Pub Date : 2014-09-04DOI: 10.2478/s13533-012-0197-5
V. Almeida, V. Janasi, D. P. Svisero, F. Nannini
Alkali-bearing Ti oxides were identified in mantle xenoliths enclosed in kimberlite-like rocks from Limeira 1 alkaline intrusion from the Alto Paranaíba Igneous Province, southeastern Brazil. The metasomatic mineral assemblages include mathiasite-loveringite and priderite associated with clinopyroxene, phlogopite, ilmenite and rutile. Mathiasite-loveringite (55–60 wt.% TiO2; 5.2–6.7 wt.% ZrO2) occurs in peridotite xenoliths rimming chromite (∼50 wt.% Cr2O3) and subordinate ilmenite (12–13.4 wt.% MgO) in double reaction rim coronas. Priderite (Ba/(K+Ba)< 0.05) occurs in phlogopite-rich xenoliths as lamellae within Mg-ilmenite (8.4–9.8 wt.% MgO) or as intergrowths in rutile crystals that may be included in sagenitic phlogopite. Mathiasite-loveringite was formed by reaction of peridotite primary minerals with alkaline melts. The priderite was formed by reaction of peridotite minerals with ultrapotassic melts. Disequilibrium textures and chemical zoning of associated minerals suggest that the metasomatic reactions responsible for the formation of the alkali-bearing Ti oxides took place shortly prior the entrainment of the xenoliths in the host magma, and is not connected to old (Proterozoic) mantle enrichment events.
{"title":"Mathiasite-loveringite and priderite in mantle xenoliths from the Alto Paranaíba Igneous Province, Brazil: genesis and constraints on mantle metasomatism","authors":"V. Almeida, V. Janasi, D. P. Svisero, F. Nannini","doi":"10.2478/s13533-012-0197-5","DOIUrl":"https://doi.org/10.2478/s13533-012-0197-5","url":null,"abstract":"Alkali-bearing Ti oxides were identified in mantle xenoliths enclosed in kimberlite-like rocks from Limeira 1 alkaline intrusion from the Alto Paranaíba Igneous Province, southeastern Brazil. The metasomatic mineral assemblages include mathiasite-loveringite and priderite associated with clinopyroxene, phlogopite, ilmenite and rutile. Mathiasite-loveringite (55–60 wt.% TiO2; 5.2–6.7 wt.% ZrO2) occurs in peridotite xenoliths rimming chromite (∼50 wt.% Cr2O3) and subordinate ilmenite (12–13.4 wt.% MgO) in double reaction rim coronas. Priderite (Ba/(K+Ba)< 0.05) occurs in phlogopite-rich xenoliths as lamellae within Mg-ilmenite (8.4–9.8 wt.% MgO) or as intergrowths in rutile crystals that may be included in sagenitic phlogopite. Mathiasite-loveringite was formed by reaction of peridotite primary minerals with alkaline melts. The priderite was formed by reaction of peridotite minerals with ultrapotassic melts. Disequilibrium textures and chemical zoning of associated minerals suggest that the metasomatic reactions responsible for the formation of the alkali-bearing Ti oxides took place shortly prior the entrainment of the xenoliths in the host magma, and is not connected to old (Proterozoic) mantle enrichment events.","PeriodicalId":49092,"journal":{"name":"Central European Journal of Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80155476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-04DOI: 10.2478/s13533-012-0190-z
F. Stoppa, M. Schiazza
Melilitolites of the Umbria Latium Ultra-alkaline District display a complete crystallisation sequence of peculiar, late-stage mineral phases and hydrothermal/cement minerals, analogous to fractionated mineral associations from the Kola Peninsula. This paper summarises 20 years of research which has resulted in the identification of a large number of mineral species, some very rare or completely new and some not yet classified. The progressive increasing alkalinity of the residual liquid allowed the formation of Zr-Ti phases and further delhayelitemacdonaldite mineral crystallisation in the groundmass. The presence of leucite and kalsilite in the igneous assemblage is unusual and gives a kamafugitic nature to the rocks. Passage to non-igneous temperatures (T<600 °C) is marked by the metastable reaction and formation of a rare and complex zeolite association (T<300 °C). Circulation of low-temperature (T<100 °C) K-Ca-Ba-CO2-SO2-fluids led to the precipitation of sulphates and hydrated and/or hydroxylated silicate-sulphate-carbonates. As a whole, this mineral assemblage can be considered typical of ultra-alkaline carbonatitic rocks.
Umbria Latium超碱性地区的千英石显示出完整的特殊晚期矿物相和热液/水泥矿物结晶序列，类似于科拉半岛的分选矿物组合。本文总结了20年来的研究成果，发现了大量矿物，有些非常罕见或全新，有些尚未分类。残余液体碱度的逐渐增加使得Zr-Ti相的形成和进一步的delhayelitemacdonaldite矿物在地块中的结晶成为可能。在火成岩组合中，白闪石和千硅石的存在是不寻常的，使岩石具有卡马辉石的性质。过渡到非火成岩温度(T<600°C)的标志是亚稳反应和形成罕见而复杂的沸石缔合物(T<300°C)。低温(T<100°C) k -ca - ba - co2 - so2流体循环导致硫酸盐和水合和/或羟基化硅酸盐-硫酸盐-碳酸盐的沉淀。整体而言，该矿物组合可视为典型的超碱性碳酸盐岩。
{"title":"Extreme chemical conditions of crystallisation of Umbrian Melilitolites and wealth of rare, late stage/hydrothermal minerals","authors":"F. Stoppa, M. Schiazza","doi":"10.2478/s13533-012-0190-z","DOIUrl":"https://doi.org/10.2478/s13533-012-0190-z","url":null,"abstract":"Melilitolites of the Umbria Latium Ultra-alkaline District display a complete crystallisation sequence of peculiar, late-stage mineral phases and hydrothermal/cement minerals, analogous to fractionated mineral associations from the Kola Peninsula. This paper summarises 20 years of research which has resulted in the identification of a large number of mineral species, some very rare or completely new and some not yet classified. The progressive increasing alkalinity of the residual liquid allowed the formation of Zr-Ti phases and further delhayelitemacdonaldite mineral crystallisation in the groundmass. The presence of leucite and kalsilite in the igneous assemblage is unusual and gives a kamafugitic nature to the rocks. Passage to non-igneous temperatures (T<600 °C) is marked by the metastable reaction and formation of a rare and complex zeolite association (T<300 °C). Circulation of low-temperature (T<100 °C) K-Ca-Ba-CO2-SO2-fluids led to the precipitation of sulphates and hydrated and/or hydroxylated silicate-sulphate-carbonates. As a whole, this mineral assemblage can be considered typical of ultra-alkaline carbonatitic rocks.","PeriodicalId":49092,"journal":{"name":"Central European Journal of Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82455373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-04DOI: 10.2478/s13533-012-0187-7
Y. Singh, G. Nagendra Babu, R. Viswanathan, M. Sai Baba, A. Rai, P. S. Parihar
The authors report the results of X-ray diffraction (XRD) and geochemical studies on bastnaesites (lanthanum cerium fluoro-carbonate) hosted in alkali Kanigiri Granite of the Prakasam district in Andhra Pradesh, India. The XRD pattern of the investigated bastnaesite displays sharply-defined reflections. The observed d-spacings of the bastnaesite are in very close agreement with those published for bastnaesite standard in International Centre for Diffraction Data (ICDD) Card No. 11–340. The calculated unit cell parameters (ao; co) and unit cell volume (V) of the studied bastnaesite (ao 7.1301–7.1413 Å, co 9.7643–9.7902Å and V 429.8940–432.3875 Å3) are almost equal to values published for bastnaesite standard (co 7.1290 Å, co 9.7744 Å and V 430.19 Å3) in the relevant data card.Geochemical data of bastnaesite reveals high content of Ce (mean 27.22%) followed by La (mean 16.82%), Nd (mean 6.12%) and Pr (mean 1.91%). Compared to light REE (LREE) content (mean 437165 ppm), heavy REE (HREE) content (mean 5867 ppm) is drastically low, with unusually high LREE/HREE ratio (mean 80). The chondrite-normalised plot also exhibits drastic enrichment of LREE relative to HREE with pronounced negative Euanomaly (mean Eu/Eu* = 0.15). High (LREE)N / (HREE)N, (La/Lu)N, (La/Yb)N and (Ce/Yb)N ratios reveal higher fractionation of LREE relative to HREE. The rare earth element (REE) contents of the studied bastnaesite are very close to REE contents of bastnaesite hosted in alkali syenite from Madagascar. The presence of bastnaesite in Kanigiri Granite and soils derived from it enhances the scope of further exploration for bastnaesite in several bodies of alkaline rocks and alkali granitoids present along the eastern margins of the Cuddapah basin, Andhra Pradesh.
{"title":"X-ray crystallography and mineral chemistry of bastnaesite from Kanigiri granite, Prakasam district, Andhra Pradesh, India","authors":"Y. Singh, G. Nagendra Babu, R. Viswanathan, M. Sai Baba, A. Rai, P. S. Parihar","doi":"10.2478/s13533-012-0187-7","DOIUrl":"https://doi.org/10.2478/s13533-012-0187-7","url":null,"abstract":"The authors report the results of X-ray diffraction (XRD) and geochemical studies on bastnaesites (lanthanum cerium fluoro-carbonate) hosted in alkali Kanigiri Granite of the Prakasam district in Andhra Pradesh, India. The XRD pattern of the investigated bastnaesite displays sharply-defined reflections. The observed d-spacings of the bastnaesite are in very close agreement with those published for bastnaesite standard in International Centre for Diffraction Data (ICDD) Card No. 11–340. The calculated unit cell parameters (ao; co) and unit cell volume (V) of the studied bastnaesite (ao 7.1301–7.1413 Å, co 9.7643–9.7902Å and V 429.8940–432.3875 Å3) are almost equal to values published for bastnaesite standard (co 7.1290 Å, co 9.7744 Å and V 430.19 Å3) in the relevant data card.Geochemical data of bastnaesite reveals high content of Ce (mean 27.22%) followed by La (mean 16.82%), Nd (mean 6.12%) and Pr (mean 1.91%). Compared to light REE (LREE) content (mean 437165 ppm), heavy REE (HREE) content (mean 5867 ppm) is drastically low, with unusually high LREE/HREE ratio (mean 80). The chondrite-normalised plot also exhibits drastic enrichment of LREE relative to HREE with pronounced negative Euanomaly (mean Eu/Eu* = 0.15). High (LREE)N / (HREE)N, (La/Lu)N, (La/Yb)N and (Ce/Yb)N ratios reveal higher fractionation of LREE relative to HREE. The rare earth element (REE) contents of the studied bastnaesite are very close to REE contents of bastnaesite hosted in alkali syenite from Madagascar. The presence of bastnaesite in Kanigiri Granite and soils derived from it enhances the scope of further exploration for bastnaesite in several bodies of alkaline rocks and alkali granitoids present along the eastern margins of the Cuddapah basin, Andhra Pradesh.","PeriodicalId":49092,"journal":{"name":"Central European Journal of Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88613291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-04DOI: 10.2478/s13533-012-0195-7
Rosana Peporine Lopes, M. Ulbrich, H. Ulbrich
Fernando de Noronha archipelago presents an older Remédios Formation with subvolcanic intrusions, belonging to two different alkaline series, the sodic (undersaturated: basanites, tephrites, essexites, tephriphonolites, phonolites), and potassic ones (mildly undersaturated to silicic, with alkali basalts, basaltic trachyandesites, trachyandesites, trachytes), and lamprophyres. The upper Quixaba Formation presents nephelinite flows and basanites. A third minor unit, São José, is constituted by basanites carrying mantle xenoliths. Magnesian olivines occur in the Remédios basanites and alkali basalts, and in nephelinites. Melilites are present as groundmass grains in melilite melanephelinites (MEM). Clinopyroxenes (cpx) are mostly salites to titaniferous salites (Remédios sodic series), grading into aegirines in the differentiated aphyric phonolites. Cpx in the lamprophyres show disequilibrium textures. In the Quixaba flows, cpx are salites, enriched in Mg (especially in MEM). Amphiboles, remarkably, are common in tephriphonolites and phonolites and in basaltic trachyandesites, sometimes with disequilibrum zoning textures, and a conspicuous phase in lamprophyres. Dark micas are present as groundmass plates in MEM, OLM and PYM (olivine and pyroxene melanephelinites), with compositional variety (enriched in Ti, Ba, Sr) depending on the composition of the parent rock; BaO can be as high as 16–19%. Feldspars crystallize as calcic plagioclases, sanidines and anorthoclases, depending on the rock types, as phenocrysts and in groundmass, both in Quixaba and Remédios rocks; they are absent in nephelinites. Nephelines are found in Remédios sodic series types and Quixaba rocks. Haüyne and noseane are rarely observed in Remédios rocks.
Fernando de Noronha群岛呈现一个较老的remsamdios组，含次火山侵入，属于两个不同的碱性系列，即钠质(不饱和:玄武岩、软质岩、铁质岩、软纹岩、空纹岩)和钾质(轻度不饱和至硅质，含碱性玄武岩、玄武岩粗质山岩、粗质山岩、粗质山岩)和煌斑岩。上基沙巴组发育辉石流和玄武岩。第三个小单元，o jos，由携带地幔捕虏体的玄武岩组成。镁质橄榄石赋存于雷姆萨迪奥斯玄武岩、碱玄武岩和钠辉石中。melmelite melepelites (MEM)中melmelite melepelites (MEM)以基质颗粒的形式存在。斜辉石岩(cpx)多为盐岩至含钛盐岩(remdios sodic系列)，在已分化的葡萄质phonolites中分级为炔类。煌斑岩中的Cpx呈不平衡结构。在Quixaba流中，cpx为盐岩，富镁(特别是MEM)。值得注意的是，角闪石在绢纹岩、绢纹岩和玄武质粗面岩中很常见，有时具有不平衡分带结构，在煌斑岩中有一个明显的阶段。暗云母在MEM、OLM和PYM(橄榄石和辉石黑绿斑岩)中以地质体板块形式存在，其成分随母岩组成的不同而变化(富Ti、Ba、Sr);BaO可高达16-19%。长石结晶为钙斜长石、钾长石和斜长石，视岩石类型而定，在基赫巴和雷姆萨迪奥斯岩石中均为斑晶和地质体;它们在钠辉石中不存在。在remsamdios钠质系列类型和Quixaba岩石中发现了霞石。在remsamdios岩石中很少观察到hayne和noseane。
{"title":"The volcanic-subvolcanic rocks of the fernando de noronha archipelago, southern atlantic ocean: Mineral chemistry","authors":"Rosana Peporine Lopes, M. Ulbrich, H. Ulbrich","doi":"10.2478/s13533-012-0195-7","DOIUrl":"https://doi.org/10.2478/s13533-012-0195-7","url":null,"abstract":"Fernando de Noronha archipelago presents an older Remédios Formation with subvolcanic intrusions, belonging to two different alkaline series, the sodic (undersaturated: basanites, tephrites, essexites, tephriphonolites, phonolites), and potassic ones (mildly undersaturated to silicic, with alkali basalts, basaltic trachyandesites, trachyandesites, trachytes), and lamprophyres. The upper Quixaba Formation presents nephelinite flows and basanites. A third minor unit, São José, is constituted by basanites carrying mantle xenoliths. Magnesian olivines occur in the Remédios basanites and alkali basalts, and in nephelinites. Melilites are present as groundmass grains in melilite melanephelinites (MEM). Clinopyroxenes (cpx) are mostly salites to titaniferous salites (Remédios sodic series), grading into aegirines in the differentiated aphyric phonolites. Cpx in the lamprophyres show disequilibrium textures. In the Quixaba flows, cpx are salites, enriched in Mg (especially in MEM). Amphiboles, remarkably, are common in tephriphonolites and phonolites and in basaltic trachyandesites, sometimes with disequilibrum zoning textures, and a conspicuous phase in lamprophyres. Dark micas are present as groundmass plates in MEM, OLM and PYM (olivine and pyroxene melanephelinites), with compositional variety (enriched in Ti, Ba, Sr) depending on the composition of the parent rock; BaO can be as high as 16–19%. Feldspars crystallize as calcic plagioclases, sanidines and anorthoclases, depending on the rock types, as phenocrysts and in groundmass, both in Quixaba and Remédios rocks; they are absent in nephelinites. Nephelines are found in Remédios sodic series types and Quixaba rocks. Haüyne and noseane are rarely observed in Remédios rocks.","PeriodicalId":49092,"journal":{"name":"Central European Journal of Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72568268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-04DOI: 10.2478/s13533-012-0196-6
P. Comin-Chiaramonti, C. B. Gomes, Â. Min, E. Ruberti, V. Girardi, F. Slejko, R. Neder, F. E. Pinho
The Planalto da Serra igneous rocks form plugs, necks and dykes of carbonate-rich ultramafic lamprophyres (aillikites and glimmerites with kamafugitic affinity) and carbonatites (alvikites and beforsites). Phlogopite and/or tetraphlogopite, diopside and melanitic garnet are restricted to aillikitic rock-types, whereas pyroclore occurs only in carbonatites. Aillikites and carbonatites are altered to hydrotermalites, having chlorite and serpentine as dominant minerals. Planalto da Serra igneous rock association has kamafugitic affinity (i.e. effusive, ultrapotassic. High LREE/HREE fractionation, incompatible elements data and Sr-Nd isotopes, suggest that the K-ultramafic alkaline and carbonatite rocks originated from a variably metasomatized mantle source enriched in radiogenic Sr. Crustal contamination is negligible or absent. Age values of 600 Ma rule out the geochronological relationship between the investigated intrusions and the Mesozoic alkaline bodies from the Azimuth 125° lineament. The TDM model ages allow to conclude that Planalto da Serra magma is derived from the partial melting of a mantle source metasomatised by K-rich carbonatated melt during the Early to Late Neoproterozoic. On the basis of alkaline magmatism repetitions at 600 Ma and 90–80 Ma we question the subsistence of a stationary mantle plume for so long time.
Planalto da Serra火成岩形成了富含碳酸盐的超镁铁质煌斑岩(与马马辉石有亲和关系的亮辉岩和闪辉岩)和碳酸盐(岩屑岩和闪辉岩)的塞状、颈状和脉状。辉云母和/或四辉云母、透辉石和黑质石榴石仅存在于无晶质岩石类型中，而辉绿石仅存在于碳酸盐岩中。爱丽石和碳酸盐蚀变为水温石，绿泥石和蛇纹石是主要矿物。Planalto da Serra火成岩组合具有kamafutic亲和性(即热流、超经典)。高LREE/HREE分异、不相容元素数据和Sr-Nd同位素表明，钾基超镁质碱性和碳酸盐岩起源于富含放射性成因sr的变交代地幔源，地壳污染可以忽略或不存在。600 Ma的年龄值排除了所研究的侵入体与方位角125°剖面中生代碱性体的年代学关系。TDM模型年龄表明，Planalto da Serra岩浆来源于新元古代早期至晚期富钾碳酸化熔融交代的地幔源的部分熔融。在600 Ma和90 ~ 80 Ma碱性岩浆活动的基础上，我们对静止地幔柱在这么长时间内的存在提出了质疑。
{"title":"Petrology of potassic alkaline ultramafic and carbonatitic rocks from Planalto da Serra (Mato Grosso State), Brazil","authors":"P. Comin-Chiaramonti, C. B. Gomes, Â. Min, E. Ruberti, V. Girardi, F. Slejko, R. Neder, F. E. Pinho","doi":"10.2478/s13533-012-0196-6","DOIUrl":"https://doi.org/10.2478/s13533-012-0196-6","url":null,"abstract":"The Planalto da Serra igneous rocks form plugs, necks and dykes of carbonate-rich ultramafic lamprophyres (aillikites and glimmerites with kamafugitic affinity) and carbonatites (alvikites and beforsites). Phlogopite and/or tetraphlogopite, diopside and melanitic garnet are restricted to aillikitic rock-types, whereas pyroclore occurs only in carbonatites. Aillikites and carbonatites are altered to hydrotermalites, having chlorite and serpentine as dominant minerals. Planalto da Serra igneous rock association has kamafugitic affinity (i.e. effusive, ultrapotassic. High LREE/HREE fractionation, incompatible elements data and Sr-Nd isotopes, suggest that the K-ultramafic alkaline and carbonatite rocks originated from a variably metasomatized mantle source enriched in radiogenic Sr. Crustal contamination is negligible or absent. Age values of 600 Ma rule out the geochronological relationship between the investigated intrusions and the Mesozoic alkaline bodies from the Azimuth 125° lineament. The TDM model ages allow to conclude that Planalto da Serra magma is derived from the partial melting of a mantle source metasomatised by K-rich carbonatated melt during the Early to Late Neoproterozoic. On the basis of alkaline magmatism repetitions at 600 Ma and 90–80 Ma we question the subsistence of a stationary mantle plume for so long time.","PeriodicalId":49092,"journal":{"name":"Central European Journal of Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78459871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-04DOI: 10.2478/s13533-012-0191-y
M. Sadiq, A. Ranjith, R. K. Umrao
The Early Cretaceous Sung Valley Ultramafic-Alkaline-Carbonatite (SUAC) complex intruded the Proterozoic Shillong Group of rocks and located in the East Khasi Hills and West Jaintia Hills districts of Meghalaya. The SUAC complex is a bowl-shaped depression covering an area of about 26 km2 and is comprised serpentinised peridotite forming the core of the complex with pyroxenite rim. Alkaline rocks are dominantly ijolite and nepheline syenite, occur as ring-shaped bodies as well as dykes. Carbonatites are, the youngest intrusive phase in the complex, where they form oval-shaped bodies, small dykes and veins. During the course of large scale mapping in parts of the Sung Valley complex, eleven carbonatite bodies were delineated. These isolated carbonatite bodies have a general NW-SE and E-W trend and vary from 20–125 m long and 10–40 m wide. Calcite carbonatite is the dominant variety and comprises minor dolomite and apatite and accessory olivine, magnetite, pyrochlore and phlogopite. The REE-bearing minerals identified in the Sung Valley carbonatites are bastnäsite-(Ce), ancylite-(Ce), belovite-(Ce), britholite-(Ce) and pyrochlore that are associated with calcite and apatite. The presence of REE carbonates and phosphates associated with REE-Nb bearing pyrochlore enhances the economic potential of the Sung Valley carbonatites. Trace-element geochemistry also reveals an enrichment of LREEs in the carbonatites and average ΣREE value of 0.102% in 26 bed rock samples. Channel samples shows average ΣREE values of 0.103 wt%. Moreover, few samples from carbonatite bodies has indicated relatively higher values for Sn, Hf, Ta and U. Since the present study focuses surface evaluation of REE, therefore, detailed subsurface exploration will be of immense help to determine the REE and other associated mineralization of the Sung Valley carbonatite prospect.
{"title":"REE mineralization in the carbonatites of the sung valley ultramafic-alkaline-carbonatite complex, Meghalaya, India","authors":"M. Sadiq, A. Ranjith, R. K. Umrao","doi":"10.2478/s13533-012-0191-y","DOIUrl":"https://doi.org/10.2478/s13533-012-0191-y","url":null,"abstract":"The Early Cretaceous Sung Valley Ultramafic-Alkaline-Carbonatite (SUAC) complex intruded the Proterozoic Shillong Group of rocks and located in the East Khasi Hills and West Jaintia Hills districts of Meghalaya. The SUAC complex is a bowl-shaped depression covering an area of about 26 km2 and is comprised serpentinised peridotite forming the core of the complex with pyroxenite rim. Alkaline rocks are dominantly ijolite and nepheline syenite, occur as ring-shaped bodies as well as dykes. Carbonatites are, the youngest intrusive phase in the complex, where they form oval-shaped bodies, small dykes and veins. During the course of large scale mapping in parts of the Sung Valley complex, eleven carbonatite bodies were delineated. These isolated carbonatite bodies have a general NW-SE and E-W trend and vary from 20–125 m long and 10–40 m wide. Calcite carbonatite is the dominant variety and comprises minor dolomite and apatite and accessory olivine, magnetite, pyrochlore and phlogopite. The REE-bearing minerals identified in the Sung Valley carbonatites are bastnäsite-(Ce), ancylite-(Ce), belovite-(Ce), britholite-(Ce) and pyrochlore that are associated with calcite and apatite. The presence of REE carbonates and phosphates associated with REE-Nb bearing pyrochlore enhances the economic potential of the Sung Valley carbonatites. Trace-element geochemistry also reveals an enrichment of LREEs in the carbonatites and average ΣREE value of 0.102% in 26 bed rock samples. Channel samples shows average ΣREE values of 0.103 wt%. Moreover, few samples from carbonatite bodies has indicated relatively higher values for Sn, Hf, Ta and U. Since the present study focuses surface evaluation of REE, therefore, detailed subsurface exploration will be of immense help to determine the REE and other associated mineralization of the Sung Valley carbonatite prospect.","PeriodicalId":49092,"journal":{"name":"Central European Journal of Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79496135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-04DOI: 10.2478/s13533-012-0186-8
T. Giovanardi, M. Mazzucchelli, A. Zanetti, A. Langone, M. Tiepolo, A. Cipriani
Phlogopite-bearing lithologies are the main constituent of the Phlogopite-Peridotite unit of the Finero sequence and the result of pervasive migration of metasomatizing melts/fluids. Conversely, the presence of phlogopite within the associated Finero Mafic Complex, a mafic-ultramafic pluton intruded into the metamorphic basement of the Adria plate, is mentioned in literature as rare. Recent detailed fieldwork has evidenced the presence of two distinct phlogopite-rich ultramafic lithologies within the Amphibole-Peridotite unit of the Finero Mafic Complex, where phlogopite is always associated with amphibole. Field and petrographic features of these occurrences, as well as major- and trace-element mineral chemistry, are here presented to i) place constraints on the nature of the parent melt from which they have been generated and ii) to address their relationship with the other lithologies of the Finero Complex. We find that these rocks were formed by late melt migrations along shear zones under high-T conditions. The geochemical affinity of these lithologies is different to the tholeiitic-transitional affinity reported in literature for the Finero Mafic Complex. The enrichment in LREE, Th, U and Sr of the associated amphibole possibly suggests that these phlogopite-bearing lithologies are genetically related to the metasomatic events that have affected the Finero mantle massif.
{"title":"Occurrence of phlogopite in the Finero Mafic layered complex","authors":"T. Giovanardi, M. Mazzucchelli, A. Zanetti, A. Langone, M. Tiepolo, A. Cipriani","doi":"10.2478/s13533-012-0186-8","DOIUrl":"https://doi.org/10.2478/s13533-012-0186-8","url":null,"abstract":"Phlogopite-bearing lithologies are the main constituent of the Phlogopite-Peridotite unit of the Finero sequence and the result of pervasive migration of metasomatizing melts/fluids. Conversely, the presence of phlogopite within the associated Finero Mafic Complex, a mafic-ultramafic pluton intruded into the metamorphic basement of the Adria plate, is mentioned in literature as rare. Recent detailed fieldwork has evidenced the presence of two distinct phlogopite-rich ultramafic lithologies within the Amphibole-Peridotite unit of the Finero Mafic Complex, where phlogopite is always associated with amphibole. Field and petrographic features of these occurrences, as well as major- and trace-element mineral chemistry, are here presented to i) place constraints on the nature of the parent melt from which they have been generated and ii) to address their relationship with the other lithologies of the Finero Complex. We find that these rocks were formed by late melt migrations along shear zones under high-T conditions. The geochemical affinity of these lithologies is different to the tholeiitic-transitional affinity reported in literature for the Finero Mafic Complex. The enrichment in LREE, Th, U and Sr of the associated amphibole possibly suggests that these phlogopite-bearing lithologies are genetically related to the metasomatic events that have affected the Finero mantle massif.","PeriodicalId":49092,"journal":{"name":"Central European Journal of Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2478/s13533-012-0186-8","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72368843","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-04DOI: 10.2478/s13533-012-0192-x
R. Duraiswami, Tahira N. Shaikh
The Kangankunde Carbonatite Complex from the Cretaceous Chilwa Alkaline Province in southern Malawi contains ankeritic and siderite carbonatite that are affected by late stage remobilisation by a carbothermal or hydrothermal fluid. The coarse pegmatitic siderite carbonatite that hosts exotic minerals like monazite, synchysite, bastnasite, strontianite and apatite in vugs and cavities constitutes some of the richest rare earth deposits in the world. Besides these minerals, our studies reveal the presence of collinsite and aragonite from the siderite carbonatite. Fine drusy monazites are seen as overgrowths on thin veinlets of siderite within the rare earth mineralised zones. We present unambiguous SEM-based surface textural evidence such as presence of dissolution-corrosion features like etching along cleavage, solution channels, solution pits, sinstered scaly surface, etc. along with rare earth mineralisation that suggests the exotic minerals in the siderite carbonatite did not crystallise from carbonate magma and are a result of sub-solidus processes involving carbonatite-derived fluids. We believe that the monazite-synchysitebastnasite-strontianite-collinsite assemblages were formed by juvenile post magmatic hydrothermal alteration of pre-existing carbonatite by a complex CO2-rich and alkali chloride-carbonate-bearing fluid at ∼250 to 400°C in an open system. This late ‘magmatic’ to ‘hydrothermal’ activity was responsible for considerable changes in rock texture and mineralogy leading to mobility of rare earth elements during fluid-rock interaction. These aspects need to be properly understood and addressed before using trace and rare earth element (REE) geochemistry in interpreting carbonatite genesis.
{"title":"Fluid-rock interaction in the Kangankunde Carbonatite Complex, Malawi: SEM based evidence for late stage pervasive hydrothermal mineralisation","authors":"R. Duraiswami, Tahira N. Shaikh","doi":"10.2478/s13533-012-0192-x","DOIUrl":"https://doi.org/10.2478/s13533-012-0192-x","url":null,"abstract":"The Kangankunde Carbonatite Complex from the Cretaceous Chilwa Alkaline Province in southern Malawi contains ankeritic and siderite carbonatite that are affected by late stage remobilisation by a carbothermal or hydrothermal fluid. The coarse pegmatitic siderite carbonatite that hosts exotic minerals like monazite, synchysite, bastnasite, strontianite and apatite in vugs and cavities constitutes some of the richest rare earth deposits in the world. Besides these minerals, our studies reveal the presence of collinsite and aragonite from the siderite carbonatite. Fine drusy monazites are seen as overgrowths on thin veinlets of siderite within the rare earth mineralised zones. We present unambiguous SEM-based surface textural evidence such as presence of dissolution-corrosion features like etching along cleavage, solution channels, solution pits, sinstered scaly surface, etc. along with rare earth mineralisation that suggests the exotic minerals in the siderite carbonatite did not crystallise from carbonate magma and are a result of sub-solidus processes involving carbonatite-derived fluids. We believe that the monazite-synchysitebastnasite-strontianite-collinsite assemblages were formed by juvenile post magmatic hydrothermal alteration of pre-existing carbonatite by a complex CO2-rich and alkali chloride-carbonate-bearing fluid at ∼250 to 400°C in an open system. This late ‘magmatic’ to ‘hydrothermal’ activity was responsible for considerable changes in rock texture and mineralogy leading to mobility of rare earth elements during fluid-rock interaction. These aspects need to be properly understood and addressed before using trace and rare earth element (REE) geochemistry in interpreting carbonatite genesis.","PeriodicalId":49092,"journal":{"name":"Central European Journal of Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76884269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-04DOI: 10.2478/s13533-012-0194-8
L. G. Gwalani, C. B. Gomes
Awarded with the degrees of a B.Sc. in Human Sciences (1961) and a Ph.D. in Petrology (1967) by the University of Trieste in Italy, Piero Comin-Chiaramonti (Figure 1) eventually spent most of his academic career in this institution, holding the positions of Assistant Professor (1967-1983) and Associated Professor (1983-1986). He was inducted as a full Professor in the Faculty of Sciences of the University of Palermo in 1986, where he remained until assigned to the Faculty of Engineering of the University of Trieste in 1993. There he initially worked as a Professor of Petrology (Faculty of Sciences) and later as a Professor of Environmental Geology and Environmental Geochemistry (Faculty of Enginnering). It was through the efforts and innovations of Professor Comin-Chiaramonti, both in the teaching process and in the development of research facilities, that the Engineering Department of the University of Trieste has ∗E-mail: lgwalani@gmail.com, http://lggwalani.jimdo.com/ †E-mail: cgomes@usp.br today attained world-wide recognition. In 2009, he was granted the award of "Eminent Scientist" by the Faculty of Engineering, and retired from active service in the following year. He is now devoting part of his time to research activites. With his remarkable skill, greater efficiency, resolute determination and untiring efforts, Professor CominChiaramonti nursed and actively participated as a member and critical reviewer of several international scientific journals and as a consultant reviewer of some organizations such as COFIN (Co-Financial support from the Italian Ministry for University and Scientific Research), CNR (National Research Council, Italy), MIUR (Ministry of University and Research) and the Georgian National Science Foundation. We take this opportunity to assure him that we shall keep his example always before us "duty before self" and shall do everything possible to keep up the progress he has initiated. Professor Comin-Chiaramonti has always been a strong proponent of international collaboration in research and the transfer of knowledge and skills in geosciences. He
皮耶罗·科明-基亚拉蒙蒂(Piero Comin-Chiaramonti)在意大利的里雅斯特大学获得了人文科学学士学位(1961年)和岩石学博士学位(1967年)，他的大部分学术生涯都在这所大学度过，担任助理教授(1967-1983年)和副教授(1983-1986年)。1986年，他被任命为巴勒莫大学(University of Palermo)理学院的正教授，1993年被分配到的里雅斯特大学(University of Trieste)工程学院。在那里，他最初担任岩石学教授(科学学院)，后来担任环境地质学和环境地球化学教授(工程学院)。正是通过Comin-Chiaramonti教授在教学过程和研究设施发展方面的努力和创新，的里雅斯特大学工程系今天获得了世界范围的认可。2009年获工程学院“杰出科学家”称号，次年退出现役。他现在把部分时间用于研究活动。CominChiaramonti教授以其卓越的技能、更高的效率、坚定的决心和不懈的努力，积极参与并担任多个国际科学期刊的成员和重要审稿人，并担任COFIN(意大利大学和科学研究部联合财政支持)、CNR(意大利国家研究委员会)等组织的顾问审稿人。大学和研究部和格鲁吉亚国家科学基金会。我们借此机会向他保证，我们将永远以他为榜样，“责任高于自我”，并尽一切可能保持他所开创的进步。Comin-Chiaramonti教授一直是地球科学研究和国际合作以及知识和技能转移的坚定支持者。他
{"title":"Preface — A special issue (Part-I): Mafic-ultramafic rocks and alkaline-carbonatitic magmatism and associated hydrothermal mineralization — Dedication to Piero Comin-Chiaramonti","authors":"L. G. Gwalani, C. B. Gomes","doi":"10.2478/s13533-012-0194-8","DOIUrl":"https://doi.org/10.2478/s13533-012-0194-8","url":null,"abstract":"Awarded with the degrees of a B.Sc. in Human Sciences (1961) and a Ph.D. in Petrology (1967) by the University of Trieste in Italy, Piero Comin-Chiaramonti (Figure 1) eventually spent most of his academic career in this institution, holding the positions of Assistant Professor (1967-1983) and Associated Professor (1983-1986). He was inducted as a full Professor in the Faculty of Sciences of the University of Palermo in 1986, where he remained until assigned to the Faculty of Engineering of the University of Trieste in 1993. There he initially worked as a Professor of Petrology (Faculty of Sciences) and later as a Professor of Environmental Geology and Environmental Geochemistry (Faculty of Enginnering). It was through the efforts and innovations of Professor Comin-Chiaramonti, both in the teaching process and in the development of research facilities, that the Engineering Department of the University of Trieste has ∗E-mail: lgwalani@gmail.com, http://lggwalani.jimdo.com/ †E-mail: cgomes@usp.br today attained world-wide recognition. In 2009, he was granted the award of \"Eminent Scientist\" by the Faculty of Engineering, and retired from active service in the following year. He is now devoting part of his time to research activites. With his remarkable skill, greater efficiency, resolute determination and untiring efforts, Professor CominChiaramonti nursed and actively participated as a member and critical reviewer of several international scientific journals and as a consultant reviewer of some organizations such as COFIN (Co-Financial support from the Italian Ministry for University and Scientific Research), CNR (National Research Council, Italy), MIUR (Ministry of University and Research) and the Georgian National Science Foundation. We take this opportunity to assure him that we shall keep his example always before us \"duty before self\" and shall do everything possible to keep up the progress he has initiated. Professor Comin-Chiaramonti has always been a strong proponent of international collaboration in research and the transfer of knowledge and skills in geosciences. He","PeriodicalId":49092,"journal":{"name":"Central European Journal of Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81366573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-09-04DOI: 10.2478/s13533-012-0185-9
M. Dora, H. Singh, A. Kundu, M. Shareef, K. Randive, S. Joshi
This paper reports the occurrence of Tsumoite (a bismuth telluride) in the Heti Cu-Ni-PGM prospect, Gondpipri mafic-ultramafic complex, Central India. The Gondpipri complex consists of several tectonically dismembered gabbronorite-gabbro-anorthositic gabbro — olivine gabbro -websterite disposed in ∼10 km long tonalite-trondhjemitegranodiorite (TTG) and charnockite-enderbite suite of rocks. The mineralization occurs in the sulphide zone hosted by gabbro variants. The host rocks have been deformed and metamorphosed to granulite grade and subjected to various degrees of hydrothermal alteration. The mineralization comprises chalcopyrite, pentlandite, pyrrhotite, cubanite, millerite, and pyrite. In addition to these, occur (1) tsumoite (2) PGM in the form of moncheite, merenskyite, Pd-mellonite, and Pt-Pd-Te-Bi-Fe-S alloy.The present study indicates that the mineralization occurs in two stages related to: (i) magmatic and (ii) hydrothermal remobilization and transport of Cu-rich sulphides, tsumoite and PGM, and their re-deposition in hydrosilicate alteration zones. It is possible that the mineralization at Heti formed at different stages of bismuth activity under variable fS2, T, and fTe2 conditions due to change in total concentration of Te and S and /or cooling. Since the role of S is limited, Te and cooling are important factor influencing mineralogy and composition of tsumoite and associated mineralization. Mineralization occurs in two different modes of occurrences. The early mineralisation occur as blebs, specks and dissemination of sulphides, viz. pyrrhotite, chalcopyrite, pentlandite and minor pyrite ± PGM, whereas later mineralisation occur as stringers, minor veins of sulphides viz. pyrite, millerite, cubanite, sijenite, tsumoite and ± PGM.Mineral assemblages and textural relationships at Heti has indicated precipitation of tsumoite and associated PGM along fractures and secondary silicates, which confirms their hydrothermal origin.
{"title":"Tsumoite (BiTe) and associated Ni-PGE mineralization from Gondpipri mafic-ultramafic complex, Bastar Craton, Central India: mineralogy and genetic significance","authors":"M. Dora, H. Singh, A. Kundu, M. Shareef, K. Randive, S. Joshi","doi":"10.2478/s13533-012-0185-9","DOIUrl":"https://doi.org/10.2478/s13533-012-0185-9","url":null,"abstract":"This paper reports the occurrence of Tsumoite (a bismuth telluride) in the Heti Cu-Ni-PGM prospect, Gondpipri mafic-ultramafic complex, Central India. The Gondpipri complex consists of several tectonically dismembered gabbronorite-gabbro-anorthositic gabbro — olivine gabbro -websterite disposed in ∼10 km long tonalite-trondhjemitegranodiorite (TTG) and charnockite-enderbite suite of rocks. The mineralization occurs in the sulphide zone hosted by gabbro variants. The host rocks have been deformed and metamorphosed to granulite grade and subjected to various degrees of hydrothermal alteration. The mineralization comprises chalcopyrite, pentlandite, pyrrhotite, cubanite, millerite, and pyrite. In addition to these, occur (1) tsumoite (2) PGM in the form of moncheite, merenskyite, Pd-mellonite, and Pt-Pd-Te-Bi-Fe-S alloy.The present study indicates that the mineralization occurs in two stages related to: (i) magmatic and (ii) hydrothermal remobilization and transport of Cu-rich sulphides, tsumoite and PGM, and their re-deposition in hydrosilicate alteration zones. It is possible that the mineralization at Heti formed at different stages of bismuth activity under variable fS2, T, and fTe2 conditions due to change in total concentration of Te and S and /or cooling. Since the role of S is limited, Te and cooling are important factor influencing mineralogy and composition of tsumoite and associated mineralization. Mineralization occurs in two different modes of occurrences. The early mineralisation occur as blebs, specks and dissemination of sulphides, viz. pyrrhotite, chalcopyrite, pentlandite and minor pyrite ± PGM, whereas later mineralisation occur as stringers, minor veins of sulphides viz. pyrite, millerite, cubanite, sijenite, tsumoite and ± PGM.Mineral assemblages and textural relationships at Heti has indicated precipitation of tsumoite and associated PGM along fractures and secondary silicates, which confirms their hydrothermal origin.","PeriodicalId":49092,"journal":{"name":"Central European Journal of Geosciences","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2014-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72642367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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