DESCRIPTIVE MODEL OF CYPRUS MASSIVE SULFIDE

MODEL 24a

By Donald A. Singer

APPROXIMATE SYNONYM Cupreous pyrite.

DESCRIPTION Massive pyrite, chalcopyrite, and sphalerite in pillow basalts (see figs. 95, 96).

GENERAL REFERENCE Franklin, and others (1981).

GEOLOGICAL ENVIRONMENT

Rock Types Ophiolite assemblage: tectonized dunite and harzburgite, gabbro, sheeted diabase dikes, pillow basalts, and fine-grained metasedimentary rocks such as chert and phyllite (fig. 95).

Figure 95. Generalized stratigraphic column through the Troodos ophiolite showing Cyprus massive sulfides and other deposit types and their associated rock types. Modified from Constantinou (1980).

Textures Diabase dikes, pillow basalts, and in some cases brecciated basalt.

Age Range Archean(?) to Tertiary--majority are Ordovician or Cretaceous.

Depositional Environment Submarine hot spring along axial grabens in oceanic or back-arc spreading ridges. Hot springs related to submarine volcanoes producing seamounts (fig. 96).

Figure 96. Cross section through the Kalavos district, Cyprus, showing relationship of massive sulfide deposits to faults and alteration zones. Section is drawn normal to the spreading axis and represents a time period prior to deposition of a thick sequence of pillow lavas and sedimentary rocks. Modified from Adamides (1980).

Tectonic Setting(s) Ophiolites. May be adjacent to steep normal faults.

Associated Deposit Types Mn and Fe-rich cherts regionally.

DEPOSIT DESCRIPTION

Mineralogy Massive: pyrite + chalcopyrite + sphalerite + marcasite + pyrrhotite. Stringer (stockwork): pyrite + pyrrhotite, minor chalcopyrite and sphalerite (cobalt, gold, and silver present in minor amounts).

Texture/Structure Massive sulfides (>60 percent sulfides) with underlying sulfide stockwork or stringer zone. Sulfides brecciated and recemented. Rarely preserved fossil worm tubes.

Alteration Stringer zone--feldspar destruction, abundant quartz and chalcedony, abundant chlorite, some illite and calcite. Some deposits overlain by ochre (Mn-poor, Fe-rich bedded sediment containing goethite, maghemite, and quartz).

Ore Controls Pillow basalt or mafic volcanic breccia, diabase dikes below; ores rarely localized in sediments above pillows. May be local faulting.

Weathering Massive limonite gossans. Gold in stream sediments.

Geochemical Signature General loss of Ca and Na and introduction and redistribution of Mn and Fe in the stringer zone.

EXAMPLES

Cyprus deposits, CYPS (Constantinou and Govett, 1973)

Oxec, GUAT (Peterson and Zantop, 1980)

York Harbour, CNNF (Duke and Hutchinson, 1974)

Turner-Albright, USOR (Koski and Derkey, 1981)