Minerals of the Carbonate Replacement Deposits (CRDs) of Mexico
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The speaker introduces the topic of Mexican carbonate replacement deposits and acknowledges individuals who have contributed to his work.
Introduction to Mexican Carbonate Replacement Deposits
- The speaker dedicates the talk to Miguel Romero and Adriana Pagano, highlighting their contributions to Mexican mineralogy.
- Acknowledgment is given to various individuals, including Jeff Skoval, Jim McGlass, Gerardo Perez Jesus Salinas, Allison, and Lauren for their support in the field.
- A birthday shoutout is given to Alex Vensky. The speaker emphasizes the importance of understanding geology alongside minerals.
- Working experience in Mexico is shared, emphasizing the significance of geological context in mineral appreciation.
Geological Context of Mexico
The speaker discusses the geological background of Mexico focusing on volcanic belts and sedimentary rocks.
Geological Background
- Description of the Trans-Mexico Volcanic Belt containing prominent volcanoes like Popocatepetl and Orizaba.
- Explanation of volcanic and plutonic rocks associated with the Sierra Madre Occidental magmatic belt hosting carbonate replacement deposits.
- Details about Mesozoic sedimentary rocks hosting carbonate replacement deposits within the Mexican fold thrust belt during the Laramide orogeny.
The speaker shares personal experiences working on a master's thesis in Mexico and encounters with notable mining districts.
Field Work Experiences
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Explanation of carbonate replacement deposits and their characteristics.
Carbonate Replacement Deposits
- Carbonate replacement deposits are high-temperature deposits found in limestone or dolomite, forming above 250 degrees Celsius.
- They are sulfide-rich and related to intrusions, with mineralization occurring as massive galena and sphalerite.
- These deposits are polymetallic, containing metals like silver, lead, zinc, copper, and gold zoned with respect to the intrusion center.
- Mineralization in these deposits is dominated by replacement rather than open space filling.
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Examples of carbonate replacement deposits globally.
Global Examples of CRDs
- U.S. examples include Bisbee, Magdalena, Leadville, Gilman, Tintic, among others.
- German and South American examples include Uchuchakwa, Santa Rita; European examples include Lavrion and Trepcha.
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Significance of understanding the geological link between different carbonate replacement deposits.
Geological Link Between CRDs
- Similar processes create diverse CRDs worldwide leading to remarkable mineralogical similarities.
- Lavrion deposit's historical importance showcases how CRDs underpin civilizations through valuable resources like silver.
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Economic significance and exploration aspects of carbonate replacement deposits.
Economic Significance & Exploration
- CRDs offer economic value with high-grade silver, zinc, lead, copper ores along with other elements like gold and tungsten.
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The process of sulfide deposition in gangue involves multiple stages, resulting in varied mineral expressions and zoning.
Sulfide Deposition Process
- The process involves eating a little carbonate and depositing sulfides in nanovoids over time. This results in superimposition of stages and products.
- Different stages exhibit varying strengths, leading to zoning, overgrowths, and pseudomorphs in specimens.
- Primary minerals formed reflect the system's chemistry and position relative to the source. Extra metals like arsenic, vanadium, tungsten, and tellurium influence mineralogy.
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The speaker discusses the discovery of the Nike deposit based on similar geological features to Ojuela, showcasing ore bodies and mineral pockets.
Discovery of Nike Deposit
- The Nike deposit was found based on geological similarities to Ojuela.
- Ore bodies were traced for 600 meters over 350 years.
- Mineral pockets containing atomite and lagrandite were discovered in the system.
- Geological features resemble a bowl of spaghetti or skeletal hand fingers.
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The speaker delves into the distribution of large deposits in North America, focusing on Mexico's geological history.
Distribution of Large Deposits
- Major deposits span from Terra del Fuego to Alaska, with significant ones in Mexico and Arizona.
- Geological reasons underlie the concentration of big deposits in specific areas.
- Ore deposit formation primarily occurred around 30 million years ago due to tectonic movements between North America and Europe.
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The discussion shifts towards magma differentiation, volcanic activities, and mineralization processes.
Magma Differentiation and Mineralization
- Magmas rising from depth differentiate into volcanoes, plutons, or CRDs depending on their eruption or placement in limestone.
- Ideal conditions for large deposits involve magmatic intrusions encountering structurally prepared carbonate rocks at high crustal levels.
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The speaker transitions into mining history, exploring the Sumbel mine in Mexico during the early 20th century.
Mining History at Sumbel Mine
- Description of company housing, engineering facilities, and worker colonies at Sumbel mine during the early 1900s.
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This section discusses the historical significance and current status of mining sites in Mexico.
Novel of the 19th Century
- In 1908, Saturlalia was thriving as a mining site, surpassing Uncle Tom's Cabin.
- Miners were meticulously checked daily due to high-grade ores at Buena Tierra and Poto C shafts.
- Nika Nika, a newer mine, lacked history before the late 1800s but improved with the introduction of a train.
Mining History and Legends
- Nica had limited mining history due to its oxidized surface; known for witches' legends.
- Witches' folklore surrounds Nika, where they are believed to emerge from old mine workings at night.
Mineralization in Mexican Mines
This section delves into why Mexican mines are excellent specimen producers.
Specimen Production Factors
- Mexican mines contain diverse elements ideal for specimen formation.
- Stable tectonics in Mexico over millions of years allowed deep oxidation and preservation of oxide species.
Mineralization Processes
The process of mineralization and specimen formation in Mexican mines is explained.
Mineral Transformation
- Primary sulfide minerals transform into secondary minerals like mimetite and adamite through oxidation.
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Explanation of mineralogy and elements found in different specimens.
Mineralogy and Elements
- When minerals oxidize, interesting mineralogy forms, such as combinations of quartz and calcite.
- Calcopyrite is associated with galena and can form epitaxial high-temperature overgrowths on sphalerite.
- Calcopyrite typically develops an oxidation coating, grows on quartz, and is overgrown by fluoride.
- Arsenopyrite crystals are common in certain deposits like Ahuela, containing a high percentage of arsenic.
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Discussion on the occurrence of silver minerals and various specimens.
Silver Minerals and Specimens
- Radiating groups of orcinopyrite are found in specific deposits like Nika.
- Silver minerals like acanthites can occasionally be found pseudomorphing argentite.
- Spectacular silvers can be discovered in mines like San Martin in Zacatecas.
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Exploration of tetrahedrite, borneonite, cinnabar, stignite, and pseudomorph formation.
Tetrahedrite and Related Minerals
- Tetrahedrite is common in places like Concepcion del Oro; it forms repeated layers with antimonial tennantite.
- Borneonite is uncommon but occurs; specimens may include calcite and calcopyrite.
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Examination of stibnite replacements after stibiconite, wadley mine's significance, pseudomorph formation after purity crystals.
Stibnite Replacements and Pseudomorph Formation
- Stibnite replacements are common from deposits like La Cobrisa; pseudomorph after purity crystals occur frequently.
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Significance of slow reaction kinetics in sulfidizing processes for exploration purposes.
Sulfidizing Processes for Exploration
Pearly Dolomite and Rhodochrosite Specimens
The speaker discusses pearly dolomite, quartz, pyrite, and rhodochrosite specimens from various locations.
Pearly Dolomite and Quartz Specimens
- Pearly dolomite with quartz and pyrite.
- Rhombohedral calcite with quartz and sphalerite from Tosco.
- Thumbnail specimen of rhodochrosite from Miguel Romero's collection.
- Different shapes of rhodochrosite specimens with green octahedral fluorites.
Crystal Growth Variations in Deposits
The speaker explores the crystal growth variations in different deposits.
Crystal Growth Variations
- Description of multi-stage crystal growth patterns like scepters and parasitic growths.
- Mention of Japan law twins common in scarring and replacement systems worldwide.
Fluorite and Quartz Combinations
Discussion on fluorite, quartz combinations, amphiboles, clinopyroxenes, pracelite green quartzes, and other minerals.
Fluorite and Quartz Combinations
- Presence of amphiboles after clinopyroxenes in quartz formations.
- Description of miniature specimens with botrietal manganese oxides covering clear quartz.
Barite, Celestine, Anhydrite Minerals
Focus on barite crystals with pyrite growths, celestine twinning patterns, anhydrite preservation in deposits.
Barite, Celestine, Anhydrite Minerals
- Barite crystals partially replaced by fluoride; solid fluorites core structures mentioned.
Introduction and Mineral Specimens
The speaker discusses various mineral specimens, their origins, and unique characteristics.
Vivianite and Zeolites
- Vivianite specimen from John Barlow's collection, developed in Saudi Arabia.
- Miniature group with zeolites like stilbites from Sun Martin.
Nifontovite and Oxidation
- Primary deposits of nifontovite become more interesting when oxidized.
- Oxidation generates open spaces for secondary mineral growth.
Oxidation Process and Mineral Formation
The speaker explains how oxidation impacts mineral formation and the resulting colorful minerals.
Sulfide Oxidation
- Advanced oxidation in Mexico leads to unique mineral formations.
- Colorful silver halides like bromargyrite form due to oxidation.
Wolfenite and Mimetite
- Wolfenite specimens from Aurora Mine in Mexico are highlighted.
- Mimetite specimens from San Pedro Corralitos are discussed for their beauty.
Secondary Minerals and Unique Formations
Discussion on secondary minerals formed through multi-stages of oxidation process.
Vanadinite and Disclosite
- Vanadinite specimens from San Carlos are mentioned along with disclosite replacing vanadinite.
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Explanation of the formation and characteristics of various minerals found in different mines.
Orthosurpriorite, Schulenburgite, and Sklodowski
- Orthosurpriorite and Schulenburgite are found in La Platosa mine, while Sklodowski is from Sadiolalia incorporated in gypsum.
- La Platosa mine is about 20 kilometers away from La Huela.
- The materials found are attractive and unique in size and composition.
Zinc Oxidation Process
- In an oxidation environment, zinc becomes highly mobile.
- Data from Prescott in 1916 shows changes in lead, zinc, iron, sulfur content during oxidation.
- Zinc gets flushed out below iron oxide layers and re-precipitated along fractures.
Formation of Zinc Oxides
- Zinc content decreases during oxidation process; it gets dispersed and re-precipitated below lead zones.
- Concentric shells of zinc and iron oxide form around high-grade lead oxides at considerable depths.
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Discussion on the mineralization process leading to the formation of various minerals like hemimorphite and adamite.
Mineralization at Ahuela Mine
- Old-timers left behind silver-rich material at Ahuela mine, leading to the presence of hemimorphite and adamite.
- Similar mineralization process observed in East Camp of Sadio Ali with oxidized lead-zinc-silver ores transitioning into fresh sulfides.
Unique Mineral Examples
- Presence of sharp fresh arsenopyrites covered by calcite pseudomorphed by smithsonite seen at Yolali.
- Bacona mine in Guadalupe Victoria known for brilliant blue botryoidal hemimorphites.
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Exploration of various minerals like hemimorphites, smithsonites, calcites, and adamites found in different mines.
Hemimorphites & Smithsonites
- Blue hemimorphites with platinuite tips seen at West Camp of Santialalia; sharp crystals observed at San Diego San Antonio mine.
Calcites & Adamites
- Aura calcite commonly overgrown by calcite seen at Euler mine; coney calcite also present overgrown by calcite.
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Discussion on the properties and variations observed in adamite minerals along with their fluorescence under specific conditions.
Properties of Adamites
- Lime green adamites contain uranium making them fluorescent; purples grow on white precursors showing contrasting colors.
Rare Minerals - Paradomite & Lagrandite
- Paradomite known from Ahuela for its beautiful flowers; recent finds include lagrandite with rice grain smithsonites.
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Exploration of supergene zinc zone leading to the development of austenite species along with cupro disclosite findings.
Supergene Zinc Zone Minerals
- Austenite commonly found as cabinet specimens; green balls emerging for the last few years due to supergene processes.
Cupro Disclosite & Lagranditie Locality
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Discussing various mineral specimens, including legrandite and gypsum, found in different locations.
Nuevo Leon Specimens
- Discusses a large specimen from Miguel Romero's collection.
- Mentions the famous yellow sprays from Abuela.
- Shows Jeff Starr's picture of a miniature specimen with nice definition.
Perkins' Collection and Caves
- Talks about a small legrandite thumbnail bought in a collection.
- Mentions an article on Perkins' mounts saving Alex Shouse's license plates.
- Describes limestone deposits with associated caves for collecting.
Cave Discoveries and Crystals
- Highlights spectacular caves like Pococy Mine and Cave of the Candles.
- Discusses crystals found in Nica mine, some affected by human influence.
Scientific Research and Crystal Growth
- Details scientific research on crystal growth in caves like the Cave of the Candles.
- Mentions protection measures to preserve crystals from deterioration.
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Announcing the theme for the 2022 Tucson Gem and Mineral Show celebrating the 50th anniversary of the Fluorescent Mineral Society and Appetite Super Group.
Theme Announcement