2 –Table 1 is far from expressing the real chronology of events which were decisive for Neves – Corvo discovery.
It is not emphasized, as it is deserved, the fundamental prospecting phase SFM carried out during the first half of the 40th decade, which lead to the discovery of the extensive volcanic rocks outcropping in the Castro Verde - Almodôvar Region and, consequently, to the definition of additional potential areas for polymetallic sulphide deposits, thus greatly enlarging the width of the previous known Pyrite Belt of Alentejo. The electromagnetic surveys by Turam method, carried out also in the 40th decade, covering almost entirely such large areas, with a grid of 100 m x 20 m, are not mentioned.
IT IS NOT EMPHASIZED THAT SFM SELECTED IN 1970-71, WITHIN AN AREA OF ABOUT 4,000 SQ KM, WHICH BECAME AVAILABLE ONLY AT THAT TIME, ON ACCOUNT OF CESSATION OF A CONTRACT WITH MINING EXPLORATIONS (INTERNATIONAL), A PATCH OF 28 SQ.KM, THAT IS 0.7% OF THE TOTAL AREA, PRECISELY THAT WHERE THE GREAT DISCOVERY WOULD HAPPEN, FOR INVESTIGATION BY GRAVITY METHOD.
It is stated erroneously that an anomaly of 0.5 mgal was detected, but, in fact, the anomaly reaches at its maximum a value higher than 1.4 mgal, and it is not put in evidence the large surface through which it spreads, allowing an estimation of reserves of about 600 million tons of mineralised formations having density of 3.5 within a geological environment with an average density of 2.75. Admittedly, not all of this mineralised formation is ore.
3 – Besides the great confusion, established through the whole article between “orebodies” and “deposits”, Delfim de Carvalho misleads the reader when he compares the number of discoveries in the period of 1940 to 1963 with those from 1963 to present date, intending to infer from this, that there was a greater contribution for these discoveries from the most recent geological studies. There is no doubt that in recent times significant advances were achieved in the geological understanding of the Pyrite Belt. I always fought very hardly in order that such advances could happen. But in Portugal the truth is that these recent geological studies weren’t at all decisive for the discoveries.
It comes out very clearly from this and other articles published about Neves – Corvo, that the former interpretation of the stratigraphic sequence intersected by borehole Nr. N-1, made with underestimation of the gravity anomaly, turned out in a delay of at least 5 years in the discovery. Once more, being dogmatic in geology, proved to be the wrong practice. Mc Kinstry is obviously right when he strongly calls the attention for this common mistake, at page 203 of his excellent book “Mining Geology” first edited in 1948.
The higher number of successes since 1963 to the present date (and here I do not understand how the author encountered 21 discoveries!) is a consequence, not so much of an increasing prospecting intensity, but mainly of the excellent preparation made in preceding decades.
It is regrettable that Delfim de Carvalho, who in this paper induces the reader to see him as the main author of Neves – Corvo discovery, besides not having had in it any participation at all, is in reality one of the main responsible persons for the notorious weakening of SFM team organized in Southern Portugal, in the beginning of the 40’s, for prospecting the Pyrite Belt of Alentejo and other areas with great geological and mining interest.
4 –The statement of Delfim de Carvalho that guides to the ore, like intersections of long lineaments and hypothetical hydrothermal alterations had a contribution to the discoveries within the Pyrite Belt is ridiculous. I do not know any case in which this occurred. About the practical value of long lineaments empirically established, I would advise the author to read what William C. Peters writes, at pages 140 – 142 of his book “Exploration and Mining Geology” published in 1978.
It is to be registered the carelessness in the representation of volcanic rocks lineaments, in fig. 6, without displacement by Messejana Fault.
5 –The percentage of basic volcanics in Castro Verde – Almodôvar Region, if it does not exceed that of acid volcanics, it will not be far from it, contrarily to the predominance of acid volcanics that Delfim de Carvalho affirms to exist. This is quite clear on map fig. 7, in which, by inadmissible lapse, the old mines of Barrigão are not represented, being certain that they were, by far, the most important copper mines of Almodôvar Region, having constituted one of the most important guides for the selection of the zone to be surveyed by gravity.
6 –Bore-hole N-2 is not vertical, as it is stated in the text. In fig. 10 it is represented with an inclination quite different from the vertical!
7 –The reference to the ore reserves of Neves – Corvo deposit, considering the dynamic phase which is going on, is incomplete, if the date in which they were calculated is not mentioned. The values which were presented seem already out of date. Besides, it is not legitimate to add proven reserves to probable reserves.
Regarding the global reserves of the Iberian Pyrite Belt, the part already eroded and the reserves still available, it would be expected that the values shown were demonstrated, or, at least, the reliable consulted source should be mentioned.
Delfim de Carvalho, who continually quotes himself, being certain that his curriculum is not characterized, either by scientific rigor or by integrity of procedures that are essential to impose him to the geological and mining community as a real authority (not a legal one), should have, at least, the care of documenting statements he could not, obviously, produce only by himself.
8 –I wish still comment the extraordinary revelation that small areas are more favourable for ore deposit discoveries than large ones. Such conclusion is against the most elementary principles of ore prospecting. It is understandable that, from the standpoint of the Portuguese Government, there is no interest in granting to the enterprises very large areas, because they, obviously, will concentrate their attention to areas with more favourable indexes, retarding the study of areas apparently less favourable, if there will be not contractual clauses preventing it. But the point of view of the enterprises is logically the opposite. If one enterprise is working according to sound principles of ore prospecting, it will be capable, since the beginning of its activity, of making a wise selection of areas.
IN THE CASE OF THE LARGE AREA GRANTED TO SMS-SEREM-SMMPP, ONE IRRECUSABLE SELECTION HAD ALREADY BEEN MADE, AND SFM CALLED THE ATTENTION FOR IT ON SEVERAL OCCASIONS.
In conclusion, I wish to express my great disappointment by seeing published in a scientific magazine of such high reputation, without the dignity it deserved, a rare case history of ore prospecting of which the Portuguese should be proud, because it is a consequence almost exclusively of intense and persistent work of a group of national technicians. The promoters of such a remarkable success were, however, forgotten and they are now spectators of the exhibition of others, who little or nothing at all had to do with the case.
Once more, we register the confirmation that, in “FIVE STAGES OF A PROJECT”, the laurels go to the uninvolved (1)
(1)From an ignored author: FIVE STAGES OF A PROJECT
STAGE 1: EXCITEMENT – EUPHORIA
STAGE 2: DISENCHANTMENT
STAGE 3: SEARCH FOR THR GUILTY
STAGE 4: PUNISHMENT OF THE INNOCENT
STAGE 5: DISTINCTION OF THE UNINVOLVED
Annex: Schematic residual gravity map ( Neves – Corvo area)
Estes comentários não foram publicados por motivos apresentados em cartas que me foram enviadas, as quais e irei transcrever no próximo post.
Foi assim traída a intenção de “Economic Geology” de prestar um bom serviço à comunidade geológica e mineira internacional. Esta comunidade acabou por ser enganada. Espero, com estes e com novos posts conseguir repor a verdade, que tão adulterada tem estado.
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