Carbonate nodules of probable stromatolitic origin in amphibolite from the Neoproterozoic terrain of southern Israel

Abstract

Several small bodies of massive to banded amphibolite occur within plagioclase-quartz-biotite hornblende gneiss at or close to its boundary with a quartz diorite pluton in the Neoproterozoic terrain of southern Israel. Entrapped within the amphibolite are nodules consisting mainly of calcite+talc, and rare banded marble. Remnant laminae and certain geochemical features such as the negative Ce anomaly and depleted d 13 C of the nodules sugggest that they initially formed as stromatolites. The local geological setting of the amphibolites together with the presence of the enclosed meta-carbonates favoured an origin as sediments, although some of the geochemical data point to a basaltic precursor and some of the carbonates have a puzzlingly high (>1000 ppm) Ni content. The origin of the amphibolites is thus enigmatic.