Geology and petrogenesis of the Kirkpatrick Basalt, Pain Mesa and Solo Nunatak, northern Victoria Land, Antarctica [microform]
- Bib ID:
- 3287655
- Format:
- Book and Microform
- Author:
- Mensing, Teresa Marie
- Description:
- 391 p.
- Summary:
-
A thick sequence of flows of the Kirkpatrick Basalt is exposed in the Mesa Range area of northern Victoria Land. The purpose of this study was to explain the petrologic processes involved in the genesis of these rocks through the use of isotopic (Sr and O) and chemical compositions. The flows on Pain Mesa were divided into a Lower Suite and an Upper Suite based on differences in their chemical compositions. The Upper Suite has higher concentrations of SiO$\sb2$, alkalies, total Fe, MnO, TiO$\sb2$, and P$\sb2$O$\sb5$ than the Lower Suite. In addition, the flows of the Upper Suite are homogeneous in chemical composition compared to the Lower Suite which is differentiated. The isotope compositions of Sr and O of the Lower Suite are positively correlated which indicates that the magma was contaminated by crustal material.
The isotopic and chemical compositions of the flows of the Lower Suite were explained by fractional crystallization and simultaneous assimilation of a crustal contaminant. In contrast to the Lower Suite, the flows of the Upper Suite are homogeneous in chemical composition. The initial Sr isotope ratios of the Upper Suite, calculated for an assumed age of 175 Ma, were lower than those of the Lower Suite, and are not constant. However, by lowering the assumed age of the Upper Suite to 92 Ma the range of the initial Sr-isotope ratios was greatly reduced. Paleomagnetic results and K-Ar dating of Ferrar rocks at the Litell Rocks Nunatak in northern Victoria Land also support the hypothesis that the Upper Suite is Cretaceous in age. The magma source of both suites has elevated $\sp{87}$Sr/$\sp$Sr ratios compared to "normal" mantle values because of prior enrichment in Rb. The Rb/Sr ratio of the source was 0.50 which is much higher than typical values for the mantle.
The differences in the ages and initial Sr isotope ratios of the two suites can be used to show that the magma source was enriched in Rb about 475 Ma years ago. This data coincides with the Ross Orogeny which may reflect a causal relationship between these events. Marie Byrd Land in West Antarctica was also affected by magmatic activity during the Cretaceous Period. The occurrence of igneous activity in northern Victoria Land during the same period, suggested by the isotopic data, strengthens tectonic reconstructions indicating that northern Victoria Land and Marie Byrd Land were juxtaposed during the Mesozoic Era but were later separated as a result of major right lateral displacement along the Transantarctic rift system.
- Notes:
-
- (UnM)AAI8726692
- Source: Dissertation Abstracts International, Volume: 48-09, Section: B, page: 2585.
- Thesis (Ph.D.)--The Ohio State University, 1987.
- Reproduction:
- Microfiche. Ann Arbor, Mich.: University Microfilms International.
- Subject:
- Geology
- Other authors/contributors:
- Ohio State University
- Copyright:
-
In Copyright
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Copyright status was determined using the following information:
- Material type:
- Literary Dramatic Musical
- Published status:
- Unpublished
- Creation date:
- 1987
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