LIONSince there are a lot of new folks here, I thought I'd repost this.
I posted this on stockhouse in the spring of 2015 from an abstract that I found. A year or two later I noticed that LIO put a link up to the original abstract but soon took it down.
...Although geologic studies can make non geologists heads spin, I found parts of this one very interesting and pertinent so I took out excerpts. It was referenced in the magnetic survey that Lion took their gravity map which can be found in their presentation.
Tuvatu Gold-Silver Telluride Deposit, Fiji: Comparisons with the Emperor Deposit
Abstract
The Tuvatu gold-silver telluride deposit with reserves of 13 t Au is the second largest gold deposit in Fiji after the large Emperor gold telluride deposit The deposits are 40 km apart and occur along the 250-km east-northeast trending Viti Levu lineament.
They are spatially associated with alkaline rocks of almost identical age (~5.4–4.6 Ma) and having a shoshonitic affinity.
The gold mineralization in both deposits is spatially and genetically related to monzonite intrusions and to a low-grade porphyry copper-style system.
The Emperor deposit occurs along the margins of the Tavua volcano whereas the Tuvatu deposit may occur adjacent to an eroded shoshonite volcano. At both locations, low-sulfidation, epithermal gold telluride mineralization occurs in flat-lying veins, steep faults, shatter zones, stockworks, and hydrothermal breccias. (At Tuvatu) Individual veins contain between 2 and 100 g/t Au, with the Upper Ridges veins containing the highest grades (5–100 g/t Au).
Mineralization in both deposits formed in multiple stages and is characterized by the presence of quartz-roscoelite telluride veins in which gold-rich tellurides were deposited prior to silver-rich tellurides. Both deposits have gold grades of about 9 g/t and contain precious metal tellurides.
Gold reserves for the Tuvatu and the Emperor gold deposits share several geological, geochemical, and geophysical attributes. These similarities suggest a common origin for the two mineralizing systems. Both are associated with prominent regional-scale gravity anomalies along the Viti-Levu lineament. The deposits are spatially related to monzonite intrusive and extrusive rocks of similar composition and of almost identical age.
Porphyry and epithermal-style mineralization at the Emperor deposit is similar to in porphyry-style mineralization at the Tuvatu deposit. Both deposits exhibit a genetic relationship between low-grade porphyry Cu mineralization and epithermal gold telluride mineralization, with the latter forming in flatmakes, steep faults, shatter zones, stockworks, and hydrothermal breccias in both deposits.
These deposits also possess similar alteration styles, pyrite morphologies paragenetic sequences, and telluride mineralogy. Although fluids responsible for porphyry-style minerallization at both places were likely boiling, those associated with the porphyry-style mineralization at Emperor were cooler (~350°C) and generally less saline (up to ~15 wt % NaCl equiv) than those associated with porphyry-style mineralization in the Tuvatu and H lodes in the Tuvatu deposit.
Implications for exploration
The Tuvatu and Emperor deposits are low-sulfidation gold deposits hosted by alkaline igneous rocks and, in this respect, share geologic affinities with other low-sulfidation deposits in the southwest Pacific (e.g., Porgera, Papua New Guinea. ) Among these geologic similarities is the transition from porphyry- to epithermal-style gold mineralization at Porgera and Ladolam, (LIHIR), which is also apparent at Far Southeast-Lepanto, Philippines.
In addition, there appears to be a genetic relationship between large epithermal gold deposits and spatially related satellite deposits or prospects. Examples include the Porgera and Mt. Kare deposits, which are 18 km apart , the Ladolam/Lihir deposit and Conical Seamount occurrence, located 10 km apart , and the Emperor and Tuvatu deposits. In each of these examples, there is a strong similarity between the geologic setting, the composition of the igneous rocks genetically related to mineralization, and the precious metal mineralization and associated alteration for the large deposit and its satellite.
Interestingly, the gravity map on Lions presention shows Tuvato with apparently a greater signature than Vatukoula. Perhaps Vatakoulu is the satelite of Tuvatu. (which I believe)
From another abstract
“Exploration for epithermal gold mineralization along the Viti Levu lineament over the last two decades has identified additional prospects in the shoshonitic Ba and Koroimavua Groups in the Vuda, Ba, and Raki Raki areas and these also may be satellites of the Emperor and Tuvatu deposits.”
....Tuvatu may have it’s own high grade gold satellites close by? Gotta like that.