O Sill de Limeira possui variação composicional ampla e aparentemente contínua, no intervalo entre basalto nas bordas de resfriamento e quartzo monzodiorito grosso na parte mais central exposta até agora nas pedreiras onde é explorado. Abaixo da borda basáltica do topo encontra-se uma camada bastante rica em amígdalas, preenchidas por minerais de origem hidrotermal, seguida pela ocorrência de ocelos de composição quartzo monzonítica. Por toda extensão do sill ocorrem veios riolíticos (em menor proporção, quartzo monzoníticos), de direção preferencial perpendicular às bordas de resfriamento. As rochas são compostas essencialmente por plagioclásio, clinopiroxênio (augita ± pigeonita) e/ou anfibólio, Ti-magnetita, illmenita, além de quartzo e feldspato alcalino (nos termos mais diferenciados). Os minerais acessórios são apatita, filossilicatos, zircão, badeleíta, esfalerita, pirita e allanita; minerais de alteração hidrotermal são zeólitas, calcita, apofilita. Augita tem composição variada entre Fs~20, nas rochas mais primitivas e Fs40 nas mais diferenciadas (quartzo monzodiorito até riolito). O plagioclásio varia desde labradorita até oligoclásio, com predomínio de andesina An50-30 nas rochas mais abundantes. A química de rocha total revela um trend de diferenciação contínuo de composições entre o basalto de borda (~48% SiO2) e o quartzo monzodiorito (~61% SiO2); um hiato entre quartzo monzodiorito e riolito é identificado no intervalo 61-69% SiO2, no entanto quartzo monzonitos com 63-64% SiO2 aparecem como corpos de pequeno volume (veios e ocelos). O teor de Ca, Mg, Ti e Fe mostra tendência contínua de queda com a diferenciação, enquanto K tem aumento contínuo e Na e Al mantêm-se quase constantes, alcançando seu valor máximo no quartzo monzonito. Ba, Rb e Zr mostram comportamento incompatível, enquanto Co, Cr e Sr são tipicamente compatíveis. Os padrões de ETR são fracionados (LaN/YbN~12), e mostram enriquecimento até o quartzo monzodiorito; em rochas mais diferenciadas passa a haver algum empobrecimento, principalmente dos ETR médios, refletindo a extração de clinopiroxênio.. A diferenciação do Sill de Limeira parece refletir processos de cristalização fracionada, que fornece resultados consistentes em balanços de massa, tanto nos estágios iniciais, como na geração dos líquidos residuais diferenciados (quartzo monzonito e riolito), onde deve ter ocorrido por filter pressing. Em um modelo em que a cristalização ocorre a partir das bordas do corpo, com líquidos residuais sendo gerados nas frentes de solidificação, os ocelos foram possivelmente originados pela migração desses líquidos. Em um estágio posterior de evolução da câmara, os líquidos residuais expulsos dessas frentes teriam percolado fraturas em porções já solidificadas, formando os veios riolíticos. / The Limeira Sill exhibits a wide and continuous compositional variation, between basalt at the chilled margins and coarse-grained quartz monzodiorite in the innermost part currently exposed in the quarried where it is exploited. Below the top basalt border there is a layer rich in amygdales filled by hydrothermal minerals, followed downwards by the appearance of quartz monzonitic occelli. Throughout the sill occur rhyolitic (less often quartz monzonitic) veins oriented preferentially normal to the chilled margins. The rocks are composed mostly of plagioclase, clinopyroxene (augite ± pigeonite) and/or amphibole, Ti-magnetite, ilmenite, plus quartz and alkali feldspar (in the more differentiated rocks). Accessory minerals include apatite, filossilicates, zircon, baddeleyite, sphalerite, pyrite and allanite; hydrothermal minerals are zeolites, calcite and apophylite. Augite compositions vary from Fs~20 in the more primitive rocks to Fs40 in the more differentiated (quartz monzodiorite to rhyolite). Plagioclase varies from labradorite to oligoclase, with predominance of andesine An50-30 in the more abundant rocks. The whole rock chemistry reveals a continuous differentiation trend with compositions between the border basalt (~48 wt% SiO2) and the quartz monzodiorite (~61 wt% SiO2); a gap between quartz monzodiorite and rhyolite is identified in the 61-69 wt% SiO2 interval, but quartz monzonites with 63-64 wt% SiO2 appear as small-volume veins and occelli. The Ca, Mg, Ti and Fe contents show a trend of continuous decrease with differentiation, while K shows a continuous increase, and Na and Al are nearly constant, reaching maximum value in the quartz monzonites. Ba, Rb and Zr show incompatible behavior, while Co, Cr and Sr are typically compatible. The REE patterns are fractionated (LaN/YbN~12), and show enrichment up to the quartz monzodiorite; in more differentiated rocks they begin to decrease, especially the medium REE, reflecting extraction of clinopyroxene. The differentiation of the Limeira Sill appears to be a reflection of crystal fractionation, as suggested by consistent results in mass balance calculations, both for the initial stage (basalt to quartz monzodiorite) and for the generation of residual liquids (quartz monzonite and rhyolite), the latter probably involving some sort of filter pressing. In a model of magma chamber where crystallization occurs at the margins and residual liquids are generated in the solidification fronts, the occelli appear to be products of upward migration of these liquids. Later in the evolution of the chamber, the residual liquids extracted from these fronts would have percolated fractures in portions already solidified, forming the rhyolitic veins.

No description available.

The Early Jurassic coal samples for the study were obtained from CRA Exploration Pty Ltd. (CRAE), drilled in the Gairdner and Mintaja Blocks, Gairdner Range of the Hill River Area, northern Perth Basin, Western Australia. The area is located approximately 280 km north of Perth. The coal measures subcrop in a half- graben bounded by the Lesueur-Peron Fault in the west, and the Warradarge Fault in the east. The coal occurs within the shallow sequence of the Cattamarra Member which is also described as the Cattamarra Coal Measures of the Cockleshell Gully Formation.Six sub-seams of seam G, namely G1 to G6, from the six drill cores, were examined for petrological and geochemical investigation. The coal predominantly comprises of banded, dull banded, and dull lithotypes, with minor bright banded, bright and fusainous types. Based on maceral analyses, the dominant maceral groups are vitrinite and inertinite, whilst the exinite and mineral matter are in minor contents. The vitrinite content has a range between 47.2 % to 73.0 %, and it is composed mainly of telocollinite and desmocollinite. The inertinite is dominated by semifusinite, fusinite, and inertodetrinite, and it has a range from 10.4 % to 24.8 %. The exinite group varies between 7.2 % to 20.8 % in content, and it is represented by sporinite, cutinite, alginite and resinite. The mineral matter dominated by clays and pyrite, ranges between 4.5 % to 20.6 %. The microlithotype analyses shows that the vitrite plus clarite content varies from 47.0 % to 70.0 %, intermediates between 8.0% to 26.0 %, whilst inertite plus durite content is relatively low, varying from 6.55 % to 14.0 %. The maximum reflectance of vitrinite has a value between 0.47 % and 0.53 %, which represents rank at sub-bituminous level based on the Australian rank values and corresponding to the sub-bituminous A and B rank of the ASTM classification and ++ / to the metalignitous type of the Pareek classification. On the basis of carbon and hydrogen content, the coal is categorised as per-hydrous meta- to ortho-lignitous type. The trace elements As, B, Be, Cd, Co, Cr, Cu, Ga, Mn, Mo, Ni, Pb, Sr, Th, U, V, Y, Zn, and Zr, are spectrographically analysed in the coal ash. The B content in the coal supports the presence of marine influence during peat deposition in the basin.On the basis of lithotype, maceral, microlithotype, trace element distribution, pyrite and total sulphur in the coal, the depositional environment for coal and the coal measures, is interpreted as an upper to lower delta type within a regressive phase of marine transgression.

The majority of economic gold deposits in NSW are associated with Ordovician-aged igneous rocks and are examples of the Cu-Au porphyry-skarn-epithermal association commonly developed in convergent margin to orogenic settings. They are among the oldest porphyry Cu-Au deposits in the Pacific Rim region. They are similar to younger deposits in terms of tectonic setting and structure, but the largest are chemically distinct, being associated with shoshonite magmas (Cadia, Ridgeway and Northparkes). The Lachlan Fold Belt (LFB) porphyries are subdivided into four sub-groups based mainly on their age relative to development of the Lachlan Transverse Zone (LTZ) structure. Two subgroups pre-date the LTZ, one group is syn�LTZ and one group post-dates the LTZ. No mineralisation has been found or reported among pre-I.TZ porphyries. but it is common in post- . l Z_ porphyries. Petrographic analysis and microprobe results establish a wide range of primary and secondary features within the Ordovician rocks examined in this study. Cale alkaline to shoshonitic affinities are supported by the variable abundance of primary K-feldspars. Primary mineral phases such as pyroxenes and igneous magnetite provide an indication of fractioning mineral assemblages responsible for igneous trends in magma chemistry. The hydrothermal mineral assemblages documented in these LFB study areas are characteristic of younger Cu-Au Porphyry style mineralisation. As expected, the most pervasive alteration is associated with highly mineralised shoshonitic Ordovician rocks at Ridgeway, and Cadia. the less strongly mineralised calc alkaline Ordovician rocks at Cargo. Copper Ilill and Fairholme. are correspondingly less strongly altered overall. although secondary mineral assemblages are locally abundant. Many varieties of oxides and carbonates are observed at the different study localities. Most of the studied samples conform to igneous chemical trends because they are weakly altered, although post magmatic processes, such as veining, are detectable in certain trends. The K2O enrichment of the studied samples is consistent with subductionmoditied mantle wedge sources. A few effects, such as the high Fe203 contents of some Ridgeway samples, probably reflect porphyry-style hydrothermal alteration processes. Host rocks at the Cadia and Ridgeway are entirely alkalic on the K2O versus SiO2 plot and shoshonitic on the Total Alkalies versus SiO2 plot. Igneous rocks at the other deposits display a range of compositions between low K tholeiites to shoshonites that in some cases reflects multiple igneous suites. The LREE and L1LE enrichments, and HFSE depletions (Nb, Ta and Ti) of the magmas associated with these deposits are characteristics of a subduction-related tectonic setting. They all fall in the volcanic-arc granite and syn-collisional granite field of the Nb-Y tectonic discrimination diagram. Several magma types are identified by differences in the HFSE and REE trends. Differences in the extent and style of magma fractionation are evident in the trace element data. The Ridgeway samples define a wider range of trace element concentrations than the Cadia samples that may indicate a greater extent of fractionation during emplacement of the Ridgeway magmas. Fairholme samples display a high Nh and /If trends that are distinct from the main fields on Zr variation diagrams. Compositional differences between larger Cu-Au deposits, Cadia-Ridgeway and smaller deposits, Copper Ifill, Cargo and Fairholme are evident in terms of Nb-Ta depletion and variation. The smaller deposits show constant Nb/Ta or negative Nb/Ta trends that extend to high Nb. The larger deposits display positive Nb/Ta trends that do not extend to high Nb. This distinction reflects a difference of preferential incorporation of Nb in a mineral phase (magnetite). Comparisons between Cadia-Ridgeway and other shoshonite (altered samples of Bajo de la Alumbrera, Argentina), calc alkaline magmas from New Zealand and rocks from other areas indicate that Nb/Ta is not directly correlated with the shoshonitic classification, K2O vs. SiO2, and that the Cadia-Ridgeway Nb and Ta variation is not the result of alteration. The fact that the weakly altered LFB Capertee shoshonites exhibit a narrow range of Nb and low Nb/Ta suggest the shoshonite trend for the LFB as a whole is a steep one on the Nb/Ta versus Nb plot. The results of this study could provide important information for exploration within the LFB. Only the Cadia and Ridgeway deposits display a wide range of Nb/Ta values and lack the near-horizontal trend seen for other localities associated with smaller deposits. The tectonic evolution of the LFB is a major factor contributing to occurrence of large porphyry Cu-Au deposits. The sequence of important events, however, commences with sub-crustal generation of oxidised magma and finishes with efficient Cu-Au accumulation by hydrothermal processes at favourable structural sites. The increase in Au-Cu deposit size from small (Copper Hill-Cargo) to world class (Cadia-Ridgeway) indicates the importance of magma composition during this process. The most obvious differences between the Cadia-Ridgeway and New Zealand rocks is that the latter are volcanic in origin and associated with an arc-back arc system. Therefore, they did not form in a tectonic regime suitable for the evolution of porphyries and the focussed movement of hydrothermal fluids during dilatant episodes. As a result, they are not linked to mineralisation despite having Nb-Ta and Nb/Ta variations that are typical of the high oxidation states in Au-prospective magmas of the LFB.

Ce mémoire a pour objet l' étude géologique, pétrographique et structurale des terrains cristallophylliens des parties occidentale et centrale du Tanneron. La région considérée présente au Nord comme au Sud des frontières naturelles qui sont respectivement les limites du Trias et les assises du Permien. Seule la partie orientale présente une limite arbitraire qui peut-être définie par une ligne passant par les fermes de QUISTON et BARBIER depuis le Carbonifère du Reyran jusqu'à la faille de Font-de-Sante. Le Tanneron oriental ne fait pas partie du cadre de ce travail ; Nous étudions successivement les différents compartiments ainsi délimités depuis l'Ouest vers l'Est : 1 - Le secteur de Gardanne limité à l'Est par la faille de Joyeuse . 2 - Le secteur de Bagnols -.Saint-Paul limité à l'Ouest par la faille de Fontcounille et à l 'Est par la faille du Ribas. 3 - Le secteur du Reyran limité à l'Est par le bassin carbonifère du même nom. 4 - Le secteur du Planestel - les Adrets de Fréjus qui se poursuit à l'Est par les secteurs non étudiés du Tanneron oriental. . 5 - Le secteur de Joyeuse - Fontcounille limité par les accidents de Joyeuse à l 'Ouest et de Fontcounille à I'Est .

Les grès du Champsaur constituent une formation turbiditique d'âge éocène terminal ou oligocène basal. Ces grauwackes volcano-détritiques se sont déposées dans un bassin d'avant-pays subalpin migrant, en avant du front orogénique alpin plissé et chevauché . Au nord, ils passent progressivement aux Flysch des Aiguilles d'Arves légèrement plus internes et plus vieux. A l'ouest, une zone d'érosion les sépare des grès de Saint-Didier plus externes, qui évoluent finalement vers la Molasse Rouge. Les grès du Champsaur se différencient pétrographiquement de ces différentes formations par une très forte proportion de débris andésitiques. Le matériel andésitique provient du démantèlement d'un arc volcanique d'âge paléogène, situé sur la bordure occidentale de la plaque adriatique. Des intercalations volcano-détritiques équivalentes, tant aux points de vue de la pétrographie, de la stratigraphie, que de la position structurale, sont connues dans l'édifice alpin. Il s'agit des grès de Taveyanne des alpes suisses et savoyardes, des grès du synclinal de Saint-Antonin des Alpes-Maritimes, des grès de Petrignacola de l'Apennin septentrional et les grès de Tusa de l'Italie du sud et de la Sicile. Dans l'arc alpin, les for mations de turbidite à matériel andésitique passent progressivement à des formations détritiques généralement plus jeunes et plus externes, lesquelles s'enrichissent progressivement en matériel ophiolitique. Ce sont les grès du Val d'Illiez de Suisse occidentale, les grès de Saint-Didier des Alpes occidentales françaises ainsi que les grès de Clumanc des Alpes-Maritimes. Les grès du Champsaur reposent en discordance angulaire sur les Schistes à Globigérines et les Calcaires à Nummulites qui sont fortement transgressifs sur le massif du Pelvoux au nord et sa couverture mésozoïque au sud. Trois unités principales peuvent être distinguées sur la base de leur position structurale et de leur composition lithologique; l'âge devient progressivement plus jeune en direction du nord-ouest. Les grès de l'unité 1 et 2, ainsi que leurs substrats nummulitiques et mésozoïques, sont entièrement parautochtones. Peu après leur sédimentation, ils ont été détachés, déformés et transportés vers l'ouest sur l'unité 3 qui est autochtone par rapport au massif du Pelvoux, durant la phase compressive alpine à l'Oligocène supérieur au Miocène. Ces unités furent ensuite recouvertes par les unités penniques, cette surcharge a induit le développement des faciès métamorphiques à zéolites caractéristique des roches volcano- détritiques.

Les premières observations géologiques sur la "bande volcano sédimentaire Frotet-Evans" ont été faites au début du XX° sc. Il ressort après toutes ces études que la "bande volcano sédimentaire Frotet - Evans" est surtout composée de métasédiments dans sa partie médiane alors qu'à ses extrémités , il y a prédominance de roches métavolcaniques d ' origine basaltique . Les méthodes de travail de terrain ont limité les observations .

Ce travail concerne le bouclier precambrien canadien et traite des roches dites grenvilliennes.

Etude géologique de cette région des Pontides.

Dans la zone de Sezia-Lanzo les roches du faciès schiste vert sont de plusieurs types. Dans les unes: gneiss albitiques, la seule paragenèse observable est celle caractéristique du faciès schiste vert. D'autres conservent une texture de roche grenue et quelques minéraux reliques, ou ont garde l'empreinte de phases métamorphiques antérieures. Bien que d'origines différentes les roches présentent des assemblages minéralogiques pratiquement identiques. L'étude minéralogique, en particulier celle de la répartition des éléments entre les minéraux, a montré que tous ces assemblages avaient cristallisé à l'équilibre et dans des conditions qui variaient peu d'un bout à l'autre de la zone. Il est probable que, lors de la phase éoalpine, se soient formés à la fois, les schistes verts et les micas schistes éclogitiques, au cours de la phase alpine, les premiers et certains des seconds auraient recristallisé dans les conditions du faciès schiste vert.