Geochemical data for alkaline igneous rock units in the Cripple Creek district, Colorado USA: 1989-2016

This data release includes new major and trace element geochemical data acquired by the U.S. Geological Survey (USGS) for igneous rocks in the Cripple Creek district in Colorado. Cripple Creek is among the largest epithermal districts in the world, with more than 800 metric tons (t) Au (less than 26.4 Moz). The ores are associated spatially, temporally, and genetically with ~34 to 28 Ma alkaline igneous rocks that were emplaced into an 18 km2- diatreme complex and surrounding Proterozoic rocks (Kelley and others, 2020). Igneous rocks associated with Cripple Creek are part of a regionally extensive episode of Oligocene alkaline magmatism that extended southward along the axis of the Rio Grande rift through New Mexico and into the Trans Pecos region of Texas and northern Mexico (McLemore, 1996; Kelley and Ludington, 2002). The deposits at Cripple Creek are known as alkalic-type gold deposits, but they have been referred to as alkalic-related and Great Plains margin deposits in previous literature (McLemore, 1996). Many of the deposits in this class are enriched in critical elements, the most common of which is tellurium (Kelley and Spry, 2016). However, not all deposits are characterized by enriched tellurium concentrations. Cripple Creek is highly enriched, whereas other deposits in New Mexico are less enriched. The objective of the USGS study was to characterize the tellurium contents (and other trace elements) of predominantly unaltered alkaline igneous rocks that are genetically associated with mineralization in order to better understand possible source(s) and mechanism of enrichment of tellurium in these systems. This data release provides the analytical results of 25 rock hand samples collected by USGS geologists in collaboration with the New Mexico Bureau of Geology and Mineral Resources (NMBGMR) during site visits to Cripple Creek in 1989, 2015, and 2016. In addition, 50 samples collected in 2013 by Anne Rahfeld (Rahfeld, 2013) were submitted and analyzed by the USGS. The mapped rock units from which the samples were collected are described in Wobus and others (1976) and brief descriptions of rock types are given in Kelley and others (1998). Several analytical methods were used and include 55 major and trace elements using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and 42 elements using inductively coupled plasma-atomic emission spectrometry (ICP-AES). Some samples were also analyzed for major elements using wavelength dispersive x-ray fluorescence spectrometry (WDXRF), for Au by fire assay ICP-MS and Au and PGE by fire assay.