La Paz

Region West, Southwest
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Focus area based on structurally-controlled mineralization in mylonitic alkalic granitoid. Outline of the resource estimate area (USMIN) based on Boyer and Ostensoe (2011).
Identified resources Identified REE resources.
Production Unknown.
Status Inactive, reserves development, advanced exploration.
Estimated resources Indicated resource of 16.2 Mt at 373.4 ppm (0.037%) total REE, equating to 12.1 million lbs REE; Inferred resource of 112 Mt at 371.5 ppm (0.037%) total REE; cutoff grade of 300 ppm (Boyer and Ostensoe, 2011).
Geologic maps Richard and others (2002), scale 1:100,000.
Geophysical data Inadequate aeromagnetic coverage. Adequate aeroradiometric coverage. Maps derived from data from Duval and others (2005), Sweeney and Hill (2001), Kucks and others (2001), and Bankey (2006).
Favorable rocks and structures Proterozoic alkalic granite, mylonite.
Deposits La Paz deposit (USMIN Site_ID: AZ00017).
Evidence from mineral occurrences USMIN.
Geochemical evidence 3000 rock chip samples (see comments).
Geophysical evidence Not enough detail.
Evidence from other sources Geological mapping, sampling, percussion drilling (5,120 m), metallurgical studies.
Comments Northeast-southwest low-angle fault with Early Proterozoic alkalic granite gneiss in the footwall, and Tertiary continental red beds and lesser metamorphosed Paleozoic and Mesozoic sedimentary and volcanic rocks in the hangingwall. Quartz veinlets and stockworks and associated potassium-feldspar, sericite, epidote, chlorite, sphene, and iron-oxide alteration. REE mainly contained in allanite averaging 10.11% Ce2O3, 0.10% Y2O, 4.97% La2O3, 1.00% Pr2O3 and 3.20% Nd2O3. Trace apatite, zircon, and other REE minerals also present. Based on assays of the drill cuttings the entire REE suite of elements is present and on average the light and heavy REE account for 80.6% and 19.4% of the total, respectively. Uranium and Th are favorably low, averaging 1.2 ppm and 6.0 ppm, respectively. Metallurgical tests conducted on rock cuttings indicate that 68.1% ΣREEO at an average grade of 1248 ppm can be concentrated and recovered through gravity separation, magnetic separation, and floatation circuits. Figure 14 in Boyer and Ostensoe (2011) show that ΣREE from 2770 samples from the higher-grade Lower Plate varies between 17 and 600 ppm with a median of 358 ppm.
Cover thickness and description Variable.
Authors Lukas Zurcher, Timothy S. Hayes, Mark E. Gettings, Joshua M. Rosera.
New data needs Geologic mapping, geophysics.
Geologic mapping and modeling needs Detailed geology-structure-alteration-mineralization mapping.
Geophysical survey and modeling needs High resolution Rank 1 aeromagnetic and aeroradiometric coverage.
Digital elevation data needs Lidar inadequate.