T.K. Kyser Barney J. Szabo 1990 <div id="15007223" class="article-section-wrapper js-article-section js-content-section " data-section-parent-id="0"><p>Stable-isotope compositions of fracture-and cavity-filling calcite from the unsaturated zone of three drill cores at Yucca Mountain Tertiary volcanic complex indicate that the water from which the minerals precipitated was probably meteoric in origin. A decrease in<span>&nbsp;</span>¹⁸O in the calcite with depth is interpreted as being due to the increase in temperature in drill holes corresponding to an estimated average geothermal gradient of 34° per kilometer. A few of the calcite samples and all of the opal samples yielded uranium-series ages older than 400,000 yr, although most of the calcite samples yielded ages between 26,000 and 310,000 yr. The stable-isotope and uranium- series dates from precipitated calcite and opal of this reconnaissance study suggest a complex history of fluid movement through the volcanic pile, and episodes of fracture filling predominantly from meteoric water during at least the past 400,000 yr.</p></div> application/pdf 10.1130/0016-7606(1990)102<1714:AASICO>2.3.CO;2 en Geological Society of America Ages and stable-isotope compositions of secondary calcite and opal in drill cores from Tertiary volcanic rocks of the Yucca Mountain area, Nevada article