The Enigma of Magnetite-(Apatite) Rocks: Unraveling the Secrets of the El Laco System

🧲📚 The El Laco system is an enigmatic and well-preserved magnetite-(apatite) deposit located in Chile, with three major genetic models for its formation.

🔍🗻 The deposit consists of strata-bound magnetite-(apatite) bodies interbedded with undecided rocks, with evidence of replacement by kaolinite and albite.

🔬🌡️ Diagnostic rocks for magnetite-(apatite) systems include magnetite with large apatite crystals, apatite with dioxide and magnetite, and dioxide with apatite and magnetite.

🔍 The origin of magnetite-(apatite) rocks and their geological characteristics.

🔬 Insights from the El Laco system, including lava lake structures and intermingling of minerals.

⚗️ Geochemical analysis revealing high field strength elements, low titanium magnetite, and isotopic signatures indicating contamination.

🔍 Conventional oxygen isotopes cannot distinguish between magnetite precipitated from a melt or from a magmatic hydrothermal fluid.

🌡️ Triple oxygen isotopes suggest contamination with early Cambrian evaporite-rich sedimentary sequences.

💧 The lack of liquid water in the volcanic system indicates extensive crystal contamination.

🔑 The El Laco system exhibits similar behavior to other systems like fertile mercado and kiruna, where rhyolite contains water-rich magnetite.

🌋 In the coastal courtyard of Chile, magnetite blades with inclusions of iron-rich magnetite and titanite are found, along with glenoperoxin and fluorapatite.

🔬 Melt inclusions in magnetite and apatite rocks suggest complex interactions and residual melts, with different compositions and temperatures.

💧 Fluid separation and formation of gastric brines occur in the system, with chlorides fractionating into the aqueous fluid while sulfates remain in the melt.

🔒 Contamination of endocytic melts in the system may come from nearby sediments, potentially from both salted group and shallow marine ports.

❓ The presence of phosphorus and fluorine in the system plays a key role in the formation of magnetite apatite crystal systems.

🔍 Magnetite-(apatite) rocks have different origins than periphery-like or silicate rich melts.

🌋 Magnetic hepatite systems are formed from highly oxidized ultramafic melts with low silica content.

🧪 The late stages of crystallization of these melts exhibit a unique assemblage and high field strength elements.

🔑 The El Laco system lacks evaporitic sediments and consists mainly of oceanic sediments with a subducting slab.

💡 There is a variation in the amount of apatite in different ioa deposits, but experimental studies show that the mineral assemblages are similar.

🌋 The formation of ultramafic melts in the El Laco system is related to the interaction of antacidic melts with sediments in a zone of volcanic activity.

🧲 Magnetite-(apatite) rocks show a mass independent fractionation trend of oxygen-17, which is similar to evaporites.

🌍 The El Laco system suggests a mixing between magnetic magmatic magnetite and evaporites.

🔬 The chilean coastal range deposits and El Laco have similarities in the presence of scapelite, but differ in depth and genesis.