Summary:
North Deposit
The North Deposit of mineralization is located 1,500 ft north of the South Deposit and is centered on a subhorizontal, pipe-like, copper- rich, magnetite-poor skarn and skarn breccia body hosted by hornfels of the Gardnerville Formation (Northwest Deposit). The higher grade mineralization in the skarn breccia grades into a zone of lower copper grade mineralization hosted by granodiorite endoskarn and marble (North Deposit).
The combined Deposit has a 3,500 ft strike length, with true widths of 200 to 900 ft, and a down-dip extent of 1,500 ft and remains open in several directions. Retrograde alteration and sulfide deposition in the North Deposit was focused along fractures at angles to bedding and overprints earlier prograde alteration. Retrograde alteration and mineralization along fractures diminishes away from the breccia core. Chalcopyrite tends to be the last sulfide phase deposited.
South Deposit
The South Deposit, the first discovery on the Property, is a skarn-IOCG magnetite-chalcopyrite body closely associated with an intrusive contact of granodiorite into limestones of the Mason Valley Formation. The deposit is roughly tabular, measuring 3,600 ft along strike, 1,800 ft down- dip, trends northeast, and dips steeply to the northwest. The mineralized section, as defined by USS, can be divided into two zones: a footwall or proximal zone consisting of a 400 to over 1,000 ft thick relatively high grade magnetite with low copper content and a hanging wall or distal zone consisting of a 100 to 800 ft thick low grade iron but with higher copper content.
Southeast Deposit
The Southeast Deposit, located 2,000 ft southeast of the South Deposit, is a 300 ft wide skarn-IOCG lens of chalcopyrite-magnetite-garnet-actinolite developed within limestones of the Mason Valley Formation. The zone is unique for the Pumpkin Hollow Property due to its elevated magnetite grades (locally up to 75%). The zone of mineralization strikes northeast and dips steeply northwest with a strike length of 1,500 ft. Magnetite-garnet-epidote skarn hosts the mineralization with chalcopyrite increasing toward the footwall marble front. The Southeast Deposit has a 600 ft vertical extent and is fault bounded, above and below, by low-angle normal faults.
Geologic similarities between the Southeast and South Deposits strongly suggest that the Southeast Deposit may be the upper portion of the South Deposit which has been displaced 2,000 ft to the southeast along the lower listric fault.
Mineralization
Granodiorite to diorite rocks belonging to the Jurassic Yerington Batholith intrude the limestones of the Triassic Mason Valley Formation and calcareous argillites and siliceous shales, siltstones and limestones of the Gardnerville Formation. Associated with this intrusive episode is the development of large areas of IOCG mineralization, which is dominantly skarn with associated copper and magnetite mineralization with varying levels of gold and silver. The skarn occurs primarily in the middle to lower portion of the Gardnerville Formation and the upper part of the Mason Valley Formation, as well as within the intrusive granitoid itself.
The geological environment reflects a classic copper skarn in one of its type localities (Basin and Range) where deposition is associated with I-type, magnetite series, calc-alkaline quartz diorite granodioritic stocks of hypabyssal character, proximity to stock contacts, assemblages of andradite garnet with diopside pyroxene, magnetite with hematite and moderate to high sulfide content consisting of pyrite, chalcopyrite, minor tennantite, and sphalerite. The large copper skarns are generally associated with altered and mineralized porphyry copper stocks and display extensive retrograde alterations.
Sulfides and iron oxides occur as disseminations, as massive streaks and in veins in skarn, and as massive replacements of marble at the skarn front. As skarns are commonly zoned, with massive garnetite near the pluton, increasing pyroxene and finally idocrase near the marble contact, sulfide mineralogy and metal ratios may also be systematically zoned relative to the pluton. Pyrite, chalcopyrite and magnetite are most abundant near the pluton with increasing chalcopyrite and finally bornite near the marble contact, with decreasing magnetite reflecting an outward decrease in total iron.
Initial contact metamorphism altered Gardnerville sediments to diopside-garnet, calc-hornfels and siliceous hornfels, and converted the limestone of the Mason Valley Formation to calcite ± dolomite ± tremolite marble. The intrusive rock is commonly altered to diopside-plagioclase endoskarn. Later metasomatism formed diopside-garnet-magnetite ± sulfide replacement zones.
Hydrothermal fluid movement and alteration were enhanced by fracturing and brecciation along and near diorite contacts, within the diorite, within beds of limestone and along fractures at a high angle to bedding in hornfels. Higher copper values are generally on the fringe of magnetite zones near a mineralized limestone contact (marble front) or within bodies associated with late stage retrograde actinolite-epidotegarnet-magnetite skarn.
Retrograde skarn development was accompanied by deposition of pyrite, pyrrhotite and chalcopyrite, and may also be synchronous with the intrusion of altered and weakly mineralized andesite and quartzmonzonite porphyry dikes. There is a general overall zonation to the mineralization, with magnetite decreasing and copper increasing in relative content away from the intrusive. These two end member zones are commonly referred to as proximal and distal zones.
Retrograde skarn development was accompanied by deposition of pyrite, pyrrhotite and chalcopyrite, and may also be synchronous with the intrusion of altered and weakly mineralized andesite and quartzmonzonite porphyry dikes. There is a general overall zonation to the mineralization, with magnetite decreasing and copper increasing in relative content away from the intrusive. These two end member zones are commonly referred to as proximal and distal zones.
All deposits are believed to be directly associated with the intrusive granodioritic mass. There is a strong possibility that all Deposits were originally part of a single unit peripheral to and within the intrusive but have since been displaced and separated to their present locales by a complex post-mineralization tectonic history.
In general, each of the Deposits displays an early pro-grade mineralogy consisting of diopside-garnetcalcite-dolomite-tremolite and plagioclase, which represents the initial metamorphism followed by diopsidegarnet-magnetite ± sulfide replacement along fractures. Retrograde alteration (actinolite-epidote-garnetmagnetite-calcite-dolomite) was accompanied by deposition of pyrite, pyrrhotite, and chalcopyrite.
All deposits are "blind" and are known strictly from drilling results. The uppermost oxidized portions of the North and South deposits lie within 100 ft of the surface but the bulk of the mineralization lies 300 to 400 ft below barren hanging wall rock. The top of the Southeast Deposit lies beneath 300 to 500 ft of barren granodiorite porphyry. The East Deposit is located beneath 1,500 ft of Tertiary Volcanics (TV), Quaternary gravels and barren hornfels units while the E2 Deposit is covered by 1,000 ft of TV and Quaternary gravels. The discoveries were made by drill evaluation of magnetic anomalies associated with large magnetite-rich bodies. The South and Southeast Deposits represent areas of large magnetite deposition within the Mason Valley FM associated copper mineralization of lower tenor, whereas the Northwest, East, and E2 Deposits, although less explored, contain localized zones of much higher grade copper mineralization. The North Deposit is a low to moderate grade copper deposit with weak magnetite content and is primarily within hornfels and silicate skarns of the Gar