Genesis-Blue Star Mines Area, Genesis pit, Lynn Mining District, Eureka County, Nevada, USAi

Regional Level Types
Genesis-Blue Star Mines Area	Mine
Genesis pit	Pit
Lynn Mining District	Mining District
Eureka County	County
Nevada	State
USA	Country

Structure: Generally northwest-trending, broad to moderate amplitude, anticlinal folds play an important role as structural traps to fluid migration within individual deposits and on a regional scale. The autochthonous carbonate sequences that form the Carlin and Lynn tectonic windows are postulated to be remnant segments of a larger north-northwest-trending regional-scale anticline, with a doubly plunging fold axis that extends from the Gold Quarry deposit northward to the Genesis deposit. In this unified tectonic window model, gold deposits of the north-central and south-central Carlin trend are clustered along both the northeast and southwest flanks of the anticline, while its central portion has been segmented into a Tertiary, postmineral graben by late-phase Basin and Range extensional block faulting. The K and Anne dikes are important dike-filled northeast fault structures in the Genesis Mine area.

Alteration: Zonation patterns for silica-sulfide breccia pipes such as Deep Star exhibit compact envelopes in which silicification and sulfidation are more intensely focused than at other Carlin deposits.

Commodity: Ore Materials: gold Gangue Materials: quartz, carbonaceous material, clay minerals

Deposit: These deposits are located in the part of the Carlin Trend that lies south of the Goldstrike stock between the Castle Reef and Gen Faults. The Popovich Formation hosts gold mineralization at Genesis-Blue Star where it consists of thin-bedded silty limestone and micrite.host rocks at Deep Star, Number 9, and part of the Genesis deposit have been metamorphosed to calc-silicate hornfels and minor skarn; the N10W Genesis fault and the N45 W Reindeer fault have been identified as the primary controls in the Genesis-Beast and the Northwest Genesis-North Star deposits, respectively. Deep Star is a compact, mineral replacement and breccia-hosted gold deposit

Deposit type: Sediment-hosted Au

Development: The earliest gold discovery in the Genesis-Blue Star area was at Blue Star, immediately south of Goldstrike, where gold was identified in 1957 in areas that had been mined for turquoise. In 1961, 800 ounces (25 kg) of gold was produced until problems with slimes in the ore led to shutdown of the 220-short-ton/day (200-t/d) cyanide mill. Trenching and drilling by Newmont in 1966 discovered low-grade gold in fault zones cutting a diorite intrusion (Goldstrike intrusion). Although this early exploration identified significant gold grades, further work was not conducted due to the low gold price. In 1984, Newmont Mining discovered the large Genesis deposit adjacent to the Blue Star deposit. The Blue Star-Genesis discovery was announced in 1985 and mining at Genesis began in 1986. Newmont began mining the North Star open pits in 1995. In 1996, open pit operations commenced production from the Beast pit. A current major exploration focus in 2004 is underground drilling along the Deep Post/Deep Star corridor, a mile-long drift connecting the two high-grade underground mines.

Geology: Age of the deposits: Drews (1993) reported three K/Ar dates ranging from 95 to 97 Ma from hydrothermal illite in high-grade (.0.20 opt gold) ore samples within the Genesis and Blue Star deposits. Post and Ressel and others, however, have constrained what appears to be the primary period of gold mineralization at the Beast deposit to late Eocene,~36-40 Ma. Multiple Tertiary-age intrusions along the Carlin trend and Tertiary-age dikes within specific deposits in the northern Carlin trend indicate the influence of a younger, gold-bearing hydrothermal event that occurred in the late Eocene, around 40 Ma. Henry and Ressel have reported 40Ar/39Ar dates from sericite ranging from 36 to 40 Ma on altered, gold-bearing dikes in the Post and Genesis fault zone. These dike swarms all occur within the Beast, Genesis, Griffin, and Meikle deposits in the northern Carlin trend. A single comparison of K/Ar and 40Ar/ 39Ar dates from the same altered dike in the Genesis deposit suggests that the potential effect of thermal resetting of K/Ar dates yields a younger age. Schutz and Williams (1995) reported a 27 Ma K/Ar date on the altered, gold-bearing K dike in the Genesis deposit; Henry and Ressel (2000) reported a 39 Ma 40Ar/39Ar date from the same altered dike.

Ore(s): The N10W-trending Genesis fault and the N45 W Reindeer fault have been identified as the primary controls in the Genesis-Beast and the Northwest Genesis-North Star deposits, respectively. Schutz and Williams (1995) described higher grade gold mineralization in the Genesis deposit as being controlled in part along the hinge zone of the N10.W-trending, northerly plunging Tuscarora anticline along the southern and deep extensions of the deposit.

Other Databases

Link to USGS MRDS:	10310439

References