Early Proterozoic crustal provinces in the southwestern U. S. : What they represent and implications about continental reconstructions

Conference · Mon Feb 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:6001682

Wooden, J L; Miller, D M; Howard, K ^[1]; Dewitt, E ^[2]; Karlstrom, K E ^[3]; Nutman, A ^[4]

---

1. Geological Survey, Menlo Park, CA (United States)
2. Geological Survey, Denver, CO (United States)
3. Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Geology
4. Australian National Univ., Canberra (Australia)

The Early Proterozoic basement of the southwestern US can be divided into at least 3 major crustal provinces on the basis of Pb isotopic and geochemical signatures. These are: (1) the Mojave of SE CA, southern NV, and western AZ; (2) the Yavapai of central and northern AZ, northern NM and southern CO; and (3) the Mazatzal of southern AZ., and central and southern NM. The boundary between the Yavapai and Mazatzal provinces is close to the age province boundary proposed by Silver. Crustal provinces defined by chronologic, structural, lithologic, or metamorphic criteria usually don't distinguish regions unique in crustal formation character because these criteria often represent events that affected the crust (well) after the time of its original formation or represent non-unique information (e.g., magmatism can occur at the same time in entirely different crustal provinces). In comparison, isotopic and certain geochemical data often provide unique criteria because they are related to distinct mantle sources, specific processes, or the specific time of crustal formation. New U-Pb zircon ages determined by the SHRIMP ion microprobe indicate that the Mojave province probably has a latest Archean/earliest Proterozoic basement on which sedimentary rocks containing 2.7--2.5 Ga and 2.0--1.8 Ga detrital zircon populations were deposited. The timing of plutonic events in the Mojave and Yavapai provinces is indistinguishable from 1.76--1.70 Ga. Plutonic rocks with Yavapai isotopic and geochemical signatures intruded the eastern edge ( ) of the Mojave province as early as 1.74 Ga. This suggests that the two provinces were in close proximity from 1.76 Ga and that the older Mojave province was a buttress against which juvenile Yavapai crust formed.

• OSTI ID: 6001682
• Report Number(s): CONF-9303212--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:1
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ARIZONA
BASEMENT ROCK
CALIFORNIA
CHEMISTRY
CONTINENTAL CRUST
DEVELOPED COUNTRIES
EARTH CRUST
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOLOGIC MODELS
ISOTOPE DATING
ISOTOPE RATIO
ISOTOPES
LEAD ISOTOPES
NEVADA
NEW MEXICO
NORTH AMERICA
PLATE TECTONICS
PRECAMBRIAN ERA
TECTONICS
USA