Vein-type Deposits around the Intrusive Igneous Masses

Veins filling Synthetic Normal Faults produced by Magmatic Upheaval

Abstract

Occasionally, normal faults, resulted from the pushing up by magmatic upheaval, are recognized around intrusive igneous masses. They occur not only in the roof rocks surrounding igneous intrusives, but also in the hood parts of the intrusives. These fissures extend along the margins of igneous intrusives and dip away from them. They are synthetic normal faults produced at the time of igneous intrusion, which is often accompanied by folding or warping of the surrounding rocks. Areas sandwiched between this kind of faults are upheaved like horst. The writer has recognized some deposits where the synthetic normal faults were mineralized to copper veins.
These fissures are similar to those accompanied by the intrusive masses of bysmalith type in the mechanism of fissure formation.
In some cases, these synthetic normal faults intersect the tension cracks, nearly at right angle, which were produced by the lateral pressure accompanied by the folding of the surrounding rocks stated above. The writer describes two examples of the case where the mineralizing solutions ascended along the synthetic normal faults and flowed into the intersected tension cracks.