Mining and the metals trade was one of the key factors for the Phoenician colonisation of the ... course of the Ebro River, an area of lead and silver mining.
Offprint from Proceedings ISA 2006, Eds. JF Moreau, R Auger, J Chabot and A Herzog, Quebec 2009 ISBN 978 2 920576 98 8
PROVENANCE OF LEAD IN FIRST IRON AGE SITES IN SOUTHERN CATALONIA (SPAIN) I. Montero-Ruiz M. Gener M. Renzi M. Hunt S. Rovira J.F. Santos-Zalduegui
1. Introduction Mining and the metals trade was one of the key factors for the Phoenician colonisation of the Iberian Peninsula. Among them, lead was strategic for the obtaining of silver, either by its presence in the argentiferous galenas or used as collector of silver in the cupellation processes. In the last two decades have been discovered elements of Phoenician commerce in the lower course of the Ebro River, an area of lead and silver mining. In the archaeological site of El Calvari del Molar (7th-6th C. BC), excavations indicate the presence of a metallurgical workshop dedicated to the lead industry. Slags, galena fragments and lead droplets constitute evidence of the activity undertaken in this place, located nearby the mining area of El Molar – Bellmunt – Falset (Armada et al. 2004). Close to El Calvari, another contemporary settlement called Puig Roig has some metallurgical remains (slags, moulds). On the other hand, Phoenician materials and remains of copperlead ingot and melting lead have also been found in the archaeological site of Sant Jaume (7th-6th C. BC).
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2. Methodology and Materials With the aim of identifying the origin of the lead materials from both sites, Lead Isotope Analysis of some samples was performed. At the same time a field survey in the Molar – Bellmunt mining area to collect galena samples and to evaluate ancient works was carried out. Some imprecise news about Roman works and a clear Medieval exploitation is documented (Martínez Elcacho 2004). Actually, modern builds and machines, and some galleries and shafts opened in the 19th and 20th centuries can be visited. Only a partially destroyed trench in the Linda Mariquita mine could be related with ancient works. Archaeological and geological samples for Lead Isotope Analysis were performed using a Finnigan MAT 262 Thermal Ionisation Mass Spectrometer (TIMS) in static collection mode, with four Faraday cups, in the Isotope Geochemistry Research facility of the University of the Basque Country (Spain). The data obtained were corrected for mass fractionation by comparison with replicate analyses of the Pb NBS-981 standard. Samples from archaeological material (slags and lead) were taken off using a 1-mm drill. See Santos-Zalduegui et al. (2004) for more details about sample preparation. Twenty galenas from different mines in this area and two galenas, one lead slag and three metallic lead samples were chosen from El Calvari, and four lead samples from Sant Jaume.
3. Geological framework The Catalonian Coastal Ranges are made of Hercynian basement and Mesozoic to Cenozoic cover. Enclosed within the Paleozoic rocks are mineralised veins (lead, zinc, silver and copper) that locally cut across lower Triassic strata. Pb- and Pb-Zn-rich veins with gangue predominantly carbonatic are enclosed exclusively within the Hercynian basement (Canals & Cardellach 1997). Only in the Molar area were surface veins found. In the comparison of the Lead Isotope results, the data from Canals and Cardellach (1997) for the Catalan coastal ranges were used, as well as the data from Sardinia (Stos-Gale et al. 1995).
3.1. Lead or silver metallurgy Among the materials of archaeometallurgical interest found in El Molar village stands out a group of fragments of lead slag, a selection of which have been exhaustively analysed in the scanning electron microscope (SEM-EDX) and through spectrometry (XRF/ED) to determine their chemical and mineralogical composition, as well as the possible presence of traces of silver mineral.
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The most abundant mineralogical phases in the fused material are silicated glasses with lead, forming a matrix with the frequent presence of crystallised rods and needles of wollastonite, allophane and other silicates. There is also an abundance of spherical lead and lead oxide inclusions. Metallic silver or silver minerals were not found. The total losses of lead in the slag are, in general, above 10 % in weight, reaching figures up to near 50 % (Gener et al. forthcoming). Both the galenas from El Calvari and those taken from the mines feature very low silver content (average of 250 ppm), so they were probably used exclusively to obtain lead, as confirmed by the study of the smelting slags. However, some other silver ores (queragirite) are known in this area.
Figure 1. Lead isotope ratios of Molar-Bellmunt samples compared with various Spanish and Sardiniann ores
4. LIA Results and Conclusions The ratios obtained from geological samples are located in a region without overlapping other Spanish mining districts. Although a double bivariate graph is common, we only show one of them in Fig. 2 to check this feature. The closest area is Linares-La Carolina (Jaén), but it is different enough to avoid doubts about archaeological material provenance hypothesis. We have also taken into account Sardinian ores, due to galenas from Pranu e San (Stos-Gale et al. 1995) showing similar ratios.
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Figure 2. Lead isotope ratios of Calvari and Sant Jaume samples, together with various Catalonian and Sardinian ores. The samples from Sant Jaume have an original lead ore from an unknown source, as their ratios are different from all other compositions
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Figure 3. Detailed lead isotope ratios of Calvari archaeological samples and Molar-Bellmunt ores. The archaeological samples are compatible with an origin from Linda Mariquita and Barranco Hondo mines
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Site/Mine
Sample
Signature
El Calvari
Galena
CVM-177-13
El Calvari
Lead
CVM-170-16
El Calvari
Lead
208Pb/
207Pb/
206Pb/
207Pb/
208Pb/
206Pb
206Pb
204Pb
204Pb
204Pb
2,103
0,856
18,335
15,697
38,558
2,103
0,856
18,321
15,688
38,52
2,101
0,856
18,308
15,67
38,464
El Calvari
Lead
CVM-170-17
2,100
0,856
18,306
15,664
38,449
El calvari
Lead Slag
UE 149
2,099
0,855
18,337
15,669
38,484
El Calvari
Galena
UE 154
Sant Jaume
Lead
2,098
0,855
18,31
15,657
38,423
2,084
0,840
18,679
15,683
38,931
Sant Jaume
Lead
2,085
0,839
18,697
15,7
38,984
Sant Jaume
Lead
SJ-1006-278
2,080
0,838
18,7
15,677
38,904
Sant Jaume
Lead
SJ-1022-209
2,084
0,840
18,688
15,689
38,947
Mineralogia
Galena
PA11948
2,080
0,858
18,408
15,8
38,928
PA11985
Mineralogia
Galena
Mineralogia
Galena
Mineralogia
Galena
Mineralogia
Galena
PA11987
2,115
0,857
18,32
15,692
38,533
2,103
0,857
18,317
15,689
38,521
2,103
0,856
18,309
15,676
38,483
2,102
0,856
18,318
15,688
38,52
Mineralogia
Galena
PA11988
2,103
0,856
18,301
15,667
38,453
Barranco Hondo
Galena
PA11997
2,101
0,856
18,301
15,662
38,44
Barranco Hondo
Galena
PA11998
2,100
0,856
18,313
15,677
38,487
Mina Regia
Galena
PA11992
2,102
0,856
18,301
15,671
38,46
Mina Regia
Galena
PA11993
2,102
0,857
18,314
15,686
38,511
Linda Mariquita
Galena
PA11954
2,101
0,856
18,323
15,68
38,503
Linda Mariquita
Galena
2,101
0,856
18,322
15,677
38,495
Linda Mariquita
copper ore
PA11996
2,101
0,852
18,368
15,658
38,506
Linda Mariquita
Galena
PA12007
2,096
0,851
18,431
15,688
38,655
Linda Mariquita
Galena
2,097
0,851
18,433
15,69
38,665
Linda Mariquita
Galena
2,098
0,856
18,322
15,688
38,524
Linda Mariquita
Galena
2,103
0,856
18,316
15,68
38,498
Raimunda
Galena
2,102
0,856
18,333
15,691
38,545
Raimunda
Galena
2,102
0,856
18,333
15,692
38,545
Raimunda
Galena
2,102
0,856
18,317
15,672
38,483
PA12008 PA11994 PA11995
Table 1. Lead Isotope Results
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The main conclusions that can be reached with the present data are: • Archaeological samples are different from both sites. • The samples from El Calvari (galena, slags and lead) show coincidence with the minerals from the area of Molar-Bellmunt, especially with those from the Linda Mariquita mine, which is the one closer to the archaeological site (about 500 m.), and Barranco Hondo mine. This supports the assumption of a mining activity in the area during this period, despite the fact that there is no actual archaeological evidence until the roman period. • Some degree of economic interaction between El Calvari and Puig Roig exists, due to Puig Roig being located close to the Barranco Hondo mine, and according with LIA data lead ore or metallic lead from Barranco Hondo could reach El Calvari. • It seems that galena from Molar-Bellmunt was used only for lead. • The leads from Sant Jaume have no relationship with those from the area of Molar-Bellmunt, and there is also no coincidence with any other samples from the Catalonian coastal ranges. At the present moment, their possible origin is unknown, as they do not correspond with the mineralisations of Murcia-Almería or Jaén, either.
Acknowledgements This investigation has been carried out within the framework of the PGC project, “Caracterización analítica de la producción metalúrgica protohistórica de plata en Cataluña (HUM2004-04861-C03)”, funded by the Ministerio de Ciencia y Tecnología (Science and Technology Ministry). Samples were provided by Nuria Rafel and Lois Armada (El Calvari) and David García (Sant Jaume).
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REFERENCES Armada X-L, Hunt MA, Juan J, Montero I, Rafel N, Ruiz de Arbulo J, 2005. Primeros datos arqueométricos sobre la metalurgia del poblado y necrópolis de Calvari del Molar (Priorat, Tarragona). Trabajos de Prehistoria 62.1: 139-155. Canals A, Cardellach E, 1997. Ore lead and sulphur isotope pattern isotope pattern from the low temperatures veins of the Catalonian Coastal Ranges (NE Spain). Mineralium Deposita, 32: 243-249. Gener M, Rovira S, Montero I, Renzi M, Rafel N, Armada X-L, forthcoming. Análisis de escorias de plomo del poblado de la Edad del Hierro de El Calvari en El Molar (Priorat, Tarragona). VI Congreso Ibérico de Arqueometria, Girona, 16 -19 november 2005. Martínez Elcacho A, 2004. La explotación de la plata en el condado de las montañas de Prades (Tarragona) durante la Baja Edad Media. En O. Puche y M. Ayarzagüena (eds.): Minería y metalurgia históricas en el Sudoeste europeo, SEDPGYM-SEHA, Madrid: 357-363. Santos-Zalduegui JF, García De Madinabeitia S, Gil Ibarguchi JI, Palero F, 2004. A Lead Isotope Database: The Los Pedroches – Alcudia Area (Spain): implications for archaeometallurgical connections across Southwestern and Southeastern Iberia. Archaeometry, 46(4): 625-634. Stos-Gale Z.A, Gale NH, Houghton J, Speakman R, 1995. Lead Isotope data from the Isotrace Laboratory, Oxford: Archaeometry Data Base 1, Ores from the Western Mediterranean. Archaeometry, 37(2): 407-415.
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