The APS minerals in my samples (the major composition is dickite) could be divided into two kinds, including aggregations (acicular and scale-like) and zoned structured crystals (mainly cubic). And we have already obtained the chemical compositions of the APS minerals in our samples.
I learned from some articles that APS minerals may form through intense weathering or hydrothermal fluids. So I wonder whether we could judge their genesis from their morphologies (maybe combined with their component information).
I would be really grateful if any specialist could answer my questions. Thank you so much.
Hello,
I think that only by the morphology of the crystals and aggregates, this group of phases cannot be recognized at all. However, APS should most likely include the mentioned cubic crystals. This would be the alunite supergroup (with isomorphic representation PO4-SO4) of minerals. But they are not de facto cubic, but pseudo-cubic (almost cubic, trigonal). In addition, there are a number of other Al phosphates and Al sulfate-phosphates. Acicular, could be sanjuanite - destinesite, for example. To solve the problem, it is necessary to use some mineralogical analysis, designed to determine the phase composition. The best powder X-ray diffraction analysis and EDX spectroscopy on SEM. Once you know the phase composition, you can deduce the genesis. However, e.g. during acidification under weathering conditions, these phases occur quite commonly in nature, by the action of fluids as well.
Dear Colleague:
APS minerals when surveyed under the SEM may show a pseudo-cubic outward appearance this is also the most common morphology of Na-K alunite s.s.s. In the majority of case the occur as massive aggregates where even with aid of SEM morphological criteria are not helpful and only EMPA and XRD can disentangle the complex s.s.s.
For further reading concerning the APS minerals with several images see:
DILL, H.G., FRICKE, A., HENNING, K.-H. and GEBERT, H. (1995) An APS mineralization in the kaolin deposit Desa Toraget from northern Sulawesi / Indonesia.- Journal of Southeast Asian Earth Sciences, 11: 289-293.
DILL, H. G., BUSCH, K. and BLUM, N. (1991) Chemistry and origin of veinlike phosphate mineralization, Nuba Mts. (Sudan). - Ore Geology Reviews, 6: 9-24.
DILL, H.G., FRICKE, A., HENNING, K.-H. and THEUNE, C.H. (1995) An aluminium-phosphate mineralization from the hypogene La Vanguardia kaolin deposit (Chile).- Clay Minerals, 30: 249-256.
DILL, H.G., FRICKE, A. and HENNING, K.-H (1995) The origin of Ba-and REE-bearing aluminium-phosphate-sulphate minerals from the Lohrheim kaolinitic clay deposit (Rheinisches Schiefergebirge, Germany).- Applied Clay Science, 10: 231-245.
DILL, H. G., BOSSE, H.-R., HENNING, K-H. , FRICKE, A. and AHREND , H. (1997) Mineralogical and chemical variations in hypogene and supergene kaolin deposits in a mobile fold belt--The Central Andes of northwestern Peru.- Mineralium Deposita, 32: 149-163.
DILL, H. G., BOSSE H.-R. and KASSBOHM J. (2000) Mineralogical and chemical studies of volcanic-related argillaceous industrial minerals of the Central American Cordillera (western El Salvador).- Economic Geology, 95: 517-538.
DILL, H.G. (2001) The geology of aluminium phosphates and sulphates of the alunite supergoup: A review.- Earth Science Reviews, 53: 35-93.
DILL, H.G., WEBER, B. and BOTZ, R. (2013) Metalliferous duricrusts (“orecretes”) - markers of weathering: A mineralogical and climatic-geomorphological approach to supergene Pb-Zn- Cu-Sb-P mineralization on different parent materials.- Neues Jahrbuch für Mineralogie Abhandlungen, 190: 123-195.
DILL, H.G., BUZATU, A., BALABAN, S.-I. and RÜSENBERG, K. A. (2023) A mineralogical-geomorphological terrain analysis of hotspot volcanic islands -The missing link between carbonatite- and pegmatite Nb-F-Zr-Li-Be-bearing REE deposits and new tools for their exploration (Canary Islands Archipelago, Spain).- Ore Geology Reviews: (open access)
DILL, H.G and RÜSENBERG, K. A. (2023) Marker minerals in volcanics and xenoliths—An approach to
categorize the inferred magmatic rocks underneath the present-day volcanic landscape of Tenerife, Spain (NW African Rare Mineral Province).- Minerals: 2023, 13, 1410. 1-56, https://doi.org/10.3390/min13111410 (open access)
For the hypogene and supergene origin of APS minerals you will find more than enough papers, considering the host rocks, physical-chemical relations etc. on a worldwide basis and from the periglacial to the tropical humid climate zones and from diagenesis to metamorphic representatives of this mineral group
All papers are available on request and can be downloaded from the Researchgate server.
With kind regards
HGD
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