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OTHER SERVICES

 
 
- Sampling and interpretation of results
- Microscope and electron microprobe studies
- Catalogue of lithologies
- Petrological characterization of mineral deposits
- Evaluation of reserves



 
 

SAMPLING AND INTERPRETATION OF RESULTS

Specialized services of in situ sampling, oriented towards studies of:

  • K-Ar, 40Ar/39Ar, U-Pb, Re-Os, 14C geochronology, depending upon the characteristics of the rocks and the objectives of the client (alteration, mineralization or crystallization age).

  • Geochemistry of rocks for petrological studies.

  • Spectroscopic characterization for ASD and/or PIMA mapping.

  • AURUM also collaborates with recognized national and international laboratories in order to obtain varied analyses, and is responsible for the graphic presentation and interpretation of results.

Example: 40Ar-39Ar dating of a pluton associated with mineralization and alteration of wallrocks.

1. Selection and collection of samples in the field

2. Samples sent to the AURUM Consultores sample store room.

3. Consultation regarding suitability for dating.

4. Selection of the most appropriate sample(s).

5. Contact with the selected laboratory.

6. Follow-up the analytical process.

7. Reception of results.

8. Interpretation of results and their implications within the geological context.

9. Preparation of a report oriented towards the requirements of the client.

Laboratory 40Ar/39Ar
   
Presentation of results of a 40Ar/39Ar age.  
a)  

a)  Step-heating spectrum, where the x axis represents the accumulated 39Ar released from the sample during the step heating process, and the y axis represents the apparent ages of individual heating steps in millions of years (Ma).

   
b)  
b) Inverse isochron; a plotting format for argon isotope data which permits the estimation of the non-radiogenic argon at the moment of closure of the isotopic system.
   

U-Pb ages

AURUM Consultants obtains U-Pb ages in recognized laboratories, selected in collaboration with the client.

 

   
Photomicrograph of zircons and ellipse diagram for 5 zircon fractions.
   

MICROSCOPE AND ELECTRON MICROPROBE STUDIES

AURUM Consultants carries out conceptual petrographic studies, with the aid of digital microphotographs and electron microprobe studies with petrological, genetic and metallurgical objectives. A network of experts in igneous petrology, mineral deposits and alteration is available for these studies.

Examples:

Graphic intergrowth of quartz and potassium feldspar in a graphic hololeucocratic syenogranite (“aplite”), from the late stages of an Upper Cretaceous plutonic complex.

   

Plagioclase phenocryst replaced by hypogene alunite.


LITHOLOGIES CATALOGUE

The correct identification of lithologies in a mineral deposit and their relationships with, or control of, the mineralization and alteration, results in improved map quality and aids both the correct exploitation of the deposit, and exploration strategies within and around it.

The catalogues of lithologies carried out by AURUM Consultants involve:

  • Determination of the dominant and/or relevant lithologies, and their macroscopic and microscopic characterization, with the aid of X-ray diffraction analysis.

  • Establishment of a protocol to standardize classifications

  • Characterization of rock units (size, volume, etc.), genetic interpretation.

  • Photographic catalogue of hand samples.

  • Library and/or spectral characterization for PIMA mapping.


PETROLOGICAL CHARACTERIZATION OF MINERAL DEPOSITS

The petrological characterization of igneous rocks which are spatially or genetically related to mineral deposits contributes to the understanding of the genesis of the mineralization and provides an additional exploration tool.

This characterization is based upon:

  • petrographic studies and modal analysis.

  • major and trace element and rare earth geochemistry for the characterization of magmatic units.

  • Comparative geochemical analysis of rocks.

More detailed studies include:

  • Electron microprobe studies

  • Geothermometry, geobarometry

  • Isotopic analyses.

Modal classification of a plutonic complex, based on the Streckeisen diagram, which defines a differentiation trend from gabbros to syenogranites, with a predominance of granitic to granodioritic compositions. This suite corresponds to a calcalkaline-tholeiitic trend (CAT-GAC).

   
Jensen cation classification diagram (Jensen and Pyke, 1982) for Lower Cretaceous volcanics (), compared with contemporaneous intrusions (+), frequently associated with mineralization. A transitional calcalkaline-tholeiitic tendency is observed for these rocks.

 

EVALUATION OF MINERAL RESOURCES

•  Geological modelling
•  Evaluation and audits of mineral reserves
•  Estimation of resources
•  Construction of a base geological model for the estimation of reserves, adjusted to the requirements of the client. Analysis and optimization of reliable databases, preparation of maps and sections, establishment of limits and geological factors which control the mineralized body.
•  Estimation of resources in distinct stages of exploration under the agreed scenario.



 
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