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The timing and duration of evaporitic deposition during the Messinian in the Mediterranean is poorly known. To assist with this problem, we have correlated sedimentological events at widely separated locations in the Mediterranean and dated paleoceanographic events in the world ocean (event stratigraphy). Our working hypothesis is as follows: The Messinian Salinity Crisis caused the formation of evaporites in a deep desiccated basin which implies that (1) the evaporites were deposited during a steady marine influx, (2) multiple intervals of isolation led to drastic changes in the sediments and in the fauna of the Mediterranean, (3) the sea level of the Mediterranean Sea was mostly several hundreds of meters below that of the Atlantic Ocean, and (4) the seaways (Betic and Rif Strait) connecting the Mediterranean with the Atlantic during the late Miocene were affected by eustatic sea level changes caused by Antarctic glaciation. We found supporting evidence in the sedimentological and paleoceanographic records in the Betic Strait (Fortuna and Sorbas basins) which was one of the sites of major inflow into the late Miocene Mediterranean Sea. Drastic sea level changes and fluctuations during the late Tortonian and Messinian caused chronologically: (1) the deposition of brackish sediments overlying marine deposits, (2) the progradation of deltas, (3) reef growth at lower levels and their destruction by erosion and coverage by conglomerates, (4) evaporite deposition alternating with marine marls containing Atlantic diatom assemblages, and (5) five marine/terrestrial cycles associated with coral reefs. Based on event stratigraphy the 1Now at following scenario for the Messinian "Salinity Crisis" is proposed: The Tripoli Formation (Chron 6R1/5N2:5.93-5.7 Ma), the Lower Evaporites (Chron 5N2, 5R: 5.7-5.5 Ma), and the Upper Evaporites (lowermost Gilbert c: 5.25-5.15 Ma) were deposited during influx of Atlantic water into the Mediterranean. During this time, a unidirectional circulation dominated from the Atlantic through the Betic Strait. Only during the intra-Messinian inundation (Chron 5N1 into lowermost Gilbert c: 5.4-5.25 Ma) that occurred after a short intra-Messinian erosional event (Chron 5Nl: 5.5-5.4 Ma) was a normal bidirectional circulation pattern established. This is reflected in the diatomires of the Chicamo Formation and the Mediterranean (site 124) as well as most likely in a reef on Cyprus. The marine record of the Pliocene filling of the Mediterranean is missing in these basins. Overall, marine water inflow into the Mediterranean through the Betic Strait dominated during the Messinian. The threefold marine/terrestrial cyclicity with severe paleoceanographic changes in the Fortuna and Sorbas basins favor the "deep, desiccated basin" model. INTRODUCTION The Mediterranean evaporite was discovered by deep-sea drilling in 1970. Upper Miocene salts were found under the Mediterranean seabed, and they have an estimated volume of about 106 km 3 [Ryan, 1973]. The Messinian desiccation of the Mediterranean is one of t...

The Skouries porphyry Cu±Au deposit, containing an indicated reserve of 206 Mt at 0.54% Cu and 0.80 g/t Au, is hosted by at least four hypabyssal monzonite±porphyry phases. In decreasing age, they are: (1) pink monzonite, (2) main monzonite, (3) intra-mineral monzonite, and (4) late-stage porphyry. Highgrade ore is directly associated with the main and intra-mineral monzonite phases. All intrusive phases are cut by late-stage monzonite dykes that are barren. The monzonites have porphyritic textures with phenocrysts of plagioclase, alkali feldspar and amphibole as well as apatite and titanite microphenocrysts in a ®ne-grained feldspar-dominated groundmass. Mineralized samples are aected to varying degrees by potassic alteration, ranging from weak biotite±magnetite disseminations, through cross-cutting veinlets of hydrothermal orthoclase, to zones with pervasive orthoclase¯ooding. The high halogen contents of the Skouries intrusions are re¯ected in the high Cl and F concentrations of mica phases (up to 0.19 and 2.48 wt% respectively). The presence of magmatic magnetite in all intrusive phases implies high oxygen fugacities of the parental melts. All four monzonite phases have relatively evolved compositions, as re¯ected by their high SiO 2 , low MgO and low mg#, and variable but low contents of mantlecompatible elements such as V, Ni and Co. However, their mg# suggests increasing degrees of fractionation of the parental melts with decreasing age. Their high K 2 O (up to 5.8 wt%) and K 2 O/ Na 2 O ratios (>1), as well as their high Ce/Yb and Th/Yb ratios (>34 and >21 respectively), which are believed to have been unaected by alteration processes, are typical of alkaline rocks of the shoshonite association. Importantly, the Skouries intrusions are characterized by very high U and Th contents (up to 18.9 ppm and 62 ppm, respectively) that are consistent with accessory thorite and rare allanite in several samples. The high initial 87 Sr/ 86 Sr ratios (0.7082) for the Skouries intrusions suggest crustal contamination during emplacement. The use of geochemical discrimination diagrams assigns the rocks to a continental arc setting in accord with the interpretation of previous workers.

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Potassic igneous rocks and associated gold copper mineralisation / Daniel Mt~ller ; David I. Groves. -2., updated and enlarged ed. -

Strontium isotopic ratios of gypsums recovered from upper Miocene (Messinian) evaporites at ODP Leg 107 Holes 652A, 653B, and 654A (Tyrrhenian Sea) Sr-ratio for evaporites in the sedimentary cycles recognized for Holes 653B and 654A, the generally low Sr isotopic ratio of river water entering the Mediterranean Sea, and the presence of dwarf marine microfossils suggest that the 87 Sr/ 86 Sr ratio of the evaporites responded to hydrologic variations in a very restricted basin with variable rates of marine and fresh water input. The strontium isotopic ratios of the Messinian anhydrites from the proposed lacustrine sequence at Hole 652A fall in the same range as the marine evaporites from Holes 654A and 653B. This suggests a common or similar origin of the brines at the three locations.The complex depositional and hydrologic conditions in the Mediterranean during the Messinian salinity crisis preclude the use of Sr isotopic values from the evaporites for stratigraphic correlation and dating. They are, however, very useful in the interpretation of the depositional history of the basin. General calculations assuming a closed system suggest that the 87 Sr/ 86 Sr ratio of Messinian seawater (-0.7090) could be reduced to that of the evaporites (-0.7087) by mixing with fresh water (e.g., Nile River) in times of I0 4 to I0 5 yr.