Geothermal activity at the archaeological site of Aghia Kyriaki and its significance to Roman industrial mineral exploitation on Melos, Greece

Abstract

The geothermal setting of the archaeological site at Aghia Kyriaki, Southeast Melos (or Milos) was investigated in order to help clarify the possible role of the site in mineral exploitation on Melos in Roman times. There are active sulfurous fumaroles in the area and these were also potential sources of sulfur and alum-group minerals in Roman times. However, geothermal activity has been ongoing in Southeast Melos for hundreds of thousands of years, and extensive hydrothermal alteration of basement rocks to the northeast of the site has produced "white rocks" containing additional potential industrial minerals such as kaolin and alunite. The archaeological remains occur within, but mainly near the surface, of a deeply gullied sequence of late Quaternary alluvial sediments, which consist mainly of metamorphic detritus but are rich in sulfates; the remains contain pottery sherds through the entire sequence of about 40 m. They were deposited on an earlier gullied topography of felsic tuffs overlying the metamorphic basement. Pervasive and veinlike intense reddish alteration of these sediments is probably mainly due to superheated fluid escaping from depth. Field observations demonstrate that this took place after the main phase of building but was likely to be ongoing during occupation of the site. While industrial minerals and geothermal energy would therefore have been available in the Roman period, any relationship of the site to mineral exploitation will have to be determined by archaeological excavation. ᭧

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“…On Melos, the majority of fumaroles occur today in the SE part of the island, around the two bays of Aghia Kyriaki and Palaeochori (Figure 1(c)). This is also the place with abundant evidence of settlements dating to Classical and Roman periods (Hall et al 2003;Photos-Jones et al 1999; Photos-Jones and Hall 2014). The material culture on these sites is associated with large deposits of pottery sherds deriving from pithoi, lekanae (shallow vessels) and amphorae embedded within sediments.…”

“…On Melos there are two mineralogically distinct sources of alum: (a) alum from white rock containing alunite and (b) from sulphurous fumaroles, either in open-air solfataras or from within caverns. Figure 3(a), adapted from Hall et al (2003), gives an illustration of how natural alunogen (Al 2 (SO 4 ) 3 • 17H 2 O) and/or alum-K (KAl(SO 4 ) 2 • 12 H 2 O efflorescences are formed around sulphur fumaroles. Steam rich in H 2 S comes to the surface and sulphur crystals form at the fumarole vent.…”

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“… 135 For a detailed study of one processing site (Aghia Kyriaki) see Photos-Jones et al 1999; Hall et al 2003. …”