Treaty Creek - Geology
Upper Triassic and Lower Jurassic rocks in the Treaty Creek property and surrounding areas are the host rocks of important mineral deposits (e.g., Kerr, Sulphurets, Mitchel (KSM), Snowfield, Bruceside), ranging from an epithermal setting to a porphyry setting, some of them exceptionally large and rich, and also hosting the potential for gold-rich VMS mineralization (e.g. Eskay Creek deposit).
There is a highly visible trend, marked by the surface alteration (oxidation) of exposed sulphide-rich mineralized rocks that produce what are called “gossans” in geologic terms. These gossans appear as orange-brownish zones that contrast with the surrounding rocks and are evidence of the development of large hydrothermal mineralizing systems. This trend of gossans and mineralized zones runs approximately 10km through the Kerr, Sulphurets, Mitchel, Snowfield, Iron Cap deposits and through the Treaty Creek property, where the same style of gold-silver-molybdenum mineralization has been found.
Within the Treaty Creek property, ten different zones have exposed mineralization and associated surface alteration. Porphyry, epithermal, and VMS systems have been identified on the property.
The Crown Jewel of the Golden Triangle is the Sulphurets Hydrothermal System (one of the seven largest in the world) that has proven to host one of the greatest concentrations of metal value on the planet with 215 million ounces gold, 1.2 billion ounces silver and 55 billion pounds copper so far (all categories). Of that 47.5 million ounces gold, 214 million ounces silver, and 10 billion pounds are reserves. That’s just in its southern half which also hosts the Brucejack Mine (Pretivm) which started its production of 8.1 million ounces @ 16.1g/t in May 2017 and the KSM (Seabridge) which contains the largest undeveloped gold deposit in the world by reserves – 38.8 million ounces gold with 10.2 billion pounds of copper.
Treaty Creek covers the northern half of the Sulphurets Hydrothermal System which is all connected at depth. The geology, geophysics, structural signatures, and exploration results all indicate the potential to host mineralization of similar scale to the southern half.
There is a common bedrock geology that extends throughout the entire hydrothermal system producing bulk tonnage porphyry deposits and high-grade epithermal & VMS systems.
“Mineralization in the Treaty Creek claims area lies within the same broad hydrothermal system that generated the several deposits on the Seabridge Gold and on the adjacent Pretivm properties that lie immediately southwest of the Treaty Creek claims” - Savell, 2012; Kruchkowski, 2014.
“This same setting and same hydrothermal system is shared by the geology underlying much of the area of the adjacent Treaty Creek claims. Given the limited drilling completed to date on the Treaty Creek claims, it would be realistic to state that the mineral potential for the Treaty Creek claims area remains largely untested and unknown, and that the local geology is part of the same enormous hydrothermal system that hosts multiple deposits of gold and copper that are changing our knowledge of the number, size and grades of the ore deposit types that comprise a porphyry copper system” – Alldrick, 2014.
“we know that the diameter of the Sulphurets system is at least 25 km; this is a measured value documented across the mapped exposure of the intensely altered, pyritized paleosurface of the hydrothermal system which is well exposed through the area as an altered dacite pyroclastic unit, including extensive exposures on the Treaty Creek claimblock” - Alldrick, 1988.
As noted by Alldrick, the “Sulphurets system” continues through Treaty Creek. This includes the Sulphurets thrust fault which is a major ore producing fault. Seabridge has stated that this fault is responsible for the many deposits in the KSM. As seen in the image to the right, the fault runs through both the KSM and Treaty Creek properties.
Above is an image of the Sulphurets Hydrothermal System extending from the bottom left (Kerr) to nearly the top right corner of Treaty Creek (border in yellow). The thin red line from the bottom left to the top right is the Sulphurets Fault. The thick red line is the “Kyba Discovery Contact” which briefly overlaps the Sulphurets fault. Proposed roads by Seabridge would connect to highway 37a about an hour and a half away from the shipping port.
Exploration on the Treaty Creek has confirmed the same types of gossans, deposits, and grades of gold found in deposits in the southern half of this large hydrothermal system. This is the case on surface and at depth.
There are thousands of porphyry copper occurrences worldwide; the BC Minfile database documents 1,394 porphyry occurrences in this province alone. However, there are just 6 other regions on earth where similar large porphyry copper systems have been delineated
Typical dimensions are 5-6 km wide and 4-6 km depth. In contrast, the Kerr-Sulphurets-Mitchell porphyry copper system is at least 25 km wide, and its ultimate depth is still unknown.
(From Sillitoe, 2010)
Normally, just one porphyry copper deposit occurs within a system like this, but at Kerr-Sulphurets-Mitchell, 5 separate, large, porphyry copper deposits have been delineated so far, and more may be discovered.
(From Sillitoe, 2010)
Porphyry copper systems hosting two or more separate porphyry copper deposits are rare (Figure 1). Globally, only six systems were known to host four or more discrete copper deposits: Chuquicamata in Chile; Globe-Miami in Arizona; Oyu Tolgoi in Mongolia; Yerington in Nevada; Pebble in Alaska; Cadia in Australia; plus – with the recently discovered Iron Cap and Deep Kerr porphyry deposits - the KSM porphyry system in the Sulphurets district of northwest British Columbia – Alldrick, 2014.
Since Alldrick made this statement in 2014 the KSM has added two more deposits and the 2017 drill program on Treaty Creek has been designed to delineate two more.
Alldrick’s comparison to the largest systems in the world was validated in the Nelson/Kyba report where Kyba points out that the KSM-Brucejack camp:
‘“is in a comparable gold league” with Freeport McMoRan’s Grasberg deposit in Indonesia (the largest gold / copper mine in the world). Grasberg has 39.7 million oz. gold in developed and undeveloped reserves, according to the company’s 2014 annual report.
Seabridge’s KSM deposit has total proven and probable reserves of 38.2 million oz. gold and 9.9 billion lb. copper at 2.2 billion tonnes of 0.55 gram gold per tonne and 0.21% copper. Pretium Resources’ Brucejack epithermal deposit has proven and probable reserves of 6.9 million oz. gold at 13.6 million tonnes of 15.7 grams gold.
Over the past five years, the northwest Stikine has built its momentum towards becoming the world’s next big mineral province. People are recognizing that these deposits have high-grade roots and big extensions they never thought were there.’ – Kyba, 2014
The “high grade roots” referred to are identified by Seabridge as “core zones”.
“In mining districts similar to KSM in size…..major new discoveries have been made late in the exploration history, often below shallow porphyry deposits and/or beneath faults.” SEA - 2014
“Core zones are typically formed under higher temperature and pressure conditions, resulting in a mineralogical character (such as potassic alteration) usually associated with significantly higher metal content. Seabridge believes that additional core zones are likely to be discovered at KSM” (SEA 2014).
A specific geological survey called a Magnetotelluric survey has been used extensively by Seabridge and Pretivm to identify these high-grade core systems deep in the earth. It has proven to be very accurate and has led to the discovery and development of the Deep Kerr, the Lower Mitchell, and the Lower Iron Cap zones. This same technology indicates extremely deep-rooted core zones on Treaty Creek that extend approximately 7km through the heart of the property.
*For more geological results see the History section