GEOCHEMISTRY AND PARAGENETIC SEQUENCE OF THE FRANKLIN MARBLE, NEW JERSEY

Petrographic study of the Proterozoic Franklin Marble in New Jersey indicates that this marble originated from shallow marine limestone of tidally influenced deposits within a hypersaline condition.

Stable isotope study including oxygen (δ¹⁸O) and carbon (δ¹³C) revealed that the formation of the Franklin marble is mainly controlled by the tectonic processes in the subduction zones that result in the metamorphism of carbonate-bearing rocks. The low δ¹⁸O (20.14 ‰ SMOW) indicated its origin in a closed back-arc system. The value of δ¹³C (- 0.5 ‰ VPDB) strongly support the organic carbon source in the marine environment.

Chemical analysis using FUS – ICP indicates the Franklin Marble is a host rock of lithophile Rare Earth Elements (LREE) including Ba (45 ppm), Sr (649 ppm), Y (11 ppm), Zr (5 ppm), and V (15 ppm). The high concentration of Sr along with the presence of REE strongly support the hydrothermal activities of the magmatic intrusion in a marine setting. Consequently, the Franklin marble was altered from the pre-existing limestones by the activities of these hydrothermal fluids.

The lithologies of the Franklin Marble are associated with three paragenetic sequence that include: 1) deposition of the carbonate facies in a shallow marine environment, 2) Infiltration of magmatic hydrothermal fluids through the pre-existing pore spaces and fractures in the sea floor to form the meta-limestone facies, 3) The subducted plates in the eastern margin of the North American provided high pressure and temperature to form medium to high grade metamorphic Marble.