.

3.2 Chemical analysis

The chemical analysis is sowed in Table 1, indicates that the presence of major elements Cu, Zn, As, Mn y Ba and Cr, V, W, Sr, Cd, Co, Ag, La, Sc, Sn, Fe y Ni as minor elements (Certificate Nº 42876 of SGS company).

Table 1. Chemical analysis of the sample Oshno. Major elements (ppm)

Cu Zn As Mn Ba

968 3996 367 1118 282

Minor elements (ppm)Cr V W Sr Cd Co Ag La Sc Sn Ni Fe

92 66 34 197,8 23 23 6,8 38,7 12,3 24 18 7,39

3.3 Mössbauer spectroscopy

The Mössbauer spectrum (ME) at room temperature of the sample from hill OSHNO at high velocity does not shows any magnetic component but show a broadened doublet, proceeding to measure at low velocity (Figure 3). A good fit spectrum include the presence of two doublets. The first doublet have hyperfine parameters of IS=0.367mm/s, DQ=0.51mm/s and =0.37mm/s and corresponds to the presence of the lepidocrocite [3] and the second doublet has IS=0.366mm/s, DQ=0.98mm/s and =0.48mm/s and the line width widened and corresponds to particles of oxides or hydroxides lower than 100Å in superparamagnetic state. See table number 2.

Figure 3. Mössbauer spectra at RT.

Table 2.-Hyperfine parameters for fitted Mössbauer spectra. is the isomer shift relative to iron, is the quadrupole splitting, 2 is the quadrupole shifts, is the line width, and A is the spectral fraction as obtained from the fit. Bhf is the hyperfine field.

(mm/s)

Area(%)

Fe

(mm/s) o 2(mm/s)

Bhf (T)

RT Lepidocrocite 0.37 53 0.367 0.51Goethite 0.48 47 0.366 0.984.2K Lepidocrocite 0.35 0.356 -0.102 44.00Goethite 0.35 0.356 -0.102 49.32

The ME at the temperature of liquid helium in zero external magnetic field shows the broadened sextet which was fitted using a hyperfine field distributions with the average isomer shift of 0.356m/s and quadrupole shift closed to zero, confirming the presence of

goethite (-FeOOH with magnetic field average of 49.32T) and the lepidocrocite (-FeOOH) with field half of 44.0T, showed in the Figure 4.

Figure 4. Mössbauer spectra at 4.2K and hyperfine-field (Bhf) distributions.

The sample of OSHNO as metallic powder grain is of interest to small and medium steel industry.

Acknowledgements

A.B.D thanks to the UNMSM for supporting this research, through the SEGUSM system and Dra. Rosa B Scorzelli from CBPF by the measurement at helio temperature.

References

1.- D. Lovera, A. Bustamante, P. Gagliuffi, J. Quiñones, L. Puente, L. Gaudencio, J. Diego, A. Romero. Revista del Instituto de Investigación FIGMMG Vol 8 Nº 16 (2005) 44-50.

2.- Brand, R.A.: Normos Programs. Duisburg Universiy (1989). 3.- Mössbauer Mineral Handbook, Editors J.G. Stevens, A.M. Khasanov, J.W. Miller,

H. Pollak, and Z. Li. Mössbauer Effect Data Center 2002.