Little Three (Ramona district)
San Diego County, California, United States
Magmatic (Ni-Cu-PGE, carbonatites)Gemmes (topaze, tourmaline)
- Type
- Gem-pocket granitic pegmatite-aplite (LCT type)
Late Cretaceous (about 100 Ma) pegmatite-aplite dikes of the Southern California batholith, 1 to 3 m thick and gently dipping, with a basal aplite zone, a pocket zone (tourmaline, beryl, quartz) and graphic pegmatite. Crystallisation from 730-700 to 565 °C, pockets at 565-525 °C under about 2 kbar, nearly closed system. Dike assigned to group A, with large pockets of cleavelandite, topaz and zoned muscovite. Indicative coordinates.
δ18O in ‰ (per mil) Values of the same system
Standard : V-SMOW
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| 10.9 ± 1.1 ‰ | 10.1 / 12.4 ‰ | 4 | quartz Mean and standard deviation recalculated from 4 analyses, P-32-11 clear (+12.4 ‰) and smoky (+10.2 ‰) parts counted separately; crystal P-31-12 from +10.4 to +12.2 ‰ with a heavy clear overgrowth (Table 3). | Taylor et al. (1979), Stable isotope and fluid inclusion studies of gem-bearing granitic … |
δD in ‰ (per mil) Values of the same system
Standard : V-SMOW
| Value | Range | n | Mineral or matrix | Source |
|---|---|---|---|---|
| −35 ‰ | 1 | pocket muscovite (green rim) Single analysis, P-46-15: the clear core of the same crystal is printed at -10 ‰, outside the range the text gives for muscovite (-35 to -100 ‰), set aside as a probable misprint. | Taylor et al. (1979), Stable isotope and fluid inclusion studies of gem-bearing granitic … |
Deposits of the same type
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- Magnet Cove alkaline complex United States
- Carolina tin-spodumene belt United States
- Sudbury Canada
Cite this page
IsoFind Atlas (2026). Little Three (Ramona district), isotope signatures. https://www.isofind.tech/isotopes/en/deposits/little-three-district-de-ramona/ (accessed 2026-10-13).
@misc{isofind2026littlethreeramonadistrictisot,
title = {Little Three (Ramona district), isotope signatures},
author = {{IsoFind Atlas}},
year = {2026},
url = {https://www.isofind.tech/isotopes/en/deposits/little-three-district-de-ramona/},
note = {Accessed 2026-10-13}
}Updated : 2026-10-13