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Norman Herz

Publications and source records attributed to Norman Herz.

6 recordsLinked to original sources
USGS1975

Titanium deposits in alkalic igneous rocks

Many types of alkalic rocks are enriched in Ti0 2 relative to the average for the crust. Silicate minerals in these rocks may have high Ti0 2 contents, but the oxides ilmenite, rutile, brookite, and perovskite are also characteristic primary phases. These tend to be higher in niobium than are the same minerals from other rock suites. At Tapira, Brazil, titanium minerals in a carbonatite complex comprise tens of millions of tons contained Ti0 2. Anatase (as "leucoxene") is present in laterite lying over parent rocks containing perovskite, ilmenite, and rutile. In other discovered localities of alkalic rocks, production of titanium minerals is at best economically marginal.

Open-File Report↗
USGS1961

Age measurements from a part of the Brazilian shield

Potassium-argon determinations on micas from Precambrian granitic rocks of the Quadrilátero Ferrífero, Minas Gerais, Brazil, suggest three ages of intrusion: 2400 m.y. determined from gneiss within the Bação complex; 1350 m.y. from rocks in the northern part of the Bação complex and also in a region 7 km north of nearest known Minas series metasedimentary rocks (Late Precambrian age ); and 450-550 m.y. The last has been determined from (1) gneiss of the eastern part of the area, (2) granitized beds of the Minas series, and (3) granite between Minas beds and the 1350 m.y. granite in the western part of the area. Other ages, ranging between 595 and 1080 m.y., may represent the effects of a younger metamorphism on older granitic rocks that are found between the peripheral area of the 1350 m.y. granites and Minas metasedimentary rocks.

Geological Society of America Bulletin↗