North Carlin
The North Bullion Zone geology has been said to have similarities with the Northern Carlin trend . Here is a really good read for some due diligence. (Not too technical, for the most part.)
EXPLORATION AND GEOLOGY, 1962 TO 2002,AT THE GOLDSTRIKE PROPERTY,CARLIN TREND, NEVADA
https://www.nbmg.unr.edu/dox/b111/goldstrike.pdf
Here are some excerpts from the report.
I took the liberty of adding a few definitions(since I was looking them up, anyway) . Its helpful to know 2 terms, (for those who don’t).
allochthonous - of rocks, deposits, etc.; found in a place other than where they and their constituents were formed
autochthonous (ô-tkth-ns): - of rocks, deposits, etc.; found where they and their constituents were formed
The term, allochthonous, is used on the new cross section diagram on the presentation. https://goldstandardv.com/pdf/gsvc_presentation.pdf
* The Goldstrike property is located close to the rifted margin of the paleo-North American craton, along an inferred deep crustal structure.(Definition: A craton is an old and stable part of the continental lithosphere. Having often survived cycles of merging and rifting of continents, along an inferred deep crustal structure. cratons are generally found in the interiors of tectonic plates. )The Carlin trend lies at a significant crustal boundary, suggestive of a major crustal fault or suture. (from GV: A large, Tertiary age , multi-phase intrusive complex underlies the Railroad District)
*Stratigraphy at Goldstrike consists of lower Paleozoic sedimentary rocks, including an autochthonous, carbonate sequence and an allochthonous siliciclastic sequence. (refer to GV diagram) (Siliciclastic rocks are sandstone(silica) based rocks). Following a depositional hiatus of up to 6 million years the Upper Devonian Rodeo Creek unit was deposited in the Popovich Formation. It is a siliciclastic unit composed of siliceous mudstone with interbedded limy to dolomitic siltstone, fine-grained sandstone, and minor limestone.
.* Dissolution of carbonate has produced collapse breccias, which commonly host high-grade ore. Supergene alteration has produced oxide ores, at depths up to 660 feet (200 m). Mineralization at Goldstrike occurs in a variety of settings, reflecting an interplay of both structural and lithological controls. Structural controls include folds, low- and high-angle faults, particularly where faults intersect, and zones of fracturing and brecciation.
*The recognition that distal low-grade gold mineralization occurred along favorable stratigraphy and structure, led to the use of drill hole grade-thickness maps to vector to ore. (in the last CC, Dave was saying how the low grade can lead to high. NBZ has 730 feet/t @ 0.019 opt gold .)
*Intrusive rocks at Goldstrike include a Late Jurassic calc-alkaline suite of diorite, rhyodacite, and lamprophyre and late Eocene calc-alkaline dacite dikes. ( A dike in geology is a type of sheet intrusion referring to any geologic body that cuts discordantly across:). These dikes, dated at approximately 39 Ma, are coeval with the Carlin gold mineralization . Similar dacite dikes occur along the Post fault zone at the Rodeo, Griffin, and Meikle deposits.
*It was also apparent that mineralization was preferentially located adjacent to the intrusion, often trapped beneath sills. (see GV’s cross section diagram in presentation and the dacite sill) a sill is a tabular sheet intrusion that has intruded between older layers of sedimentary rock.Dacite ( /'de?sa?t/) is an igneous, volcanic rock.Dacite usually forms as an intrusive rock such as a dike or sill. (at RR: Numerous dikes are found adjacent and peripheral to the Bullion Stock. )
* The north-northwest-striking faults and folds are important ore controls. North-northeast-striking, northwest dipping faults are also important ore controls
* Breccias are commonly associated with gold mineralization at Goldstrike and in general are the host to the highest grade orebodies. They are the dominant ore host at the Meikle deposit,the Deep Post and Betze subdeposits, the lower zone of the Rodeo deposit, and at the Deep Star deposit, in the southernpart of the subdistrict. Hydrothermal dissolution of carbonate(decarbonatization), both pre- and post-ore, has produced extensive collapse breccias, which in some cases overprint sedimentary debris-flow breccias. Fault breccias occur in all in all deposits and are conduits for hydrothermal fluids into brecciated, fractured, or otherwise permeable host rocks.
Emsbo suggested that the extreme dissolution and removal of carbonate, both pre- and post-ore is one of the factors that has enhanced the grade of the Meikle deposit. In contrast to BetzePost and Meikle. The high-grade breccias at the Deep Star deposit are tectonic breccias. (In the last conference call Mathewson said the combination of both tectonic and dissolution breccias down deep create an environment similar to the northern Carlin mines)
* Supergene alteration at Goldstrike extends as deep as 660 feet (200 m) and has resulted in the liberation of gold. This deep oxidation had important economic implications, as ore with gold grades as low as 0.008 opt (0.27g/t) were mined and processed by heap leaching. (They talked about finding supergene oxidation at the NBZ and the deep oxidation of the Railroad fault in the cc)
* Gravity data at Goldstrike show the large intrusions and their metamorphic aureoles, as well as the massive carbonates of the Bootstrap limestone. (ditto RR)
* In the northern part of the Goldstrike property, a sequence of fossiliferous limestones and dolomites were deposited on a shelf as a shoal . The Meikle deposit is located close to the intersection of the Post fault with the massive Bootstrap limestone . Much of the ore at Meikle is in collapse breccias, developed in the Bootstrap limestone, (which I believe is the same as what GV calls ‘Devils Gate limestone. (The blue on the Carlin Trend cross sectional on GV’s presentation. (Mathewson 2002) ?
* Exploration and development drilling at Goldstrike and many other Carlin type deposits is difficult and expensive, due to extensive fracturing, variable alteration, and groundwater conditions. The depth of formation of the mineralization is still debatable, as is the source of the ore fluids and metals.
There are a lot of correlations to be found between the districts if you go through the studies. The comparison of the gold and arsenic soil sampling maps of the two areas is very intriguing. They used the maps to help locate some of the mines up there. (from GV: Prominent zones of detectable gold correspond with the juxtaposition of the favorable Mississippian/Devonian as well as prominent north-south, northwest, and northeast faults)
* Total gold endowment in the Blue Star-Goldstrike subdistrict (production,reserves, resources as of 2002) is approximately 63 million ounces (1,960 t), with approximately 90% of this total located in the northern part of the subdistrict.( just a few miles,actually)
Railroad is just 37 miles away on the same trend, it has the same types of rocks, is likely the same age, and apparently has a similar history to North Carlin. ( Much less thry're beginning to find similar gold)
No one knew there were high grade zones down deep in the Carlin trend until 1987, which is not long ago. Its high time for a new chapter.