Dark enclaves rich in amphibole and biotite are ubiquitous in granitoid rocks and generally thought to represent fragments of mafic magmas, cumulates or restites. However, magmatic assimilation of metamorphic or sedimentary country rock can also form dark enclaves. To develop criteria for identifying dark enclaves of non-magmatic origin, we investigated dark enclaves from a complete spectrum of light (carbonate- or feldspar-rich) to dark (amphibole-rich, biotite-rich, or composite) enclaves, reflecting progressive thermal and chemical equilibration with host tonalite from the Domenigoni Valley pluton in the Peninsular Ranges Batholith, California. Metasedimentary dark enclaves have a number of major and trace element characteristics that overlap those of literature-compiled igneous dark enclaves. Comparison to modeled igneous differentiation paths shows metasedimentary enclaves can have anomalous CaO and K2O contents for a given SiO2, but other major element systematics may not deviate noticeably from igneous differentiation trends. In addition, the fact that there are literature-compiled mafic enclaves trending towards high K2O and high CaO suggests that not all mafic enclaves are of igneous origin. While the majority of dark enclaves may not be metasedimentary, this work provides some criteria for identifying enclaves should a case of metasedimentary origin arise.

The Rävliden mine is located in the Skellefte district in northern Sweden. In close proximity lays the Kristineberg deposit containing zinc, copper and lead ore which has been mined since the 1940’s. The district is rich in massive sulphide deposits and the mining history can be dated back to the 1920’s. New deposits are still being discovered and understanding the origin of the ores and their formation processes are more and more important when looking for new orebodies. The area itself is ca 1.8 Ga and most rocks have undergone hydrothermal alteration and been metamorphosed. The main purpose of this study was to determine the host rock protolith and the method chosen was developed by MacLean and Barrett (2005) in which immobile element ratios are used for determining the chemostratigraphy.     Two main alteration types are recognized and two minor ones. The dominant ones being sericite and chlorite alteration. The boreholes also display some silicification and carbonate alteration. While the TAS-diagram shows that most samples are either dacitic or rhyolitic with a small group of andesitic rocks. Further usage of both the Alteration box plot and various immobile element plots show that the amount of dacitic samples are low. Instead rhyolite is the predominant rock type with four subgroups, there is also one dacite group and one probable andesitic intrusion. The mineralisation is low so it was not possible to correlate alteration type to ore occurrence, nor was it possible to see any correlation between protolith and mineralisation. The study did determine the protolith for the boreholes and the data and therefore the method can be used for exploration in other areas. / Rävlidengruvan ligger i Skelleftedistriktet i norra Sverige och i dess närhet ligger även  Kritinebergsgruvan där zink, koppar och bly har brutits ur malmkroppen sedan 1940-talet. Distriktet är rikt på massiva sulfid avlagringar och gruvdrift i området kan dateras tillbaka till 1920-talet. Nya fyndigheter upptäcks fortfarande och förståelse för deras uppkomst och malmernas bildningsprocesser blir är allt viktigare när man ska söka nya malmkroppar. Skelleftedistriktet är ca 1,8 Ga och de flesta bergarter har antingen genomgått metamorfos eller hydrotermal omvandling. Huvudsyftet med denna studie var att fastställa ursprungsbergarten för området, innan hydrotermal omvandling skedde, med hjälp av en metod som har utvecklats av MacLean och Barrett. Metoden grundar sig i att man jämför relationerna mellan immobila grundämnen för att på så sätt fastställa kemostratigrafin.     Fyra omvandlingstyper återfinns i borrhålen där två är mer prominenta, serecit och klorit omvandling. De mindre vanliga omvandlingstyperna är silicifiering eller kvartsomvandlig samt karbonatomvandling. De flesta prover är antingen daciter eller ryoliter med en liten grupp andesiter så visar de olika diagrammen med immobila elementet på att mängden daciter är få. Istället finns det fyra typer av ryoliter, en grupp daciter och en trolig andesitisk intrusion. Mängden mineralisering var låg så det var inte möjligt att korrelera omvandlingstyp till malm bildning, inte heller var det möjligt att se något samband mellan protoliten och mineralisering. Studien besvarade hypotesen om ursprungsbergarten för borrhålen och metoden kan användas för andra prospekteringsområden.

<p> The Larder Lake Break (LLB) is one of the structures controlling the location of gold deposits in the Kirland Lake camp. This intensly carbonated and often strongly foliated zone is part of the Larder Lake Group as defined by Downs (1980). Protoliths at the LLB are problematical. Misema River is a well exposed occurrence of the LLB, showing chlorite schist, pervasively fuchsite quartz carbonate and syenite dyke material. It is divided into three sections. Section I samples indicate an ultramafic protolith as suggested by Jensen Cation plots, and the section is interpreted as komatiitic flow(s). Section II is well foliated and shows both ultramafic and calc-alkalic components which decrease and increase in intensity respectively away from the section I-section II contact. Section II is interpreted as a polymodal sediment. Section III is similar chemically and texturally to section I, and is therefore a komatiitic flow(s). The intrusion of syenite dykes into section I occurred after initial carbonatization and defonnation of the flows and associated sediments. Radiochemical neutron activation analysis shows all but one of the syenite dyke samples to contain greater than 10 ppb gold whereas the other rock types averages approximately 2 ppb. A peak content of 64 ppb occurred at a dyke contact. The high gold contents clearly originate from the syenite dykes, which also provide a heat source for a second period of carbonatization. </p> / Thesis / Bachelor of Science (BSc)