Abstract

Traditionally, mineral explorationists have defined lineaments as the topographic expressions of major fractures or the apparent alignment of plutons, mining districts and individual ore deposits. Patterns formed by lineaments are used as a framework for ore search on the premise that lineaments are major faults along which fluids ascend from depth and deposit metal in response to declining temperature and pressure and reaction with the enveloping rocks.

Reexamination of both premise and practice suggests that both are valid for regions and deposits characteristic of tensional tectonics and continental style igneous activity. The clearest example is distribution of carbonatites along major rifts. However, the premise is tenuous and the practice very questionable for stratabound deposits which are contemporaneous with their wall rocks and occur in the compressional setting of orogenic belts. Under such circumstances, as exemplified by massive base metal sulphide deposits, the prominent lineaments commonly are the trace of post-ore faults, not passageways for ore-forming fluids. Hence, the simplistic idea of a hydrothermal plumbing system reflected in the geometry of lineaments must be conditioned by an appreciation of the deposit’s nature and setting and must not include empirical plotting of deposits and districts irrespective of their geology.