Petrogenesis and Tectonic Implications of the Cryogenian I-Type Granodiorites from Gabgaba Terrane (NE Sudan)

Abstract

The widely distributed granitic intrusions in the Nubian Shield can provide comprehensive data for understanding its crustal evolution. We present new bulk-rock geochemistry and isotopic (zircon U-Pb and Lu-Hf) data from the Haweit granodiorites in the Gabgaba Terrane (NE Sudan). The dated zircons presented a 206Pb/238U Concordia age of 718.5 ± 2.2 Ma, indicating that they crystallized during the Cryogenian. The granodiorites contain both biotite and amphibole as the main mafic constituents. The samples exhibit metaluminous (A/CNK = 0.84–0.94) and calc-alkaline signatures. Their mineralogical composition and remarkable low P2O5, Zr, Ce, and Nb concentrations confirm that they belong to I-type granites. They exhibit subduction-related magma geochemical characters such as enrichment in LILEs and LREEs and depletion in HFSEs and HREEs, with a low (La/Yb)N ratio (3.0–5.9) and apparent negative Nb anomaly. The positive Hf(t) values (+7.34 to +11.21) and young crustal model age (TDMC = 734–985 Ma) indicates a juvenile composition of the granodiorites. The data suggest that the Haweit granodiorites may have formed from partially melting a juvenile low-K mafic source. During subduction, the ascending asthenosphere melts might heat and partially melt the pre-existing lower crust mafic materials to generate the Haweit granodiorites in the middle segment of the Nubian Shield.

Two Distinct Fractional Crystallization Mechanisms of A-Type Granites in the Nanling Range, South China: A Case Study of the Jiuyishan Complex Massif and Xianghualing Intrusive Stocks

“…The intensive fractionation of feldspars is also proven by a discovery that A-type granites have especially highly stable Ca isotope compositions, likely the result of the rapid or extensive crystallization of plagioclase [75]. Whole-rock Zr/Hf, Rb/Sr and K/Rb ratios commonly serve as efficient criteria to determine the influence of fractional crystallization [6,76,77]. The Shaziling, Xishan, Jinjiling and Pangxiemu granites have gradually increased Rb/Sr ratios, but decreased Zr/Hf and K/Rb ratios (Figure 13a,b).…”

“…Although a series of studies have been proposed to prove the different fractional crystallization mechanisms between the Jiuyishan complex and the Xianghualing stocks, previous studies have considered that the formation of granitic rocks was not only controlled by one mechanism, but a combined action of multiple mechanisms [77]. A simple model can be proposed to demonstrate the formation of the Jiuyishan complex massif and Xianghualing intrusive stocks (Figure 16).…”

Assessing environmental and radiological impacts and lithological mapping of beryl-bearing rocks in Egypt using high-resolution sentinel-2 remote sensing images

“…Igla mine area locates in the CED of Egypt (Fig. 4 a) and is dominated by metavolcanics, older granites, and biotite pink granites 31 , 32 . The metavolcanics rocks are well exposed in the southern part of the study area (Fig.…”

Geochemical and remote sensing integrated with satellite gravity data of Darhib and Atshan talc deposits, South Eastern Desert, Egypt

“…During the collision of the East and West supercontinents (Gondwana), the Neoproterozoic northern extension (Arabian Nubian Shield, ANS) of the Mozambique belt was formed by the accretion of arcs and other continents 16 – 19 . The ANS represents one of the best-preserved juvenile crusts that provides information about the nature and sources of the widespread rocks during the East African Orogeny 20 – 23 . The ANS crustal growths comprise remnants of ophiolitic rocks and arc assemblages (820–720 Ma), variable collisional rocks (630–620 Ma), and post-collisional granitic rocks (620–580 Ma), forming three tectonic events 14 , 24 .…”