Nelsonity suwalskie - nowe dane mineralogiczne i geochemiczne
Abstract
SUWAŁKI NELSONITES - NEW MINERALOGICAL AND GEOCHEMICAL DATA
Summary
The ore-bearing apatite rocks, similar to nelsonites (Philpotts, 1967; Kolker, 1982) were found for the first time in Poland, in north-west part of the Suwałki Anorthosite Massif, in the Łopuchowo IG 1 borehole (Fig. 1). They form fine-grained veins between norite, gabbronorite andanorthosite(Fig. 2). Nine zones of nelsonites were distinguished in the depth interval from 2100 to 2208 m. Major mineraIs of the studied rocks include fluorapatite (50-70 vol %), magnetite (5-20 vol %), ilmenite (2-5 vol %), pyrrhotite (2-10 vol %), pyrite (1-2 vol %) allanite and anhydrite (Fig. 3, 4). As far as ore minerals are concerned, parts enriched in oxides and poor in sulfides (Fig. 3) and enriched in sulfides (Fig. 4, 5) are observed. Biotite is an accessory mineral filling apatite interstices in the contact zone (Fig. 6). Hogbomite Fe5-Al16-Ti030(OH)2, occurs in association with magnetite and pleonaste (Fig. 7). MineraIs of sulfidization phase such asbravoite, linneite, millerite, sfalerite, cubanite, pyrite and chalcocite occur in traces as exsolution or replacement products in magmatic stage mineraIs (Tab. 1). Quantitative chemical analyses of the whole rock and separated apatite crystals were carried out by ICP AES method. The studied rocks are enriched in Ni, Cu, Cr, Co, and REE compared to the other types of rocks such as anorthosite, norite, diorite, of the Suwałki intrusion. Results of X-ray diffraction study combined with IR spectroscopic investigation reveal the presence of fluoroapatite with minor content of OH - in the structure. High contents of LREE egoCe, Nd, La were encountered in nelsonites but REE content of apatites is 8000-9000 ppm as compared to 5500 ppm in nelsonites (Fig. 8 & 9). This high content of REE is partially related to Ce and Nd-allanite (Fig. 10-12) or rims of Ce - and Nd-rhabdophane (Fig. 13) very well seen in CL images. CL analyses were performed onnelsonites and their mineraIs. CL spectra of apatite show strong to medium yellow luminescence, that is indicative for La and Ce admixtures (Fig. 14, 15). Apatite, apparently homogeneous in SEM study, was frequently zoned as revealed by CL observations (Fig. 16 & 17). This method enabled identification of secondary mineraIs such as anhydrite, allanite, rhabdophane, calcite (Fig. 18-21). Modal projection of nelsonite from Łopuchowo and other nelsonitesis different because of sulfide content in nelsonite from Łopuchowo (Fig. 23). LREE distribution pattern for apatites from Łopuchowo and apatites from Norwegian Ti-nelsonites, are similar (Fig. 24) and reflect their origin from mature anorthosite facies.
Summary
The ore-bearing apatite rocks, similar to nelsonites (Philpotts, 1967; Kolker, 1982) were found for the first time in Poland, in north-west part of the Suwałki Anorthosite Massif, in the Łopuchowo IG 1 borehole (Fig. 1). They form fine-grained veins between norite, gabbronorite andanorthosite(Fig. 2). Nine zones of nelsonites were distinguished in the depth interval from 2100 to 2208 m. Major mineraIs of the studied rocks include fluorapatite (50-70 vol %), magnetite (5-20 vol %), ilmenite (2-5 vol %), pyrrhotite (2-10 vol %), pyrite (1-2 vol %) allanite and anhydrite (Fig. 3, 4). As far as ore minerals are concerned, parts enriched in oxides and poor in sulfides (Fig. 3) and enriched in sulfides (Fig. 4, 5) are observed. Biotite is an accessory mineral filling apatite interstices in the contact zone (Fig. 6). Hogbomite Fe5-Al16-Ti030(OH)2, occurs in association with magnetite and pleonaste (Fig. 7). MineraIs of sulfidization phase such asbravoite, linneite, millerite, sfalerite, cubanite, pyrite and chalcocite occur in traces as exsolution or replacement products in magmatic stage mineraIs (Tab. 1). Quantitative chemical analyses of the whole rock and separated apatite crystals were carried out by ICP AES method. The studied rocks are enriched in Ni, Cu, Cr, Co, and REE compared to the other types of rocks such as anorthosite, norite, diorite, of the Suwałki intrusion. Results of X-ray diffraction study combined with IR spectroscopic investigation reveal the presence of fluoroapatite with minor content of OH - in the structure. High contents of LREE egoCe, Nd, La were encountered in nelsonites but REE content of apatites is 8000-9000 ppm as compared to 5500 ppm in nelsonites (Fig. 8 & 9). This high content of REE is partially related to Ce and Nd-allanite (Fig. 10-12) or rims of Ce - and Nd-rhabdophane (Fig. 13) very well seen in CL images. CL analyses were performed onnelsonites and their mineraIs. CL spectra of apatite show strong to medium yellow luminescence, that is indicative for La and Ce admixtures (Fig. 14, 15). Apatite, apparently homogeneous in SEM study, was frequently zoned as revealed by CL observations (Fig. 16 & 17). This method enabled identification of secondary mineraIs such as anhydrite, allanite, rhabdophane, calcite (Fig. 18-21). Modal projection of nelsonite from Łopuchowo and other nelsonitesis different because of sulfide content in nelsonite from Łopuchowo (Fig. 23). LREE distribution pattern for apatites from Łopuchowo and apatites from Norwegian Ti-nelsonites, are similar (Fig. 24) and reflect their origin from mature anorthosite facies.