Round Top Mountain rhyolite (Texas, USA), a massive, unique Y-bearing-fluorite-hosted heavy rare earth element (HREE) deposit

Pingitore, Nicholas E.; Clague, J. W.; Gorski, Daniel

doi:10.1016/s1002-0721(14)60037-5

Cited by 32 publications

(24 citation statements)

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“…In yttrofluorite the trivalent (3 + ) Y and HREEs substitute for from 5% to 30% of the bivalent Ca 2+ cations, yielding the formula (Ca 1−x Y,HREE x )F 2+x [18]. The only currently known yttrofluorite YHREE deposit is Round Top Mountain, located near the town of Sierra Blanca in Hudspeth County, west Texas, USA [19]. The mountain is a rhyolite laccolith, a mushroom-shaped igneous intrusion that formed when magma pushed its way upward toward the earth's surface and spread out between older flat lying rock units.…”

Section: Introductionmentioning

confidence: 99%

“…In consideration of the massive size of the deposit, the enrichment in valuable YHREEs, and the laboratory demonstration that the host mineral, yttrofluorite, is soluble in dilute sulfuric acid, Texas Mineral Resources Corporation has proposed to extract the YHREEs and byproduct elements by heap leach with dilute H 2 SO 4 [19] [22] [24] [25]. Because the deposit is exposed at the surface there is little overburden to be excavated before surface mining could begin.…”

Section: Introductionmentioning

confidence: 99%

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Remarkably Consistent Rare Earth Element Grades at Round Top Yttrofluorite Deposit

Pingitore¹,

Clague²,

Gorski³

2018

AMPC

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The peraluminous rhyolite that forms Round Top Mountain (approximately 375 m high × nearly 2 km in diameter), near Sierra Blanca, Hudspeth County, west Texas, USA, is enriched in yttrium and heavy rare earth elements (YHREEs), as well as Li, Be, U, Th, Sn, F, Rb, Cs, Nb, and Ta. Texas Mineral Resources Corp. (USA) proposes to release the YHREEs from their unique yttrofluorite host via heap leaching with dilute sulfuric acid. The inexpensive process also releases portions of valuable byproduct Be, Li, and U from accessory minerals amid the insoluble feldspars and quartz that comprise 90% -95% of the surface-exposed rhyolite mountain. The objective of this study is to determine the consistency of mineralization grade, an important consideration in mine planning and preliminary economic analysis. The method is to plot elemental analyses of Y, Dy, Ho, Tm, Yb, Ce, Pr, Nd, Eu, Gd, Tb, U, and Nb from more than 1400 reverse circulation cuttings taken from 64 exploration drill holes against sample depth. The result of inspection of the plots reveals a remarkably homogeneous distribution of minor and trace elements throughout the sampled portion of the massive, 1.6-billion-tonne laccolith. The plots drive the conclusion that Round Top mine feedstock should remain constant for the life of the mine (multiple decades). Thus mining mechanics could be optimized at the start of operations and not require expensive later changes. The physical and chemical design of the heap leach and recovery and purification of target elements from pregnant leach solution also could be perfected during early development.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Remarkably Consistent Rare Earth Element Grades at Round Top Yttrofluorite Deposit

Pingitore¹,

Clague²,

Gorski³

2018

AMPC

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“…At Round Top, these include YHREEs, light REEs (LREEs), Sn, Be, Li, Cs, Rb, U, Th, Ga, Nb, and Ta. Although a number of REE-bearing minerals have been reported in the deposit, synchrotron-based X-ray absorption spectroscopy documented that yttrofluorite hosts essentially all of the YHREEs [7]. Yttrofluorite is a variety of the common mineral fluorite (CaF2, isometric) in which the trivalent (3+) Y and HREEs substitute for ~5% to 30% of the bivalent Ca 2+ cations, yielding the formula (Ca1−x,Y,HREEx)F2+x [8].…”

Section: Introductionmentioning

confidence: 99%

Porosity and Permeability of Round Top Mountain Rhyolite (Texas, USA) Favor Coarse Crush Size for Rare Earth Element Heap Leach

Negron

Pingitore

Gorski³

2016

Minerals

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Water-saturation porosity and dye-penetration permeability measurements of Round Top Mountain rhyolite confirm that a ½-inch (13-mm) crush size would permit efficient acid heap leaching of yttrium and heavy rare earth elements (YHREEs) hosted in yttrofluorite, a YHREE-substituted variety of fluorite. Laboratory acid leaching has extracted up to 90% of the YHREEs. The bulk insoluble gangue mineralogy of the rhyolite, 90% to 95% quartz and feldspars, assures low acid consumption. Different crush sizes were weighed, soaked in water, and reweighed over time to determine water-penetration estimated porosity. Typical porosities were 1% to 2% for gray and 3% to 8% for pink varieties of Round Top rhyolite. The same samples were re-tested after soaking in dilute sulfuric to simulate heap leaching effects. Post-leach porosity favorably increased 15% in pink and 50% in gray varieties, due to internal mineral dissolution. Next, drops of water-based writing ink were placed on rhyolite slabs up to~10 mm thick, and monitored over time for visual dye breakthrough to the lower side. Ink penetration through 0.5 to 2.5-mm-thick slabs was rapid, with breakthrough in minutes to a few hours. Pink rhyolite breakthrough was faster than gray. Thicker slabs, 4 to 10 mm, took hours to three days for breakthrough. Porosity and permeability of the Round Top rhyolite and acid solubility of the yttrofluorite host should permit liberation of YHREEs from the bulk rock by inexpensive heap leaching at a coarse and inexpensive nominal ½-inch (13-mm) crush size. The rate-limiting step in heap leach extraction would be diffusion of acid into, and back-diffusion of dissolution products out of, the crushed particles. The exceptional porosity and permeability that we document at Round Top suggest that there may be other crystalline rock deposits that economically can be exploited by a coarse-crush bulk heap leach approach.

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“…The rhyolites are peralkaline to peraluminous [198], 36.2 Ma [166], and enriched in Li, Be, F, Zn, Rb, Y, Zr, Nb, Sn, REE, and Th [175,176]. Fluorspar replacement bodies, enriched in Be, Zr, REE, and other elements are found at the contacts of the laccoliths and Cretaceous limestones [173][174][175][176]183,184]. …”

Section: Sierra Blanca (Round Top Mountain)mentioning

confidence: 99%

“…Chondrite-normalized enriched REE patterns exhibit depleted light REE patterns with a negative Eu anomaly (Figure 21). REE minerals include Y-bearing fluorite, bastnaesite, xenotime, and fluocerite [184,186]. Beryllium occurs mostly in contact metasomatic veins and replacements in limestones as behoite (Be(OH)2), with lesser amounts of berborite (Be2 (BO3)(OH,F)·H2O), bertrandite, chrysoberyl, phenakite, fluorite and garnet [175,176,179].…”

Section: Sierra Blanca (Round Top Mountain)mentioning

confidence: 99%

Rare Earth Elements (REE) Deposits Associated with Great Plain Margin Deposits (Alkaline-Related), Southwestern United States and Eastern Mexico

McLemore

2018

Resources

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W.G. Lindgren in 1933 first noted that a belt of alkaline-igneous rocks extends along the eastern edge of the Rocky Mountains and Basin and Range provinces from Alaska and British Columbia southward into New Mexico, Trans-Pecos Texas, and eastern Mexico and that these rocks contain relatively large quantities of important commodities such as, gold, fluorine, zirconium, rare earth elements (REE), tellurium, gallium, and other critical elements. In New Mexico, these deposits were called Great Plain Margin (GPM) deposits, because this north-south belt of alkaline-igneous rocks roughly coincides with crustal thickening along the margin between the Great Plains physiographic province with the Basin and Range (including the Rio Grande rift) and Rocky Mountains physiographic provinces, which extends into Trans-Pecos Texas and eastern Mexico. Since 1996, only minor exploration and development of these deposits in New Mexico, Texas, and eastern Mexico has occurred because of low commodity prices, permitting issues, and environmental concerns. However, as the current demand for gold and critical elements, such as REE and tellurium has increased, new exploration programs have encouraged additional research on the geology of these deposits. The lack of abundant quartz in these systems results in these deposits being less resistant to erosion, being covered, and not as well exposed as other types of quartz-rich deposits, therefore additional undiscovered alkaline-related gold and REE deposits are likely in these areas. Deposits of Th-REE-fluorite (±U, Nb) epithermal veins and breccias are found in the several GPM districts, but typically do not contain significant gold, although trace amounts of gold are found in most GPM districts. Gold-rich deposits in these districts tend to have moderate to low REE and anomalously high tungsten and sporadic amounts of tellurium. Carbonatites are only found in New Mexico and Mexico. The diversity of igneous rocks, including alkaline-igneous rocks, and associated mineral deposits along this boundary suggests that this region is characterized by highly fractionated and differentiated, multiple pulses of mantle-derived magmas evolving to lower crustal magmas related to the subduction of the Farallon plate. The differences in incompatible trace elements, including REE and beryllium, between the different granitic to rhyolite rocks are likely related to either differences in the crustal rocks that were assimilated during magmatic differentiation or by potential minor contamination from crustal sources and/or magma mixing. Deep-seated fracture systems or crustal lineaments apparently channeled the magmas and hydrothermal fluids. Once magmas and metal-rich fluids reached shallow levels, the distribution and style of these intrusions, as well as the resulting associated mineral deposits were controlled by local structures and associated igneous rock compositions.

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Round Top Mountain rhyolite (Texas, USA), a massive, unique Y-bearing-fluorite-hosted heavy rare earth element (HREE) deposit

Cited by 32 publications

References 3 publications

Remarkably Consistent Rare Earth Element Grades at Round Top Yttrofluorite Deposit

Remarkably Consistent Rare Earth Element Grades at Round Top Yttrofluorite Deposit

Porosity and Permeability of Round Top Mountain Rhyolite (Texas, USA) Favor Coarse Crush Size for Rare Earth Element Heap Leach

Rare Earth Elements (REE) Deposits Associated with Great Plain Margin Deposits (Alkaline-Related), Southwestern United States and Eastern Mexico

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