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A Scientific and mineralogical trip to the Iberian Pyrite Belt - (6)
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Mark Ost




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PostPosted: Apr 17, 2013 20:43    Post subject: Re: A Scientific and mineralogical trip to the Iberian Pyrite Belt - (6)  

The Baryte is beautiful. Thanks for tour.
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PostPosted: Jul 07, 2013 22:13    Post subject: Re: A Scientific and mineralogical trip to the Iberian Pyrite Belt - (6)  

Here, I pick the tour through IPB up from the last addition about the interesting Neves-Corvo deposit.
As I explained in the beginning of this thread, the IPB deposits could be divided in two types, well differentiated in age and origin of the main mineralization. The Neves-Corvo deposit belong to the "Southern" class of volcano-sedimentary massive sulfide deposits in the IPB. This class of deposit is of interest to our research team, because of its main characteristics:
-shale hosted deposit: The mineralized massive sulfide bodies are included in the VSC (volcano-sedimentary complex), a complex formation that include dacitic-rhyolitic domes, sills, lava flows and volcanoclastics units interbedded with detrital sedimentary rocks, formed between 360-330 Ma.
- Age: The formation of the sulfides begun during late Fammenian (Devonian), in a black mud in a submarine environment and are coincident with the major biological crisis of the D-C boundary.

The origin of the mineral in this type of deposit is still a matter of debate. Some authors suggest that is exhalative, but some evidences suggest that is a brine pool type: the volcanic activity were formed in a small basin that suffered an anoxic episode due to the displacement of seawater by dense and saline hydrothermal fluids. This leads to the precipitation of sulfide, generated by the activity of anaerobic sulfate-reducing bacteria, among others parallel phenomena, as the formation of rich stockworks. The formation of pyrite in the form of fall-out of a very tiny crystals is the explanation to the extraordinary thin grain of massive pyrite in this type of deposits.

The deposits as Neves-Corvo and Tharsis show us a dramatic episode during Earth history: the volcanic activity and climate changes lead to a major ecological crisis and geochemical change that left the massive sulfide deposits as a generous clue.

The Neves-Corvo deposit has some particular features, that differentiate it from others deposits of similar origin, as Tharsis. For example, the contribution of magmatic-hydrothermal fluids to the mineralization, that generate an unique mineral assemblage, very rich in tin (with the presence of about 300000 tons of metal), associated with copper minerals in form of stannite and casiterite, among others rarer minerals. The origin and accumulation of tin is still a not fully resolved question, anyway.

Also, Neves-Corvo is a source of "high-tech" metals, particularly indium and germanium. The chalcopyrite and sphalerite of Neves-Corvo is one of the richest indium sources and this metal is recovered mainly from zinc concentrates. Despite of this indium richness, this metal rarely form visible minerals, observable at microscopic level (roquesite).

Other curiosity: the 23th april of 2013, the mine reached 1000 m deep, being the deepest mine workings in the IPB. To visit this mine is a exciting experience, although, as usual in active mining operations, is not easy to obtain permissions.
Anyway, as usual also in the IPB mines and in general in all volcano-sedimentary deposits, to obtain collectible specimens is very difficult, as Jorge Santos said. The Neves-Corvo mine was a unique case and beautiful crystals of tetrahedrite-group minerals, chalcopyrite, galena and Baryte occasionally appear.

...next chapters: Lousal mine, converted in a beautiful educational and divulgative initiative, and revisiting the most intriguing and complex deposit of IPB: Las Cruces.



Neves Corvo Pozo Santa Barbara .jpg
 Description:
Neves-Corvo Mine, Santa Bárbara de Padrőes, Castro Verde, Beja District, Portugal
The impressive headframe of Santa Barbara shaft, used for the extraction of mineral.
 Viewed:  6656 Time(s)

Neves Corvo Pozo Santa Barbara .jpg



placa mil metros.jpg
 Description:
Neves-Corvo Mine, Santa Bárbara de Padrőes, Castro Verde, Beja District, Portugal
The shores of hell: plaque remembering the day the miners reached the -1000 m level. The climate at that depth is oppressive: 50şC and 120% humidity in a mist, dark and suffocating atmosphere in spite of air circulation system.
 Viewed:  6670 Time(s)

placa mil metros.jpg



tetrahedrita-tennantita neves corvo.jpg
 Description:
Tetrahedrite group
Neves-Corvo Mine, Santa Bárbara de Padrőes, Castro Verde, Beja District, Portugal
aprox. 10 cm FOV
Tetrahedrite group mineral taken in situ. The presence of tetrahedrite, tennantite and freibergite (usually in intermediate composition) has been reported. Without analysis of the sample, the correct label is tetrahedrite group or tetrahedrite-tennantite.
 Viewed:  6653 Time(s)

tetrahedrita-tennantita neves corvo.jpg



stockwork segunda parada.jpg
 Description:
Chalcopyrite
Neves-Corvo Mine, Santa Bárbara de Padrőes, Castro Verde, Beja District, Portugal
View of a chalcopyrite stockwork in the Lombador orebody. Occasionally, epithermal veins and deformation fractures lead to the formation of crystals of chalcopyrite and other sulfides.
 Viewed:  6685 Time(s)

stockwork segunda parada.jpg



calcopirita 2.jpg
 Description:
Chalcopyrite
Neves-Corvo Mine, Santa Bárbara de Padrőes, Castro Verde, Beja District, Portugal
crystal 4.7 mm
Chalcopyrite and carbonate crystals in a closed fracture in shale hosted pyrite stockwork from Corvo orebody. Chalcopyrite is a plastic mineral and tends to flow and recrystallize in fractures.
 Viewed:  6653 Time(s)

calcopirita 2.jpg



tetrahedrita neves corvo.jpg
 Description:
Tetrahedrite group
Neves-Corvo Mine, Santa Bárbara de Padrőes, Castro Verde, Beja District, Portugal
crystal 2 mm
Tetrahedrite-tennantite crystal surrounded by galena. Some authors suggest that these assemblages in volcanogenic sulfide deposits come from the mixing of hydrothermal fluids with cold seawater, with precipitation of galena-tetrahedrite group association.
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tetrahedrita neves corvo.jpg


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Cesar M. Salvan
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PostPosted: Jul 12, 2013 19:15    Post subject: Re: A Scientific and mineralogical trip to the Iberian Pyrite Belt - (6)  

And a little bit more on Neves Corvo mine...we found some rare secondary copper minerals in small fractures in chalcopyrite.


calcopirita + sulfate.jpg
 Description:
Chalcopyrite, Redgillite
Neves-Corvo Mine, Santa Bárbara de Padrőes, Castro Verde, Beja District, Portugal
FOV 0.9 mm
Small balls (aggregates of lath like crystals) of the rare sulfate Redgillite, found in a small fracture of massive Chalcopyrite of Corvo mass.
 Viewed:  6583 Time(s)

calcopirita + sulfate.jpg



calcopirita + chloride.jpg
 Description:
Chalcopyrite+undetermined chloride
Neves-Corvo Mine, Santa Bárbara de Padrőes, Castro Verde, Beja District, Portugal
FOV 0.9 mm
Crystals of a not fully determined copper chloride (Botallackite?, Bobkingite?) on chalcopyrite. Corvo orebody.
 Viewed:  6569 Time(s)

calcopirita + chloride.jpg



dolomita sobre calcopirita2.jpg
 Description:
Dolomite
Neves-Corvo Mine, Santa Bárbara de Padrőes, Castro Verde, Beja District, Portugal
A beautiful SEM image: dolomite, brochantite and copper chloride (Botallackite? Bobkingite?) on chalcopyrite. From the Corvo orebody.
 Viewed:  6573 Time(s)

dolomita sobre calcopirita2.jpg



galena.jpg
 Description:
Galena
Neves-Corvo Mine, Santa Bárbara de Padrőes, Castro Verde, Beja District, Portugal
FOV 2.5 mm
 Viewed:  6567 Time(s)

galena.jpg



2012-07-03 neves corvo 044.jpg
 Description:
Chalcopyrite
Neves-Corvo Mine, Santa Bárbara de Padrőes, Castro Verde, Beja District, Portugal
Usually is not the underground workings the best place to study the metallogeny of a mine. Instead, the drill cores gives us better and more complete information about the geology and mineralogy of a mine. In the picture, a chalcopyrite stockwork (a network of ore veins)
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2012-07-03 neves corvo 044.jpg


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PostPosted: Aug 23, 2013 07:57    Post subject: Re: A Scientific and mineralogical trip to the Iberian Pyrite Belt - (6)  

As promised in the latest post, I continue here with this brief trip along the Iberian Pyrite Belt, with the, by far, most interesting deposit of the belt from both a mineralogical and general scientific point of view: the Las Cruces mine (Gerena, Sevilla, Spain).

As the audience here seems to have a low interest in the metallogenic and ore deposit geological aspects, I will not annoy with long explanations. Instead, I will complete the glimpse of the deposit's mineralogy.



bornita fov 2 mm.jpg
 Description:
Bornite
Las Cruces mine, Gerena, Seville, Andalusia, Spain
FOV 2 mm
A recent novelty in the mine: beautiful (although small) pseudo-cubic crystals of bornite.
 Viewed:  6377 Time(s)

bornita fov 2 mm.jpg



bornita fov 2 mm 3.jpg
 Description:
Bornite
Las Cruces mine, Gerena, Seville, Andalusia, Spain
FOV 2 mm
Another view of the bornite crystals
 Viewed:  6388 Time(s)

bornita fov 2 mm 3.jpg



calcosina mayo 2013 copia.jpg
 Description:
Chalcocite
Las Cruces mine, Gerena, Seville, Andalusia, Spain
4 mm crystal.
Beautiful chalcocite crystal on calcite. The bests crystals have been recovered from recrystallization on fractures and hydrothermal veins, usually covered with carbonates.
 Viewed:  6372 Time(s)

calcosina mayo 2013 copia.jpg



harmotome.jpg
 Description:
Harmotome
Las Cruces mine, Gerena, Seville, Andalusia, Spain
FOV 2 mm
This low temperature barium zeolite is widespread along the hydrothermal veins and fractures that cut the secondary enrichment zone, giving clues on the complex processes that happened here.
 Viewed:  6365 Time(s)

harmotome.jpg



harmotoma.jpg
 Description:
Harmotome
Las Cruces mine, Gerena, Seville, Andalusia, Spain
FOV 5 mm
Harmotome radial groups, with pearceite on chalcocite matrix.
 Viewed:  6379 Time(s)

harmotoma.jpg



tennantita FOV 1.6 mm.jpg
 Description:
Tennantite
Las Cruces mine, Gerena, Seville, Andalusia, Spain
FOV 1.6 mm
The tennantite is a frequent mineral, although is rare in crystals higher than 1 mm. When crystallized, always form perfect tetrahedrons, usually covered with other minerals, in this case chalcocite in spheroidal groups of very tiny tabular crystals.
 Viewed:  6359 Time(s)

tennantita FOV 1.6 mm.jpg



galena plumosa lcc-0613-2.jpg
 Description:
Galena
Las Cruces mine, Gerena, Seville, Andalusia, Spain
Fast sulfur sobresaturation in a zone of the deposit lead to interesting galena forms.
 Viewed:  6368 Time(s)

galena plumosa lcc-0613-2.jpg



silver las cruces.jpg
 Description:
Silver
Las Cruces mine, Gerena, Seville, Andalusia, Spain
FOV 1.2 mm
Native silver is a very rare mineral in Las Cruces, as expected given the mineralization processes. But, is occassionally found as small wires, usually accompanied by proustite.
 Viewed:  6354 Time(s)

silver las cruces.jpg


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amigo




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PostPosted: Feb 08, 2017 22:24    Post subject: Re: A Scientific and mineralogical trip to the Iberian Pyrite Belt - (6)  

hello, what a great site. Does anyone have any information or pictures of Lomero Poyatos mine. Australian mining company Winmar Resources has commenced drilling today. Would be very keen and interested if anyone could offer their thoughts on Lomero. Thankyou
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Jordi Fabre
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PostPosted: Feb 25, 2017 16:33    Post subject: Re: A Scientific and mineralogical trip to the Iberian Pyrite Belt - (6)  

amigo wrote:
hello, what a great site. Does anyone have any information or pictures of Lomero Poyatos mine. Australian mining company Winmar Resources has commenced drilling today. Would be very keen and interested if anyone could offer their thoughts on Lomero. Thankyou

Some info here (them all in Spanish language) :
http://www.foro-minerales.com/forum/viewtopic.php?p=125271#125271

http://www.mtiblog.com/2012/12/mina-lomero-poyatos-cortegana-el-cerro.html

http://contramina.blogspot.com.es/2009/03/mina-lomero-poyatos.html
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