Abstract Late Mesozoic evolution of the Neotethys Ocean is critical and still remains unclear along the entire Sakarya Zone (SZ), Turkey, because previous interpretations of the Middle to Late Jurassic rifting of the SZ have not been consensually accepted. We identified, for the first time, the Early Cretaceous dykes intruded into the Late Jurassic and Late Carboniferous bodies in the Camlikaya (Erzurum) area in the SZ. Here, we present a data set of new field observations, 40Ar/39Ar geochronology, whole-rock geochemical and Sr–Nd isotopes to find out the tectonic setting of previously undated basic to intermediate igneous rocks. 40Ar/39Ar technique on the groundmass separations yielded the plateau ages of 128.78 ± 1.02 to 122.89 ± 0.82 Ma. The investigated dykes are compositionally divided into two sub-groups: calc-alkaline lamprophyres (CAL) and high-Nb alkaline basalts (HNB). They show enrichment in large ion lithophile elements (LILE: e.g., Rb, Ba, K) and depletion in high field strength elements (HFSE: Nb and Ti) as well as moderate fractionation of light rare earth elements relative to heavy rare earth elements. The HNB have high Mg# (47–66), and relatively unradiogenic Sr [87Sr/86Sr(t) = 0.70385 to 0.70510] and Nd [eNd(t) = +0.5 to +5.3] isotopic composition, whereas the CAL possess moderate to high Mg# (32–72), and relatively high Sr [87Sr/86Sr(t) = 0.70586 to 0.71379] and Nd [eNd(t) = +1.5 to −9.9] isotopic composition. Early Cretaceous high-angle subduction triggered upwelling of the asthenosphere at 126 Ma, which likely generated a heat anomaly. This anomaly has probably induced melting of the oceanic slab and the metasomatized mantle to form the CAL and HNB. The HNB were generated by low degrees of melting of mantle domain that was previously reacted by oceanic slab-related adakitic melts at the depths of the garnet stability field (≥70 km). However, the CAL were probably formed at shallower mantle levels within the garnet-amphibole field by a relatively higher degree of melting of the mantle, also modified by subducted slab sediments. A new field, age, and petrochemical data from the Early Cretaceous dykes, combined with the presence of Aptian deep-water sediments to the north and the Late Jurassic-Early Cretaceous platform carbonates deposited in the passive margin setting along the entire SZ, imply the initiation of active-margin magmatism in the SZ. We suggest that the coexistence of the Early Cretaceous CAL and HNB points to the formation of an Andean-type active margin above a north-dipping Neotethyan oceanic slab. Their emplacement ages are associated with the inception of the magmatic arc structure and refer to a significant geodynamic turnover from passive-margin to active-margin tectonics along the SZ.

中文翻译：

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土耳其东北部早白垩世斑岩和高 Nb 玄武岩脉的性质：它们与新特提斯大洋岩石圈俯冲开始的联系的限制

摘要 新特提斯洋的晚中生代演化在土耳其整个萨卡里亚带 (SZ) 沿线的关键和仍不清楚，因为先前对 SZ 中侏罗世裂谷的解释尚未被一致接受。我们首次发现早白垩世岩脉侵入了SZ Camlikaya（Erzurum）地区的晚侏罗世和晚石炭世体。在这里，我们提供了一组新的野外观测数据、40Ar/39Ar 年代学、全岩地球化学和 Sr-Nd 同位素，以找出以前未注明日期的基性至中级火成岩的构造环境。40Ar/39Ar 技术对地块分离产生了 128.78 ± 1.02 到 122.89 ± 0.82 Ma 的高原年龄。调查的堤坝在成分上分为两个子组：钙碱性斑岩 (CAL) 和高 Nb 碱性玄武岩 (HNB)。它们显示出大离子亲石元素（LILE：例如，Rb、Ba、K）的富集和高场强元素（HFSE：Nb 和 Ti）的耗尽以及轻稀土元素相对于重稀土元素的适度分馏。HNB 具有高 Mg# (47–66) 和相对无放射性的 Sr [87Sr/86Sr(t) = 0.70385 至 0.70510] 和 Nd [eNd(t) = +0.5 至 +5.3] 同位素组成，而 CAL 具有中等同位素组成至高 Mg# (32–72) 和相对较高的 Sr [87Sr/86Sr(t) = 0.70586 至 0.71379] 和 Nd [eNd(t) = +1.5 至 -9.9] 同位素组成。早白垩世大角度俯冲在 126 Ma 触发了软流圈的上升流，这可能会产生热异常。这种异常可能引起了大洋板块和交代地幔的熔化，形成了 CAL 和 HNB。HNB 是由地幔域的低程度熔融产生的，该地幔域先前在石榴石稳定场（≥70 公里）深处由与大洋板块相关的埃达克质熔体反应。然而，CAL 可能是在石榴石-角闪石场内较浅的地幔水平形成的，由相对较高程度的地幔熔融形成，也受到俯冲板片沉积物的修改。来自早白垩世岩脉的新油田、年龄和石油化学数据，结合北部阿普蒂安深水沉积物的存在，以及沉积在整个 SZ 被动边缘环境中的晚侏罗世-早白垩世台地碳酸盐岩，表明SZ 活动边缘岩浆活动的开始。我们认为，早白垩世 CAL 和 HNB 的共存表明在北倾的新特提斯洋板块上方形成了安第斯型活动边缘。它们的侵位年龄与岩浆弧结构的开始有关，是指沿 SZ 从被动边缘到主动边缘构造的显着地球动力学转换。