...P. Limtrakun; Khin Zaw; C. G. Ryan; T. P. Mernagh Abstract The Denchai gem sapphire deposits in Phrae Province, northern Thailand are closely associated with late Cenozoic alkaline basaltic rocks. The sapphires occur in alluvial placer deposits in palaeo-channels at shallow depths. Electron...

...Figure 1. Oxygen isotope values of corundums. A: δ 18 O range of different types of primary ruby and sapphire deposits around world. B: Main economic primary and placer gem deposits sold in international gemstone market. Color in diamonds represents color of rubies (in red and pink) and colored...

...V. Garnier; D. Ohnenstetter; G. Giuliani; A. E. Fallick; T. Phan Trong; V. Hoàng Quang; L. Pham Van; D. Schwarz Abstract Basalts associated with sapphire deposits are widespread in Europe, Africa, Asia and Australia. In Vietnam, blue, green and yellow sapphires are recovered from eluvial...

... isotope values from the same deposit into different groups, except for sapphire from Denchai, which has an outlier of 8.4‰, these corundum deposits can be approximately divided into two groups according to oxygen isotope ranges, one group with higher δ 18 O is 6.2–9.3‰ where Yushishan corundum is located...

... are Carboniferous and older rocks, minor Triassic granitoid plutons, and Late Cenozoic basalt and unconsolidated colluvial and alluvial deposits of the Lampang, Phrae, and other Late Cenozoic basins ( Fig. 2). Fig. 2. Geological map of the Lampang–Denchai–Phrae area, after Pyasin (1972, 1975) and DMR (1982...

... 0.999 Maximum 0.9997 Olivine (δ 18 O) Corundum (δ 18 O) Fractionation factors Min Max Mean Min Max Mean Min Max Mean Podgelbanochnyi volcano, Russia 1 5 5.5 6.4 5.95 0.9986 0.9995 0.999 Denchai alluvial deposit, Thailand 3 4.9 5.1 5.05...

... commercial factor. More value is ascribed to particular deposits of gems compared to others with similar geology. F igure 2 A crystal of orange spessartine and a faceted gem from the Little Three mine near Ramona, San Diego County, California. The orange color is due to Mn 2+ in the eight...

... corundum deposits are compared to consider their origins. Sapphires from Weldborough, NE Tasmania, are magmatic (high-Ga, av. 200 ppm) and dominated by Fe (av. 3300 ppm) and variable Ti (av. 400 ppm) as chromophores. They contain Cl, Fe, Ga, Ti and CO 2 -rich fluid inclusions and give δ 18 O values (5.1...

... and intrusive rocks from the Yukon–Tanana terrane in the Finlayson Lake region, Yukon, Canada —Stephen J. Piercey, James K. Mortensen, and Robert A. Creaser 77 Bentonite deposits of Northern Patagonia— B. Lombardi, M. Baschini and R.M. Torres Sánchez 309 Evaluation of sequential...

.... Soc 1978 54 43 60 Barr S. M. Macdonald A. S. Geochemistry and petrogenesis of late Cenozoic alkaline basalts of Thailand J. geol. Soc. Malaysia 1978 10 25 52 Barr S. M. Macdonald A. S. Palaeomagnetism, age and geochemistry of the Denchai basalt, Northern...

... crystallized these megacrysts and (2) from where were the melts derived? Major sapphire (or corundum) deposits occur in Tertiary alkali-basalt fields and related alluvial placers ( Hughes 1997 ). They are mainly distributed along the western edge of the Pacific (eastern Australia, Thailand, Cambodia, Laos...

...) for country of origin and 97.9% (sapphire) and 95.4% (ruby) for deposit of origin. Individual deposits are not recognized by the concentrations of a few elements; rather, the unique compositional signature of each deposit consists of the ratios of many elements, primarily Ca, Zr, Fe, Ba, Mt, Ti, Sr, Si, Cr, H...

... in this study have low Cr 2 O 3 content (0.00–0.81 wt%). Hercynite forms exsolution lamellae in magnetite of a xenolith composed of sapphire, zircon and magnetite found at Khao Wua, Thailand ( Coenraads et al. , 1995 ). The Thai area is a major source of gem corundum from its eluvial/alluvial deposits...

...Aaron C. Palke; Jacqueline Wong; Charles Verdel; Janaína N. Ávila Abstract A wide number of genetic models have been proposed for volcanically transported ruby and sapphire deposits around the world. In this contribution we compare the trace element chemistry, mineral and melt inclusions...

..., Distribution, Exploitation and Uses . Department of Mines. Canadian Geological Survey Memoir , 57 , 377 pp. Barr , S.M. and MacDonald , A.S. ( 1979 ) Palaeomagnetism, age and geochemistry of the Denchai basalt, northern Thailand . Earth and Planetary Science Letters , 46 , 113 – 124...

...F. L. Sutherland; R. R. Coenraads; D. Schwarz; L. R. Raynor; B. J. Barron; G. B. Webb Abstract Alluvial rubies and sapphires are found in palaeodrainage deposits along the Cudgegong-Macquarie River system, central eastern New South Wales, Australia. A pink to red suite contains Cr (up to 0.6 wt...

... mantle domains veined by such felsic pegmatites, during ascent of later-stage basic magma generated at greater depth, might well explain the presence of xenocrysts of sodic or Na–K-rich feldspar, corundum, and zircon in alkali basalt lavas or tuffs and associated alluvial deposits. Abstract Des filons...

... , where a major extensional detachment created during E-W extension results in exhumation of the lower crust (Mahattanachai et al., 2021). Subsequently, during NNW-SSE extension, associated with a transtensional phase of deformation, the Miocene-Recent sedimentary section was deposited on the exhumed...

...–13 Amphoe Denchai, Phrae province (north) clayey skeletal, mixed, isohyperthermic, Rhodic Paleustalf 1080 19 basalt gravelly CL upland crop 2 Bt2 60–120 v. gravelly C 7 Tha Mai A 0–25 Amphoe Lam Sing, Chantaburi province (east coast) clayey, kaolinitic, isohyperthermic...