Geology topics
B. R. Lipin
Publications and source records attributed to B. R. Lipin.
U.S. Geological Survey mineral databases; MRDS and MAS/MILS
These two CD-ROM's contain the latest version of the Mineral Resources Data System (MRDS) database and the Minerals Availability System/Minerals Industry Location System (MAS/MILS) database for coverage of North America and the world outside North America. The records in the MRDS database each contain almost 200 data fields describing metallic and nonmetallic mineral resources, deposits, and commodities. The records in the MAS/MILS database each contain almost 100 data fields describing mines and mineral processing plans.
Pressure increases, the formation of chromite seams, and the development of the ultramafic series in the Stillwater Complex, Montana
This paper explores the hypothesis that chromite seams in the Stillwater Complex formed in response to periodic increases in total pressure in the chamber. Total pressure increased because of the positive δ V of nucleation of CO 2 bubbles in the melt and their subsequent rise through the magma chamber, during which the bubbles increased in volume by a factor of 4–6. By analogy with the pressure changes in the summit chambers of Kilauea and Krafla volcanoes, the maximum variation was 0⋅2–0⋅25 kbar, or 5–10% of the total pressure in the Stillwater chamber. An evaluation of the likelihood of fountaining and mixing of a new, primitive liquid that entered the chamber with the somewhat more evolved liquid already in the chamber is based upon calculations using observed and inferred velocities and flow rates of basaltic magmas moving through volcanic fissures. The calculations indicate that hot, dense magma would have oozed, rather than fountained into the chamber, and early mixing of the new and residual magmas that could have resulted in chromite crystallizing alone did not take place.
Platinum-group element abundance and distribution in chromite deposits of the Acoje Block, Zambales Ophiolite Complex, Philippines
Platinum-group elements (PGE) occur in ore-grade concentration in some of the chromite deposits related to the ultramafic section of the Acoje Block of the Zambales Ophiolite Complex. The deposits are of three types: Type 1 - associated with cumulate peridotites at the base of the crust; Type 2 - in dunite pods from the top 1 km of mantle harzburgite; and Type 3 - like Type 2, but in deeper levels of the harzburgite. Most of the deposites have chromite compositions that are high in Cr with Cr/(Cr + Al) (expressed as chromium index, Cr#) > 0.6; high-Al (Cr# < 0.6) chromite deposits are relatively rare, occurring as interspersed orebodies in regions of Types 2 and 3. Sulfide-bearing Type 1 high-Cr deposits are PGE-enriched; the high-Al deposits have lowest Ir and Pd. Among the PGEs, Ir ranges from <20 to 550 ppb, Rh from <100 to 1100 ppb, Rh from 0.7 to 760 ppb, Pt from <1.0 to 5960 ppb and Pd from <0.5 to 8350 ppb. Chondrite-normalized (CN) PGE patterns are diverse, and include those with both negative slope (Ir > Pd, thought to be characteristic of PGE-barren deposits) and positive slope (Ir < Pd, characteristic of PGE-rich deposits). Iridium, Ru and Os commonly occur as micron-size laurite (sulfide) inclusions in unfractured chromite. Laurite and native Os are also found as inclusions in interstitial sulfides. Platinum and Pd occur as alloy inclusions (and possibly as solid solution) in interstitial Ni-Cu sulfides and as tellurobismuthides in serpentine and altered sulfides.
Petrology of chromite-bearing rocks from the lowermost cyclic units in the Stillwater Complex, Montana
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International strategic minerals inventory summary report; chromium
Major world resources of chromium, a strategic mineral commodity, are described in this summary report of information in the International Strategic Minerals Inventory {ISMI}. ISMI is a cooperative data-collection effort of earth-science and mineral-resource agencies in Australia, Canada, the Federal Republic of Germany, the Republic of South Africa, and the United States of America. This report, designed to be of benefit to policy analysts, contains two parts. Part I presents an overview of the resources and potential supply of chromium on the basis of inventory information. Part II contains tables of some of the geologic information and mineral-resource and production data that were collected by ISMI participants.
The Emma Bell deposit, Siskiyou Co., California: A possible low-grade source of chromite
The Emma Bell chromite deposit in Siskiyou County, California contains over 5 million tons of dunite averaging about 4 percent Cr 2 O 3 . Chromite is not evenly disseminated throughout the dunite, however. For the most part the deposit consists of many chromite-rich bands in sharp contact with, and separated by, common dunite containing 1 to 2 percent accessory chromite. Electron microprobe and petrographic analysis of accessory chromite shows that it is fine grained (average grain size 0.14 mm), generally lower in Cr 2 O 3 , and has a lower Cr/Fe ratio than segregated chromite. In addition, unusual patchy zoning is exhibited by some accessory chromite. These patchy zones are extremely rich in iron (>60 percent total iron oxide). The negative factors such as the fine-grained nature of the accessory chromite and high iron content compared to segregated chromite, could be overcome by the very large tonnage in the deposit.
Preliminary map of chromite provinces in the conterminous United States
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