scholarly journals Mineral Inventory of the Algares 30-Level Adit, Aljustrel Mine, Iberian Pyrite Belt, Portugal

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 853
Author(s):  
Teresa P. Silva ◽  
João X. Matos ◽  
Daniel De Oliveira ◽  
João P. Veiga ◽  
Igor Morais ◽  
...  
Keyword(s):  
Hydrothermal Alteration ◽  
Iberian Pyrite Belt ◽  
Mining Activity ◽  
Massive Sulphide ◽  
Principal Characteristics ◽  
Secondary Minerals ◽  
Crystalline Aggregates

Mining activity in Algares (Aljustrel Mine, Portuguese sector of the Iberian Pyrite Belt, IPB) stems prior to Roman times. As the orebody is vertical and relatively thin, mining was carried out mainly along underground adits (galleries). Nowadays, the deposit is considered exhausted and the area is being rehabilitated for a different use. The Algares +30 level adit intersects two volcanic units of the IPB Volcano-Sedimentary Complex. The massive sulphide and related stockwork zone are hosted by the Mine Tuff volcanic unit and are exposed in the walls of the gallery, showing intense hydrothermal alteration. Along the mine adit, the geological sequence is affected by strong oxidation and supergene alteration, giving rise to the formation of secondary minerals through the oxidation of the sulphides. The most common minerals found were melanterite (FeSO4·7H2O) and chalcanthite (CuSO4·5H2O), forming essentially massive or crystalline aggregates, ranging from greenish to bluish colours. Melanterite from the walls revealed to be Cu-rich by opposition to that from stalactites/stalagmites formed below the old ore storage silo revealing the low-copper-grade ores exploited underground. The mineralogy of the efflorescent salts was used to ascertain the processes involved in their formation, and moreover, the inventory of minerals is presented, as well as their principal characteristics.

scholarly journals Vectors to ore in replacive VMS deposits of the northern Iberian Pyrite Belt: mineral zoning, whole rock geochemistry, and use of portable XRF

2021 ◽  
Author(s):  
Guillem Gisbert ◽  
Fernando Tornos ◽  
Emma Losantos ◽  
Juan Manuel Pons ◽  
Juan Carlos Videira
Keyword(s):  
Hydrothermal Alteration ◽  
Hanging Wall ◽  
Iberian Pyrite Belt ◽  
Major Elements ◽  
Massive Sulphide ◽  
Alteration Zone ◽  
Portable Xrf ◽  
Sequence Characterization ◽  
Vms Deposits ◽  
Mineral Zoning

Abstract. Volcanogenic Massive Sulphide (VMS) deposits represent a major source of base, precious and other metals of economic and industrial importance. As in other mineral systems, progressive exhaustion of the shallowest and most easily accessible deposits is leading to increasingly complex exploration. In this context vectors to ore play a vital role. The Iberian Pyrite Belt (IPB) is an outstanding VMS district located in the SW Iberian Peninsula, which represents the main mining area in Spain and one of the main zones of base metal production in Europe. But the work on vectors to ore in the IPB is far from systematic or complete. In this work we have performed a detailed study of the main vectors to ore related to mineral zoning and whole rock geochemistry that are currently used in the exploration of VMS systems to a representative volcanic rock hosted replacive VMS deposit located in the northern IPB, the Aguas Teñidas deposit. Results have been compared to other deposits in the IPB and in other VMS districts. The investigated vectors include: mineralogical zoning, host sequence characterization and mineralized unit identification based on whole rock geochemistry, the study of the characteristics and behaviour of whole rock geochemical anomalies around the ore (e.g. alteration-related compositional changes, characteristics and extent of geochemical halos around the deposit), with definition of threshold values for the mineralization-related indicative elements, and application of portable XRF analysis to the detection of the previous vectors. In the footwall, a concentric cone-shaped hydrothermal alteration bearing the stockwork passes laterally, from core to edge, from quartz (only locally), to chlorite, sericite–chlorite, and sericite alteration zones. The hydrothermal alteration is also found in the hanging wall despite its thrusted character: a proximal sericite alteration zone is followed by a more distal albite one, which is described here for the first time in the IPB. Whole rock major elements show an increase in alteration indexes (e.g. AI, CCPI) towards the mineralization, with a general SiO2 enrichment, FeO enrichment in the central portion of the system, K2O and Na2O leaching towards the outside areas, and a less systematic MgO behaviour. Copper, Pb and Zn produce proximal anomalies around mineralized areas, with the more mobile Sb, Tl and Ba generating wider halos. Whereas Sb and Tl halos form around all mineralized areas, Ba anomalies are restricted to areas around the massive sulphide body. Our results show that proposed vectors, or adaptations designed to overcome p-XRF limitations, can be confidently used by analysing unprepared hand specimens, including the external rough curved surface of drill cores. The data presented in this work are not only applicable to VMS exploration in the IPB, but on a broader scale they will also contribute to improve our general understating of vectors to ore in replacive-type VMS deposits.

Geochemical proximity indicators of massive sulphide mineralization in the Iberian Pyrite Belt and the East Pontic metallotect

1983 ◽  
Vol 18 (S2) ◽  
Author(s):  
P. M�ller ◽  
M.A. Dieterle ◽  
P. Dulski ◽  
K. Germann ◽  
H.-J. Schneider ◽  
...  
Keyword(s):  
Iberian Pyrite Belt ◽  
Massive Sulphide ◽  
Sulphide Mineralization
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