Mid-Paleoproterozoic (Jatulian) large igneous province of the Phanerozoic type, eastern Fennoscandian Shield

The Mid-Paleoprotrozoic Jatulian large igneous province (LIP) are located at the eastern Fennoscandian Shield. It is formed by lava plateaus in riftogenic structures, dyke swarms and different intrusions, and developed in range 2.35-2.06 Ga. All volcanics were undergone by greenschist alterations with practically complete replacement of original minerals by albite, actinolite, epidote, and chlorite, however, their primary structures and textures are often survived. Pillow-lavas are rare, which evidence about predominance of subaerial eruptions and it is in agreement with continental conditions of their formation. Jatulian complexes has studied about a hundred years, however, their geochemistry is known poor. So, we present here the new data for the better understanding this province. Jatulian rocks in Karelia are represented by basalts and andesibasalts of normal alkalinity with subordinate alkali basalts. The rocks are characterized by narrow variations of SiO2 (usually up to 53 wt.%); TiO2 content is vary from 0.72 to 3.06 wt.%, and mg# from 30 to 65. Spectrums REE of the basalts are characterized by low to moderate fractionation: (La/YbN= 1.28-5.27) under low fractionation of LREE (La/SmN=0.9-2.15) and HREE (Gd/YbN=1.19-2.55) and slight Eu-anomaly right up to it absence. At that group of high-Ti rocks is characterized by higher REE content. On multicomponet diagrams Jatulian rocks have moderate negative Nb-anomaly, which decreases up to section and sometimes becomes positive under weakly positive or absent Ti-anomaly. Jatulian volcanics on Kola Craton are located in Pechenga structure (Kuetsjarvi and Kolosiok Formation) and in Imandra-Varzuga structure (Umba Fm). Rocks of Kuetsjarvi Fm are characterized by very wide diversity, vary on SiO2 content from alkali basalts via trachyandesites, trachydacites to rhyolites. Such series of rocks very rare in the early Precambrian, which sharply distinguish them from the most Precambrian volcanics on the shield. Majority of Kuetsjarvi Fm rocks are represented by alkali basalts and trachyandesites under subordinate role of tholeiites; TiO2 content vary from 0.83 to 3.76. Tholeiites are fractionated high-Ti basalts, enriched in HFSE (mg#38). Alkaline varieties demonstrate higher variations of mg# in range 32-52, which often higher or close to its value in tholeiites. It is testify that these rocks was not formed in one process of fractionation, which support by variation diagrams 'inert component-SiO2', where rocks do not form single trends. All rocks are characterized by high concentrations of HFSE, whereas LILE concentrations strongly vary, demonstrating positive correlation with K2O and Ba. Spectrums REE of tholeiites are characterized moderate fractionation of LRRE and flat HREE graph: La/YbN=3.6-4.5; La/SmN=2.2-2.4, Gd/YbN=1.5-1.7 and negligible Eu-anomaly. Spectrums REE alkaline series rocks essential differ in more fractionation of LRRE and HREE (La/YbN=43.9-5.8; La/SmN=2.2-2.4, Gd/YbN=2.04-3.92) and Eu-anomaly from 0.53 to 1; alkaline rocks are enriched in U, Th and Nb. Thus, the middle Paleoproterozoic Jatulian LIP is rather close in composition of rocks and their geochemistry to typical Phanerozoic LIPs such as Siberian (Russia), Karoo (S.Africa), Dekkan (India), etc., and represent the oldest LIP of such type.