Fluids double-fracturing genetic mechanism and mineralization of gold-copper of the breccia pipe at Qibaoshan in Shandong Province

After studying the characteristics and special texture of the fluidogenous tectonics, mineral assemblage in the cemented vein between breccia and thei r special distribution, and stress analyzing the joint structures in and ar ound the breccia pipe, it is found that the observed phenomena are caused b y a new tectonic dynamic mechanics of fluid-double-fracturing caused by tem perature and pressure of fluids and pulsating expansion. Under the actions of thermal stress and the pressure of fluids, thermal cracks and joints tha t developed along parts of the thermal cracks formed systematically in the rocks. Under these conditions, up-arching fracture zones that pulsatively e xpanded upward and cylindrical pressing breccia body were formed. Rocks at the peak of the pyramidal fractures zone break down instantly. Where the di fference between pressure of fluids and the overburden pressure exceeded gr eatly the competence of the rocks, fluid junctions occurred and the velocit y of the fluid flow increased as a result. Explosive body expanded upward i n the shape of an inverse cone, cone-like explosive breccia body and cover- like shattering breccia body located on the upper part of the breccia pipe were ultimately formed. Gold-rich fluids were enriched and mineralized near the boiling surface in the lower part of the inverse cone-like explosive b reccia body where temperature and pressure decreased rapidly, while copper- rich fluids were enriched and mineralized in the junction area where temper ature and pressure were relatively high.