A dig into the rich past of a tiny isle in the Aegean archipelago could soon answer one of the riddles of prehistoric archaeology: why the remote outcrop produced so many of the flat-faced marble figurines that went on to inspire Pablo Picasso and Henry Moore.

Greek and British archaeologists hope their planned excavation will shed light on whether windswept Keros was a major sanctuary for the mysterious Cycladic civilisation 4,500 years ago. The tantalising suggestion that the uninhabited isle may have housed the gateway to the underworld has also not been ruled out.

"We really hope to find the answers to questions that have [provoked] a lot of study, a lot of debate," said Peggy Sotirakopoulou, a curator at Athens' Museum of Cycladic Art. "This is a unique site. Nowhere in the Cyclades have the remains of so many marble figurines been found; figurines that were intentionally broken in antiquity, in quite peculiar places, like the pelvis and chest."

Until its discovery by the modern art movement in the 20th century, Cycladic art was spurned by lovers of the classical period as the barbaric works of a primitive race. But their influence on artists such as Picasso triggered a demand for early bronze age sites - and widespread looting.

Keros, perhaps more than any other in the barren island chain, was targeted in the 1950s and 1960s by plunderers intent on finding the naked, elongated figures. The thousands of fragments of marble vases and figures that flooded the international antiquities market - and were so assiduously bought by museums and private collectors - were known as the "Keros Hoard".

The looting, and the trail of destruction it left behind in an area known as Kavos Daskaleio, made the task of unravelling the enigmatic civilisation much more difficult. By the second millennium BC the mariner-race was superseded by Crete and Mycenaean Greece; its elegant artworks and seafaring superiority soon forgotten.

Subsequent digs at Kavos Daskaleio, where a cave was also found, failed to reveal the secrets of the site or the purpose of the figurines, which could have depicted gods or may simply have been children's toys.

But archaeologists hope their dig, which begins next week and includes an area of virgin ground, will both illuminate the island's role and explain why it was so much more important than its bigger, less rugged neighbours. Some have mooted the idea that the finds not only filled graves but were removed with bones from cemeteries elsewhere and reburied in Keros in front of the cave's mouth.

"It's still unclear whether it was an exceptionally rich cemetery or ritual site," said British archaeologist Lord Colin Renfrew, who will be co-leading the team. "We hope to clarify the real nature of the site by finding a settlement. It is possible, but not yet certain, that [the breaking of the figurines] were ritual actions relating to ceremonies in honour of the dead."