Mineralization on the Bramaderos property is dominated by a cluster of broadly north-northeast aligned centres of porphyry-related quartz stockwork mineralization associated potassic alteration centered within and above centers of hornblende diorite intrusions. These intrusive centers are overprinted and surrounded by extensive zones of phyllic and argillic alteration that collectively overlap and merge into an altered corridor approximately 5 kilometres long by up to 1.5 kilometres wide.
The Brama prospect is a porphyry gold-copper system located near the centre of the Bramaderos property. It has received the most drilling of all prospects on the property and with the most encouraging and consistent gold intersections.
A broad and likely structurally-controlled northwest-trending ridge extends southeast from the conical Bramaderos Hill and hosts stockwork and sheeted quartz veining over an area of approximately 840m in the northwest dimension by 440m in the northeast dimension. Veins comprise both quartz and quartz-magnetite B-veins as well as fine magnetite micro-veins. The stockwork and potassic alteration is focused on quartz hornblende diorite intrusions that have intruded volcaniclastic breccias, tuffs and volcanic sediments of the Celica Formation.
The main alteration minerals in the potassic alteration zones are silica, magnetite, chlorite +/- relic biotite +/- epidote +/- actinolite +/- pyrite +/- chalcopyrite. The zones of potassic alteration at Brama have been deeply overprinted by retrograde phyllic and/or argillic and intermediate argillic alteration, such that biotite is largely converted to chlorite, magnetite is partially converted to hematite, illitic clays are widespread and the main indicator of the potassic precursor alteration is the high abundance of disseminated and veinlet magnetite.
The mineralized quartz veins at Brama are typically B generation veins that form thin, spidery and curving networks as well as zones of strong sheeted veining suggesting local structural controls on the stockworks.
The wall rocks to the stockwork veined intrusive rocks tend to weather recessively due to the widespread phyllic/argillic alteration that is most intensely developed in the more permeable strata of the host Celica Formation. A number of gullies incise deeply into the sides of the Brama ridge and Bramaderos Hill, and the surrounding hills. These gullies expose thick sequences of late-stage argillic alteration that is associated with typically red-orange hued clays due to oxidation of sulphide, predominantly pyrite from the interpreted ‘pyrite shell’ that forms a halo around the Brama porphyry system.
Drilling by Sunstone at Brama is ongoing and to date has comprised more than 12 effective diamond drill holes (one hole abandoned) for ~7,500m.
The drilling has intersected gold-copper mineralisation hosted in diorite and intrusive breccias, within a broader domain of quartz diorites.
The Limon porphyry system lies slightly off trend, northeast of the linear north-northeast trend of quartz stockwork systems that define the prospects at Brama, Melonal, Porotillo, Sandia and Yeso. 4 drill holes have been completed at Limon, and intersected mineralisation and alteration suggesting a proximal positions to a porphyry system. Further drilling will be undertaken once targets are defined.
The potassic cores and associated quartz stockworks of the porphyry systems tend to form distinct conical shaped hills on the property and are surrounded at lower elevations by zones of phyllic and argillic alteration that in turn are transitional outward to propylitic alteration.
Lying in peripheral areas west of these centres of porphyry mineralization are epithermal prospects including Espiritu.