ZONED TOURMALINE ASSOCIATED WITH CASSITERITE: IMPLICATIONS FOR FLUID EVOLUTION AND TIN MINERALIZATION IN THE SAN RAFAEL SN CU DEPOSIT, SOUTHEASTERN PERU
50
Citation
44
Reference
10
Related Paper
Citation Trend
Abstract:
The composition of tourmaline in the San Rafael Sn–Cu lode, in southeastern Peru, provides an important record of the early evolution of the hydrothermal system that produced the world’s richest tin deposit. Many forms, colors and compositions of tourmaline, ranging from dravite to schorl, are present in the deposit, but the late tourmaline that accompanied deposition of early cassiterite has an unusual dark green color, and exhibits a strong trend of enrichment in iron. Appearance of this tourmaline in the paragenesis coincided with a marked change in the vein style, reflecting an opening of the vein system, and a dramatic change in the mineralogy of vein and alteration assemblages, evident from the precipitation of other iron-rich minerals (Fe-rich chlorite and cassiterite). This abrupt change in the plumbing of the hydrothermal system was associated with the introduction of dilute, relatively oxidizing, externally derived waters of meteoric origin that mixed with hot magmatic brines carrying high concentrations of dissolved tin and iron. The resulting sudden cooling, dilution, and oxidation of the ore fluids created the conditions required for massive precipitation of cassiterite and formation of a very large, high-grade ore deposit.Keywords:
Cassiterite
Tourmaline
The paper shows differences in character of tin mineralization in skarns which develop after dolomites (magnesial) and limestones (limy). Cassiterite is not deposited in the former, since because of the relatively high alkalinity and the high activity of boron (B203), tin preferentially enters the crystal structures of Sn-borates such as hulseite, ludwigite, and nordenskioldine rather than cassiterite. In limy skarns, tin is largely dissipated in garnets (up to 0.62%), axinites (up to 0.2%), and other minerals. It is only at the end of the appropriate stage, at relatively high acidity, that tin is deposited as cassiterite in magnetitic and amphibole-axinitic skarns. The latter are very favorable for development of economic ore bodies. Conclusions are made to the effect that a) tin is present in the postmagmatic solutions during each of the three stages, and also b) concerning optimum conditions for deposition of tin minerals in any stage (depending on magnitudes of Eh and pH environments and B2O3 and S2- activities. -- Author.
Cassiterite
Greisen
Cite
Citations (14)
Greisen
Tourmaline
Cassiterite
Batholith
Fluorite
Andradite
Cite
Citations (144)
Cassiterite
Tourmaline
Greisen
Rare-earth element
Cite
Citations (178)
Abstract Permian-Triassic granites and associated tin deposits are widespread in the Eastern and Western belts of Peninsular Malaysia. The ages and key controlling factors of tin mineralization, however, are poorly constrained. Cassiterite separates from the Sintok and Rahman tin deposits in the Western belt, and Bandi, Setahum, Lembing, and Cherul tin deposits in the Eastern belt have U-Pb ages of 218.9 ± 3.4 and 226.8 ± 7.6 Ma, and 213.1 ± 3.9, 270.6 ± 4.6, 282.7 ± 4.6, and 281.3 ± 3.5 Ma, respectively. These ages directly constrain the tin mineralization in Peninsular Malaysia to two separate periods: 290 to 270 Ma and 230 to 210 Ma. Zircon crystals from tin-bearing granites in the Cherul and Sintok deposits have U-Pb ages of 276.0 ± 1.9 and 221.9 ± 0.6 Ma, respectively, consistent with the cassiterite U-Pb ages within uncertainties. Zircon crystals from barren granites of the Kuantan pluton in the Eastern belt have a U-Pb age of 260.5 ± 0.7 Ma, which is between the two tin mineralization periods. Zircon from these barren granites have εHf(t) values from −5.4 to 3.6, two-stage Hf model ages (TDM2) from 1.4 to 1.0 Ga, and Ce4+/Ce3+ ratios from 40 to 120. By comparison, zircon crystals from the tin-bearing granites have low εHf(t) values (−9.7 to −3.2) and Ce4+/Ce3+ ratios (4–67) and high TDM2 (1.8–1.4 Ga). Zircon ages, Hf isotopes, and trace elements indicate that the tin-bearing granitic magmas in Peninsular Malaysia had relatively low oxygen fugacity and were derived from reworking of Paleo- to Mesoproterozoic sedimentary rock-dominated crust in response to the Paleo-Tethyan subduction and continental collision. This study confirms that the nature of magma sources and redox states of magmas were key in the formation of the tin-rich granites and associated tin deposits and that the granite-related tin mineralization in Peninsular Malaysia was closely related to the evolution of the eastern Paleo-Tethys.
Cassiterite
Cite
Citations (36)
Cassiterite
Tourmaline
Greisen
Cite
Citations (44)
Abstract The tin mineralization at Rondonia, W. Brazil, is characterized by the association cassiterite and topaz. Both minerals occur as replacements in Precambrian to Early Paleozoic granites. The tin mineralization of the Eastern Cordilleras of Bolivia, on the other hand, has cassiterite and tourmaline as characteristic mineral association, and is related to the occurence of large granitic batholiths. The origin of the two tin mineralizations is discussed.
Cassiterite
Tourmaline
Topaz
Batholith
Greisen
Wolframite
Cite
Citations (5)
Abstract Primary cassiterite mineralization is often associated with highly evolved granites, but the magmatic and hydrothermal processes that produce these deposits are often difficult to decipher. In this study, we employed the chemical and Sr-Nd isotope compositions of tourmaline to monitor processes of Sn enrichment in the magmatic and hydrothermal stages of the Ardlethan granite (Australia) and its associated Sn deposits. Initial 87Sr/86Sr (0.710–0.717) and ɛNd (–5.0 to −1.0) values of late magmatic tourmalines indicate derivation of the Ardlethan granite via an assimilation-fractional crystallization (AFC) process in which incorporation of Ordovician sediment into an I-type granitic parental magma produced an enrichment of Sn at least 30 times over that of the assumed mafic-dominated igneous source of the granite. The rare earth element and Sn concentrations of tourmaline in the greisen deposits together with δ18O of coprecipitated quartz indicate that exsolution of a late-stage, Cl-rich fluid from the Ardlethan granite led to cassiterite mineralization in these deposits. In contrast the Fe/(Fe + Mg) and initial εNd (–9.2 to −12.9) compositions of tourmaline that coprecipitated with cassiterite in the large breccia pipes adjacent to the Ardlethan granite suggest that granite-derived fluids scavenged Sn by chemical leaching of an older S-type granite that hosts the pipes. This study shows that tourmaline can act as a robust monitor of key geologic processes in complex and dynamic magmatic-hydrothermal Sn systems and that its 87Sr/86Sr and ɛNd isotope compositions are especially useful for constraining the nature of magmatic and hydrothermal sources that contributed to these deposits.
Cassiterite
Tourmaline
Greisen
Pegmatite
Cite
Citations (13)
The composition of tourmaline in the San Rafael Sn–Cu lode, in southeastern Peru, provides an important record of the early evolution of the hydrothermal system that produced the world’s richest tin deposit. Many forms, colors and compositions of tourmaline, ranging from dravite to schorl, are present in the deposit, but the late tourmaline that accompanied deposition of early cassiterite has an unusual dark green color, and exhibits a strong trend of enrichment in iron. Appearance of this tourmaline in the paragenesis coincided with a marked change in the vein style, reflecting an opening of the vein system, and a dramatic change in the mineralogy of vein and alteration assemblages, evident from the precipitation of other iron-rich minerals (Fe-rich chlorite and cassiterite). This abrupt change in the plumbing of the hydrothermal system was associated with the introduction of dilute, relatively oxidizing, externally derived waters of meteoric origin that mixed with hot magmatic brines carrying high concentrations of dissolved tin and iron. The resulting sudden cooling, dilution, and oxidation of the ore fluids created the conditions required for massive precipitation of cassiterite and formation of a very large, high-grade ore deposit.
Cassiterite
Tourmaline
Cite
Citations (50)