article_snippet.sent: These materials tell us about secondary fluids that were transported through the region after the rock formed.'
article_snippet.sent: Veins such as these form where fluids move through cracked rock and leave minerals in the fractures, often affecting the chemistry of the rock surrounding the fractures.
article_snippet.sent: Kah said, 'At least two secondary fluids have left evidence here. '
article_snippet.sent: us want to understand the chemistry of the different fluids that were here and the sequence of events.
article_snippet.sent: How have later fluids affected the rock?'
article_snippet.sent: Some of the sequence is known: Mud that formed lake-bed mudstones must have dried and hardened before the fractures formed.
article_snippet.sent: The dark material that lines the fracture walls reflects an earlier episode of fluid flow than the white, calcium-sulphate-rich veins do - although both flows occurred after the cracks formed.