Plume‐orogenic lithosphere interaction recorded in the Haladala layered intrusion in the Southwest Tianshan Orogen, NW China

Abstract

The plume‐orogenic lithosphere interaction may be common and important for the generation of large igneous provinces. The information regarding such a process is recorded by the Haladala gabbroic intrusion (~300 Ma), the largest layered ultramafic‐mafic intrusion hosting V‐Ti magnetite deposits in the Southwest Tianshan Orogen, NW China. The Haladala gabbros exhibit unfractionated chondrite‐normalized rare earth element patterns with negative Nb and Ta anomalies and positive Pb anomaly on the primitive mantle‐normalized multielement variation diagram. They are characterized by low initial Sr isotopes, slightly decoupled but high positive bulk rock εNd(t) and εHf(t), and high 207Pb/204Pb and 208Pb/204Pb relative to 206Pb/204Pb, delineating a DUPAL signature in the sources. The Haladala gabbros cannot be arc or postcollisional magmatism, given the lack of hydrous minerals and low K contents, respectively. This is further supported by the relatively low oxygen fugacity required for the gradual enrichment of V‐Ti magnetite during the magma fractionation and by an overall anhydrous mantle source suggested by troctolite mineral assemblage (olivine + plagioclase). The emplacement age of the Haladala gabbros is identical to that of the Wajilitag kimberlites in the Tarim's interior, which have been interpreted as the first magmatic expression of the Tarim mantle plume. We thus propose that the Haladala gabbroic intrusion was generated in a hybrid geodynamic setting in which the Southwest Tianshan Orogen was impacted by an upwelling mantle plume. In this sense, the Haladala layered gabbroic intrusion records the early phase of magmatism of the Tarim plume, which was preferentially emplaced in a lithospheric weak zone.

Petrogenesis of Transitional Large Igneous Province: Insights From Bimodal Volcanic Suite in the Tarim Large Igneous Province

“…In deviation to the previous models, our study shows that the TLIP has a strong continental rift affinity, where “triple junction” rift structure is expected to develop. Within this framework, the plume‐derived material and heat will migrate and conduct along the rift structures and induce magmatism only at the intersection point with the CAOB, as exemplified by the Haladala gabbroic intrusions in the western part and Eastern Tianshan Ni‐Cu‐(PGE) sulfide deposits at the eastern part (He et al, 2016; Yao et al, 2018; Zhang & Zou, 2013), instead of having a full impact on the CAOB.…”

Tarim Large Igneous Province Caused by a Wide and Wet Mantle Plume

“…Recently, interactions between the Tarim plume and the South Tianshan have been suggested based on the presence of thick V-Ti magnetic mineral-rich deposits in the Haladala intrusions (He et al, 2016). In particular, Han et al (2019) proposed that the absence of both continental-type high-pressure rocks and significant surface uplift during the collision between the Tarim and Central Tianshan-Yili blocks at the end of the Carboniferous is attributed to the involvement of the Tarim plume during this period.…”

Crustal and Upper Mantle Structure of the Tien Shan Orogenic Belt From Full‐Wave Ambient Noise Tomography

“…Our tomographic model observes the connected high‐velocity upper mantle structure from Tarim Basin across eastern Tien Shan to Junggar Basin (Figure d), suggesting that the Tarim and Junggar Basins have converged together beneath the eastern Tien Shan. The occurrence of the gabbroic intrusion in the eastern Tien Shan suggests that generation of intraplate mafic volcanism may be related to the underthrusting of the Tarim and Junggar lithosphere (He et al, ). The lithosphere convergence may form a barrier, which consequently prevents asthenosphere upwelling.…”