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Genetic implications of new Sr and Nd isotopic data of the intrusive rocks from the Laramide Arc in Northern Sonora, Mexico/Implicaciones geneticas de nuevos datos de Sr y Nd de rocas intrusivas del Arco Laramide en el Norte de Sonora, Mexico.

1. Introduction

The Sr, Nd, and Pb radiogenic isotopes have been used to understand magma petrogenesis and also to define the composition of basement rocks through which the magmas raised to the upper crust (Kistler and Peterman, 1973; DePaolo, 1981; Farmer and DePaolo, 1983; Faure, 2001). In northwest Mexico (Fig. 1), Sonora is an important region to understand the paleotectonics of North America since Precambrian, because of the presence of remnants of hypothetical Rodinia continent suggested by Stewart et al. (2002), and also due to the probable connection between Laurentia and Gondwana during Paleozoic (Poole et al., 2005). The effect of the Basin and Range tectonics on this region is an inconvenience for the study of the intrusive bodies (Stewart and Roldan-Quintana, 1994), and also the presence of the voluminous Tertiary magmatism which covers the batholiths, mainly on the border between Sonora and Chihuahua (Lanphere et al., 1980; Ferrari et al., 2007). However, it is possible to identify a broad magmatic arc of cordilleran type that was active during the Late Cretaceous-Early Tertiary (Coney and Reynolds, 1977; Atwater, 1989), which produced abundant volcanic and intrusive rocks.

There are very few isotopic data from Sonora to understand the relationship between the basement and the Laramide magmas (Roldan-Quintana et al., 2000; Valencia et al., 2001; Housh and Mc Dowell, 2005). The origin of Tertiary magmatism in the Sierra Madre Occidental has been considered as mantle derived (McDowell et al, 1999; Lanphere et al., 1980) despite an important contribution from the upper crust has been also proposed (Verma, 1984). The aim of this study is to present new Sr and Nd isotopic data from some intrusive rocks of Laramide Arc to discuss their geochemistry, age, different magmas relationship, and the role and type of basement involved.

2. The pre-Laramide substratum

The pre-Laramide substratum is present in the northern Sonora area since the Precambrian. Paleoproterozoic metamorphic and intrusive rocks of 1.8 to 1.7 and 1.7 to 1.6 Ga have been identified at Caborca and Cananea regions, respectively (Anderson and Silver, 1977, 1979; Iriondo et al, 2005). Both assemblages had been juxtaposed during Jurassic probably due to displacements caused by the Mojave-Sonora Megashear (Anderson and Silver, 1979).

Sandstones and dolomites (miogeoclinal series) were deposited in the Neoproterozoic (760-700 Ma) in the Caborca terrane (Campa and Coney, 1983), in the Cambrian to Lower Permian in the Caborca and Cananea regions (Cooper and Arellano, 1946; Mulchay and Velasco, 1954) and all over central Sonora (Stewart et al., 1997, 2002). Eugeoclinal deep basin rocks, consisting of siliceous sediments, sandstones, carbonaceous shales and barite layers, ranging from the Ordovician to Lower Permian, are present in central Sonora (Poole et al., 1991, 2005), between the 28[degrees] 00' N and 28[degrees] 30' N. These eugeoclinal sequences are considered as allochthonous and overthrusted over the miogeoclinal rocks during the Late Permian-Triassic time (Poole et al., 2005). A Mesozoic sequence (continental or deltaic sandstone and carbonaceous shale including some coal layers) was deposited unconformably (Barranca Formation) over the allochthonous rocks (Wilson and Rocha, 1949; Alencaster-De Cserna, 1961; Stewart et al, 1991). In the Caborca region (at El Antimonio area), the Triassic-Jurassic sedimentary rocks exhibit marine signature and were deposited over paleozoic platform rocks (White and Guiza, 1949; Gonzalez-Leon, 1997; Gonzalez-Leon et al., 2005). A Jurassic volcanic arc composed of andesites, tuffs and rhyolites, occasionally metamorphosed to greenschist facies, is well documented in the Sonoran desert between Santa Ana and Sonoyta (Anderson and Silver, 1979; Corona, 1979), as well as in Cananea (Valentine, 1936; Wodzicki, 1995). Sedimentary rocks of Lower Cretaceous age are well developed in Sahuaripa, Cerro de Oro, Arizpe and Cananea (Rangin, 1982; Pubellier et al., 1995; Jacques-Ayala, 1995; Gonzalez-Leon et al., 2000). The continental volcanic and volcano-sedimentary arc of Upper Cretaceous age is exposed all over Sonoran region, which is also known as Tarahumara Formation in the Yaqui river area (McDowell et al., 2001; Roldan-Quintana, 2002). Rock units equivalent to the Tarahumara Formation are also exposed along the Sonora coast (Gastil et al., 1977), Caborca (Jacques-Ayala, 1999), Sierra Manzanal (Gonzalez-Leon et al., 2000), and Cananea (Valentine, 1936; Meinert, 1982; Wodzicki, 1995). The Laramide Intrusive Arc was emplaced in several parts of the described substratum.

3. The Laramide Intrusive Arc

The Laramide Intrusive Arc (LIA) constitutes a broad discontinuous belt of intrusive rocks (Fig. 1), 300 km wide in a section from Bahia Kino to Moctezuma, without correcting for the tertiary distensive tectonics. The LIA represents the intrusive component of the Laramide Magmatic Arc (Roldan-Quintana, 2002; Roldan-Quintana et al, 2009), which is the product of subduction of the Farallon Plate underneath the North America Plate, from the Late Cretaceous to Early Tertiary (Coney and Reynolds, 1977; Atwater, 1989). At surface, these rocks are expressed by several NNW-SSE oriented sierras, which represent lifted blocks during the Upper Tertiary Basin and Range tectonics. To the south of the 28[degrees] 30' N, their outcrops are more dispersed, always following a NNW-SSE trend, even if the sierras are less conspicuous.

[FIGURE 1 OMITTED]

Most of the LIA batholiths have not been studied in detail, except few of them exposed along the coast (Valencia-Moreno et al., 2003; Ramos-Velazquez et al., 2008), Mazatan (Richard, 1991), Aconchi and La Madera sierras (Roldan-Quintana, 1991, 1994), Cananea (Wodzicki, 1995) and along the San Carlos-Maycoba transect (Roldan-Quintana, 2002).

The batholiths along the coast are composed of tonalite to granodiorite (Valencia-Moreno et al., 2001, 2003), whereas inland they are composed of tonalite-granodiorite-granite (Roldan-Quintana, 1991, 2002). Two magmatic suites are often recognized in the Mazatan, Aconchi and Magdalena sierras: calc-alkaline series and per-aluminous series (Nourse, 1990; Richard, 1991; Roldan-Quintana, 1991). The key minerals present in the first case are hornblende and biotite, whereas the second one is defined by the presence of muscovite with or without biotite (Damon et al., 1983). There is evidence of multiple intrusions, which have been identified by the presence of basic xenoliths in the calc-alkaline granitoids (i.e. El Jaralito and Sierra La Madera batholiths), and by the intrusion of per-aluminous granitoids into the calc-alkaline cortege. The temporal definition for the LIA is generally accepted for the 90-40 Ma period, as it has been defined by Damon et al. (1983), but the magmatic period overlaps the Late Cretaceous, since the volcanic component of this arc, i.e. Tarahumara Formation, has been dated up to 100 Ma (McDowell et al., 2001). One temporal-spatial evolution has been frequently postulated, with a diminish in age from the coast to inland (Damon et al., 1981; Clark et al., 1982; Damon, 1986; Valencia-Moreno et al., 2006). But new ages on the intrusive rocks from Central-East Sonora, as old as 90 Ma (Perez-Segura et al., 2009 and this work), suggest that space-time evolution of the LIA is more complicate than the simplistic schematic model.

4. Isotope Data

Sr and/or Nd isotopes data for 73 samples of laramide intrusive rocks were compiled (Fig. 1 and Table 1) from previous works (Damon et al., 1983, Mead et al., 1988; Wodzicki, 1995; Espinosa-Perea, 1999; Schaaf et al., 1999; Valencia-Moreno et al., 2001, 2003; Housh and McDowell, 2005; Roldan-Quintana, 2002 and Roldan-Quintana et al., 2009).

[FIGURE 2 OMITTED]

4.1. Samples of this study

Seven representative samples from Northern Sonora were selected for isotopic analyses (Fig. 1): two samples from the Bacanora area, four samples from the Cananea District and one sample from the La Caridad District. The coordinates of samples are given in Table 1. The initial [sup.87]Sr/[sup.86]Sr, [sup.143]Nd/[sup.144]Nd, [epsilon]Sr, [epsilon]Nd values and the model ages for Nd in relation to depleted mantle (DM) were calculated using the equations published by DePaolo (1981) and Farmer and DePaolo (1983). For samples 1 and 2 new isotopic ages determined in this work were used; for samples 3 and 4 (Lucy and Can-12) ages were taken from the Cuitaca Granodiorite published by Anderson and Silver (1977); for samples 5 and 6 (IntrCan and IntrMaria, respectively), the ages are from the Wodzicki (1995) work; and for sample 7 (Car-5) the age used was from the granodiorite reported by Valencia et al. (2005) and Barra et al, 2005).

Samples 1 and 2 are from the Bacanora area (Fig. 1, 2 and 3). Sample 1 is biotite-hornblende bearing granodiorite with quartz (15%), potassic feldspar (20%), sodic plagioclase (50%), hornblende (7%) and biotite (8%).

Sample 2 is quartz-monzonite porphyry related to skarn mineralization near the San Lucas Ranch (Fig. 3a). This rock intrudes propilitized andesites correlated with Tarahumara Formation (Late Cretaceous). The rock is made of quartz phenocrysts (5%), plagioclase (35%) and biotite + hornblende (10%), disseminated in a felsitic groundmass made of potassic feldspar (50%).

[FIGURE 3 OMITTED]

Samples 3 and 6 are from Mariquita mineralized zone, and they were weakly affected by phyllic alteration. Sample 3 corresponds to the Cuitaca Granodiorite, which is mineralized at the Lucy open pit, and the sample 6 is quartz-monzonite porphyry related to mineralization at the Maria open pit.

Samples 4 and 5 are from the Cananea District. The sample 4 was collected from the Puerto Cananea, which corresponds to the Cuitaca Granodiorite, whereas sample 5 was collected from one of the porphyries related with mineralization at the Cananea mine.

Sample 7 was collected from the La Caridad mine. This sample (Car-5) comes from a core of a diamond drill hole at a deeper level than the lowest bench (1245 m) of current open pit. The rock is granodiorite in a potassic alteration zone with rare anhydrite veinlets.

4.2. Analytical procedures

Sr and Nd isotopes were analyzed by Mihai Ducea at the geochemistry laboratory of the Geosciences Department, University of Arizona, following the methodology and standards described by Ducea et al. (2002). The Sr isotopic ratios of standards and samples were normalized to [sup.86]Sr/[sup.88]Sr = 0.1194, whereas the Nd isotopic ratios were normalized to [sup.146]Nd/[sup.144]Nd = 0.7219. The estimated analytical [+ or -] 2[sigma] uncertainties are similar to those reported in Ducea et al. (2002) and Otamendi et al. (2009). The measured [sup.87]Sr/[sup.86]Sr (Otamendi et al, 2009) for the SRM987 Sr standard were 0.710285 [+ or -] 7 (n=10) and the measured [sup.143]Nd/[sup.144]Nd for the La Jolla Nd standard were 0.511853 [+ or -] 2 (n=10). We also note that our results were not adjusted to any accepted values for these standards.

U/Pb and Ar/Ar geochronology were performed by Alexander Iriondo. For U/Pb geochronology a sensitive high-resolution ion microprobe-reverse geometry (SHRIMP-RG) instrument at the Stanford University was used; dating techniques in zircons were those reported by Williams (1998) and Nourse et al. (2005). [sup.40]Ar/[sup.39]Ar dating was carried out at the USGS in Denver, following the methodology described by Iriondo et al. (2004).

[FIGURE 4 OMITTED]

Chemical analyses for major and trace elements (including REE) were carried out at the Centre de Recherches Petrographiques et Geochimiques (CRPG) of Nancy, France.

4.3. Results

Geochemistry

Analytical values in major and trace elements for samples 3, 5, 6 and 7 are presented in Table 2. The rare earth elements (REE) values were normalized using the data proposed by McDonough et al. (1991). The REE pattern for the studied rocks is observed on Figure 2a. Normalization to depleted mantle was made just to compare with the spectrum from Wodzicki (1995) for the Cananea rocks (Fig. 2b). The rocks analyzed indicate patterns enriched in LREE and depleated in HREE, which is a characteristic feature of continental arcs. It is important to mention that the sample 3 corresponding to the mineralized plutonic intrusive at Lucy and the number 6, belonging to the mineralized hypabysal porphyry at Maria open pit, show a very similar geochemistry behavior, suggesting a comagmatic origin. Sample 5 coming from a mineralized porphyry stock of Cananea is affected by a strong hydrothermal alteration, as it is evidenced by absence of CaO (Table 2) and a very high value of 12.7 % on Lose on Ignition (LOI). This sample show HREE depleted pattern with a concave curve and an apparent absence of negative Eu anomaly. Similar pattern is in the 8-110 mineralized porphyry reported by Wodzicki (1995), with a significant positive Eu anomaly (Fig. 2b). In general the REE pattern of Cananea fresh rocks suggests a comagmatic origin; depletion in HREE elements for the mineralized porphyries is probably caused by hydrothermal alteration. The behavior of REE pattern for the sample 7 (Car-5), corresponding to the La Caridad Granodiorite, shows a similar pattern to those from Lucy and Maria (3 and 6), but with a slightly impoverishment in LREE and an enrichment in HREE.

Geochronology

Sample 2 (03-116 in Figure 3a and coordinates indicated in Table 1) was dated by U/Pb and Ar/Ar. U/Pb in zircons yield an age of 95.2 [+ or -] 1.8 Ma (Fig. 3b and Table 3); but ages obtained by [sup.40]Ar/[sup.39]Ar in potassic feldspar of porphyry groundmass goes from 53-71 Ma, for C-H hot steps (Fig. 3c and Table 4).

For the Sr and Nd isotopic calculation of Sample 1 (03102) we used the age of sample 03-101 (Mercator coordinates: 3203 487 N and 650 739 E), located 17 km to the west of Sample 1 (Fig. 4a). Sample 03-101 shows apparent ages (Fig. 4b, Table 4) very homogeneous for steps B-J in 56-57 Ma., and it is possible to plot an isochron line with B to F data yielding an age of 55.8 [+ or -] 0.29 Ma (Fig. 4c). There is no evidence of older ages.

Sr and Nd isotopic data

Table 5 show the isotopic analysis and calculated data for Sr and Nd of our samples. A summary of the same data is also given in Table 1.

Samples 1 and 2 from the Bacanora area gave initial [sup.87]Sr/[sup.86]Sr of 0.7066 and [epsilon]Nd of -5.0 (granodiorite); and of 0.7070 and -6.0 (porphyry), respectively. Samples 3 and 6 (Mariquita mineralized zone) have initial 87Sr/86Sr and [epsilon]Nd of 0.7081 and -5.5 for sample 3 (granodiorite) and 0.7080 and -5.5 for sample 4 (porphyry). Samples 4 and 5, from the Cananea District, present an initial [sup.87]Sr/[sup.86]Sr and [epsilon]Nd of 0.7077 and -3 for Sample 4 (Cuitaca Granodiorite), and of 0.7074 and -5.5 for sample 5 (porphyry). Finally, Sample 7 (granodiorite) from the La Caridad mine, has initial [sup.87]Sr/[sup.86]Sr and [epsilon]Nd of 0.7080 and -4.5, respectively.

[FIGURE 5 OMITTED]

5. Interpretation of the results

5.1. Geochronology

The age of 95 Ma for sample 2, is similar to other U-Pb ages from zircons on a dyke correlative with the same porphyry (Mercator coordinates: 3215270 N and 646945 E) which yield 88 Ma (Perez-Segura et al., 2009). The 95 Ma age is interpreted as a crystallization age, whereas the Ar-Ar ages from 52 to 71 Ma for the same sample are interpreted as cooling ages. Variations in the range of the Ar-Ar ages, indicate that the rock was subjected long time above the blocking temperature of the potassic feldspar, or that the rock was reheated during different periods.

The age of sample 03-101 around 56 Ma is considered as a cooling age. This age is in agreement with the better known ages (50 to 60 Ma) for the LIA in Sonora (Damon et al, 1983). It is also similar to one age reported by Pubellier et al. (1995) in Sierra Chiltepin (22 km N30[degrees]E from 03-101) dated 64 Ma (K-Ar) in a granitoid rock. However, the U-Pb age obtained from sample 2 (95 Ma) and other ages reported using the same method in the area, ranging from 88 to 91 Ma (Perez-Segura et al., 2009) do not allow to discard the possibility that ages older than 56 Ma have been probably erased.

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

[FIGURE 8 OMITTED]

5.2. Sr and Nd isotopic data

Bacanora area

The isotopic values of 0.7066 to 0.7070 for initial [sup.87]Sr/[sup.86]Sr and -5.0 to -6.0 for [epsilon]Nd, as well as the model ages for Nd in relation to the depleted mantle of 1.11 to 1.04 Ga, are very similar to previous isotopic values reported in northern Sonora, which indicates the probable presence of a Proterozoic basement in the area; in fact, other geological evidences indicate the presence of Neoproterozoic rocks between Bacanora and Sahuaripa (Stewart et al., 1999, 2001, 2002). Also the relative uniformity of the isotopic data for samples 1 and 2 could be interpreted as that the source of the magma in the area of Bacanora remained constant at least during the period between 95 and 56 Ma, if the last age was close to the age of crystallization of the plutonic rocks.

Cananea District

Seven samples have been reported from the Cananea District (3, 4, 5, 6, 78, 79 and 80; Fig. 1). The first four samples refer to the data reported here, and the other samples were from Woodzicki (1995). All the initial [sup.87]Sr/[sup.86] values range for the Cuitaca Granodiorite goes from 0.7069 to 0.7081 and [epsilon]Nd from -3.0 to -5.5, whereas for the porphyries the initial [sup.87]Sr/[sup.86]Sr varies from 0.7074 to 0.7086 and [epsilon]Nd from -5.3 to -5.7. The very similar values in Sr and Nd for the Cuitaca Granodiorite and the mineralized porphyry in Maria mine indicate a co-magmatic origin for both units and that hydrothermal alteration did not have any influence on the isotopic behavior; but in the case of Cananea mine there are small differences in initial [sup.87]Sr/[sup.86]Sr probably due to differences in the rock composition as it has been demonstrated for other igneous rock series (Verma, 2001). The co-magmatic origin for Cuitaca Granodiorite and mineralized porphyries is also supported by the REE behavior. It is possible to suppose that the magmas that gave origin to the intrusives in the area of Cananea and Maria were derived from the same source at depth. The origin of both could be due to melting of the Proterozoic lower crust, as it is suggested by the Sr and Nd data in xenoliths from Arizona and Northern Mexico (Ruiz et al, 1988). However, considering the lower Sr and less negative Nd values in Sonora compared with the values reported in southern Arizona (Wodzicki, 1995; Lang and Titley, 1998; Valencia-Moreno et al., 2001), we do not exclude some mantle contribution.

La Caridad District

Four samples have been compiled for Sr isotopic data from this region which range from 0.7064 to 0.7080 (Damon et al., 1983, and this study). Other data from Sr in Bella Esperanza (localities 12 and 72 in figure 1) indicates 0.7062 and 0.7070, respectively. The only available Nd data from this region indicates a value of -4.5 (sample 4). In this regard, we have analyzed a granodiorite with potassic hydrothermal alteration (Sample 7 in Table 2). The sample shows very low CaO (0.11%) and high [K.sub.2]O (6.4%) with relatively high loss on ignition (LOI-2.6%). The value of initial [sup.87]Sr/[sup.86]Sr in sample 7 as well as of sample 3 are somewhat higher compared to other samples reported from the area (Damon et al., 1983; Housh and McDowell, 2005; see also Table 2), differences could be caused by hydrothermal alteration as it has been observed in oceanic basalts and in the volcanic geothermal field of Los Azufres (Verma, 1992; Verma et al, 2005). The isotopic values of Sr and Nd from La Caridad and Cananea are very similar suggesting the same origin for the magmas in both districts.

6. Correlation with other areas of Sonora and with the pre-Laramide substratum

Values for initial [sup.87]Sr/[sup.86]Sr and [epsilon]Nd grouped by different ranges are represented on Figures 5 and 6, trying to relate the distribution with geography. One problem for interpretation is that most of data are located in central and northern Sonora. In any event it is evident that initial [sup.87]Sr/[sup.86]Sr upper than 0.7060 and [epsilon]Nd more negatives than -4 are located broadly north to the 28[degrees] parallel and to the east of coastline from Kino Bay. South and west of the same line, values for initial [sup.87]Sr/[sup.86]Sr are lower than 0.7060 and [epsilon]Nd less negatives than -4; as well as in central-eastern Sonora on the San Nicolas batholith (Roldan-Quintana, 2002). Some of the most important tectonic features are shown on the Figure 7, trying to relate different geological terranes with the isotopic values. Following this logic and using isotopic data published up to date, four isotopic regions can be proposed for Sonora:Zone 1. To the north of the limit of the Sonora Allochthonous (Poole et al, 2005) and with values of initial [sup.87]Sr/[sup.86]Sr >0.7060 and [epsilon]Nd <-4.

Zone 2. Corresponding to the zone where the Sonora Allochthonous overlaps the inferred continental crust. In terms of isotopic values it is characterized by [sup.87]Sr/[sup.86]Sr between 0.7060-0.7070 and [epsilon]Nd from -6 to -3.

The south isotopic limits follows a line trough the north of Tiburon Island.

Zone 3. This zone corresponds to the San Nicolas Batholith with variable [sup.87]Sr/[sup.86]Sr but with a very constant [epsilon]Nd between -4.1 to -3.7.

Zone 4. Located to the south of the supposed as the limit of continental crust (Poole et al, 2005). Typical values for this zone are [sup.87]Sr/[sup.86]Sr <0.7055 and [epsilon]Nd>-4.

Initial [sup.87]Sr/[sup.86]Sr and [epsilon]Nd data are plotted in Fig. 8. For comparison, the fields for intrusive rocks in southern Arizona and other parts of Mexico are also included.

The data discussed in this paper are located in here called zone and most of the known analytical data are located in the zones 1 and 2. These zones are characterized by initial [sup.87]Sr/[sup.86]Sr greater than 0.7060 and initial [epsilon]Nd < -4 and they roughly coincide to the south with the limit of the continental crust proposed by Poole et al. (2005); however, the limit to the west is parallel to the coast of Sonora and continues obliquely to north of Tiburon Island (Fig. 7). In both zones 1 and 2, the isotopic data allow us to presume the presence of Proterozoic basement at depth.

The zone 4, south and west of the previous one, shows few data, where we only have information along the coast between San Carlos and Punta Tepopa. The isotopic values although punctual, indicate initial [sup.87]Sr/[sup.86]Sr < 0.7060 and [epsilon]Nd > -4. These data plus the model ages for Nd of 1.43 and 0.85 Ga allow us to interpret that the intrusive rocks were emplaced at the external border of the Proterozoic basement. The prelaramide geology in southern Sonora is very little known, this region belongs partially to the Cortes and Guerrero Terranes (Campa and Coney, 1983) or the Tahue Terrane (Centeno-Garcia et al., 2008). It is known that metavolcanic rocks, and metasediments of lower Paleozoic are exposed in northern Sinaloa (Mullan, 1978; Centeno-Garcia et al., 2008). Similar series are correlated by other authors with the eugeoclinal rocks from central Sonora related to Gondwana (Poole et al, 2005). In southern Sonora, there are many exposed rocks of the Late Triassic Sonobari Complex (Mullan, 1978; Centeno-Garcia et al., 2008), these protoliths have been proposed as tholeiitic volcanic rocks originated in an oceanic rift (Keppie et al, 2006; Vega-Granillo et al, 2012). According to the data mentioned previously, the magmas which originated the granitoids south of the parallel 28[degrees] were not derived from a Proterozoic basement related to the North American Craton, instead of that it is derived from a source with an important mantle contribution, including contamination from the lower crust of the Tahue Terrane (Centeno-Garcia et al, 2008). This could be valid also for the granitoids exposed along the coast of Sonora between San Carlos and Punta Tepopa. The wide range of the model ages for Nd may indicate the heterogeneity in the composition of the Lower Crust.

Finally, in zone 3, the values of initial [sup.87]Sr/[sup.86]Sr are in a wide range (0.7054 to 0.7080) and [epsilon]Nd are relatively constant (-4.1 to -3.7), similar to values in the area of Tomochic, Chihuahua (Mcdowell et al., 1999). This, allow us to speculate on the absence of Sonoran proterozoic basement in this zone and relate the isotopic data to a pre-Laramidic geologic history similar to that of central Chihuahua (Housh and Mcdowell, 2005).

7. Conclusions

New isotopic data on hydrothermally mineralized rocks as for the Maria and La Caridad mines indicate that the isotopic compositions may change with respect to the fresh rock values, as it has been documented by other authors (Verma, 1992; Verma et al., 2005). This is important for future interpretations taking into account that many of the published isotopic data come from mineralized areas (Damon et al., 1983; Sansores-Bolivar and Wayne, 1977; Mead et al., 1988). Another important aspect in the Bacanora and Cananea regions is that the isotopic signature of the magmatic source did not change during the Early to Late Cretaceous (95-55 Ma).

According with new isotopic data and those published so far, various isotopic zones can be delineated in Sonora related to the major pre-Laramide tectonic features. Two of these zones have also been suggested by other authors. The isotopic characteristics and relation with substratum for the different regions proposed by us are:

Zones 1 and 2 located at North and Central Sonora (Fig. 7) are characterized by > 0.7060 initial [sup.87]Sr/[sup.86]Sr and < - 4 [epsilon]Nd values. They plot into the range values field of laramidic intrusions in Southern Arizona (Fig. 8). Proterozoic and Neoproterozoic rocks have been recognized in the region of zones 1 and 2 at Cananea, Caborca, Bacanora and Sahuaripa and the limit to the south coincide with the continental crust limit proposed by Poole et al. (2005). It means that the Proterozoic basement of North America underlies zones 1 and 2, as it has been suggested by other authors (Valencia-Moreno et al., 1999, 2001, 2006; Poole et al. 2005). We assume that the Sr and Nd isotopic data of the laramidic intrusions in zones 1 and 2 could have a large influence of the underlying Proterozoic crust, that does not crop out continuously due to the Tertiary tectonics of the Basin and Range province. We also emphasize that the Mojave-Sonora Megashear (Anderson and Silver, 1979) had no influence on the isotopic signatures in these areas.

The zone 4 with isotopic data of < 0.7060 initial [sup.87]Sr/[sup.86]Sr and > - 4 [epsilon]Nd is clearly separated from zones 1 and 2 (Fig. 8). We interpret that Laramide age intrusive rocks are related to magmas with a probable mantle contribution, or due to contamination from the Tahue Terrane in which tholeiitic volcanic rocks of Paleozoic and Mesozoic age are present (Vega-Granillo et al, 2012).

The zone 3 with a wide range in initial [sup.87]Sr/[sup.86]Sr values from 0.7054 to 0.7080 and a very restricted [epsilon]Nd values of - 4.1 to - 3.7. The position in the Sr/Nd diagram (Fig. 8) between zones 3 and 4 suggests a different type of substratum. In this case the underlying basement must be the same of central Chihuahua, consisting of a Paleozoic arc accreted to the Proterozoic North American craton during Late Paleozoic. The variation in Sr isotopic data of laramidic intrusions can reflect a more complex petrology of this substratum.

http://dx.doi.org/10.5209/rev_JIGE.2013.v39.n1.41755

Acknowledgments

Efren Perez-Segura thanks the University of Sonora and the PROMEP program for their support during the development of this research. We also thank the National University of Mexico (UNAM) for financial support to carry out the analytical studies through projects of Eduardo Gonzalez-Partida and Jaime Roldan-Quintana. The authors are in debt with S.P.Verma, Alvaro Marquez and Andrea Dini, their suggestions helped us to improve the manuscript.

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E. Perez-Segura (1) *, E. Gonzalez-Partida (2), J. Roldan-Quintana (3)

(1) department of Geology, University of Sonora, Rosales y Bd. Luis Encinas, 83000, Hermosillo, Sonora, Mexico.

(2) Center of Geociences, National University of Mexico, Campus Juriquilla, 76, 230, Queretaro, Qro., Mexico.

(3) Regional Northwest Station (ERNO), Institute of Geology, National University of Mexico, Bd. Luis Donaldo Colosio y Madrid, Hermosillo, Sonora, Mexico.

* Corresponding author: efrenpese@yahoo.com

Received: 28/04/2011 / Accepted: 11/04/2013
Table 1. Compilation isotopic data for [sup.87]Sr/[sup.86]Sr and
[epsilon]Nd according with references indicated. Data 1 to 7 are
reported by the first time in this work.

Tabla 1. Recopilacion de datos isotopicos para [sup.87]Sr/[sup.86]Sr
y [epsilon]Nd segun las referencias. Los datos 1 a 7 son publicados
por primera vez en este trabajo.

Locality   Number                   Coordinates

1          03-102                   3203423N; 649209E
2          03-116                   3217317N; 646483E
3          Lucy                     3438.6N; 548.9E
4          Can-12                   3430.0N; 552.5E
5          IntrCan                  3427.8N; 560.5E
6          IntMaria                 3436.0N; 554.4E
7          Car-5                    3357.8N; 642.5E
8          19 Batamote              30-26-48N; 109-26-47W
9          20La Caridad             30-20N; 109-32W
10         21La Caridad             30-19N; 109-31W
11         22La Caridad             30-19N; 109-31W
12         25Bella Esperanza        30-16-17N; 109-42-22W
13         35San Felipe             29-53N; 110-18W
14         39Washington             29-54-29N; 110-05-26
15         41Cerro Mariachi         29-05-20N; 110-56-08W
16         44Sierra Oposura         29-52N; 109-27W
17         46Granito Hermita        28-52-18N; 110-45W
18         48Cobachi                28-50-32N; 110-12-20W
19         49Rebeico                28-53-06N; 109-48-54W
20         50San Javier             28-37N; 109-53-18W
21         54Lucia                  28-25-32N; 109-51-53W
22         55Suaqui La Verde        28-24-41N; 109-48-11W
23         56Suaqui La Verde        28-25-12N; 109-49-01W
24         57San Nicolas            28-24-36N; 109-14-12W
25         58Santa Rosa             28-24-30N; 109-10-54W
26         58-96                    3142.50N; 560.87E
27         101-97                   3093.62N; 498.69E
28         102-97                   3090.31N; 490.31E;
29         127-97                   3142.29N; 578.85E
30         1-98                     3137.74N; 602.75E
31         9-98                     3147.46N; 685.17E
32         11-98                    3143.14N; 732.22E
33         13-98                    3135.66N; 644.10E
34         TC9822                   3140.57N; 651.81E
35         TC9825                   3147.74N; 683.51E
36         1-99                     3137.22N; 619.05E
37         SO-80                    3128.70N; 623.10E
38         SO-2                     3165.55N; 606.65E
39         SO-3                     3164.65N; 624.10E
40         SO-5                     3160.20N; 631.60E
41         SO-25                    3094.65N; 487.55E
42         SO-63                    3140.45N; 563.05E
43         SO-64                    3140.45N; 591.25E
44         MV-6 R. El Encino        29-52-54N; 109-26-54W
45         MV-7 NE Puerta del Sol   29-34-05N; 110-01-05W
46         MV-12 Hermosillo         29-06-49N; 110-56-19W
47         MV-17 Cruz Galvez        28-53-51N; 111-07-43W
48         MV-19 Barita de Sonora   28-53-51N; 109-54-16W
49         A-163 Bacanuchi          30-39-30N; 110-10-30W
50         MV-1 San Nicolas         28-26-10N; 109-10-21W
51         MV-4 Tecoripa            28-36-49N; 109-54-07W
52         MV-9 Cerro Bola          28-36-16N; 110-0114W
53         MV-11Gran. Hermita       28-48-49N; 110-37-43W
54         MV-21 San Carlos         27-56-29N; 111-04-23W
55         Ant-1 Jaralito           29-40-37N; 110-17-00W
56         Ant-1 Jaralito           29-40-37N; 110-17-00W
57         He-4 Palo Verde          29-02-34N; 110-59-00W
58         SA-8 San Alberto         27-21N; 108-57W
59         77-2044 Los Verdes       28-25N; 109-11W
60         77-2046 Los Verdes       28-25N; 109-11W
61         77-2047 Los Verdes       28-25N; 109-11W
62         77-2048 Los Verdes       28-25N; 109-11W
63         77-2050 Los Verdes       28-25N; 109-11W
64         BC25                     28-56.1N*; 112-1.1W
65         BC26                     28-54.1N*; 112-55.9W
66         BC70                     29-20.1N*; 112-24.1W
67         BC76                     29-17.1*; 112-11.6W
68         BC99                     29-2.2N*; 112-3.8W
69         SO7                      3166.3N; 588.0E
70         SO8                      3179.5N; 557.8E
71         SO26                     3173.0N; 513.3E
72         CH98-11                  3348.3N; 625.5E
73         CH98-17                  3306.6N; 652.0E
74         Tgdpx                    27-10N; 109-1.2W
75         Tqfp                     27-10N; 109-1.2W
76         Tgdp(tb)                 27-10N; 109-1.2W
77         Tqd                      27-10N; 109-1.2W
78         BD2397-489 Por Q-Feld    3427.8N; 560.5E
79         38.3 Porf 8-110          3427.8N; 560.5E
80         224 Gdi Cuitaca          3429.2N; 551.0E

Locality   Age                   [sup.87]Sr/[sup.86]Sr    [sup.87]Sr/
                                 Measured                 [sup.86]Sri

1          56                    0.7067                   0.7066
2          95                    0.7074                   0.7070
3          64                    0.7082                   0.7081
4          64                    0.7081                   0.7077
5          59                    0.7073                   0.7074
6          60                    0.7082                   0.7080
7          54                    0.7082                   0.7080
8          56.8 biotite          0.7080                   0.7070
9          52.5 biotite          0.7088                   0.7064
10         54.3 biotite          0.7075                   0.7067
11         50.0 biotite          0.7077                   0.7064
12         55.5 sericite         0.7075                   0.7062
13         51.1 orthoclase       0.7141                   0.7103
14         56.4 biotite          0.7079                   0.7067
15         64.1hn 49.6biotite    0.7071                   0.7066
16         62.7 biotite          0.7109                   0.7071
17         62.9hn 55.5 biotite   0.7092                   0.7072
18         66.7, 65.9 biotite    0.7076                   0.7070
19         61.2 matrix           0.7053                   0.7051
20         62.0hn 61.2 biotite   0.7076                   0.7064
21         56.9 sericite         0.7112                   0.7064
22         56.7 sericite         0.7074                   0.7074
23         58.8hn 56.4 biotite   0.7065                   0.7065
24         49.6 biotite          0.7080                   0.7080
25         49.5hn 49.3 biotite   0.7060                   0.7060
26         60                    0.7073                   0.7064
27         83                    0.7061                   0.7055
28         83                    0.7066                   0.7060
29         44                    0.7076                   0.7069
30         60                    0.7075                   0.7065
31         49.9                  0.7073                   0.7064
32         63.6                  0.7075                   0.7065
33         55.3                  0.7077                   0.7061
34         60                    0.7102                   0.7066
35         62                    0.7071                   0.7062
36         70                    0.7078                   0.7072
37         63                    0.7073                   0.7063
38         65                    0.7079                   0.7068
39         67                    0.7072                   0.7069
40         59                    0.7063                   0.7062
41         81                    0.7063                   0.7057
42         44                    0.7076                   0.7069
43         63                    0.7074                   0.7067
44         60                    0.7109                   0.7073
45         57                    -                        -
46         64                    0.7092                   0.7088
47         64                    0.7076                   0.7070
48         62                    0.7097                   0.7089
49         68                    0.7099                   0.7075
50         57                    0.7085                   0.7074
51         62                    0.7076                   0.7064
52         62                    0.7091                   0.7079
53         63                    0.7092                   0.7072
54         83                    0.7066                   0.7059
55         47                    0.7100                   0.7091
56         47                    0.7099                   0.7089
57         42                    0.7072                   0.7068
58         53                    0.7059                   0.7055
59         59                    0.7084                   0.7059
60         59                    0.7107                   0.7058
61         59                    0.7068                   0.7061
62         59                    0.7101                   0.7059
63         59                    0.7064                   0.7054
64         82                    0.7068                   0.7060
65         82                    0.7067                   0.7059
66         82                    0.7076                   0.7068
67         82                    0.7076                   0.7062
68         82                    0.7067                   0.7063
69         66                    0.7080                   0.7067
70         55                    0.7128                   0.7080
71         60                    0.7074                   0.7070
72         56.9                  0.7074                   0.7070
73         63.6                  0.7076                   0.7070
74         62
75         62
76         62.2
77         61.7
78         64                    0.7100                   0.7081
79         64                    0.7158                   0.7086
80         64                    0.7089                   0.7069

Locality   [sup.143]Nd/    143Nd/144Ndi   [epsilon]Nd   [T.sub.DM] Ga
           [sup.144]Ndac

1          0.512355        0.512311       -5.0          1.11
2          0.51227         0.512208       -6.0          1.04
3          0.512317        0.512275       -5.5          0.98
4          0.512454        0.512407       -3.0          0.98
5          0.512324        0.512284       -5.3          0.93
6          0.51232         0.512279       -5.5          1.01
7          0.512375        0.512337       -4.5          0.96
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26         0.512370        0.51232        -4.6          1.27
27         0.512423        0.51236        -3.3          1.12
28         0.512421        0.51236        -3.4          1.21
29         0.512388        0.512357       -4.4          1.08
30         0.512379        0.512337       -4.4          1.12
31         0.512405        0.512369       -4.0          1.10
32         0.512391        0.512343       -4.1          1.17
33         0.512396        0.512349       -4.1          1.25
34         0.512414        0.512375       -3.6          1.00
35         0.512401        0.512358       -3.9          1.10
36         0.512277        0.512226       -6.3          1.32
37         0.512414        0.512366       -3.7          1.16
38         0.512315        0.512255       -5.9
39         0.512217        0.512156       -7.7
40         0.512411        0.512357       -4
41         0.512434        0.512360       -3.4
42         0.512301        0.512357       -6.2          1.08
43
44         0.512381        0.512343       -4.2          1.03
45         0.512362        0.512336       -4.5          1.11
46         0.512331        0.512318       -5.3          0.98
47         0.512322        0.512283       -5.3          1.12
48         0.512345        0.512281       -5.4          0.98
49         0.512420        0.512295       -5.0          1.05
50         -               0.512375       -3.7          1.03
51         0.512342        -              -             -
52         -               0.512298       -5.1          1.0
53         0.512423        -              -             -
54                         0.512358       -3.4          1.01
55
56
57
58
59
60
61
62
63
64         0.512470        0.512407       -2.5          0.91
65         0.512360        0.512293       -4.7          1.17
66         0.512479        0.512416       -2.3          0.90
67         0.512417        0.512360       -3.4          0.90
68         0.512368        0.512308       -4.4          1.02
69         0.512310        0.51225        -6.1
70         0.512110        0.51206        -9.8
71
72
73         0.512406        0.51235        -4.1
74         0.512531        0.512466       -1.8          1.43
75         0.512442        0.512390       -3.3          1.08
76         0.512491        0.512445       -2.2          0.85
77         0.512505        0.512457       -2.0          0.87
78         0.512307        0.512265       -5.7          0.99
79         0.512322        0.512275       -5.5          1.10
80         0.512333        0.512285       -5.3          1.10

Locality   Ref(*)

1          TW
2          TW
3          TW
4          TW
5          TW
6          TW
7          TW
8          1
9          1
10         1
11         1
12         1
13         1
14         1
15         1
16         1
17         1
18         1
19         1
20         1
21         1
22         1
23         1
24         1
25         1
26         2, 3
27         2, 3
28         2, 3
29         2, 3
30         2,3
31         2, 3
32         2, 3
33         2, 3
34         2, 3
35         2, 3
36         2, 3
37         2, 3
38         2, 4
39         2, 4
40         2, 4
41         2,4
42         2,4
43         2, 4
44         5
45         5
46         5
47         5
48         5
49         5
50         5
51         5
52         5
53         5
54         5
55         6
56         6
57         6
58         6
59         6
60         6
61         6
62         6
63         6
64         7
65         7
66         7
67         7
68         7
69         4
70         4
71         4
72         4
73         4
74         8
75         8
76         8
77         8
78         9
79         9
80         9

(*) TW. This work. 1. Damon et al. (1983); [sup.87]Sr/[sup.86]Sr
calculated by us. 2. Roldan/Quintana (2006). 3. Roldan/Quintana et
al. (2009). 4. McDowell and Housh (2005). 5. Valencia/Moreno et al.
(2001). 6. Mead et al. (1988); [sup.87]Sr/[sup.86]Sr calculated by us
using the ages of Mead et al. (1988) and Sansores/Bolivar and Wine
(1977). 7. Valencia/Moreno et al. (2003); 8. Espinosa/Perea (1999);
[sup.143]Nd/[sup.144Nd/and [epsilon]Nd recalculated by us. 9.
Woodzicki (1995).

Table 2. Major and REE by ICP-MS for samples 3, 5, 6 and 7. The
analyses  were carried out at the Centre de Recherches
Petrographiques et Geochimiques (CRPG) of Nancy, France.

Tabla 2. Elementos mayores y REE por ICP-MS para las muestras 3, 5, 6
y 7. Los analisis se realizaron en el Centre de Recherches
Petrographiques  et Geochimiques (CRPG) en Nancy, Francia.

                       Sample 3     Sample 5     Sample 6     Sample 7
Composition           Lucy Intr.    Can Intr    Maria Intr   Car-5 Intr

Si[O.sub.2]             67.11        62.92        66.24        70.63
Ti[O.sub.2]              0.50         0.24         0.52         0.28
[Al.sub.2][O.sub.3]     15.36        17.70        15.51        16.26
[Fe.sub.2][O.sub.2]      3.75         1.01         3.79         0.99
MnO                      0.04          --          0.03          --
MgO                      1.48         0.64         1.53         0.43
CaO                      2.66          --          2.77         0.11
[Na.sub.2]O              2.78          --          3.80         2.34
[K.sub.2]O               4.04         4.60         3.86         6.42
[P.sub.2][O.sub.5]       0.15         0.13         0.16         0.19
LOI                      2.03        12.72         1.65         2.56
TOTAL                    99.9        99.86        99.86        100.21
REE
La                      56.35        27.99        35.77        28.78
Ce                      98.47        48.28        69.87         55.0
Pr                      10.14        5.006        7.919        6.335
Nd                      33.06        16.33        27.43        22.51
Sm                      5.172        2.449        4.659        3.985
Eu                      1.002        0.526        0.995        0.801
Gd                      3.548         1.48        3.395        3.259
Tb                      0.501        0.171        0.498        0.528
Dy                      2.571        0.723        2.676        3.335
Ho                      0.461        0.115        0.501        0.704
Er                      1.272         0.34        1.397        1.992
Tm                      0.193         0.06        0.217        0.286
Yb                      1.372         0.48        1.546        1.872
Lu                      0.217        0.094        0.247        0.287
Y                       13.97        3.318        15.18        24.73

Table 3.-Analytic and individual U-Pb dating data in zircons for
sample 03-116 using SHRIMP.

Tabla 3.-Datos analiticos y dataciones individuales por U-Pb en
zircones para la muestra 03-116 utilizando SHRIMP.

Spot              Common         U       Th     [sup.232]Th/
Number        [sup.206]Pb (%)   (ppm)   (ppm)    [sup.238]U

03-116
116-1.1            2.044         112     61         0.57
116-2.1            2.456         90      78         0.90
116-3.1            1.348         230     135        0.61
116-4.1            0.376         284     230        0.84
116-5.1            0.551         322     185        0.59
116-6.1            0.522         601     454        0.78
116-7.1            0.686         345     190        0.57
116-8.1            0.078        1485    1439        1.00
116-9.1            0.271         841     408        0.50
116-10.1           0.657         619     310        0.52
116-11.1           0.803         194     103        0.55
116-11.2           0.283        1276    1392        1.13
116-12.1           0.401         527     268        0.53
116-13.1           0.310         616     241        0.40
116-14.1           0.182         556     208        0.39
116-15.1           0.422         406     300        0.76

Spot          [sup.238]U/              [sup.207]Pb/
Number        [sup.206]Pb *            [sup.208]Pb

03-116
116-1.1       72.64291 [+ or -] 3.68   0.06396 [+ or -] 7.18
116-2.1       63.35987 [+ or -] 3.56   0.06748 [+ or -] 7.31
116-3.1       66.06958 [+ or -] 3.16   0.05863 [+ or -] 5.18
116-4.1       64.58546 [+ or -] 3.11   0.05097 [+ or -] 5.07
116-5.1       66.86318 [+ or -] 3.06   0.05229 [+ or -] 4.53
116-6.1       66.59238 [+ or -] 2.96   0.05207 [+ or -] 3.30
116-7.1       65.19800 [+ or -] 3.04   0.05341 [+ or -] 4.23
116-8.1       67.60167 [+ or -] 2.89   0.04852 [+ or -] 2.23
116-9.1       66.38932 [+ or -] 2.92   0.05009 [+ or -] 2.78
116-10.1      70.29456 [+ or -] 2.96   0.05304 [+ or -] 3.34
116-11.1      67.58890 [+ or -] 3.19   0.05426 [+ or -] 7.03
116-11.2      63.92289 [+ or -] 2.89   0.05026 [+ or -] 2.19
116-12.1      70.47863 [+ or -] 2.97   0.04466 [+ or -] 3.87
116-13.1      64.93592 [+ or -] 2.95   0.05044 [+ or -] 3.50
116-14.1      66.34091 [+ or -] 2.97   0.04938 [+ or -] 3.50
116-15.1      65.99665 [+ or -] 3.01   0.05130 [+ or -] 4.98

Spot          [sup.238]U/              [sup.207]Pb/
Number        [sup.206][Pb.sup.+]      [sup.206]Pb [+ or -]

03-116
116-1.1       76.34087 [+ or -] 4.55   0.02439 [+ or -] 94.35
116-2.1       63.35987 [+ or -] 3.56   0.06748 [+ or -] 7.31
116-3.1       67.98020 [+ or -] 3.35   0.03598 [+ or -] 27.87
116-4.1       66.60247 [+ or -] 3.30   0.02626 [+ or -] 37.51
116-5.1       66.86318 [+ or -] 3.06   0.05229 [+ or -] 4.53
116-6.1       66.59238 [+ or -] 2.96   0.05207 [+ or -] 3.30
116-7.1       65.19800 [+ or -] 3.04   0.05341 [+ or -] 4.23
116-8.1       67.60167 [+ or -] 2.89   0.04852 [+ or -] 2.23
116-9.1       66.38932 [+ or -] 2.92   0.05009 [+ or -] 2.78
116-10.1      70.29456 [+ or -] 2.96   0.05304 [+ or -] 3.34
116-11.1      70.01618 [+ or -] 3.60   0.02599 [+ or -] 56.55
116-11.2      63.92289 [+ or -] 2.89   0.05026 [+ or -] 2.19
116-12.1      70.47863 [+ or -] 2.97   0.04466 [+ or -] 3.87
116-13.1      65.29203 [+ or -] 2.96   0.04610 [+ or -] 5.92
116-14.1      66.88931 [+ or -] 2.99   0.04283 [+ or -] 8.93
116-15.1      65.99665 [+ or -] 3.01   0.05130 [+ or -] 4.98

Spot          [sup.206]Pb/           Degree of
Number        [sup.238][U.sup.#]   discordance (%)

03-116
116-1.1       86.3 [+ or -] 3.2         -2301
116-2.1       98.5 [+ or -] 3.6          745
116-3.1       95.5 [+ or -] 3.0         -772
116-4.1       98.7 [+ or -] 3.1         -1752
116-5.1       95.2 [+ or -] 2.9          212
116-6.1       95.6 [+ or -] 2.8          200
116-7.1       97.5 [+ or -] 3.0          253
116-8.1       94.6 [+ or -] 2.7          32
116-9.1       96.1 [+ or -] 2.8          107
116-10.1      90.5 [+ or -] 2.7          263
116-11.1      93.9 [+ or -] 3.0         -1877
116-11.2      99.8 [+ or -] 2.9          107
116-12.1      91.2 [+ or -] 2.7         -182
116-13.1      98.2 [+ or -] 2.9          -97
116-14.1      96.3 [+ or -] 2.8         -286
116-15.1      96.5 [+ or -] 2.9          162

* uncorrected ratios. + [sup.204]Pb corrected for common lead.
[sup.#207]Pb corrected for common lead. All errors are at one sigma
level expressed in %, i.e., they are relative standard deviation ex-
pressed in % (%RSD, see Verma, 2005). For more details on SHRIMP
results, see Nourse et al. (2005).

Table 4. Analysis for [sup.40]Ar-[sup.39]Ar in potassic feldspar a
t different step-heating for samples 03-116 and 03-101.

Tabla 4. Analisis por [sup.40]Ar-[sup.39]Ar en feldespato potasico
para diferentes etapas de calentamiento (step-heating) para las
muestras 03-116 y 03-101.

Step     Temp.      %[sup.39]Ar of   Radiogenic
       [degrees]C       total        Yield (%)

03-116 Arroyo San Lucas monzonite porphyry K-feldspar J=0.004895 [+
or -] 0.50% wt=19.2 mg #85KD45

A         550            4.1            27.4
B         650            9.0            75.9
C         750            8.0            81.1
D         950            14.1           79.9
E         1100           17.5           76.9
F         1200           22.7           64.6
G         1225           20.0           67.0
H         1250           4.5            59.3
       Total Gas        100.0           70.0

03-101 Bacanora-Novillo Granodiorite K-feldspar J=0.004903 [+ or -]
0.50% wt=20.7 mg #79KD45

A         750            7.3            53.0
B         950            22.3           95.8
C         1000           9.4            97.7
D         1100           9.5            96.3
E         1175           7.8            88.3
F         1200           6.9            84.0
G         1225           10.1           88.1
H         1250           15.2           91.9
I         1275           9.2            91.4
J         1300           2.1            86.7
        TotalGas        100.0           89.5

Step     [sup.39][Ar.sub.k]     [sup.40][Ar.sub.*]   Apparent
       (Moles x [10.sup.-12])   [sup.39][Ar.sub.k]     K/Ca

03-116 Arroyo San Lucas monzonite porphyry K-feldspar J=0.004895 [+
or -] 0.50% wt=19.2 mg #85KD45

A             0.11576                 5.711            9.8
B             0.25846                 5.918            6.1
C             0.22677                 6.091            15.5
D             0.39869                 6.513            33.4
E             0.49559                 6.037            36.1
F             0.64028                 6.792            30.6
G             0.56584                 7.605            30.4
H             0.12851                 8.192            12.6
              2.82630                 6.668            26.8

03-101 Bacanora-Novillo Granodiorite K-feldspar J=0.004903 [+ or -]
0.50% wt=20.7 mg #79KD45

A             0.43299                 6.156            5.8
B             1.33138                 6.386            8.9
C             0.56239                 6.422            16.2
D             0.56758                 6.419            12.9
E             0.46768                 6.371            6.8
F             0.41043                 6.413            6.6
G             0.60359                 6.453            11.7
H             0.90728                 6.473            23.2
I             0.54909                 6.497            22.3
J             0.12602                 6.498            7.0
              5.95843                 6.409            13.1

Step   Apparent   Apparent Error
         K/Cl     Age (Ma) (Ma)

03-116 Arroyo San Lucas monzonite porphyry K-feldspar J=0.004895 [+
or -] 0.50% wt=19.2 mg #85KD45

A         40      49.74 [+ or -] 0.91
B        312      51.52 [+ or -] 0.17
C        385      53.00 [+ or -] 0.17
D        348      56.62 [+ or -] 0.09
E        369      52.54 [+ or -] 0.10
F         68      59.00 [+ or -] 0.15
G        116      65.94 [+ or -] 0.12
H         90      70.93 [+ or -] 0.36
         217      57.94

03-101 Bacanora-Novillo Granodiorite K-feldspar J=0.004903 [+ or -]
0.50% wt=20.7 mg #79KD45

A        150      53.64 [+ or -] 0.16
B        3087     55.62 [+ or -] 0.03
C        4301     55.93 [+ or -] 0.06
D        1335     55.90 [+ or -] 0.06
E         97      55.49 [+ or -] 0.08
F        321      55.85 [+ or -] 0.07
G        394      56.19 [+ or -] 0.09
H        538      56.37 [+ or -] 0.04
I        669      56.57 [+ or -] 0.06
J        526      56.58 [+ or -] 0.35
         1458     55.82

Ages calculated assuming an initial [sup.40]Ar-[sup.36]Ar = 295.5 [+
or -] 0. All precision estimates are at the one sigma level of
precision. Ages of individual steps do not include error in the
irradiation parameter J. No error is calculated for the total gas
age.

Table 5.- Isotope and trace element data for samples 1 to 7.

Tabla 5.-Datos isotopicos y de elementos traza para las muestras 1 a
7.

Sample    Sample      Rb       Sr     [sup.87]Rb/[sup.86]Sr
Number               (ppm)    (ppm)         measured

1          03-102    13.84    404.7           0.099
2          03-116    27.14    248.8           0.315
3           Lucy     20.54    337.2           0.176
4          Can-12    71.07    444.5           0.463
5         IntrCan    222.65   243.6           2.645
6         IntMaria   25.61    394.4           0.188
7          Car-5     39.24    435.1           0.261

Sample    [sup.87]Sr/[sup.86]Sr   [sup.87]Sr/   [epsilon]Sr    Sm
Number          measured          [sup.86]Sri                 (ppm)

1                0.70671            0.70663         31        3.47
2                0.70741            0.70699         37        3.39
3                0.70821            0.70805         51        4.47
4                0.70813            0.70771         47        3.62
5                0.70965            0.70740         43        1.80
6                0.70815            0.70799         51        4.66
7                0.70823            0.70803         51        2.97

Sample     Nd     [sup.147]Sm/[sup.144]Nd    [sup.143]Nd/[sup.144]Nd
Number    (ppm)           measured                   measured

1         17.50            0.1200                    0.512355
2         20.29            0.1009                    0.512270
3         26.89            0.1006                    0.512317
4         17.92            0.1222                    0.512454
5         11.33            0.0961                    0.512324
6         26.88            0.1049                    0.512320
7         16.60            0.1080                    0.512375

Sample    [sup.143]Nd/[sup.144]Nd    [epsilon]Nd   [t.sub.DM ]Ga
Number            initial

1                 0.512311              -5.0            1.11
2                 0.512208              -6.0            1.04
3                 0.512275              -5.5            0.98
4                 0.512407              -3.0            0.98
5                 0.512284              -5.3            0.93
6                 0.512279              -5.5            1.01
7                 0.512337              -4.5            0.96

The Sr isotopic ratios of standards and samples were normalized to
[sup.86]Sr/[sup.88]Sr = 0.1194, whereas the Nd isotopic ratios were
normalized to [sup.146]Nd/[sup.144]Nd = 0.7219. The estimated
analytical [+ or -] 2a uncertainties are similar to those reported in
Ducea   et al. (2002) and Otamendi et al. (2009).
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Title Annotation:articulo en ingles
Author:Perez-Segura, E.; Gonzalez-Partida, E.; Roldan-Quintana, J.
Publication:Journal of Iberian Geology
Date:Jan 1, 2013
Words:11926
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