RE: RE: New SH - For Love of the GameThere are Eocene volcanics on the Railroad property and there is a large GraniteRhyolite intrusion sitting to the west of the latest discovery. The Eocene volcanics are good candidates for the heat pump that is required for these hydrothermal breccias to form. I do think that since the targets are buried, hitting a basal breccia in 2010 drilling is great news and a strong indication that the breccia suite that is found at Rain is also at Railroad.
Here is a paper by Newmont Geologists describing the Rain/Railroad (by inference).
Gold-Bearing Breccias of the Rain Mine, Carlin Trend, Nevada
CINDY L. WILLIAMS,
Newmont Mining Company, 1700 Lincoln St., Denver, Colorado 80203
TOMMY B. THOMPSON,†
Center for Research in Economic Geology (CREG), Mackay School of Mines/169, University of Nevada, Reno, Nevada 89557-0232
JON. L. POWELL, AND W. WARREN DUNBAR
Newmont Mining Company, P.O. Box 669, Carlin, Nevada 89822
Abstract
The Rain mine includes two mined-out open pits that contained 36.4 t (1.17 Moz) gold, averaging 1.8 g/t
gold, and underground reserves, including underground production, estimated at 4.9 t (157,000 oz) gold averaging
7.7 g/t. Rain orebodies are localized in a breccia complex within the hanging wall of the Rain fault and
hosted within the Mississippian Webb Formation immediately overlying the contact with the Devonian Devils
Gate Limestone.
The ore host includes four texturally and genetically distinct breccia types: (1) crackle breccia; (2) hydrothermal
breccia; (3) tuffisite with accretionary lapilli; and (4) collapse breccia. Crackle breccia forms a capping
over multistage hydrothermal breccias that are cut by tabular- to pipe-shaped tuffisite dikes, with some
containing accretionary lapilli. Pre- and synore hydrothermal breccias formed during at least three episodes of
convective fluidization, followed by quartz-sulfide-barite cementation. High-grade gold was deposited as a late
phase along the upper portion of the hydrothermal breccia mass and extended into the crackle breccia zone.
Collapse breccias occur along the floor of the composite breccia mass and have irregular upper and lower contacts.
The lower contact occurs on a dissolution boundary with the Devils Gate Limestone.
Matrix-supported, heterolithic, hydrothermal breccias at Rain consist of sedimentary rock fragments composed
of sandstone, siltstone, mudstone, limestone, and conglomerate. Some fragments contain as much as 8
percent introduced biotite in veinlets and/or fragment matrix replacements. The veinlets consist of euhedral
quartz, biotite, sphalerite, and pyrite. Barite constitutes as much as 60 percent of the hydrothermal breccias in
the form of fragments and as a cement to the breccias. Quartz replacement of fragments and as a breccia cement
is pervasive. The total sulfide content in unoxidized ores is less than 5 volume percent.
The Rain orebody resulted from five interpreted stages of development: (1) structural preparation along the
right-lateral oblique Rain fault system and conjugate left-lateral oblique northeast-striking faults; (2) multiple
episodes of hydrothermal breccia formation, with high-grade gold deposition immediately following the last
brecciation event; (3) late channelized and fluidized rock fragments and fine clays forming tuffisite bodies with
accretionary lapilli; (4) postmineral extensional reactivation of structures; and (5) collapse brecciation resulting
from postore supergene acidic fluid ponding on and dissolving the upper Devils Gate Limestone.
The age of the Rain orebody is poorly constrained. It is older than 22 Ma supergene alunite, but no maximum
age constraints other than the Mississippian host rock are known.
From the body of the paper
"Sediment-hosted Carlin/Rain-type rain deposits are found on or near the Webb/Devils Gate contact adjacent to major structural zones. Three consistent features are associated with this deposit type:
1. Major District Scale Fault
2. Mississippian Webb/Devonian Devils Gate Formation Contact
3. Extensive Breccia Bodies hosting mineralization at the contact or within either unit near the contact"
All of the pieces are in place at Railroad IMO, nice to be a shareholder.
DYODD