Ar ar dating of basalts

Early differentiation and crystal settling in the sills is evidenced by granophyre layers up to 10-m thick and felsite dikes, and by olivinerich layers.The relationship of these intrusives to the Cardenas flows remains obscure because direct feeders to the flows and sills have never been recognized. Our goal was to more than double the K-Ar data for these Precambrian rocks of Grand Canyon, allowing a better and more comprehensive interpretation of K-Ar “ages.” Thus, collection of new samples of Cardenas Basalt and Precambrian diabase had three purposes: Complete location data for the nine published K-Ar analyses and the 13 new analyses are found in the appendix.We seek to test theories which explain why K-Ar “ages” are significantly younger than the widely accepted Rb-Sr isochron “age.” Mafic igneous rocks occur as sills, dikes, and flows in the Upper Precambrian (Proterozoic) Unkar Group of the Grand Canyon, Arizona (figs. The extrusive rocks form a 300-m-thick flow sequence called the Cardenas Basalt which rests conformably on the Dox Formation in the middle of the 4000-m-thick Proterozoic Grand Canyon Supergroup sedimentary sequence.7 This sedimentary sequence rests nonconformably on the older metamorphic and igneous rocks, including the Vishnu Schist and Zoroaster Granite.

Three models are proposed as alternatives to argon loss models, but these invalidate using the K-Ar system as conventional geochronology would assume.

This paper was originally published in the Proceedings of the Fourth International Conference on Creationism, pp.

Individual flows vary in thickness from about 20 to 50 m, each flow being separated from adjacent flows by laterally persistent siltstone and sandstone beds which generally range in thickness from 0.3 to 3 m.

Amygdaloidal zones, from 2 to 5 m thick, are common near the bases and tops of the flows; scoriaceous flow breccia is conspicuous at the tops of several of them.

Thirteen new K-Ar analyses of Proterozoic mafic rocks of Grand Canyon are added to nine published K-Ar analyses.

We report a new fourteen-point K-Ar isochron “age” of 516 ± 30 Ma which is strongly discordant with the published Rb-Sr isochron “age” of 1.07 ± 0.07 Ga for Cardenas Basalt.The published geologic literature contains seven K-Ar analyses of Cardenas Basalt and two K-Ar analyses of Precambrian diabase.1115 Descriptions of these rocks are found in the appendix of this paper and the K-Ar data have been collected into Table 1. The new K-Ar data have been combined with the published data into table 1.Of the 13 new analyses, eight are from Cardenas Basalt and five are from Precambrian diabase. Google(); req('single_work'); $('.js-splash-single-step-signup-download-button').one('click', function(e){ req_and_ready('single_work', function() ); new c. For more than twenty years it has been known that the Rb-Sr and K-Ar systems give discordant “ages” for Cardenas Basalt and associated Proterozoic diabase sills and dikes of Grand Canyon.Some of the flows exhibit crude columnar jointing in their middle to upper portions, whereas none of the flows exhibits any evidence of interaction with water.


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