Introduction

Orogens are major sites for crustal growth on Earth. They record a unique formation and evolutionary history of the continental crust that distinguishes Earth from other planets. Therefore, orogenesis and crustal growth, and particularly their relationships, are fundamental issues in the Earth sciences.

Orogens are characterized and categorized using a range of features, leading to the identification of convergent and extensional or small-cold and large-hot orogens1,2, the external and internal orogenic systems3, and Alpine-, Himalayan-, and Turkic-type collisional orogenic belts4. They are commonly grouped into collisional, accretionary, or intracratonic5,6,7,8,9.

However, orogens are mostly composite and experience multiple stages of the orogenic processes, such as the accretion of relatively small terranes (or soft collision) and continental collision, and these orogens are commonly called composite orogens4,8,10, Thus, orogens vary in their nature and style, defining a broad spectrum of types that encompass the Wilson Cycle11. There are a lack of robust ways or methods to quantitatively characterize, define, and/or classify the various types of orogens (particularly composite orogens), although some previous studies have sought to compare accretionary orogens based on terrane longevity, accretion rates, and juvenile crust production4,5,6,12. Every orogen contains a distinct complex history, which also makes the comparison with other orogens very difficult. Seeking a way or method to objectively and quantitatively characterize and/or classify orogens based on their final compositional architecture and crustal growth patterns (or stages) is crucial.

In this paper, we applied Nd isotope mapping as a “Big Data” approach to evaluating the compositional architecture and crustal growth patterns of the eight well-studied Phanerozoic orogens to provide a semi-quantitative basis for comparison. Specifically, the areal proportion of primitive/juvenile to evolved/reworked crust has been used as a semi-quantitative criterion to characterize the crustal compositional architecture and evolution of orogens. This study provides insights into the relationships between orogenesis and crustal growth.

Results

Representative and well-studied orogens

Two end-members of orogens have been commonly proposed: accretionary and collisional5,6,8,9. Accretionary orogens form by the accretion of diverse components (e.g., dominantly oceanic components including island arcs, ophiolites, and fragments of oceanic plateaus and microcratons) accreted from the downgoing plate and eroded from the upper plate at active oceanic subduction zones, whereas collisional orogens form as continental plates are progressively subducted5,8,13. Most accretionary orogens now occur as “fossil” orogenic belts within and/or at the margins of consolidated continents14. Phanerozoic accretionary and collisional examples include the eight orogens discussed below (Fig. 1 and Supplementary Note 1).

Fig. 1: A map of the eight representative and well-studied orogens in the world, showing their locations and tectonic background.
figure 1

NCC North China Craton; SCC South China Craton. The digit topographic map comes from https://services.arcgisonline.com.

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The Altaids, or Altaid tectonic collage4,15, or the southern Central Asian Orogenic Belt (CAOB)16,17, is located between the Siberian, Baltic, and Tarim-North China cratons (Fig. 1). It records protracted accretion of the Paleo-Asian Ocean and subsequent collision of ancient terranes from 1000 (mainly 650) to 220 Ma12,17,18. followed by the accretion and closure of the Mongol-Okhotsk Ocean from 300 to 150 Ma4,12,15,17,18,19. The Altaids is generally considered to be the world’s largest accretionary orogen and the important site of considerable Phanerozoic continental growth12,16,17,18. The Appalachian Orogen in North America was formed by accretion and/or soft collision of several juvenile terranes and ancient crustal blocks and the terminal continent-continent amalgamation of Laurentia and Gondwana in the Permian10,20. One of the best-exposed cross-sections through the orogen is exposed in Newfoundland10. The North American Cordillera is considered to be an archetypal accretionary orogen5,7. The major accretionary processes occurred during the Mesozoic, although evidence exists that subduction began ~420 Ma ago21,22. The Lachlan Orogen is part of the Paleozoic Tasman Orogenic system of eastern Australia and Gondwana23. The orogen formed during the stepwise closure (500–340 Ma) of sequential oceanic back-arc basins formed behind a long-lived, outboard migrating subduction zone that is preserved in the New England Fold Belt23.

The following four representative and well-studied Phanerozoic collisional orogens are investigated here (Supplementary Note 1). The Caledonian Orogen or Caledonides formed during the Silurian collision between Laurentia and Baltica24. The Variscan Orogen or Variscides was the result of the late Paleozoic collision between Gondwana and Laurussia25. The Qinling-Dabie Orogen initially formed during the closure of the Proto-Tethyan Ocean and finally due to the closure of the Paleo-Tethyan oceans and the early Mesozoic collision between the North China Craton and South China Craton26. The Tethyan Tibetan Orogen (i.e., the Tibetan Plateau) experienced Mesozoic accretion–collision of terranes following the closure of the Proto- and Paleo-Tethyan Oceans, and the final Cenozoic (60–50 Ma) India–Eurasia collision during the closure of the Neo-Tethys Ocean27,28.

Isotopic mapping of the eight orogens

We used felsic and intermediate igneous rocks (as classified in the original literature, see Supplementary Note 1) to undertake Nd isotope mapping and then to investigate the compositional architecture and crustal growth patterns, i.e., the final result of preservation of long-term crustal growth formed during (accretionary and collisional) orogenesis. Felsic igneous rocks (e.g., granitoids) are generally derived from the crust and their isotope features commonly reflect the basement rocks of the crust. Some intermediate igneous rocks may be produced by fractional crystallization of mantle-derived mafic magmas, but many are considered hybrids generated by magma mixing or contamination, as indicated by consistently old (Nd and Hf) model ages relative to emplacement age. Thus, we assumed that their isotopic features represent the overall, mixed characteristics of the deep crust. More importantly, we selected these felsic and intermediate igneous rocks to ensure a broad range of rock types within each orogen, which increased the number of isotopic analyses to make the comparisons more credible and reduce statistical uncertainties. Data were collected from the literature and websites. The data are reliable according to the sources, which was confirmed by the good linear correlation of their εNd(t) values vs. two-stage Nd depleted mantle model ages (TDM2; Supplementary Note 2).

We conducted whole-rock Nd isotope mapping (methods in Supplementary Note 3) using the compiled datasets of 9332 Sm-Nd data with ages, including 240 new analyses, i.e., 71 from the Appalachian (Newfoundland) orogen and 169 from the Altaids (Supplementary Data 1-8). The isotopic maps cover all outcrop areas of a whole orogen such as the Altaids (~7,010,625 km2), North American Cordillera (~6,693,675 km2), Newfoundland Appalachians (~115,236 km2), Lachlan (532,550 km2), Tethyan Tibet (~2,403,600 km2), Variscan (~1,237,600 km2), and the Qinling-Dabie (~294,075 km2) orogens. For the Caledonian orogen that has been split by the Atlantic Ocean opening, the mapped areas (~666,800 km2) cover most of the outcrop areas of the orogen, including the British, Scandinavian, Svalbard, and Greenland regions (Fig. 2).

Fig. 2: εNd(t) contour maps of the eight orogens, showing spatial variations of εNd(t) values and distribution of Nd isotopic domains.
figure 2

a Altaids, b North American Cordillera, c Newfoundland Appalachians, d Lachlan, e Tethyan Tibet, f Caledonides, g Variscides, and h Qinling-Dabie orogens, showing spatial variations of εNd(t) values and distribution of Nd isotopic domains. The lower row legend shows the colors expressed as variations in εNd(t) values. E. = Eastern; C. = Central; W. = Western. See the explanations and uncertainties in the text and dataset in Supplementary Data 1–8. The digit topographic map comes from https://services.arcgisonline.com.

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Nd isotope parameters, specifically εNd(t) values and two-stage model ages (TDM2, Ga), are shown as contour maps in Fig. 2 and Supplementary Note 2. These maps demonstrate the distribution of isotopic domains and their areal extent (Supplementary Data 9). The domains are defined by per 2 εNd(t) value interval and shown in Fig. 2 by 15 different color zones (Fig. 2). These domains can be grouped into six isotopic provinces (Supplementary Data 10): (I) extremely or highly primitive (i.e., juvenile), characterized by εNd(t) value > +6 and young Nd mode ages (TDM2 < 0.4 Ga); (II) moderately primitive by εNd(t) = +4 to +6, relatively young TDM2 values (0.4–0.8 Ga); (III) slightly primitive by εNd(t) value = +4 to 0, TDM2 = 0.8–1.0 Ga; (IV) slightly evolved, by εNd(t) =−4 to 0, TDM2 = 1.0–1.2 Ga; (V) moderately evolved, by εNd(t) = −10 to −4, TDM2 = 1.2–1.6 Ga; (VI) highly evolved provinces, by εNd(t) <−10, TDM2 = 1.6–2.8 Ga.

These isotopic domains reflect the distributions of isotopic signatures of the source rocks in the basement. Effectively, the approach is “basement terrane mapping”. Accordingly, we denote juvenile versus reworked crust and place constraints on the compositional architecture. The juvenile crust is generally defined by positive εNd(t) values (>0), which are commonly used (e.g., refs. 5,6). The juvenile crust in the isotopic maps is characterized by provinces I to III. Correspondingly, the reworked crust is defined by negative εNd(t) value (<0), characterized by provinces IV to VI.

From these maps, we obtain the relative areal proportions of primitive and evolved isotopic compositions and can determine juvenile and reworked crustal provinces, respectively (Figs. 2 and 3 and Supplementary Data 9). The juvenile areal proportions of the Altaids, North American Cordillera, Newfoundland Appalachians, Lachlan, Tethyan Tibet, Caledonides, Variscides, and the Qinling-Dabie Orogen are ~58%, ~54%, ~40%, ~31%, ~3%, ~1%, ~1%, and 1 < % of total areas of each orogen, respectively, quantitatively evaluating the degree of preservation of crustal growth (Fig. 3). The percentages were calculated from the areas of the isotopic provinces or domains and their precision depends on the numbers of isotopic data and their homogeneity in distribution (Fig. 2). With increasing data, the isotopic mapping may be more precise, but the percentage results may be approximately similar.

Fig. 3: Diagrams of εNd(t) value vs. area percent of isotopic domains (upper row), showing the total areal percent of the primitive province or juvenile crust (εNd(t) > 0; blue area) for each orogen.
figure 3

The color scales are defined by per 2 εNd(t) value interval, the same as those in Fig. 2. The lower row diagrams are histograms of TDM2 for each orogen. Blue areas denote primitive domains or juvenile crust younger than TDM2 corresponding to εNd(t) = 0; whereas the warmer colors reflect increasing amounts of ancient crust. The color scales are defined by per 200 Myr TDM2 interval, the same as those in Supplementary Fig. 2. All the data are listed in Supplementary Data 9 and 10.

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Figure 4 shows types of crustal growth curves. These curves reflect the percentages of the areas of εNd(t) and TDM2 isotopic domains (Fig. 3 and Supplementary Data 10), so they directly denote crustal growth, which is different from commonly used crustal growth curves made by cumulative frequency plots of global isotopic datasets29,30,31,32,33,34. The curves of the four accretionary orogens (Altaids, North American Cordillera, Newfoundland Appalachians, and Lachlan) all extend to the right side (more positive εNd(t) and young TDM2) compared with other curves (Fig. 4), demonstrating these accretionary orogens contain more (>30%) juvenile crust. Among them, the Altaids hosts the highest accumulation and/or percentage of juvenile crust, followed by the North American Cordillera, Newfoundland Appalachians, and the Lachlan Orogens, with the Tethyan Tibet, Caledonides, Variscides, and the Qinling-Dabie Orogens having the least amount of juvenile crust. Clearly, the accretionary orogens contain much larger volumes of juvenile crust than the collisional orogens (Figs. 2–4), quantitatively confirming that accretionary orogens are primary sites of juvenile continental crust production, as many previous studies show5,13,35,36.

Fig. 4: Crustal growth curves for the eight orogens.
figure 4

The curves show a the percentage areas of crust produced per two εNd(t) value intervals and b per 200 Myr TDM2 interval. The percentages are drawn from the areas of εNd(t) and TDM2 isotopic domains respectively (Fig. 3 and Supplementary Data 10). So, these crustal growth curves directly denote crustal growth, which is different from commonly used crustal growth curves made by cumulative frequency plots of global isotopic datasets29,30,31,32,33,34. The vertical dashed lines (b) represent TDM2 corresponding to εNd(t) = 0, and the dotted horizontal lines denote the percentages of the crust when εNd(t) = 0, the distinction between juvenile and evolved. Taking the Altaids for instance, ~58% of juvenile crust had been generated at ~1.0 Ga. The colors of the solid and dotted lines represent different orogens. Data are listed in Supplementary Data 9.

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Our Nd isotope mapping results are consistent with those of zircon Hf isotope mapping and xenocryst studies of some orogens, such as in the Altai–Junggar–Tianshan region of the southern Altaids37,38,39, the Qinling-Dabie40, and the Tethyan Tibet28. In the Altai–Junggar region, Hf isotopic mapping of the Palaeozoic granitoids indicated a sharp contrast between the deep crustal compositions of the Altai and Junggar regions: the reworked (ancient) crust in the central Altai and juvenile in the Junggar38. This is consistent with the result of our Nd isotopic mapping (Fig. 2a). The isotopic mapping results are also consistent with geophysical investigations41. For example, primitive isotopic domains (province I; Supplementary Data 10) reveal the existence of deep-seated highly juvenile crust in the western Junggar of the Altaids. Similarly, magnetotelluric imaging also revealed this deep-seated Paleozoic paleo-oceanic crust42. Furthermore, shear wave (Vs) seismic tomography at depths of 30–40 km, based on >200 stations, identified a high-velocity body in the western Junggar orogen, and low-velocity bodies in the Altai and Tianshan mountains41. These coincide with provinces I and II in the western Junggar orogen and evolved Provinces V and IV in the Tianshan and Altai mountains.

Compositional architecture (crustal patterns) of the eight orogens

The proportions of juvenile to reworked crust contrast between the orogens. The Altaids contains a large area of juvenile crust accounting for ~ 4,107,350 km2 and ~58% area (Figs. 2 and 3 and Supplementary Data 9 and 10). Considering (1) the Altaids is an (extensional) accretionary orogen that preserves significant amounts of oceanic crust, accretionary wedges, and other juvenile tectonic terranes; and (2) there are few significant over-thrusts (different from the Tethyan Tibit and Qinling-Danie orogen), we assume that the deep-seated juvenile crust largely represents the whole crust. Then we estimate the juvenile crust in the Altaids as a volume of ~184,830,750 km3, using the total areas of isotopic mapping (~7,010,375 km2) and a 40–50 km (an average of 45 km) crustal thickness43. Accordingly, the Altaids hosts both the highest percentage (~58%) and the largest volume of juvenile crust among the eight orogens. Comparably, the North American Cordillera (~54%), Newfoundland Appalachians (~40%), and the Lachlan (~31%) contain less juvenile crust and more evolved crust, similar to the complex accretionary orogens defined by Condie6. These are consistent with their geological characteristics. For instance, the Newfoundland Appalachian was subjected to the successive accretion of Gondwana-derived terranes with an older pre-orogenic history of crustal formation, interspersed with oceanic fragments10. The Paleozoic Lachlan Orogen acquired its transitional character by the deposition of cratonic (Proterozoic) sediments into sequentially formed backarc basins and the sediments were progressively buried and melted during various stages of orogeny to produce S-type granites35. Elsewhere in the orogen, the juvenile meta-igneous crust was melted to produce I-type granites.

In contrast, the above four collisional orogens, located on the left sides of the curves (Fig. 4), contain much less juvenile (or much larger reworked) crust (Fig. 2). The Qinling-Dabie Orogen contains not only the least (<1%) juvenile crust (or the largest reworked crust) but also the most ancient crust (εNd(t) <−16; Figs. 3 and 4). This is consistent with the orogen’s character that the South China Craton was overridden by the dominantly Archean North China Craton (deep continental subduction) as indicated by the continental ultra-high-pressure metamorphism44.

Discussion

From the above, we propose an approach to divide the orogens, based on the areal proportions of juvenile (primitive) or reworked crust, into dominantly juvenile (primitive isotope values) and reworked (evolved isotope values) types (Fig. 5). We propose that an orogen can be placed into six categories, based on its composition and timing of orogeny (Fig. 5).

Fig. 5: A hemispheric diagram showing the classification and characteristics of orogens in terms of their compositional architecture (areal percent of juvenile compositions) and ages of orogens.
figure 5

Sectors represent a continuous transition from highly primitive (juvenile crust 100%) to highly evolved (juvenile crust ~0%) compositions. Concentric semi-circles with logarithmic coordinates denote the age range of the orogens (such as 500–340 Ma for the Lachlan Orogen).

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Previous studies demonstrated that orogens are mostly composite and evolve with time, and most accretionary orogens end up in a collisional phase (e.g.45,). It is potentially difficult to distinguish between accretionary and collisional orogens in practice; even the two “terms” are inconsistently understood by different authors. For instance, the Altaids, a typical accretionary orogen12,17,18, still hosts collisional features and has been called a Turkic-type collisional orogenic belt4. The Appalachian orogen is also viewed as a collisional orogen5. The Variscides is generally considered to be a collisional orogen25, but is still considered to be accretionary prior to collision (e.g.,5,pp149). Condie5,6 further divided accretionary orogens into simple (chiefly juvenile terranes with lifespans of <100 m.y.) and complex (with both juvenile accreted, components and exotic microcratons, with terrane lifespans of ≥100 m.y.) types. Our characterization and classification of orogens enable us to objectively and semi-quantitatively contrast between them (Fig. 5). Orogens with juvenile crust between 70–50% correspond to simple (typical) accretionary (e.g., the Altaids, ~58%), and 50–30% to complex accretionary (e.g., North American Cordillera (~54%), Newfoundland Appalachians (~40%), Lachlan Orogen (~31%)). Furthermore, we consider orogens with 30–10% juvenile component as complex collisional (which contains more juvenile crust than typical collisional and can be viewed as falling in between accretionary and collisional), 10–1% as simple (or typical) collisional (e.g., Tethyan Tibet (~3%), Caledonides (~1%), and Variscides (~1%)). Typical oceanic arcs containing >70% juvenile crust and collisional orogens with <1% juvenile crust (e.g., the Qinling-Dabie Orogen) may be regarded as the end members of the entire orogenic array, and the formers may be preserved in an accretionary orogenic system. Oceanic arcs built on continental ribbons may vary between endmember and simple accretionary orogens depending on the proportion of the old basement. We predict New Zealand and Japan would fit the simple accretionary category. This study provides a semi-quantitative approach to characterizing orogen types.

It is important to further distinguish the collisional and accretionary phases of an orogen and to compare the evolutionary phase of an orogen with a similar phase in another orogen, if possible. Figures 2 and 3 show the percentage area of primitive and/or evolved isotopic domains and the crustal growth curves of the eight orogens. These provide a quantitative comparison of the amount of juvenile and reworked crust of these orogens in different phases, but it is difficult to distinguish the accretionary (juvenile) and collisional (reworked) phases for one orogen and to compare the orogen with a similar phase in another orogen. As an example, we produced isotopic maps for the syn-accretionary (600–320 Ma) and post-accretionary or collisional (320–150 Ma) igneous rocks in the Altaids41, which assumes collision occurred at 320 Ma. However, some authors suggest final closure of the major intervening (Paleo-Asian) ocean occurred in the Permian or Triassic. Assuming 320 Ma collision, the results show that the accretionary phase contributed ~3,156,900 km2 of the juvenile crust, accounting for ~45 % of the surface area of the Altaids (all isotopic provinces), and the collision (320–150 Ma) ~950,450 km2, accounting for ~14%. They may be considered to be representatives of the earlier accretionary and latter collisional phases, respectively.

In general, it is not easy to identify and date an accretionary and a collisional phase, particularly if the collisional process was diachronous, where both phases of orogeny involved a long-lasting terminal orogenic process (e.g., the Altaids and Appalachians). Similarly, if the accretionary orogen underwent repeated extension-contraction phases, some syn-accretionary granites might be regarded as “post-collisional”. For example, many S-type granites in the Lachlan orogen are called “post-collisional” (e.g., ref. 46), but most are Silurian and accretion continued until the Middle-Late Devonian following a significant Early Devonian extension phase. Therefore, this study mainly focuses on a comparison of the overall architecture formed during all major syn-orogenic (accretionary and collisional) processes, which is achieved by a comparison study of similar igneous rock types that formed during the major orogenic (accretionary and collisional) processes. Although it would be better to compare the similar phases of the evolution of the complete lifetime of an orogen if there were sufficient data, the present work establishes a first-order difference between accretionary and collisional orogens.

From the point of view of the Wilson Cycle, orogens begin as accretionary and evolve into collisional, culminating in the termination phase during supercontinent amalgamation6,9,11. Thus, each orogen may be viewed as having reached a certain stage of its evolution path in the Wilson Cycle. Moreover, active accretionary orogens will continue to evolve; for instance, the active accretionary orogenic systems around the margins of the Pacific Ocean, such as the North and South American Cordillera, may evolve or be reformed into collisional or even intracratonic orogens if the Pacific Ocean closes in the future (e.g., ref. 47). Based on this expected orogenic evolution, we can use the decrease in the juvenile crustal areal proportions to semi-quantitatively trace the orogenic stages from accretion to collision as each orogen progresses through the Wilson Cycle (Fig. 5).

This study also marks strong links between orogenesis and crustal growth. Crustal growth is defined as the addition of mantle-derived material to the crust, and rates are usually based on cumulative frequency plots of global isotopic data29,30,31,32,33,34. However, there are many unconstrained aspects of the statistical treatment of data (such as data size and their homogeneous distribution), and such global compilations do not reflect the relationship between orogenesis and crustal growth. Here we have applied areal proportions of juvenile crust determined by isotopic mapping to individual orogens to show which have contributed significantly to crustal growth and which have not.

The Altaids was regarded as the best example of Neoproterozoic-Phanerozoic continental growth15,16,48. However, this has been questioned recently, where it is argued that no unusual continental growth occurred at this time49. Our study indicates that the Altaids contains both the largest volume and highest proportion of juvenile crust (see above) and much of it formed during the Neoproterozoic-Phanerozoic (Figs. 2–4). Accordingly, the Altaids can be viewed as a “fossil” of the largest Phanerozoic crustal growth area in orogens worldwide41 and it serves as the best example of Phanerozoic accretion and crustal growth to compare with the Archean Cratons to test for similarities or differences in the formation of continents through time50. Additionally, our datasets can be used to confirm the onset of accretionary orogenic systems and plate tectonics in the Archean Eon. Our study helps to untangle the mystery of whether or not significant continental crustal growth occurs during orogenesis, including the Phanerozoic orogenesis16,29,31,33,34.

Untangling the mystery of crustal growth and its mechanisms is an interesting and fundamental issue in the Earth sciences. Several mechanisms have been invoked for the generation of juvenile crust during (Phanerozoic) subduction/accretion5,6,31,51,52. Accretion, particularly extensional accretion, is beneficial for the generation of juvenile crust5,6,8,9, which is produced by the melting of a mantle wedge metasomatized by subducted fluids, by melting of subducted oceanic crust, or by rapid remelting of basaltic underplates at the base of arcs (e.g., ref. 52). Some researchers (e.g., ref. 51) suggested that collisional orogens (or collision zones) are primary sites not only for continental crustal growth but also for net continental crustal growth (e.g., the Tethyan Tibet), and the juvenile crust (syncollisional andesites) are isotopically dominated by mantle signatures inherited from ocean crust that was derived from the mantle at mid-ocean ridges or derived from mantle-derived magmas generated during break-off or delamination in a post-collisional setting (e.g., ref. 28). The crustal growth estimated by the isotopic mapping is observed as preservation of juvenile crust; so, it is net growth. Our Nd isotopic mapping confirms the observations (e.g., ref. 45) that a large amount (30–60%) of juvenile crust occurs in accretionary orogens, but less (<5%) juvenile crust occurs in collisional orogens (Fig. 5) and provides a quantitative amount and proportion of juvenile crust.

Preservation is important for net crustal growth. Oroclines and soft collision may provide good conditions for the preservation of juvenile crust, such as a large number of oroclines in the Altaids4,18,19. Numerous oroclines with different sizes have been identified in the Altaids15.18,19. These oroclines contain many trapped structures, e.g., the trapped structures in the Junggar region of the western Altaids, and these structures preserve a large proportion of the oceanic crustal systems and other types of juvenile continental crust. Additionally, soft collision facilitates the preservation of accretionary terranes and suture zones dominated by juvenile crust. These soft collision zones are typical of accretionary orogens and are distinct from the hard collision events of collisional orogens that may result in the removal of the juvenile crust by crustal-scale thrusting and subsequent erosion or by deep subduction of continental crust.

In summary, the crustal pattern or compositional architecture of an orogen reflects both the production and preservation of juvenile crust. Delineation of the compositional architecture and crustal patterns by isotope mapping allows objective and quantitative characterization and classification of orogens, obtaining an indelible imprint that relates to the areal proportion of juvenile crust preserved in the system. Accordingly, we can unveil the relationships between orogenesis and crustal growth, providing an alternative approach for constraining the evolution of Earth. We provide an innovative way to directly compare different complex orogens and divide the orogens into different evolution stages through isotope mapping and estimating percentages of areas (volume) of juvenile crust quantitatively.

Methods

We used the chondritic values (143Nd/144Nd)CHUR = 0.512638 and (147Sm/144Nd)CHUR = 0.196753 to calculate all Nd data (Fig. 2) and to obtain εNd(t) values and Nd depleted mantle model ages (one-stage, TDM1, and two-stage TDM2; Supplementary Note 2). The juvenile crust is defined as having positive εNd(t) values (i.e., >0)54.

Neodymium and model age contour maps were produced in two steps. Firstly, we used the inverse distance weighted interpolation method and Surfer v.13.0 software for gridding. Given the uneven distribution of the isotope datasets, we sequentially used two spacings and searched radii (i.e., 50–500 and 5–100 km, respectively) for the gridding. Secondly, we converted the grid data to *.img format in ArcGIS, reclassified the data into equal intervals and then produced the contour maps with Spatial Analyst Tools. The obtained and compiled data, data sources, and analytical methods are presented in Supplementary Data 1–8 and Supplementary Note 3.