Chapter 2.1b Ferrar Large Igneous Province: petrology

2021 ◽  
pp. M55-2018-39 ◽  
Author(s):  
David H. Elliot ◽  
Thomas. H. Fleming
Keyword(s):  
Ross Sea ◽  
Lower Jurassic ◽  
Weddell Sea ◽  
Geochemical Characteristics ◽  
Large Igneous Province ◽  
Geographical Pattern ◽  
Chemical Type ◽  
Igneous Province ◽  
Intrusive Rocks ◽  
Basic Rocks

AbstractThe Lower Jurassic Ferrar Large Igneous Province consists predominantly of intrusive rocks, which crop out over a distance of 3500 km. In comparison, extrusive rocks are more restricted geographically. Geochemically, the province is divided into the Mount Fazio Chemical Type, forming more than 99% of the exposed province, and the Scarab Peak Chemical Type, which in the Ross Sea sector is restricted to the uppermost lava. The former exhibits a range of compositions (SiO2 = 52–59%; MgO = 9.2–2.6%; Zr = 60–175 ppm; Sri = 0.7081–0.7138; εNd = −6.0 to −3.8), whereas the latter has a restricted composition (SiO2 = c. 58%; MgO = c. 2.3%; Zr = c. 230 ppm; Sri = 0.7090–0.7097; εNd = −4.4 to −4.1). Both chemical types are characterized by enriched initial isotope compositions of neodymium and strontium, low abundances of high field strength elements, and crust-like trace element patterns. The most basic rocks, olivine-bearing dolerites, indicate that these geochemical characteristics were inherited from a mantle source modified by subduction processes, possibly the incorporation of sediment. In one model, magmas were derived from a linear source having multiple sites of generation each of which evolved to yield, in sum, the province-wide coherent geochemistry. The preferred interpretation is that the remarkably coherent geochemistry and short duration of emplacement demonstrate derivation from a single source inferred to have been located in the proto-Weddell Sea region. The spatial variation in geochemical characteristics of the lavas suggests distinct magma batches erupted at the surface, whereas no clear geographical pattern is evident for intrusive rocks.

scholarly journals Geology of the Mesoproterozoic Pillar Lake Volcanics and Inspiration Sill, Armstrong, Ontario: Evidence of Early Midcontinent Rift Magmatism in the Northwestern Nipigon Embayment

2021 ◽  
Author(s):  
Pete Hollings ◽  
Mark Smyk ◽  
Wouter Bleeker ◽  
Michael A. Hamilton ◽  
Robert Cundari ◽  
...  
Keyword(s):  
North America ◽  
Direct Contact ◽  
Large Igneous Province ◽  
Rift System ◽  
Flood Basalts ◽  
Midcontinent Rift ◽  
Igneous Province ◽  
Intrusive Rocks ◽  
Midcontinent Rift System ◽  
Northern Edge

The Midcontinent Rift System of North America is a ~1.1 Ga large igneous province comprising mainly flood basalts and intrusive rocks. We present new data for the Pillar Lake Volcanics and Inspiration Sill from the northern edge of the Midcontinent Rift in the northwestern Nipigon Embayment. The Pillar Lake Volcanics comprise a ~20-40 m-thick, flat-lying sequence of mafic pillowed and massive flows, pillowed flow breccia, and hyaloclastite breccia. They are characterized by SiO2 of 52-54 wt%, TiO2 of 1.2 to 1.3 wt% and K2O of 0.9 to 1.1 wt%. They are LREE-enriched, with La/Smn of 3.0 to 4.4 with fractionated HREE (Gd/Ybn = 1.4 to 1.7). The Inspiration diabase sill is < 50 m thick and is in direct contact with the underlying Pillar Lake Volcanics. Baddeleyite and zircon data from the Inspiration Sill yield a combined U-Pb upper intercept age of 1105.6 ± 1.6 Ma. The Inspiration Sill is characterized by uniform SiO2 of 52 to 53 wt%, TiO2 of 1.1 to 1.2 and K2O of 0.9 to 1.2 wt%. Inspiration Sill samples are LREE enriched with La/Smn of 3.2 to 3.3 and fractionated HREE of (Gd/Ybn = 1.6). The Pillar Lake Volcanics are at least 1120 Ma, and perhaps as old as 1130 Ma and represent an early, thin, and restricted mafic volcanic sequence, largely preserved below the younger Inspiration Sill. The Pillar Lake Volcanics and Inspiration Sill display a marked geochemical similarity, suggesting that they may represent magmatism associated with the earliest stages of Midcontinent rifting.

scholarly journals Nature of Cretaceous dolerite dikes with two distinct trends in the Damodar Valley, eastern India: Constraints on their linkage to mantle plumes and large igneous provinces from 40Ar/39Ar geochronology and geochemistry

Lithosphere ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 40-52 ◽  
Author(s):  
Rajesh K. Srivastava ◽  
Fei Wang ◽  
Wenbei Shi ◽  
Anup K. Sinha ◽  
Kenneth L. Buchan
Keyword(s):  
Sedimentary Basins ◽  
Geochemical Characteristics ◽  
Large Igneous Province ◽  
Mantle Plumes ◽  
Eastern India ◽  
Group I ◽  
Igneous Provinces ◽  
Damodar Valley ◽  
Igneous Province ◽  
Reunion Plume

Abstract Two distinct sets of Cretaceous dolerite dikes intrude the Chhotanagpur gneissic complex of eastern India, mostly within the Damodar Valley Gondwanan sedimentary basins. One dike set trends NNE to ENE, whereas the other set, which includes the prominent Salma dike, trends NW to NNW. One dike from each set in the Raniganj Basin was dated using the 40Ar/39Ar method in order to resolve a controversy concerning the emplacement age of the Salma dike. The NE-trending dike yielded a plateau age of 70.5 ± 0.9 Ma, whereas the NNW-trending Salma dike is much older, with a plateau age of 116.0 ± 1.4 Ma. These results demonstrate that the Salma dike was emplaced at ca. 116 Ma and not at ca. 65 Ma, as suggested in an earlier study. Geochemical characteristics of the two dikes are also distinct and indicate that they belong to previously identified high-Ti and low-Ti dolerite groups, respectively. The observed geochemical characteristics of both dike sets are comparable with the geochemistry of basalts of the Kerguelen Plateau, Bunbury Island, and Rajmahal Group I and suggest a connection to mantle plumes. The new age data presented herein indicate that these two magmatic episodes in the eastern Indian Shield were related to the ca. 120–100 Ma Kerguelen mantle plume and its associated Greater Kerguelen large igneous province and the ca. 70–65 Ma Réunion plume and its associated Deccan large igneous province, respectively.

scholarly journals Geochemical characteristics of the Muong Hum alkaline granite in the Phan Si Pan zone, Northwestern Vietnam

2017 ◽  
Vol 1 (T2) ◽  
pp. 114-123
Author(s):  
Minh Pham ◽  
Hieu Trung Pham ◽  
Hoang Kim Nguyen
Keyword(s):  
Geochemical Characteristics ◽  
Red River ◽  
Large Igneous Province ◽  
Direct Result ◽  
Chemical Characteristics ◽  
Late Permian ◽  
Alkaline Granite ◽  
Igneous Province ◽  
Mineral Assemblages ◽  
Alkaline Feldspar

Alkaline granites of the Muong Hum are distributed mainly in the NW Phan Si Pan zone. The granite closely has striped or clear gneissoid structures, coinciding with general NW-SE trends. It consists mainly of plagioclase (~20–30 %), alkaline feldspar (~30–50 %), quartz (~20–25 %), biotite (~1–5 %), aegirine (~1–3 %), and riebeckite (~1–2 %). It has 10,000×Ga/Al ratios of 4.70–4.93, A/CNK values of 0.87–0.90, and negative Eu-anomalies as well as apparent depletion of Ba, Sr, Ti, and P. The mineral assemblages and chemical characteristics show that it is typical of A-type granites. Compared with other adjacent Late Permian to Early Triassic A-type granitic plutons, geochemical characteristics of the Muong Hum granite are similar to the Phu Sa Phìn, Phan Si Pan, Ye Yen Sun, and Nam Xe-Tam Duong granites in NW Vietnam as well as the Taihe, and Panzhihua granites in SW China. Thus, the Phan Si Pan zone must have been a displaced portion of the Emeishan large igneous province. This might be a direct result of the left-lateral Cenozoic Red River shear zone.

scholarly journals Geochemistry of the 1100 Ma intrusive rocks from the Ahlmannryggen region, Dronning Maud Land, Antarctica

2014 ◽  
Vol 26 (4) ◽  
pp. 389-399 ◽  
Author(s):  
Teal R. Riley ◽  
Ian L. Millar
Keyword(s):  
Lithospheric Mantle ◽  
Crustal Contamination ◽  
Lava Flows ◽  
Large Igneous Province ◽  
Sedimentary Sequence ◽  
Igneous Province ◽  
Intrusive Rocks ◽  
Dronning Maud Land ◽  
Lithospheric Mantle Source ◽  
Land Region

AbstractThe recognition of a Mesoproterozoic large igneous province (LIP) across large parts of southern Africa has been strengthened by recent geochronology, geochemistry and petrology. The c. 1100 Ma Umkondo province has been recognized across parts of Botswana, Zimbabwe, South Africa and Mozambique where tholeiitic sills, dykes and rare lava flows have been correlated into a single magmatic province emplaced in the interval 1108–1112 Ma. The extension of the province into the Dronning Maud Land region of Antarctica has been suggested by several workers, but detailed analyses of geochemistry and petrogenesis are lacking, as are comparative studies. This study investigates 25 dykes and sills of the Borgmassivet intrusions which include several of the major diorite sills of the province, up to 300 m in thickness. The dykes and sills are also considered to be c. 1100 Ma and they were emplaced, in part, synchronously with the Ritscherflya Supergroup sedimentary sequence. The Borgmassivet intrusions are characterized by geochemical signatures that suggest the magmas were either extensively contaminated by continental crust or derived from an enriched lithospheric mantle source, where the enrichment was related to earlier subduction. The limited geochemical range of the Borgmassivet and Umkondo intrusions are probably not consistent with significant levels of crustal contamination. Furthermore, the trace element ratios indicate a source in the sub-lithospheric mantle, followed by gabbroic fractionation and interaction with lithospheric wall rocks.

Lithostratigraphy of the Palaeoproterozoic Hekpoort Formation (Pretoria Group, Transvaal Supergroup), South Africa

2020 ◽  
Vol 123 (4) ◽  
pp. 655-668
Author(s):  
N. Lenhardt ◽  
W. Altermann ◽  
F. Humbert ◽  
M. de Kock
Keyword(s):  
South Africa ◽  
Bushveld Complex ◽  
Sedimentary Rocks ◽  
Type Locality ◽  
Large Igneous Province ◽  
Braided River ◽  
River Systems ◽  
The West ◽  
Igneous Province ◽  
Transvaal Supergroup

Abstract The Palaeoproterozoic Hekpoort Formation of the Pretoria Group is a lava-dominated unit that has a basin-wide extent throughout the Transvaal sub-basin of South Africa. Additional correlative units may be present in the Kanye sub-basin of Botswana. The key characteristic of the formation is its general geochemical uniformity. Volcaniclastic and other sedimentary rocks are relatively rare throughout the succession but may be dominant in some locations. Hekpoort Formation outcrops are sporadic throughout the basin and mostly occur in the form of gentle hills and valleys, mainly encircling Archaean domes and the Palaeoproterozoic Bushveld Complex (BC). The unit is exposed in the western Pretoria Group basin, sitting unconformably either on the Timeball Hill Formation or Boshoek Formation, which is lenticular there, and on top of the Boshoek Formation in the east of the basin. The unit is unconformably overlain by the Dwaalheuwel Formation. The type-locality for the Hekpoort Formation is the Hekpoort farm (504 IQ Hekpoort), ca. 60 km to the west-southwest of Pretoria. However, no stratotype has ever been proposed. A lectostratotype, i.e., the Mooikloof area in Pretoria East, that can be enhanced by two reference stratotypes are proposed herein. The Hekpoort Formation was deposited in a cratonic subaerial setting, forming a large igneous province (LIP) in which short-termed localised ponds and small braided river systems existed. It therefore forms one of the major Palaeoproterozoic magmatic events on the Kaapvaal Craton.

Ultramafic-alkaline-carbonatite complexes as a result of two-stage melting of mantle plume: evidence from the mid-paleoproterozoic Tiksheozero intrusion, Northern Karelia, Russia

2019 ◽  
Vol 486 (4) ◽  
pp. 460-465
Author(s):  
E. V. Sharkov ◽  
A. V. Chistyakov ◽  
M. M. Bogina ◽  
O. A. Bogatikov ◽  
V. V. Shchiptsov ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Mantle Plume ◽  
Large Igneous Province ◽  
Intrusive Complex ◽  
Incongruent Melting ◽  
Isotopic Data ◽  
Two Stage ◽  
Similar Composition ◽  
Igneous Province ◽  
Alkaline Magmas

Tiksheozero ultramafic-alkaline-carbonatite intrusive complex, like numerous carbonatite-bearing complexes of similar composition, is a part of large igneous province, related to the ascent of thermochemical mantle plume. Our geochemical and isotopic data evidence that ultramafites and alkaline rocks are joined by fractional crystallization, whereas carbonatitic magmas has independent origin. We suggest that origin of parental magmas of the Tiksheozero complex, as well as other ultramafic-alkaline-carbonatite complexes, was provided by two-stage melting of the mantle-plume head: 1) adiabatic melting of its inner part, which produced moderately-alkaline picrites, which fractional crystallization led to appearance of alkaline magmas, and 2) incongruent melting of the upper cooled margin of the plume head under the influence of CO2-rich fluids  that arrived from underlying zone of adiabatic melting gave rise to carbonatite magmas.

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