Triggers on sulfide saturation in Fe–Ti oxide-bearing, mafic-ultramafic layered intrusions in the Tarim large igneous province, NW China

Late Magmatic Activity in the Tarim Large Igneous Province: Evidence from the Puchang Granites

“…Previous data showed that SiO 2 was from 55 to 65 wt % and distributed in the alkalic–subalkalic transition region (Figure ). The alkali content (Na 2 O + K 2 O) of the entire rock is positively correlated with SiO 2 , reflecting that it is mainly controlled by the plagioclase, and Fe 2 O 3 T and TiO 2 are negatively correlated with SiO 2 , while CaO and Al 2 O 3 are positively correlated with SiO 2 , which indicates that the entire rock composition is mainly influenced by the Fe–Ti oxide mineral content. , The distribution characteristics of major elements of granites are basically consistent with that in this study, while the granitic pluton has slightly lower K 2 O and higher SiO 2 than the granites, which all have the characteristics of intraplate non-orogenic A-type granites . The granites in the major and trace elements have undergone extensive crystal fractionation in the magma chamber or magmatic ascent and have distinguishable geochemical characteristics from the Puchang complex, which are likely to be derived from an OIB-like mantle source …”

“…The ages of Puchang gabbros are consistent with those of TLIP and show multistage mineralization . SHRIMP zircon U–Pb age of gabbro samples from the Puchang complex ranged from 269.4 ± 2.2 Ma . The study results show that the crystalline ages of porphyry granites and hosting rocks are consistent within the error range and are the products of the near synchronous magmatic activity.…”

“…Previous studies have shown that the magmatic rocks in the TLIP can be roughly divided into basalts (290–285 Ma) in the early period, ultramafic–mafic intrusive rocks, and syenite intrusive rocks (284–274 Ma) in the late period . Time series mapping informed by the detailed evaluation and screening of the age data of the early Permian magmatic rocks in Tarim yielded four periods of magmatic events in the TLIP: the first stage is characterized by the formation of kimberlite dykes; the second stage is dominated by continental flood basalt and rhyolite, which are mainly supplied by the melting of lithospheric mantle and crustal materials, respectively, and are the products of the continuous interaction between mantle plume and lithospheric mantle; and the third stage is dominated by pyroxenite, gabbro, and syenite, followed by diorite, diabase, and granite, which is the main period of magma formation in the area . Furthermore, the fourth stage shows nephelinolite and alkalic granite, followed by the latest alkalic intrusion .…”

“…In the early Permian, rifts occurred at the junction of the southern Tianshan mountains and Tarim to form alkalic basalt, alkalic gabbro–syenite-granite assemblages, and late diabase and granites . V–Ti-magnetite-mineralized intrusive complexes, such as Wajilitag and Puchang, − and Cu–Ni sulfide deposits, such as Karatungk and Huangshandong, , are believed to come from the partial melting of the Permian asthenosphere and metasomatic lithospheric mantle, respectively . Halajun is one of the representative areas in the western section of the South Tianshan tectonomagmatic belt, which is mainly composed of Permian granitoids, followed by Permian volcanic rocks, intrusive complexes, syenites, granites, alkalic granites, and carbonatites among others.…”

“…The resource quantities of iron and TiO 2 are medium-sized deposit, and the associated V 2 O 5 resource is small . Previous studies on geochemistry, Sr–Nb isotopes, and SHIMP zircon U–Pb chronology of gabbros in the Puchang complex indicate that partial melting under the subduction metasomatic lithospheric mantle source of the South Tianshan Ocean in the Early Mesozoic is a significant causality for the formation of the Puchang complex. − Based on the study of platinum group elements and the Re–Os of titanomagnetite, different degrees of crustal contamination are inferred to be the key factors leading to changes in sulfide saturation and segregation, along with the potential Cu–Ni sulfide deposits in the area , and the prospect of rare earth mineralization . Many granites cut through strata, and plutons are developed in the mining area, but the genetic relationship among granites, intermediate-acid plutons, and ore-bearing complex and the relationship between granites and regional magmatic-tectonic evolution are undefined.…”